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    10 May 2021, Volume 40 Issue 5
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    Effects of stand density on community structure of soil phoDharboring microorganisms and bacteria in Pinus massoniana plantations.
    PAN Fu-jing, CHEN Ying-qian, LIANG Yue-ming, MA Jiang-ming, YANG Zhang-qi, YAN Pei-dong, LING Tian-wang, LI Ming-jin
    2021, 40(5):  1233-1243.  doi:10.13292/j.1000-4890.202105.015
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    Forest growth is commonly limited by soil phosphorus (P) availability. Understanding the relationships between soil P availability and the community structure of soil phoD harboring microorganisms and bacteria in different stand densities of Pinus massoniana plantations would provide a theoretical basis for selecting an appropriate management strategy. We analyzed the community structures of soil phoDharboring microorganisms and bacteria under four density stands of Pinus massoniana: low density (2500 trees·hm-2), medium density (3300 trees·hm-2), mediumhigh density (4500 trees·hm-2), and high density (6000 trees·hm-2) stands. We used the HiSeq 2500 high-throughput sequencing method to analyze soil microbial community. In addition, the effects of stand density on the community structures of microorganisms were analyzed from an ecological stoichiometry perspective. The results showed that the concentrations of soil organic C and needle leaf P were the highest in the medium-density stands. Soil C∶N ratios, nitrate concentration, exchangeable calcium concentration, six P fractions (CaCl-P, citrate-P, HCl-P, total available P, enzyme-P, and microbial biomass P), acid and alkaline phosphomonoesterase activity, and needle leaf C∶P and N∶P ratios were the lowest in the medium-density stands. The community structure of soil phoDharboring microorganisms and bacteria were significantly different among the four density stands. The Shannon diversity of the microbes was not significantly different among the stands. The relative abundance of the dominant genus Bradyrhizobium was the lowest in the mediumdensity stand. Results of redundancy analysis highlighted the role of soil pH and nutrients in driving variations in the community structures of soil phoDharboring microorganisms and bacteria among different density stands, indicating that the differences in community structures of soil phoDharboring microorganisms and bacteria were driven by stand density and soil factors, with greater contribution from stand density. These results suggest that medium-density Pinus massoniana plantation is least limited by P availability, and thus is a suitable plantation density.
    Community structure and driving factors for rhizosphere ectomycorrhizal fungi of Betula platyphylla in Daqing Mountain.
    LI Min, GAO Xiu-hong
    2021, 40(5):  1244-1252.  doi:10.13292/j.1000-4890.202105.004
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    Mycorrhizal fungi are one of the most important functional groups in soils, which significantly affect plant community composition and ecosystem function. Betula platyphylla, a typical ectomycorrhizal fungi-dominated tree species, is a pioneer species in natural secondary succession of forests. To better understand the composition of ectomycorrhizal fungi, Illumina MiSeq high-throughput sequencing was used to examine the diversity and community structure of ectomycorrhizal fungi in the rhizosphere soil of B. platyphylla in three sites of Jingerliang (JEL), Hadamen Forest Park (HDM), and Xiaojinggou (XJG) in Daqing Mountain, Hohhot. The results showed that the ectomycorrhizal fungi belonged to 2 phyla, 3 classes, 7 orders, 17 families, and 25 genera. At the phylum level, Basidiomycota accounted for 98.79% of all ectomycorrhizal fungi, with the rest being Ascomycota (1.21%). At the genus level, Russula,Cortinarius, Clavulina, Hysterangium,Hebeloma, Hygrophorus,Amanita and Tuber were the dominant ectomycorrhizal fungi. The diversity and richness of ectomycorrhizal fungi communities significantly differed among the three sites, with XJG being the highest, followed by HDM, and JEL being the lowest. The PCA clustering results of ectomycorrhizal fungi communities showed that the ectomycorrhizal fungal community structure in HDM and XJG was similar, which was quite different from that in JEL. The RDA was employed to analyze the ecological causes of the differences in the community composition of ectomycorrhizal fungi in the three sites. All soil factors explained 98.3% of the differences in the community composition of ectomycorrhizal fungi, with AP, TN, OM and AK being the main factors driving the differences of community composition of ectomycorrhizal fungi among the three sites.
    Community dynamics of arbor layer in subalpine forest of western Sichuan by different restoration approaches from 2005-2015.
