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    10 December 2021, Volume 40 Issue 12
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    Variations of leaf traits of typical shrub and herb species along a climate gradient in arid areas of Northwest China.
    YANG Yong, HUANG Yue, WEI Wei
    2021, 40(12):  3769-3777.  doi:10.13292/j.1000-4890.202112.002
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    Identifying the relationship between leaf traits and environmental factors in arid areas will provide scientific guidance for revealing plant survival strategies and optimizing vegetation management practices in water-limited areas. Based on large-scale field investigations in arid regions of Northwest China, we quantitatively identified the variability of leaf traits of typical shrub and herb species, and explored the responses and adaptation mechanisms of leaf traits to variability of climate factors. The results showed that: (1) The average leaf area, leaf thickness, and specific leaf area of shrub species were 136.77 mm2, 0.41 mm, and 55.36 cm2·g-1, respectively, while the values for herb species were 351.45 mm2, 0.31 mm, and 111.45 cm2·g-1, respectively. There were significant differences in leaf traits between shrub and herb species, with leaf size and specific leaf area being more sensitive than other parameters. (2) Similar responses of leaf traits to the variability of climate factors were found in shrub and herb species. Leaf length, leaf width, leaf area, and specific leaf area decreased with increasing drought intensity, while leaf thickness showed an increasing trend. (3) The sensitivity of shrubs to climate variability was higher than that of herbs. Results of redundancy analysis showed that climatic factors accounted for 52% and 12% of the variation of leaf traits of shrub and herb species, respectively. Annual mean precipitation had higher effect on variability of plant leaf traits than annual mean potential evapotranspiration, while the latter had higher effect than annual mean temperature. Our results can help understand plant responses to environmental stress in arid areas.
    Effects of understory vegetation on soil phosphorus fraction and availability in nongrowing season in poplar plantation.
    2021, 40(12):  3778-3787.  doi:10.13292/j.1000-4890.202111.024
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    Soil phosphorus (P) fractions and transformation during the non-growing season directly affect soil P supply in the following spring in forest plantations. The species and diversity of understory vegetation can affect soil P fraction and transformation in non-growing season by altering the microenvironment and the composition and quality of litter. In order to clarify the effects of the species identity and diversity of understory vegetation on soil P fraction and availability, four understory vegetation treatments, including understory vegetation removal (UR), retention of natural diverse understory vegetation (RD), retention of single main understory vegetation species (RS), and planting single N-fixing plant species (PN), were employed in polar (Populus deltoides ‘Nanlin3804’) plantation in August 2017. Soil samples from surface layer (0-5 cm) were collected in January 2019 for P fractionation analysis. In addition, soil P transformation process was studied using in situ buried bag culture method during the nongrowing season. The results showed that soil total labile P content was significantly higher under RD treatment than under UR and RS treatment, indicating obvious improvement of soil P availability in non-growing season with the retention of understory vegetation. Soil intermediate labile P content was significantly lower, while the net production rates of soil labile P and labile organic P were significantly higher under PN treatment than under RS treatment. Soil stable P content was the highest under UN treatment, indicating a decline in P availability when understory vegetation was removed. For all the treatments, soil inorganic P occupied relatively higher proportion (43.4%-48.1%) of soil total P compared with soil organic P, which contributed to 26.9%-34.5% of soil total P. The total inorganic P content was significantly higher under PN treatment than under RS treatment. In conclusion, understory vegetation in poplar plantations significantly reduced soil stable P fractions and improved P availability in nongrowing season. Furthermore, soil labile P significantly increased with increasing species diversity of understory vegetation. In addition, planting N-fixing plants could effectively enhance soil P availability by promoting P transformation and net production of labile P.
    Spatiotemporal variations of habitat quality in forestry ecological project region of the Yangtze River Economic Belt.
    LI Chen-yu, ZHU Jian-hua, GUO Xue-yuan, LI Qi, ZHANG Qian-ru, LIU Hua-yan, XIAO Wen-fa
    2021, 40(12):  3788-3799.  doi:10.13292/j.1000-4890.202112.012
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    The rapid economic development in recent years has caused many eco-environmental problems in the Yangtze River Economic Belt. Habitat quality is important for the restoration of the regional eco-environment. The development of forestry ecological projects has substantially increased vegetation coverage in the Yangtze River Economic Belt, improved ecosystem quality, and restrained the decline rate of habitat quality. Here, we evaluated the temporal and spatial variations of habitat quality in the Yangtze River Economic Zone from 2000 to 2015, as well as the impacts of the Yangtze River Shelterbelt Project and the Natural Forest Protection Project on the habitat quality, by applying InVEST module and setting up a single driving force scenario for forestry ecological projects. The results showed that habitat quality of the Yangtze River Economic Belt was lower in the east and higher in the west. The areas with low-level habitat quality were mainly distributed in the northern Yangtze River Delta, Jianghan Plain, and Sichuan Basin, while Yunnan, Jiangxi, and Zhejiang had higher average habitat quality index. The implementation of forestry ecological project did not lead to a decisive change in the spatial distribution of habitat quality in the Yangtze River Economic Belt. From 2000 to 2015, the habitat quality of the Yangtze River Economic Belt was developing towards polarizations. Areas with medium-level habitat quality gradually shifted to low or high level, resulting in no changes of the average habitat quality index. Forestry ecological projects had a certain effect on the improvement of habitat quality, which was specifically manifested in further improving the habitat quality of areas under medium and high levels, but had minor effect on areas with low levels of habitat quality.
    The composition and distribution status of alien plant species in Shaanxi Province, China.
    SONG Xing-jiang, ZHANG Wen-gang, CHEN Xiao-yan, LIU Rui-ling, YAO Xin, MA Jing-hao, WANG Jia-ning, SHI Yan, RAN Jun-jie, AN Yu-xia, LIU Gang
    2021, 40(12):  3800-3809.  doi:10.13292/j.1000-4890.202112.014
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    By integrating the data of alien plant species in Shaanxi Province, we analyzed the species composition, origination, and geographical distribution of alien plant species and the correlations between the number of invasive plant species and potential influencing factors (e.g., GDP). The results showed that there were 415 generalized alien plant species in Shaanxi Province, belonging to 68 families and 268 genera, including 132 invasive species and 283 noninvasive species. The habitat types with the highest occupation by alien plants were cropland and wasteland (accounting for 70% habitats). Alien species mainly came from Eurasia and America, with species originated from these two continents accounting for 29.23% and 28.83% of all the alien species in Shaanxi Province, respectively. The spatial distribution of alien species in the province was uneven, with more alien species in the south and less in the north. There were significantly positive correlations between the percentage of tertiary sector in GDP and the number of invasive plant species (R2=0.42, P=0.04), between GDP per capita per unit area and the proportion of invasive plants in all alien plants (R2=0.60, P=0.01), and between the GDP per capita per unit area and the number of invasive alien plants per unit area (R2=0.41, P=0.04). These results indicate that anthropogenic activities facilitate the introduction and invasion processes of alien plants. Our results suggest that the risk of introduction and invasion of alien plants in Shaanxi Province is unexpectedly high, and that it is critically needed to construct a biological prevention and control system for the invasion of alien plants.
    Effects of climate change on spatial pattern of forest fire regimes in China.
    SU Jia-jia, LIU Zhi-hua, JIAO Ke-wei, YU Yue, LI Kai-li, LYU Qiu-shuang, FANG Lei, WANG Wen-juan
    2021, 40(12):  3810-3821.  doi:10.13292/j.1000-4890.202112.019
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    Fire is a common natural disturbance in forest ecosystems and has extensive and profound impacts on ecosystem structure and function. It is important to examine the spatial-temporal pattern of forest fire and its spatial controls for a better understanding on the feedback among climate change, fire regimes, and forest ecosystems. In this study, three forest fire regime components (fire occurrence density, burned rate, and median fire size) from 2003 to 2016 in China were extracted based on the Global Fire Atlas dataset. Three models (Boosted Regression Tree, Random Forest and Support Vector Machine) were used to systematically analyze the impacts of climate, human activities, vegetation, and topography on forest fire regimes in China. Finally, the effects of climate change on future forest fire regimes were evaluated. The results showed that forest fires were spatially heterogeneously distributed in China, and fire occurrence density, burned rate and median fire size were higher in Northeast China than other regions. Different forest fire regime components were controlled by different factors, with climate as the dominant driver at national level. Climate warming will increase the frequency, size, and burned area of forest fire. The occurrence density, burned rate and median size of forest fire will increase by 39.4%-95.8%, 85.2%-143.0%, and 220.4%-206.6% under SSP126 and SSP585 scenarios. Future research needs to focus on evaluating the effects of climate factors on multiple fire regime components to gain a better understanding of future trends of forest fire regimes.