    CHEN Xiao-xia, BAO Wei-kai, HE Qi-hua, BU Huan-huan, LIAO Li-bin, ZHOU Zhi-qiong, SHI Fu-sun
    2021, 40(5):  1253-1263.  doi:10.13292/j.1000-4890.202105.020
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    Secondary forest formed by natural restoration and artificial forest are the most typical forest types with the largest distribution in the mountainous areas of southwest China. This study focuses on the naturally restored secondary forests as well as the Pinus armandii and Pinus tabuliformis plantations in the Dagou Watershed of Maoxian County, western Sichuan. We examined changes in the species composition and structure of tree community under different restoration pathways during 2005-2015, aiming to provide a scientific basis for forest management. The results showed that tree density and the range of tree diameter class and height distribution increased in Pinus tabuliformis forest along with forest succession. The seedling regeneration of tree layer species was weak and the number of largediameter individuals increased, indicating stable community succession. Tree density in Pinus armandii and secondary forests decreased firstly and then increased, while the distribution of tree diameter class and height showed increased firstly and then decreased with an increase in abundance of young trees. The number of tree layer species in all three forest types showed an increasing trend, especially in Pinus armandii forest, which increased from 12 to 23. The importance value decreased in the planted tree species and increased in the remaining native broad-leaved tree species in the retention belt, which drove the shift of Pinus armandii forest from coniferous forest to coniferous and broad-leaved mixed forest. High planting density in Pinus tabuliformis forest inhibited the regeneration and growth of native broad-leaved species, with forest gap being the main factor driving succession. In secondary forest, the importance value of native tree species increased from 35.48% in 2005 to 81.12% in 2015. Native broad-leaved species including Quercus aliena var. acutiserrata were the dominant species, which was the main factor driving the succession of secondary forest. The richness and diversity in Pinus tabuliformis forest were significantly lower than that of secondary forest. The diversity in Pinus armandii forest significantly increased with time, quite close to the secondary forest. In the long term, the effect of Pinus armandii forest with low density “contour-staggered configuration afforestation model” was similar to that of natural restoration in terms of biodiversity restoration.
    Allocation of nonstructural carbohydrates of different aged Pinus sylvestris var.mongolica in sandland.
    WANG Kai, PANG Ying-ying, ZHANG Ri-sheng, SHEN Chao, SONG Li-ning
    2021, 40(5):  1264-1274.  doi:10.13292/j.1000-4890.202105.022
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    The concentration and allocation of non-structural carbohydrates (NSC) reflect carbon supply and demand of trees, which is a crucial factor determining the survival and growth of trees. To understand carbon dynamics in different growth stages of Pinus sylvestris var. mongolica, we analyzed the concentrations of NSC, soluble sugar, and starch, and ratio of soluble sugar to starch in needles, branches, and roots of P. sylvestris var. mongolica across a chronosequence (12-, 22-, 31-, 42-, 52-, and 59-year-old) and examined the carbon allocation and balance relationships. The results showed that, with the increases of stand age, NSC concentrationsdecreased first and then increased, whereas soluble sugar concentrations increased and subsequently reduced in current-year needles. However, NSC concentrations in one- and two-year-old needles showed a downward trend with an exception at the stand of 42 years old. The concentrations of NSC and soluble sugar in current-year-old and one-year-old branches exhibited trends of initial decreasing and then increasing afterward decreasing, while NSC and starch concentrations in two-year-old branches first reduced and subsequently rose. Soluble sugar concentrations showed upward trends in two-year-old branches with stand age. Starch concentrations decreased whereas ratios of soluble sugar to starch increased in roots after the age of 31 years. In general, NSC, soluble sugar and starch concentrations in each organ followed the order of needle > branch > root, while their variabilities followed the order of root > branch > needle. The variability of ratios of soluble sugar to starch followed the order of needle and root > branch. Our results indicated that concentrations of NSC and its components and proportions among different organs of P. sylvestris var. mongolicavaried with stand age. Trees would decline when starch in roots was consumed and the allocation of NSC among organs was imbalanced.
    Evaluation of the stability of the radial growth of Larix sibirica at different altitudes in response to climate change in Altai Mountains, Xinjiang.
    XUE Ru-hong, JIAO Liang, LIU Xiao-ping, CHEN Ke
    2021, 40(5):  1275-1284.  doi:10.13292/j.1000-4890.202105.021
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    The radial growth of trees in high-latitude and high-altitude regions of the northern hemisphere usually shows significant unstable and nonlinear divergent responses to climate change as global warming intensifies. The stability of the response of dominant conifers at different altitudes in the Altai Mountains in Northwestern China to climate change remains unknown. With tree-ring samples of Siberian larch (Larix sibirica) collected from high, middle and low altitudes in the middle section of the Altai Mountains, we analyzed the characteristics of three treering width series chronology and the relationship between tree radial growth and climate. The results showed that the radial growth of Siberian larch at high altitude was mainly affected by temperature (including mean temperature, mean minimum and mean maximum temperatures) in April, June, and July. The radial growth of Siberian larch at mid-altitude was mainly affected by mean temperature and mean maximum temperature in May, mean temperature and mean minimum temperatures in June, and precipitation in January and March. However, the radial growth of Siberian larch at low altitude was mainly driven by precipitation in October. In addition, in terms of temporal stability, the limiting effect of temperature on the growth of Siberian larch at high altitude was gradually weakened, while the limiting effect of precipitation on the growth of Siberian larch at middle and low altitudes was increased. Our results provide scientific supports for the management and protection of Siberian larch at different altitudes in Altai Mountains.

     

    Seasonal dynamics of biomass, root turnover, and carbon, nitrogen and phosphorus storage in Zoige alpine marsh.
    YANG Wei-zong, MA Xiao, YANG Wen, LIU Hong-qiang, ZHAO Li, WANG Huo-yi, ZHANG Cong, DONG Li-qin, ZHANG Kun
    2021, 40(5):  1285-1292.  doi:10.13292/j.1000-4890.202105.005
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    Wetland vegetation is an important part of wetland ecosystems and exerts both direct and indirect effects on underground carbon pools. In this study, we measured the seasonal dynamics of biomass and fine root turnover in Zoige alpine marsh. The results showed that the seasonal dynamics of both aboveground and underground biomass of Zoige alpine marsh showed a unimodal pattern, with the maximum values of aboveground biomass and underground biomass being 518.3 and 2147.4 g·m-2, respectively. In July, August, and September 2019, underground biomass in the 0-10 cm soil layer accounted for more than 50% of the total biomass in the 0-50 cm soil layer. The maximum value of underground biomass in the 0-10 cm soil layer was found in early September. The average annual turnover rates of fine roots in the 0-50 cm soil layers were 0.795-0.936 a-1, with the maximum in the 0-10 cm soil layer. The carbon and phosphorus reserves of plants were mainly distributed in the underground part, whereas the nitrogen reserve was mainly distributed in the aboveground part. Our results provide basic support for quantitative assessment of net primary productivity of the Zoige alpine marsh.
    Benefit evaluation of carbon sequestration, oxygen release, cooling and humidifying of the main landscape tree species in small towns along Huaihe River in Anhui Province.
    YAO Xia-mei, OU Chun, XIA Lu, YAO Xiao-jie, CHEN Yuan-yuan, WANG Ning-xin
    2021, 40(5):  1293-1304.  doi:10.13292/j.1000-4890.202105.014
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    Clarifying the photosynthetic transpiration characteristics of the main landscape tree species in small towns, as well as their capacity in carbon fixation, oxygen release, cooling and humidifying can provide scientific basis for rational allocation of landscape tree species and the quantification of their ecological and environmental benefits. We measured photosynthetic characteristics of 19 main landscape tree species in the public spaces of Zhongyuan HuaduFragrant Town of Yingzhou District, Balihe Tourist Town of Yingshang County, and Maji Hair Art Town of Taihe County in Fuyang City along the Huaihe River in Anhui Province by LI-6400XT portable photosynthesis system, and analyzed their carbon sequestration and oxygen release as well as cooling and humidifying efficiency. The results showed that: (1) Except for Photinia serratifolia and Camellia japonica, carbon sequestration, oxygen release and cooling and humidifying capacities per unit leaf area of all the tree species in each season were in the order of summer > spring > autumn. (2) Carbon sequestration and humidifying of tree species were significantly correlated with net photosynthetic rate, transpiration rate, and stomatal conductance. (3) From the perspective of the photosynthesis and transpiration efficiency, we evaluated carbon fixation, oxygen release, humidifying and cooling capabilities of the tree species with the principal component analysis. They followed the order of Platanus acerifolia > Rosa chinensis > Hibiscus syriacus > Salix babylonica > Prunus cerasifera > Malus halliana  > Cinnamomum camphora  > Pyracantha fortuneana > Celtis sinensis > Viburnum odoratissimum > P. serratifolia > Chimonanthus praecox > Cerasus serrulata > Osmanthus fragrans > Buxus megistophylla > Magnolia grandiflora > Michelia denudata > Ginkgo biloba > C. japonica. Therefore, in the disposition of landscape tree species in small towns along the Huaihe River in Anhui Province, the tree species with higher ability of carbon fixation, oxygen release and humidifying and cooling can be selected. The preferred arbor species are P. acerifolia, S. babylonica, P. cerasifera andC. camphora, and the shrub species are R. chinensis, H. syriacus, M. halliana, P. fortuneana and V. odoratissimum.

     

    Stoichiometric characteristics of Sophora alopecuroides roots in different habitats of Yili River Valley and their relationship with soil physicochemical factors.