    Prediction of potential suitable area of Ulmus elongata in China under climate change scenario.
    ZHANG Ming-zhu, YE Xing-zhuang, LI Jia-hui, LIU Yi-peng, CHEN Shi-pin, LIU Bao
    2021, 40(12):  3822-3835.  doi:10.13292/j.1000-4890.202112.018
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    Ulmus elongatais one of the key rare and endangered species in China, with important scientific and economic values. Due to natural and anthropogenic disturbances, the natural resource of U. elongata is rare and scattered. The geographical distribution of plants is profoundly affected by climate change. In this study, we modeled the impacts of climate change on the geographical distribution of U. elongata in order to provide theoretical basis for the natural resource protection and introduction of this species. Based on the data of 42 natural distribution sites of U. elongata in China and 16 environmental factors, the MaxEnt optimization model and geographic information system were used to construct the suitable distribution model. We analyzed the key environmental factors affecting the potential suitable distribution of U. elongata and predicted the potential distribution area during the last interglacial, last glacial maximum, mid-Holocene, current and the climate scenarios of RCP2.6 and RCP8.5 in the future 2050s (2041-2060) and 2070s (2061-2080). Our results showed that the model was accurate and the predicted distribution range was consistent with the actual distribution when the feature combination (FC) was HPT (H: Hinge; P: Product; T: Threshold) and the regularization multiplier (RM) was 2. A comprehensive evaluation showed that precipitation in the driest month, annual precipitation, elevation, topsoil pH, minimum temperature of coldest month and maximum temperature of warmest month played important roles in the potential geographical distribution of U. elongata. Under the RCP 2.6 climate scenario, the increased temperature within 2 ℃ may provide a more suitable environmentfor U. elongata. Under the RCP 8.5 climate scenario, the centroid of U. elongata distribution will migrate from low latitude to high latitude from current to 2070s.
    Spatiotemporal variation in net primary productivity and factor detection in Yunnan Province based on geodetector.
    SUN Zhi-juan, XIE Shi-you
    2021, 40(12):  3836-3848.  doi:10.13292/j.1000-4890.202111.033
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    We examined the spatiotemporal variation and driving factors of net primary productivity (NPP) in Yunnan Province, using trend analysis, correlation analysis, and geodetector method based on NPP data from 2000 to 2015, as well as meteorological, DEM, land use, NDVI and population density data. The interannual variation of NPP in Yunnan Province showed a fluctuating increasing trend with a mean annual growth rate of 2.13 g C·m-2·a-1. The average annual NPP had large spatial variations, and generally increased from the northeast to southwest. The NPP in 88.5% of the total areas remained basically unchanged or increased from 2000 to 2015. In terms of each individual factor, the dominant factor for NPP changed from vegetation coverage to precipitation in 2010 and the influence of human interference increased. In terms of two-factor interaction, the interaction of two factors enhanced the explanatory power of spatial differentiation of NPP in Yunnan Province. Therefore, the synergistic effects of multiple factors on NPP should be emphasized in future ecological environment planning to understand the status of ecosystem health in Yunnan Province.
    Effects of Moso bamboo expansion on community diversity of endophytic fungi in leaves of Rhododendron latoucheae.
    BAI Hao-nan, NIU Xiang, WANG Bing, SONG Qing-feng, TAO Yu-zhu
    2021, 40(12):  3849-3859.  doi:10.13292/j.1000-4890.202112.011
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    We examined the effects of Phyllostachys edulis expansion on the diversity of endophytic fungal community in leaves of Rhododendron latoucheae in an evergreen forest which were affected by different degrees of P. edulis expansion (non-expanded, slightly expanded and severely expanded) in Dagangshan forest ecological station, Jiangxi Province. High throughput sequencing technique was used to characterize endophytic fungi in leaves of R. latoucheae. We found that P. edulis expansion significantly increased leaf cellulose content, lignin content, and leaf tissue density, but significantly decreased flavonoid content of R. latoucheae. There were differences in the taxa and relative abundance of endophytic fungi in the leaves of R. latoucheae under different degrees of P. edulis expansion. A total of 5 phyla, 18 classes and 81 genera were recorded by high-density sequencing. Ascomycota and Basidiomycotawere the dominant phyla of endophytic fungi in the leaves of R. latoucheae. The relative abundances of G_hyphoderma,F_hyphodermataceae, C_leotiomycetes, O_helotiales, G_roussoella, O_thelephorales, F_thelephorceae, F_Thyridariaceae, G_Tomentella, F_Diaporthaceae, andG_Diaporthe changed significantly, which could be used as the indicator species showing the difference in endophytic fungi of R. latoucheae leaves under the influence of P. edulisexpansion. P. edulisexpansion did not affect α-diversity of endophytic fungi. The results of principal coordinate analysis showed that P. edulisinvasion changed the community structure of endophytic fungi in R. latoucheae leaves. The results of redundancy analysis and Spearman analysis showed that cellulose, lignin, and leaf toughness had significant effects on community assembly of endophytic fungi. Cellulose is an important factor that indirectly affects the diversity of endophytic fungal community in R. latoucheae leaves under the P. edulisexpansion.
    Population spatial distribution pattern and association of Abies georgei in Shangri LaPotatso National Park.
    GU Rong, ZHANG Cai-cai, HE Zheng-hua, YANG Rong, CHEN Yao, FENG Ping, SINA Qu-zong, ZHAO Dong-lian, YIXI Yang-chu, WU Jun-hua, LIN Lu-xiang
    2021, 40(12):  3860-3869.  doi:10.13292/j.1000-4890.202112.015
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    The spatial distribution pattern and association of plant species at different developmental stages can reflect the status and growth trend of plant populations, and also can uncover the underlying ecological processes. We investigated the population of Abies georgei in a 1 hm2 dynamic plot, which was the dominant species in the subalpine cold temperate coniferous forest in ShangriLa Potatso National Park. We analyzed the diameter class structure of A. georgei, and the spatial distribution pattern for each of the three different developmental stages of A. georgei population and their spatial associations using Ripley’s L function. We found that: (1) The diameter class structure of A. georgei population presented a form of pyramid. The individual number of saplings (1 cm≤DBH<5 cm), mid-sized trees (5 cm≤DBH≤15 cm), and adults (DBH≥15 cm) accounted for 47.42%, 31.55%, and 21.03% of the total abundance, respectively, indicating a growing population with a good natural regeneration status. (2) The spatial distribution of A. georgei populations differed among different developmental stages. Results from the analysis with complete spatial randomness null model showed that saplings and mid-sized trees tended to be significantly aggregated at 0-45 m and 0-35 m scales respectively, and that adults were randomly distributed at all the scales. We used the heterogeneous Poisson process null model to eliminate the effects of habitat heterogeneity and found that saplings, mid-sized trees and adults were randomly distributed at all the scales. This result indicated that habitat heterogeneity was the main reason for the aggregation of A. georgei population at different developmental stages. (3) Saplings showed positive spatial correlation with mid-sized trees at neighborhood scale. Both were negatively correlated with adults at the neighborhood scale, but such negative correlation turned to be weakened and uncorrelated with increasing spatial scale. The potential negative density-dependence effect may result in the shift of spatial distribution from spatial aggregation for saplings and mid-sized trees to randomness for adults. The aggregated spatial pattern and the resulting positive correlation between saplings and mid-sized trees may be both resulted from habitat filtering. The negative spatial correlation between adults and saplings/mid-sized trees might be caused by the potential asymmetrical competition of adults with mid-sized trees and the attack of specific pathogens and pests on saplings.
    Effects of nitrogen and water addition on C, N, P stoichiometry in different organs of poplar seedlings.
    WANG Kai, GAO Shuang, LIU Huan-bin, LYU Lin-you, JIAO Xiang-li
    2021, 40(12):  3870-3880.  doi:10.13292/j.1000-4890.202112.020
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    To clarify the response of poplar to nitrogen deposition and water enhancement, Populus ×xiaozhuanica cv. Zhangwu seedlings were grown under a full-factorial experiment of two factors (nitrogen and water addition),i.e., four N fertilization levels (0, 5, 10 and 15 g N·m-2·a-1) and three levels of water addition (natural precipitation, 50% increase in precipitation, 100% increase in precipitation) with randomized block design. We measured the concentrations of C, N, and P in different organs (leaf, branch, stem, coarse root and fine root) and analyzed the relationships between element concentrations in different organs. The results showed that with increasing N addition level, N concentration and N∶P in coarse roots and fine roots and P concentration in fine roots showed upward trends, whereas C∶N in coarse roots and fine roots and C∶P in fine roots showed downward trends. With increasing water addition levels, leaf and fine root C concentrations reduced, stem and coarse root C concentrations remained constant, whereas N∶P in coarse roots increased. Nitrogen addition and water addition interacted to affect C∶N∶P stoichiometry in the poplar seedlings. With increasing nitrogen addition, under natural precipitation treatment, no significant variations were found in C concentrations in branches, stems, coarse roots and fine roots, and N and P concentrations in leaves, branches and stems. Under 50% increase in precipitation, upward trends were found in C concentrations in leaves, branches and fine roots, N concentrations in all organs, and P concentrations in leaves, stems and coarse roots. Under 100% increase in precipitation, C and P concentrations in leaves, stems and coarse roots remained unchanged with increased nitrogen addition. Significant positive relationships were found among different organs within the same element (C, N, P) under water and nitrogen addition. Nitrogen concentrations showed significantly positive correlation with P concentrations in leaves and fine roots. Therefore, nitrogen addition only affected underground part N and P distribution of poplar seedlings under natural precipitation, whereas it promoted C, N, and P distribution among organs under 50% increase in precipitation. However, the effects of nitrogen addition were diminished under 100% increase in precipitation.
    Effects of spring warming on phenology and growth of subtropical woody species.
    DAI Kui, ZENG Xiu, WANG Xin-yang, XUE Qian-huai, DU Yan-jun
    2021, 40(12):  3881-3889.  doi:10.13292/j.1000-4890.202112.030
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    Climate warming advances the spring phenology of species in temperate regions. There are only a few phenological events recorded and studied in subtropical and tropical regions, and the driving factors of climate are still unclear, which seriously hinders the accurate prediction of the impacts of climate change on plant phenology in these unique ecoregions in the future. To determine the differences of the response of plant phenology to temperature changes in subtropical region in spring, we designed a climate chamber experiment and a field experiment to test the effects of two spring warming treatments (T1: 20 ℃ during the day and 15 ℃ at night; T2: 25 ℃ during the day and 20 ℃ at night. The length of day and night is 12 hours) on the timing of budburst and leaf-out and seedling height growth of 10 subtropical woody species (four deciduous species and six evergreen species). The results showed that spring warming significantly advanced the budburst and leaf out of deciduous trees. The timing of budburst ranged from -0.006 to -1.8 d·℃-1, while the timing of leaf-out ranged from -0.7 to -1.6 d·℃-1. The seedling growth of three deciduous trees was markedly promoted by spring warming. Compared with evergreen species, the effects of temperature change on spring phenology and growth are more important to deciduous tree species. These results are of great significance for the conservation and management of tropical and subtropical plant populations under climate change.
    Preferential flow characteristics and its influencing factors on slope positions in different vegetation types in Guandi Mountain, Lüliang.
    CHENG Jing-feng, YAN Jia-liang, XU Man-hou, ZHANG Bao-gui
    2021, 40(12):  3890-3900.  doi:10.13292/j.1000-4890.202112.009
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    Soil preferential flow affects slope runoff and water cycle in watershed. Understanding the characteristics and influencing factors of preferential flow are helpful for uncovering the mechanism of preferential flow in different vegetations. In this study, we investigated the spatial heterogeneity of soil preferential flow in a mixed broadleaf-conifer forest, coniferous forest, and shrubland in Guandi Mountain by using bright blue tracer and image analysis, and analyzed the impactsof soil physical and chemical properties. The results showed that: (1) Soil preferential flow under the mixed broadleaf-conifer forest and shrubland was in an order of upper slope > lower slope > middle slope, while the preferential flow in the coniferous forest decreased with increasing slope position. (2) The horizontal dyeing pathway in the coniferous forest and shrubland was mainly >10 mm. The total number of dyeing pathway in the coniferous forest was firstly increased and then decreased with increasing slope position, while that in the shrubland decreased with increasing slope position. (3) Electrical conductivity, organic matter content, slope position, and clay content were the main factors affecting the vertical dyeing characteristics of preferential flow, while organic matter content, sand content, silt content, and slope position were the main factors affecting the horizontal dyeing characteristics of preferential flow. Our results indicated that slope position and vegetation types had important impacts on the occurrence and development of preferential flow, improving the understanding of the effects and underlying mechanism of slope position on the preferential flow.
    Factors influencing acid buffering capacity of main soil types in eastern China.
    LI Bo, ZHAO Qiong, MAO Bing, SUN Qing-ye
    2021, 40(12):  3901-3910.  doi:10.13292/j.1000-4890.202112.001
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    To clarify acid buffering capacity of different soil types and the main influencing factors, we collected 0-20 cm top soils from eight types of representative soils in eastern China (black soils, aeolian soils, brown earths, chernozems, purplish soils, red earths, yellow earths, and laterite), and measured acid buffering capacity and the related physicochemical properties. In areas under agricultural cultivation, soils were collected simultaneously from adjacent natural vegetation (woodland or grassland) and farmland. The results showed that acid buffering capacity of soils in the northern part of eastern China (44.8 mmol·kg-1) was significantly higher than that of the soils in the southern part (15.8 mmol·kg-1), which can be ascribed to the greatly higher concentrations of carbonate, exchangeable base cations, and organic matter in the northern soils. Differences in soil minerals, temperature, and precipitation between northern and southern parts of eastern China were responsible for the differences in soil acid buffering capacity and related physicochemical properties. The acid buffering capacity of farmland soils (36.6 mmol·kg-1) was significantly higher than that of forest soils (25.0 mmol·kg-1), which might be due to higher carbonate concentration and base saturation in farmland soils. Fertilization in farmland was responsible for the above differences. Soil acid buffering capacity was positively correlated with the concentrations of carbonate, exchangeable calcium, and organic matter (P<0.01), positively correlated with base saturation, exchangeable magnesium concentration, and cation exchangeable capacity (P<0.05), but negatively correlated with exchangeable acid concentration (P<0.05). Therefore, concentrations of soil carbonate, exchangeable calcium and organic matter are the main factors influencing soil acid buffering capacity in eastern China.
    Community characteristics and niche of soil macrofauna in the Nianchu River Basin, Tibet.
    WANG Zhuang-zhuang, LIU Yang, HE Kai, FAN Hai-de, PU Bu
    2021, 40(12):  3911-3921.  doi:10.13292/j.1000-4890.202112.026
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    We examined the characteristics of soil macrofauna community and the niche width and niche overlap of major groups of soil macrofauna in four habitat types of the Nianchu River Basin, Tibet, including grassland, wetland, cropland, and seabuckthorn forest. In May (spring) and August (summer) of 2020, soil macrofauna were collected, with the specimens being stored in 75% alcohol solution. A total of 2048 soil macrofauna specimens were captured and classified into 52 groups, 37 families, 25 orders, 5 classes, and 3 phyla. The highest numbers of individual and group of soil macrofauna were found in wetland in spring and summer, and the lowest in the grassland. The diversity index was the highest in seabuckthorn forest in spring and summer. The dominance index was the highest in grassland and seabuckthorn forest in spring, and the highest in wetland in summer. The evenness index was the highest in grassland in spring, and the highest in cropland and seabuckthorn forest in summer. The similarity index of soil macrofauna communities among four habitats in spring ranged from extreme dissimilarity to medium dissimilarity, and ranged from medium dissimilarity to medium similarity in summer. The similarity index of soil macrofauna communities between spring and summer ranged from medium dissimilarity to medium similarity. Diptera larva had the largest niche width, while Pentatomidae, Phalangiidea, and Lymnaeidae had the smallest niche width in spring and summer. The distribution range of niche overlap value of soil macrofauna communities was \[0, 1\]. The high niche overlap value accounted for 23.07% of the total pairs, the moderate niche overlap value accounted for 16.67%, and the low niche overlap accounted for 73.07%. Formicidae, Carabidae, Lycosidae, and Lymnaeidae were the dominant taxa in the Nianchu River Basin. The characteristics of soil fauna community were different in spatial distribution, but the diversity index of soil fauna community showed no significant difference between seasons. Diptera larva and Lycosidae, the main components of soil fauna communities, had strong adaptability to soil environment and had a wide range of ecological adaptation. The degree of niche overlap in soil fauna communities was low, with low degree of similarity in resource utilization and weak inter-group competition, indicating a relatively stable community structure.
    Effect of deep vertically rotary tillage on particle size distribution and stability of latosolic red soil aggregates.
    ZHANG Yu, JIANG Dai-hua, HUANG Jin-lan, WANG Ming-shi, DENG Hua-wei
    2021, 40(12):  3922-3932.  doi:10.13292/j.1000-4890.202112.028
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    Tillage has important impacts on soil quality and crop yield. The purpose of this study was to clarify the impacts of deep vertically rotary tillage on soil physicochemical properties, particle size distribution, and stability of latosolic red soil aggregates. We analyzed various indices of soil aggregates stability in sugarcane field under four tillage treatments, including rotary tillage (XG), subsoiling (SF), deep vertically rotary tillage to 20 cm (FL20), and deep vertically rotary tillage to 40 cm (FL40). The results showed that soil fertility decreased in the four tillage treatments after planting sugarcane for one year. Soil pH increased significantly by 0.27-0.31  in the FL40 treatment compared with the XG treatment. There were no significant differences in soil organic matter (SOM) among the various tillage treatments. In 0-40 cm soil layer, content of water-stable aggregates at 0.25-0.5 mm particle size under FL20 treatment was 22.38%-27.33% and 23.78%-31.59% higher than those under XG and SF treatments, respectively. FL40 treatment increased water-stable aggregates at 0.25-0.5 mm particle size in 20-40 cm soil layer. In addition, geometric mean diameter (GMD) and mean weight diameter (MWD) of mechanical-stable and water-stable aggregates under FL20 and FL40 treatments were higher than those under XG and SF treatments. FL20 and FL40 treatments increased aggregate stability rate (WSAR) of water-stable aggregates. The destruction rate (PAD) of water-stable aggregates under FL20 and FL40 treatments was lower than that under XG and SF treatments. The PAD was ertremely significantly negatively correlated with WSAR, bias coefficient (CS), wet sieve means weight diameter (WMWD), wet sieve geometric mean diameter (WGMD), and >0.25 mm particle size of water-stable aggregates (P<0.01), and was ertremely significantly positively correlated with peak convex coefficient (CE) and <0.25 mm particle size of water-stable aggregates (P<0.01). Overall, deep vertically rotary tillage significantly enhanced aggregates content and the stability of medium and small particle sizes, as well as soil permeability, and improved soil structure, which in turn could promote soil nutrient mineralization and improve nutrient use efficiency of crops. Therefore, this tillage practice can be used as an efficient and popularized method in latosolic red soil areas.
    Effects of planting density and irrigation quota on soil salinity in machine-harvested cotton field.
    CHENG Shao-yu, LIN Tao, WU Feng-quan, HOU Pei-ke, TANG Qiu-xiang
    2021, 40(12):  3933-3943.  doi:10.13292/j.1000-4890.202112.029
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    Increasing plant density under insufficient or lowirrigation conditions is a new water-saving production technology for cotton, especially in the dry and short growing season cotton regions of Xinjiang, China. Increasing planting density would increase canopy coverage and total water consumption, and change rhizosphere salt distribution. We conducted a field experiment with three planting densities (low density M1, 135000 plants·hm-2; medium density M2, 180000 plants·hm-2; high density M3, 225000 plants·hm-2) and three irrigation quota\[severe- deficit W1 (50% ETC, crop water demand), 3150 m3·hm-2; mild deficit W2 (75% ETC), 4050 m3·hm-2; full irrigation W3 (100% ETC), 4980 m3·hm-2\], to analyze their effects on 0-60 cm soil salt content, uniformity coefficient, surface accumulation coefficient, variation, and salt rejection rate. The results showed that with increasing planting density, soil salt content and surface accumulation coefficient were significantly reduced, while the uniformity of salt distribution increased. Increasing irrigation quota reduced soil salt content of different planting densities, but the salt distribution gradually changed from the “bottom accumulation in the film” to “surface accumulation in the film”, and the uniformity of which was significantly reduced. In addition, there were significant differences in salt change and salt rejection rate under different treatments. With increasing planting density, salt change and rejection rate were gradually reduced, and the results were completely opposite with increasing irrigation quota. The combinations of low density + mild deficit irrigation, medium density + full irrigation, and high density + full irrigation led to the greatest change in salt content and the highest rejection rate, which were 0.041 g·kg-1 vs. 18.2%, 0.041 g·kg-1 vs. 25.6%, and 0.055 g·kg-1 vs.30.50%,respectively. The sensitivity of soil salt to different irrigation quota depended on planting density. When the irrigation quota fall into the range of 3150-4050 m3·hm-2 (50%-75% ETC), planting density is recommended to be 135000 plants·hm-2; when the irrigation quota is 4980 m3·hm-2 (100% ETC), the planting density to be 180000-225000 plants·hm-2,which can effectively reduce soil salinization level, conserve water, and maintain a higher productivity level. Our results provide reference for reasonable selection of planting density and irrigation quota with drip irrigation under plastic films in machine-harvested cotton fields.
    Impacts of composted pig manure and straw amendments on the growth of Beckmannia syzigachne in wheat field of a rice-wheat rotation system.
    HONG Ai-mei, DUAN Yun-hui, ZHANG Hai-yan, HAN Min, LI Yong, SHEN Xin, SUN Guo-jun, SHEN Jia-he, RAN Wei, ZHANG Ming
    2021, 40(12):  3944-3951.  doi:10.13292/j.1000-4890.202112.033
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    To understand the effects of long-term fertilization regimes on the growth of Beckmannia syzigachne, a dominant wheat-associated weed in wheat field of a rice (Oryza sativa) wheat (Triticum aestivum) rotation system, we carried out an experiment with four fertilization treatments \[no fertilization (CK), chemical fertilizer only (CF), replacement of a portion of chemical fertilizer with composted pig manure (PM), and straw return combined with chemical fertilizer (SF)\] for 10 consecutive years since October 2010. We examined the density of seedlings, tillers and ears during vegetative growth stage, plant height, stem base thickness, length and width of the upper three functional leaves, aboveground biomass, and seed yield during flowering and fruiting stage of B. syzigachne and wheat yield in wheat season in 2019 and 2020. The results showed that the average density of seedlings, tillers, and ears was 84.00 and 115.50, 172.75 and 181.00, 83.00 and 24.25 plants·m-2 respectively in 2019 and 2020 in treatment CF, which was significantly higher than that in treatments SF and PM. The average plant height, the length and width of the upper three functional leaves were higher in treatment CF than those in treatments PM and SF. The average dry mass was 0.64 and 0.89 g·plant-1 in 2019 and 2020 in treatment CF, which was significantly higher than that in treatments PM and SF. The average seed yield was 698.10 and 681.30 seeds·plant-1 in 2019 and 2020 in treatment CF, which was significantly higher than that in treatments PM and SF. Long-term chemical fertilizer application was more beneficial to the growth and reproduction of B. syzigachne, while the combined application of pig manure compost and straw return with chemical fertilizer inhibited the growth and reproduction of B. syzigachne.
    Synergistic effects of planting density and nitrogen application rate on the nitrogen useefficiency of rice.
    LIU Hong-jiang, GUO Zhi, ZHANG Yue-fang, ZHOU Wei, SHENG Jing, CHEN Liu-gen
    2021, 40(12):  3952-3960.  doi:10.13292/j.1000-4890.202112.025
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    A field experiment was carried out to study the synergistic effects of transplanting density and nitrogen application rate on yield formation and nitrogen use efficiency of rice (cultivar Nanjing 9108). We set up three basic seedling densities of D1 (90×104 ind·hm-2), D2 (120×104 ind·hm-2), and D3 (150×104 ind·hm-2), and four nitrogen application rates of N1 (0 kg·hm-2), N2 (240 kg·hm-2), N3 (270 kg·hm-2), and N4 (300 kg·hm-2). The results showed that under treatment N2D3, spikelets per panicle and filled grain percentage of rice were relatively small, but the effective panicle number was 29.3% higher than that of N2D1 and N2D2, which indicated that the higher number of effective panicles of rice resulted in unchanged yield. The biomass yield of N2D3 was 17.0% higher than that of N2D1 and N2D2, and such obvious enhancement of biomass yield ensure the high yield of rice. N2D3 treatment significantly increased rice nitrogen accumulation by 13.8% and nitrogen dry matter production efficiency by 7.1%. There was no variation in nitrogen use efficiency of grain yield of rice, but the nitrogen harvest index significantly decreased under the treatment of N2D3. Compared with N2D1 and N2D2, N2D3 treatment increased the N fertilizer absorption and utilization rate, partial productivity, agronomic utilization rate, and physiological utilization rate by 32.4%, 13.8%, 54.6% and 17.1%, respectively. Higher nitrogen application rate ensured the higher available nitrogen content in soil under different transplanting densities. When the input of nitrogen fertilizer was low, soil available nitrogen content could maintain a high level under high transplanting density. In conclusion, on the basis of conventional nitrogen application rate of 300 kg·hm-2, by increasing planting density of rice and 20% reduction of nitrogen fertilization rate, the D3N2 treatment could ensure rice yield, improve N absorption and N use efficiency of rice, and maintain soil fertility of paddy field.
    Effects of ridgebed cultivation on rice root characteristics and soil physical properties.
    TANG Zhi-wei, ZHOU Wen-tao, WANG bo-ran, ZHONG Kang-yu, XIONG Rui, LONG Pan, XU Ying, FU Zhi-qiang
    2021, 40(12):  3961-3969.  doi:10.13292/j.1000-4890.202112.004
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    A doubleseason rice field trial was carried out in Liuyang City of Hunan to explore the effects of different cultivation methods on rice root characteristics and soil physical properties, with the aim to provide a basis for rice ridge cultivation techniques. The results showed that, compared with flat cultivation, ridge cultivation significantly increased total root length and root volume of early rice at the booting stage and root bleeding intensity at each stage of early rice and the peak tillering stage of late rice. The total length of roots, root surface area, and root volume of late rice at the full heading stage were significantly increased by 36.9%, 41.1%, and 44.9%. Furrow cultivation significantly reduced total root length and root volume of early rice at the peak tillering stage and full heading stage, and reduced root surface area at each stage of early rice by 40.6%-44.5%. Root bleeding intensity was significantly increased at the full heading stage of early rice, while significantly reduced at the booting stage of late rice. Compared with flat cultivation, soil bulk density of early rice in ridge cultivation and furrow cultivation was significantly reduced by 6.8%-10.6%, while total soil porosity and capillary porosity was increased by 7.2%-10.6% and 6.5%-10.4%, respectively. Ridge cultivation and furrow cultivation increased the average mass diameter of soil aggregates in early rice. Ridge cultivation and furrow cultivation increased the content of 0.25-2 mm water-stable aggregates in the soil of early rice and late rice, respectively, and reduced the content of water-stable aggregates of <0.053 mm in the soil of early rice and late rice, respectively. Ridge cultivation and furrow cultivation improved soil physical properties and increased yield of late rice. Ridge cultivation promoted and furrow cultivation hindered root growth and development of rice.
    Effects of reduced chemical fertilizer application combined with organic materials on soil nematode community structure in rape field.
    LI Qi-sheng, ZHANG Shun-tao, ZHAO He, GAO Fei, JIAO Jia-guo, HU Feng, LI Hui-xin, LU Jian-wei
    2021, 40(12):  3970-3981.  doi:10.13292/j.1000-4890.202112.003
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    Longterm fertilization can change soil fertility and microbial characteristics, and indirectly alter soil nematode community composition. The aim of this study was to analyze the effects of optimized chemical fertilizer application combined with organic materials on soil nematode community structure and the correlation between soil nematode community and soil properties and extracellular enzyme activities, and to explore the responses of soil nematode community composition to soil fertility. There were five treatments, including CK (no fertilization), CF (chemical fertilizer), RF (reduced chemical fertilizer), RFS (reduced chemical fertilizer + straw returning) and RFMS (reduced chemical fertilizer + organic fertilizer + straw returning), in theexperiment. The results showed that a total of 33 nematode genera were identified. Bacterialfeeding nematodes and phytophagous nematodes were the dominant nutritional groups in all treatments. The abundance of soil nematodes in different treatments followed an order of RFMS >RFS >RF >CF > CK. The abundance of soil nematodes in RFMS and RFS treatments was significantly higher than that in other treatments (P<0.05). Compared with CK, the abundance of bacterial-feeding nematodes and omnivorous/predatory nematodes was increased and the reproduction of phytophagous nematodes was inhibited by single chemical fertilizer application and chemical fertilizer + organic materials application. The Wasilewska index (WI), maturity index (MI), structure index (SI), and enrichment index (EI) of RFMS treatment were 1.42, 1.35, 67.3 and 70.94, respectively, which were higher than those of the other treatments. Compared with CK treatment, RFS and RFMS treatments significantly reduced the ratio of plant parasite indexPPI) to MI. The abundance of soil nematodes and bacterial-feeding nematodes were positively correlated with soil organic matter content, total nitrogen content, and soil extracellular enzyme activities. Results of redundancy analysis showed that soil total phosphorus, organic matter, and total nitrogen had great impacts on soil nematode community composition. Therefore, reduced chemical fertilizer application combined with organic materials can help the reproduction of nematodes, enhance nematode species diversity, enrich the structure of soil nematode food web, and reduce the degree of disturbance by enhancing the stability of nematode food web, which would thus be an important option to maintain soil biological health.
    Effects of walnut leaf litter decomposition on physiological characteristics and medicinal quality in Paris polyphylla var.yunnanensis.
    ZHAO Jing-jing, LI Zhuo-wei, XU Ling-feng, DING Bo, GUO Dong-qin, ZHOU Nong
    2021, 40(12):  3982-3989.  doi:10.13292/j.1000-4890.202112.013
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    The walnut understory industry is growing rapidly. To understand the allelopathy effects of walnut leaf litter decomposition and provide a theoretical basis for the forest medicine compound planting model, we conducted a pot experiment to examine the effects of walnut litter decomposition on physiological characteristics and medicinal quality of rhizome of Paris polyphylla var.yunnanensis. There were five litter application rates, i.e. 0 (CK), 30 (H1), 60 (H2), 120 (H3), and 180 g·pot-1 (H4). The results showed that the regulation effect of walnut leaf litter on leaf photosynthetic pigment content, rhizome fresh weight, dry weight, and dryness rate of P. polyphylla var.yunnanensis leaves followed the trend of “promoting at low concentration and suppressing at high concentration”. Compared with CK, H1 treatment had a positive effect on the growth of P. polyphylla var. yunnanensis. There was a negative effect on growth of P. polyphylla var.yunnanensis when the application amount of litter exceeded the tolerance threshold. Contents of malondialdehyde, soluble sugar, soluble protein and activities of superoxide dismutase, catalase and peroxide were gradually enhanced with increasing application amount of walnut leaf litter. The positive or negative effects of walnut leaf litter degradation increased with increasing application amount. Overall, low-dose application of walnut leaf litter can promote the growth of P. polyphylla var.yunnanensis, while high-dose application has a strong allelopathic effectby promoting oxidative damage and inhibiting chlorophyll synthesis. The planting density of walnuts should be strictly controlled in the compound planting of walnut + P. polyphylla var.yunnanensis.
    Antimicrobial activity of endosymbiotic bacteria isolated from Melanotus cribricollis larva against Metarhizium pingshaense.
    FANG Lin-xin, LI Zhi-hong, ZHANG Ya-bo, ZHANG Wei, SHU Jin-ping, WANG Hao-jie
    2021, 40(12):  3990-3997.  doi:10.13292/j.1000-4890.202112.007
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    Metarhizium spp. is an important biocontrol resource for the management of underground pests. While it is known that the control efficiency as entomopathogenic fungi is often affected by other microorganisms, the underlying mechanism is unclear. In this study, we examined the inhibitory effect of Acinetobacter gyllenbergii, a secondary endosymbiont isolated from Melanotus cribricollis larva, on the activity of Metarhizium pingshaense that effectively infects wireworm. The results showed that both the fermentation broth and volatiles of A. gyllenbergii showed significant inhibitory effects on spore germination and production of M. pingshaense.The fermentation broth of A. gyllenbergii significantly inhibited mycelium growth of M. pingshaense in seven days, while the volatiles of A. gyllenbergii did not affect mycelium growth of M. pingshaense. Nine effective volatile compounds of A. gyllenbergii were identified by GC-MS analysis. Seven compounds, inclduing α-pinene, aniline, nonanal, 2,4-di-tert-butylphenol, limonene, 1-dodecene and dimethyl trisulfide, had significant inhibitory effects on the activity ofM. pingshaense. Therefore, the endosymbiotic bacteria ofM. cribricollis larva showed a strong inhibitory effect on the growth of M. pingshaense.
    Transport characteristics of nitrogen and phosphorus in dammed channelized rivers and their responses to eutrophication.
    BAO Lin-lin, QIAN Jun, TONG Hong-jin, CHEN Jie, JI Yu-tong, GU Hao
    2021, 40(12):  3998-4007.  doi:10.13292/j.1000-4890.202112.005
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    Dam construction has significantly improved water resource utilization efficiency of rivers. River channelization caused by dam construction is one of the key factors affecting nitrogen and phosphorus transport and water eutrophication. By estimating nitrogen and phosphorus fluxes and assessing water trophic state, we analyzed nitrogen and phosphorus retention characteristics of dammed channelized rivers and their response to water eutrophication during the water stable period in four dammed river segments and one normal river segment of Weiyuan River and Xushui River in the Fuxi River Basin. The results showed that total phosphorus, ammonium, and organic matters were the main pollutants, with their concentrations being higher in small tributaries. The average retention efficiency (RL) of total nitrogen and phosphorus in the selected river segments was 101.5 and 4.7 mg·s-1·km-1, respectively. Nitrogen and phosphorus retention efficiency in the dammed river segments of Xushui River was the highest (310.0 and 12.9 mg·s-1·km-1), indicating a net nutrient retention (RL>0). Conversely, the lower retention efficiency recorded for the dammed river segments of Weiyuan River (-55.1, -0.2 mg·s-1·km-1) and the normal river segment (-2.3, -1.9 mg·s-1·km-1) indicated a net nutrient output (RL<0). Flow rate, together with external and internal nitrogen and phosphorus loadings resulted in the lower nutrient retention efficiency in dammed channelized rivers of Fuxi River Basin than that in reservoirs and other river impoundments. The average trophic level index (TLI) of the dammed channelized river segments was 54.1, indicating a mild eutrophic state, while that for the natural river segment was 42.9, indicating a mesotrophic state. As phytoplankton chlorophyll-a was negatively correlated with flow rate and positively correlated with nutrient concentration, the dammed channelized rivers with heavy nitrogen and phosphorus pollution showed higher eutrophication risk. Therefore, further control of pollutants from external and internal sources in the Fuxi River Basin and optimizing river hydraulic conditions are recommended to alleviate eutrophication risk.
    Activity rhythm and interspecific association of sympatric Lady Amherst’s pheasant and Temminck’s tragopan in the Yaoshan Mountains.
    ZHAO Chen-guang, CHEN Fei, YAN Zai-kui, LIU Xing-yuan, LIU Lu-ming, LI Wei-wei, DUAN Yu-bao
    2021, 40(12):  4008-4014.  doi:10.13292/j.1000-4890.202112.016
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    Understanding interspecific coexistence by dividing resources has always been a hot issue in the research field of biodiversity. This study aimed to examine the spatial and temporal relationship between Lady Amherst’s pheasant and Temminck’s tragopan in the Yaoshan National Nature Reserve of Yunnan Province. From March 2017 to December 2018, a total of 45 infrared cameras were deployed in the reserve, with a total of 116 independent, effective photos ofLady Amherst’s pheasant and 147 of Temminck’s tragopan being recorded. The analysis of diurnal activity patterns showed that the activity time of Lady Amherst’s pheasant was from 06:00 to 20:00, and the activity peak was from 08:00-10:00 and 17:00-19:00, with the highest peak at 09:00 and 18:00, respectively. The activity time of Temminck’s tragopan was from 05:00-21:00, and the activity peak was from 07:00-09:00 and 17:00-19:00, with the highest peak at 08:00 and 18:00 respectively. Both species were diurnal, without interspecific difference in the diurnal activity patterns (P>0.05). The activity frequency of those two species was different in different seasons. Lady Amherst’s pheasant was the most active in May and October, followed by March and April, while Temminck’s tragopan was most active in May, August and October. The interspecific competition between those two species was reduced by lowering the spatial niche overlap. The interspecific correlation was not strong. This spatial differentiation was conducive to their coexistence.
    Brood amalgamation in Scaly-sided Merganser (Mergus squamatus) in Changbai Mountains, China.
    LIU Dong-ping, YAO Wen-zhi, LI Guo-dong, XU Li-jun
    2021, 40(12):  4015-4019.  doi:10.13292/j.1000-4890.202111.015
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    Brood amalgamation is the phenomenon that the adults merge non-filial young into their family group and provide parental care to them. We examined the brood amalgamation in the Scaly-sided Merganser (Mergus squamatus) in Changbai Mountains, China. During the four breeding seasons in 2017-2020, there was （0.65±0.17） nests·km-1 (n=4) and （0.39±0.05） broods·km-1 (n=4) along Manjiang River in Changbai Mountains, with an averaged brood size of （8.5±2.8） (n=37). The occurrence of brood amalgamation was 26.5%±6.8%, with no interannual variation. The brood size did not significantly differ between broods with amalgamation occurrence (8.3±2.3) and other broods (8.5±3.0), but significantly increased after brood amalgamation (18.3±8.3). Brood amalgamation of Scaly-sided Merganser occurred in foraging sites or resting grounds, mostly (83.3%) before the ducklings were in 30 days of age, due to competition between adults or accident mixture of chicks. Brood amalgamation of Scaly-sided Merganser probably resulted from competition for chick-rearing territory by adults due to high nestling density, and lack of efficient care for chicks by single parent. We suggest using color marking and molecular techniques to further understand the mechanism of brood amalgamation in Scaly-sided Merganser and assess the effects of fitness losses and gains of the adults that donate and receive chicks.
    Diversity and spatial distribution pattern of benthic macroinvertebrates in summer in the Anning River Basin.
    MA Bao-shan, WEI Kai-jin, XU Jin, XU Bin, ZHU Xiang-yun
    2021, 40(12):  4020-4028.  doi:10.13292/j.1000-4890.202112.022
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    To understand the spatial distribution pattern and key driving factors of benthic macroinvertebrates, surveys were conducted in the Anning River and its tributaries between June and July 2018. The spatial pattern of benthic macroinvertebrates along the longitudinal gradient of the river was analyzed. In total, 57 species of benthic macroinvertebrates belonging to 34 families of 5 phyla were identified, among which aquatic insects (44 species) were dominant taxa. Species richness in the mainstream of the Anning River was lower than that in its tributaries. The dominant species in the mainstream were Limnodrilus hoffmeisteri, Baetis sp., Aethalopsyche sp. and Physa acuta, while the dominant species in the tributaries were Cheumatopsychesp.,Drunellasp1, Heptagenia sp. and Stenopsyche sp. The macroinvertebrate density in the mainstream was nearly equal to that in its tributaries, but it decreased along the longitudinal gradient fromupstream to downstream. The results of canonical correspondences analysis (CCA) showed that the density of dominant macroinvertebrate species in the Anning River was closely related to water temperature, pH and substrate types.
    Effects of temperature on metamorphosis duration and response patterns to phytohemagglutinin P in the tadpoles of Pelophylax nigromaculatus.
    ZHANG Zhi-qiang, WANG Jia-hui, JIN Bing-yan, CHEN Li, YANG Yu-qing, DIAO Ying-zhu, WU Liang
    2021, 40(12):  4029-4033.  doi:10.13292/j.1000-4890.202112.032
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    To explore the effects of temperature on tadpole metamorphosis duration and immune function, we measured the metamorphosis duration of tadpoles ofPelophylax nigromaculatus at Gonser stage 37 under water temperature of 21, 23, 25, and 27 ℃, and compared the variations of response to phytohemagglutinin P (PHA-P) at metamorphosis completion period among different water temperature treatments. The results showed that there was no significant difference in body mass, snout-vent length, and ratio of body mass to snout-vent length among different water temperature treatments (P>0.05). The metamorphosis duration was significantly higher in 21  and 23 ℃ treatments than in 25  and 27 ℃ treatments (P<0.05). The responsiveness to PHA-P all peaked at 3 h after injection for all temperature treatments, with an increasing tendency from 21 ℃ group to 27 ℃ group. There was no significant difference for the maximal PHA-P values (P>0.05). The responsiveness to PHA-P was significantly higher at 3 h after injection than at 0, 9 and 12 h after injection under 21 ℃ treatment (P<0.05), but was significantly higher at 3 h after injection than at 0 and 12 h under 23 ℃ treatment (P<0.05). Under 25  and 27 ℃ treatments, the responsiveness to PHA-P was significantly higher at 3  and 6 h after injection than at 0 h. Increasing temperature greatly shortened the metamorphosis duration of tadpoles of P. nigromaculatus. There was an enhanced tendency for the responsiveness to PHA-P, but no forward or delayed responsiveness to PHA-P was observed. Our results indicate that moderately elevated temperature would not reduce cell-mediated immunity during development of tadpoles.
    Mechanism underlying the effects of biochar combined with surfactant enhanced washing on removal of PAHs from contaminated soil.
    YU Jin-long, SUN Li-zong, XUE Chen-yang, JIA Chun-yun, TAI Pei-dong, LI Ying-hua
    2021, 40(12):  4034-4043.  doi:10.13292/j.1000-4890.202112.008
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    Biochar adsorption and surfactant washing were used to remediate PAHs contaminated soil. Rice husk biochar prepared at 700 ℃ was added to examine the effect of biochar addition on the washing of PAHs by nonionic surfactant TX-100. The underlying mechanism of biochar adsorption combined with TX-100 washing was examined by simulating contaminated soil with pyrene-containing kaolin after aging. The results of enhanced washing remediation showed that when the concentration of TX-100 was 10 g·L-1, washing time was 16 h, the ratio of solid to liquid was 1∶10, and the rotating speed was 150 r·min-1, a desorption rate of 66.2% was obtained for the contaminated soil with PAHs concentration of 94.97 mg·kg-1. After the rice husk biochar with 1% soil mass was added and stabilized for 14 days, the desorption rate of PAHs by TX-100 increased from 66.2% to 80.6% (P<0.05), and the desorption rate of tetracyclic PAHs was the highest (42.1%). Kaolin simulation results showed that after adding biochar 1% of soil mass for 14 days, the content of pyrene in kaolin decreased from 50 mg·kg-1 to 27.77 mg·kg-1. TX-100 could effectively wash out pyrene adsorbed on biochar, with desorption rate reaching 82.4%. Scanning electron microscope and spectroscopic analysis showed that biochar could adsorb TX-100, while the adsorbed TX-100 occupied part of the pores of biochar, and the absorption vibration peaks of C=O and C=C at 1600 cm-1 and C-O-C at 1103-1025 cm-1 were obviously weakened, which further led to the migration of PAHs from solid phase to liquid phase. Therefore, before using surfactants for washing and remediation, biochar addition can significantly improve the desorption rate of soil PAHs.
    Numerical simulation on the effects of street trees on PM2.5 concentration in street canyon.
    LI Ping-ping, MIAO Chun-ping, CHEN Wei, HU Yuan-man, HE Xing-yuan
    2021, 40(12):  4044-4052.  doi:10.13292/j.1000-4890.202111.036
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    The pollution of atmospheric particulate matter in urban human settlements is one of the major environmental problems faced by human beings. Street canyon is one of the most important space forms and characteristics of modern cities, with the highest frequency of utilization, the most serious pollution by automobile exhaust, and the highest population density. The geometry of urban street canyons plays a crucial role in the dispersion of atmospheric particulate matters. Here, we quantified the impacts of street trees on the distribution of atmospheric particulate matter PM2.5 in the street canyons of Shenyang, China. Meteorological parameters and distribution of street trees were used in ENVI-met software with three aspect ratios (H/W=0.5, 1 and 2), three street canyon directions (NE-SW, NW-SE, E-W), two kinds of street trees (poplar and pine). The diurnal variation of PM2.5 showed a trend of “two peaks and two valleys”. The aspect ratio of street canyons had a significant effect on the concentration of PM2.5, with the highest values in street canyons with an aspect ratio of 1. However, there were obvious differences in the PM2.5 of different types of street trees under street canyons in the same direction and the same aspect ratio. Our results suggest that street trees have negative effects on the reduction of atmospheric fine particulate matters at pedestrian heights in the street canyons.
    Evaluation of ecological quality variation in mining area of Northeast China based on RSEI Index: A case study of Gongchangling District, Liaoning Province.
    HU Si-han, YAO Yu-zeng, FU Jian-fei, ZHAO Jin-tong, HAO Da-hai
    2021, 40(12):  4053-4060.  doi:10.13292/j.1000-4890.202112.006
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    As one of the important anthropogenic disturbance, mining exploitation has great influence on regional ecological quality. In this study, remote sensing ecological index (RSEI) was computed based on the Landsat remote sensing images in 1999, 2003, 2010, 2015, and 2020, to evaluate the ecological environment quality in Gongchangling, Liaoyang, Liaoning. The results showed that the overall ecological quality was mainly excellent from 1999 to 2020, accounting for more than 80% of the total area. The average RSEI values in the five periods were 0.927, 0.931, 0.891, 0.883, and 0.894, respectively. The whole RSEI manifested as firstly slightly increasing, then decreasing, and finally increasing. The areas with obvious ecological degradation were mining districts and towns. The variation of ecological quality in Gongchangling was closely related to the mining exploitation activities.
    Mycorrhiza and vegetation growth: Interactions in a changing environment.
    WANG Tian-tian, TIAN Yu-hong, WU Xiu-chen, ZHANG Hao-qiang
    2021, 40(12):  4061-4068.  doi:10.13292/j.1000-4890.202112.031
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    As an important symbiont composed of mycorrhizal fungi and plant roots, mycorrhizas affect water absorption and nutrient transportation in the plantsoil system, with consequence on vegetation growth. Under global environmental change, vegetation growth is suffered from multiple stresses. It is of great significance to systematically understand the underlying processes and mechanisms for the effects of mycorrhiza on vegetation growth in a changing environment. We summarized the research progress on the interactions between mycorrhiza and vegetation growth under changing environment, particularly emphasizing on the relationships between mycorrhiza and vegetation growth under nutrient limitation, drought stress, salt stress, and heavy metal stress. Then, we briefly summarized the mechanisms and modes underlying the effects of mycorrhiza on vegetation growth under changing environment. Finally, we summarized the key know ledge gaps in the current research. We propose that it is crucial to systematically study the mycorrhizal ecology and uncover the mechanisms underlying the mycorrhiza effects on plant growth and vegetation restoration, which is important for sustainable ecological restoration and construction under the background of rapid global environmental changes.
    Research progress in morphological deformities of chironomid larvae induced by contaminants in water and sediments.
    TIAN Wen-long, HOU Gui-lin, ZHANG Yuan-ling, YANG Jia, PAN Yu-chen, CAO Yan-min
    2021, 40(12):  4069-4080.  doi:10.13292/j.1000-4890.202112.024
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    Contaminants in water and sediments have the potential to exert teratogenic effects on benthos. Larvae of Chironomid (Diptera: Chironomidae) are highly sensitive to environmental changes in water. Morphological deformities in the mouthparts of chironomid larvae have been proposed as potential biomarkers in the assessment of sediment quality and environmental stress. Here, we reviewed the discovery, morphology, and types of mouthpart deformity in chironomids, showed the potential teratogenic contaminants and mechanisms, and explained the challenges of such research. Current progress on chironomid mouthpart deformities could be summarized into three aspects: (1) ubiquitous: mouthpart deformities in chironomid larvae commonly exist in polluted water, and abnormal morphologies in different taxa and different parts of the mouthpart have been well described; (2) regional variability: there are large discrepancies in deformity frequency among reports on different polluted waters, which might stem from the inconsistency of standards for deformity analysis and calculation of deformity incidence; and (3) causal nonlinearity: both trace metals and organic contaminants are found to have significant teratogenic effects on chironomid larvae, and series of bioassays on teratogenic effects of specific pollutants have been conducted globally, but the dose-effect relationship between specific contaminants and morphological abnormality is still ambiguous and the teratogenic processes and mechanisms should be demonstrated. Future studies using chironomid deformity in water quality monitoring and toxicity assessment of contaminants should focus on the following four issues: (1) establish clear dose-effect relationship between specific pollutants and chironomid deformity; (2) develop unambiguous indices to represent deformity occurrence; (3) establish laboratory protocols of standardized chironomid deformation assay; and (4) carry out domestic studies on mouthpart deformity in chironomid larvae through field investigation and laboratory bioassays, because related studies are scarcely conducted in China, to develop effective bioindicators suitable for local water quality assessment and early warning signals for the ecological effects of pollutants.
    Influences of urbanization on phosphorus cycle.  
    WANG Ming-qi, LI Zhi-jian, ZENG Hui
    2021, 40(12):  4081-4087.  doi:10.13292/j.1000-4890.202112.021
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    Effects of urbanization on phosphorus cycle and the resultant negative ecoenvironmental effects have received great attention in the research field of resource and environment. Here, we summarized the impacts of various human activities on phosphorus cycle in the process of urbanization and addressed future research directions. We found that phosphorus cycle in urban areas is mainly affected by three factors, including industrialization, socioeconomic features and urban spatial evolution during urbanization. The exploitation and utilization of phosphate resources, changes in human lifestyle, and spatial expansion and evolution of urban landscape patterns are the three most important factors affecting phosphorus cycle in urbanized areas. These factors intertwined in terms of direct and indirect effects can also change the characteristics of land cover and part of hydrological or soil processes, and jointly control urban phosphorus cycle. Therefore, the urban phosphorus problem is a systematic issue related to various factors. Comprehensive fundamental research combined with searching of problem-solving pathways can provide guidance to manage phosphorus resource along with controlling phosphorus pollution under urbanization.
    Progress of researches and practices of urban ventilation corridors in China.
    FANG Xiao-yi, LI Lei, LIU Wan, REN Chao, WANG Jia-wen, CHENG Chen, YU Ying, ZHANG Shuo, DU Wu-peng, LIU Yong-hong
    2021, 40(12):  4088-4098.  doi:10.13292/j.1000-4890.202112.010
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    As an effective method to solve urban climate problems, ventilation corridor has been incorporated into land space planning. Here, we reviewed the origin, function and mechanism, as well as the progress of researches and practices of urban ventilation corridor in China, aiming to provide useful reference for scientific and reasonable corridor planning. The main function of ventilation corridor is to provide a channel for air flow into the urban builtup area and to guide the optimization of urban spatial form to reduce the loss of wind. By combining with the scientific protection of urban open space, local air circulation can be promoted, which could alleviate urban heat island effect, reduce air pollution and building energy consumption, and improve the livability of cities. However, land type, space form, building height and density of cities will affect the function of ventilation corridor to a large extent. The research and practice of ventilation corridor planning in China has experienced four stages: ancient Fengshui and Yingcheng, the restoration stage from the founding of People’s Republic of China to the end of 1990s, the development stage in the early 21st century, and the new stage of ecological priority since 2012. More than two-thirds of the provinces in China have carried out relevant work and achieved important progress in technical methods, application strategies, policies and regulations. Ventilation corridor planning reflects the pursuit of development quality of Chinese cities under rapid urbanization. There are some problems with respect to intervention time, cross domain integration, convergence with urban design, and corridor performance evaluation mechanism in the process of city planning. Further improvements in the technical aspects of meteorological observation analysis, simulation, and effect evaluation should be given full consideration.
    Real-time detection and weight estimation of grassland livestock based on unmanned aircraft system video streams.
    WANG Dong-liang, LIAO Xiao-han, ZHANG Yang-jian, CONG Nan, YE Hu-ping, SHAO Quan-qin, XIN Xiao-ping
    2021, 40(12):  4099-4108.  doi:10.13292/j.1000-4890.202111.008
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    Accurate and realtime livestock data are crucial to developing modern animal husbandry, ensuring effective supply of animal products, and promoting ecosystem balance and sustainable development of grasslands. The acquirement of livestock data mainly relies on field surveys and grassroots’ reports. These data are laborious and non-real-time. In this study, a real-time monitoring system is developed based on browser/server architecture (http://218.202.104.82:5806/vid). A deep-learning-based livestock detection model and a weight estimation model are developed. The system could detect and count livestock, and estimate their weight using unmanned aircraft system (UAS) live video streams. The livestock detection model is trained using 13803 UAS image tiles and video picture frames. The true positive rate, false positive rate, and loss positive rate of the model for cattle detection are 90.51%, 11.64%, and 9.49%, respectively. The true positive rate, false positive rate, and loss positive rate of the model for sheep detection are 91.47%, 7.04%, and 8.53%, respectively. The weight estimation model is built based on the head-body length and weight data collected in Inner Mongolia Autonomous Region and Qinghai Province, with accuracy of 90.28% and 90.00% for cattle and sheep weight estimation, respectively. The system utilizes UASs and deep learning technologies for livestock monitoring, having an expected application prospect in the fields of grassland supervision (including grazing prohibition and rest grazing), and assisting herdsmen in remotely monitoring their livestock.
    Construction and application of an evaluation index system for ecological and environmental protection effectiveness of national parks.
    FU Meng-di, LIU Wei-wei, LI Bo-yan, REN Yue-heng, LI Shuang, BAI Xue, LI Jun-sheng, ZHU Yan-peng
    2021, 40(12):  4109-4118.  doi:10.13292/j.1000-4890.202112.023
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    Evaluating the effectiveness of ecological and environmental protection of national parks is of great significance for promoting effective management and macro-decision-making. Focusing on the goals and orientations of national park construction, based on the protection of the authenticity and integrity of natural ecosystems, using quantitative methods with supporting of qualitative methods, we established an evaluation index system for ecological and environmental protection effectiveness of national parks. There were five types of indices, including ecosystem status, species diversity status, environmental quality status, biosafety status, and eco-environmental damage status, with 12 first-level indicators and 16 second-level indicators. We determined the index calculation methods and evaluation processes. Taking China’s first national park system pilot, Three-RiverSource National Park, as an example, we evaluated the ecological and environmental protection effectiveness since the pilot and discussed the applicability of the index system. The results showed that the area of natural ecosystems and the integrity of natural ecosystems were generally unchanged. In 2016 and 2019, the water conservation capacity index was 0.56 and 0.59, respectively, and the soil conservation capacity index was 0.11 in both years. In 2016, the diversity index of major biological groups was 0.32. As the key species in the park, the population of Tibetan antelope significantly increased. In 2016 and 2019, the protection effectiveness index (PEI) was 7.61 and 7.64, respectively, and the ΔPEI was 0.03. There were no ecological damage events and no biosafety risks. The comprehensive judgment showed that the national park’s ecological environmental protection effectiveness was at the normal level. The evaluation system reflects the dynamic changes of the ecological environment of the ThreeRiver-Source National Park, providing a reference for the establishment of the evaluation standard system of the national park’s ecological environmental protection effectiveness.
    Evaluation model building for climatic quality of main kiwifruit cultivars.
    CHEN Xi, YUE Wei, XU Jian-peng, CHEN Jin-hua, JIA Bing, YE Zhen-feng, LIU Hong-min
    2021, 40(12):  4119-4127.  doi:10.13292/j.1000-4890.202112.027
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    To quantify the climatic impacts on the quality of kiwifruit, we used correlation analysis, path analysis, and regression analysis to select the key climatic factors and establish the climatic quality evaluation models of Actinidia chinensis and Actinidia deliciosa, based on the quality data (total soluble solid and total acid) of kiwifruit in different areas including Guizhou, Shaanxi, Zhejiang, Hunan, and Anhui, as well as the corresponding daily meteorological observational data including sunshine, temperature and precipitation. The results showed that the key period for quality formulation of kiwifruit was sugar-transformation stage and rapid swelling stage of fruit, with temperature and sunlight as the main factors affecting the quality of kiwifruit. The climatic indicators affecting the quality of Actinidia chinensis were diurnal range of temperature during the 13th to 15th ten days before maturity (TD13-15), sunshine hours during the 1st to 6th ten days before maturity (SSH1-6), daily range of annual temperature (TDy), as well as the diurnal range of temperature in fruit growth period (TDp). For Actinidia deliciosa, the climaticindicators were the maximum temperature during the 13th to 18th ten days before maturity (Tmax13-18), maximum temperature during the 1st to 3rd ten days before maturity (Tmax1-3), daily range of temperature during 7th to the 9th ten days before maturity (TD7-9), the minimum temperature during 16th to the 18th ten days before maturity (Tmin16-18), average temperature during 1st to 6th ten days before maturity (T1-6), precipitation during fruit growth period (Pp) and sunshine hours during 1st to 3rd ten days before maturity (SSH1-3). The back substitution test and prediction test were carried out on the established climatic quality evaluation models of Actinidia deliciosaandActinidia chinensis. The proportions of the deviation between the simulated test grade and actual grade with no more than one grade were more than 90%. Thus, the models can objectively reflect the impacts of climate on kiwifruit quality.
    Hyperspctral estimation of soil organic matter content in Yinchuan plain, China based on PCA sensitive band screening and SVM modeling.
    SHANG Tian-hao, MAO Hong-xin, ZHANG Jun-hua, CHEN Rui-hua, WANG Fang, JIA Ke-li
    2021, 40(12):  4128-4136.  doi:10.13292/j.1000-4890.202112.017
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    The rapid monitoring of soil organic matter (SOM) content based on hyperspectral data is of great significance for evaluating soil fertility. To achieve rapid and accurate monitoring of SOM in the Yinchuan Plain, we collected 171 soil samples at 0-20 cm in Yinchuan Plain by 5 km×5 km grid method, and measured the SOM content in the laboratory and the spectral reflectance by ASD FieldSpc4 Spectrum Analyzers in the field. After spectral preprocessing and resampling, we obtained five spectral indices, including standard normal variable (SNV), maximum normalization (MAN), first order differential (FDR), logarithm of reciprocal (LR), and reciprocal of logarithm (RL). We determined the sensitive bands of SOM using the correlation coefficient method, and screened out the optimal modeling variables from the sensitive bands by stepwise regression (SR), gray correlation degree (GCD), and principal component analysis (PCA). We established estimation models of SOM by ridge regression (RR), partial squaresregression (PLSR), support vector machine (SVM), and back propagation neural network (BPNN), respectively. The results showed that, compared with resampling spectral reflectance (REF), the correlation between the five spectral indices and SOM did not change significantly after conventional transformation. The spectral index SNV was the common input variable when the optimal modeling variables were extracted by SR, GCD, and PCA. Compared with SR and GCD, the PCA screening approach was the best with respect to the accuracy of model estimation. In the PCASVM models, the model based on spectral index RL had the highest accuracy, with Rc2, RP2 and RPD of 0.74, 0.78 and 2.08, respectively. This study determined RL-PCA-SVM as the optimal estimation model by comparing and analyzing the model accuracy under different spectral transformation, variable screening methods and modeling approaches. The model could provide reference for the rapid monitoring of SOM content in Yinchuan Plain and similar areas.