    YANG Xia, CUI Dong, ZHAO Yang, YAN Jun-jie, ZHANG Sai-sai, LIU Yan-yan
    2021, 40(5):  1305-1312.  doi:10.13292/j.1000-4890.202105.034
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    Sophora alopecuroides is a mid-xerotrophic and salt-tolerant plant species that grows mostly in deserts and semi-desert areas. It is one of the typical poisonous grasses in the mountain grasslands of the Yili River Valley in Xinjiang. Root is the important organ for absorbing soil nutrients. In this study, we collected roots and rhizosphere soil of S. alopecuroides in four different habitats (forest, wasteland, roadside, and cropland) in the Yili River Valley to analyze their stoichiometric characteristics and the relationship between stoichiometric characteristics of S. alopecuroides roots and soil physicochemical factors by redundancy analysis. The results showed that the average root C, N, and P concentrations were 422.99, 10.06, and 1.16 g·kg-1, respectively. Among those three elements, the coefficient of variation of N concentration was the largest (0.25), and that of P concentration was the smallest (0.17). The C/N ratio was 9.93, C/P ratio was 10.54, and N/P ratio was 1.06. We quantified the importance of soil physical and chemical factors to the stoichiometric characteristics of S. alopecuroides roots in different habitats by redundancy analysis. The importance of all the factors ranked as available potassium > nitrate > total carbon > available phosphorus > organic matter > total phosphorus > pH > total potassium > total nitrogen > ammonium in forest habitat; as ammonium > pH > total phosphorus > available potassium > total potassium > organic matter > total carbon > available phosphorus > total nitrogen > nitrate in roadside habitat; as organic matter > pH > available potassium > nitrate > available phosphorus > total phosphorus > total carbon > total potassium > total nitrogen > ammonium in uncultivated land; as organic matter > nitrate > total nitrogen > pH > available potassium > total carbon > available phosphorus > total potassium > ammonium > total phosphorus in cropland habitat. Our results provide a theoretical basis for controlling poisonous grasses in the Yili mountain grassland.
    Climatic suitability regionalization of Camellia oleifera Abel. in China.
    WU Ding-rong, WANG Pei-juan, HUO Zhi-guo, YUAN Xiao-kang, JIANG Hui-fei, YANG Jian-ying, MA Yu-ping, GUO Shui-lian
    2021, 40(5):  1313-1323.  doi:10.13292/j.1000-4890.202105.019
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    Development of oil-tea camellia industry can effectively increase farmers’ incomes, promote precise alleviation of poverty, and improve ecological environment. A national-scale climate suitability regionalization of oil-tea camellia could provide a scientific basis for the development of the oiltea camellia industry. The objective of this study was to determine the main production regions of Camellia oleifera Abel., a species with the largest planting area and total production in China. Values of key climate factors were calculated for the main planting regions (i.e., counties and cities with more than 6667 hm2 of actual planted area), including mean annual temperature, mean temperatures in January and July, annual precipitation, and sunshine hours. Based on those variables, the regional climatic planting suitability was tested using an improved climate similarity distance method on a national 1 km×1 km grid. Results showed that the most suitable area for C. oleifera production was 98×104 km2 that was mainly located in Hunan, Jiangxi, Fujian and Zhejiang provinces and the neighboring areas. Areas that were classified as suitable and sub-suitable levels were 52×104 km2 and 80×104 km2, respectively, which were located on the periphery of the most suitable area. The north and west boundaries of the subsuitable area were about 33.5°N and 111.5°E, respectively. There were no clear southern and eastern boundaries. Hunan Province had the largest most suitable area, followed by Jiangxi, Guangxi, Zhejiang and Fujian provinces. These areas accounted for about 70% of the total production area in China. Compared with the actual planting area recorded in multiple sources, this regionalization well represented the actual distribution of C. oleifera. Compared with the climatic characteristics of the main production areas, this regionalization accurately distinguished the climatic characteristics of the most suitable, suitable and subsuitable areas for C. oleifera production. Through identifying the distributions of the climate suitable regions for C. oleifera production, our results provide scientific support for the planning and development of the camellia industry.
    Competitive effects of mung bean (Vigna radiata L.) on the growth of three dominant weeds in summer maize fields.
    LIU Xiao-min, LI Jie, XU Xian, ZHAO Bo-chui, LI Bing-hua, LIU Shao-xing, WANG Gui-qi
    2021, 40(5):  1324-1330.  doi:10.13292/j.1000-4890.202105.031
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    Crabgrass (Digitaria sanguinalis), goosegrass (Eleusine indica), redroot pigweed (Amaranthus retroflexus) are the three dominant weed species in summer maize fields. To get more scientific weed control strategies, we adapted the De Wit replacement series design to examine the competitive effects of mung bean on the three weed species under different mixed ratios. Results showed that plant height and biomass of crabgrass, goosegrass, and pigweed decreased with increasing mixed ratios of mung bean and weeds. Compared with the monoculture, plant height of crabgrass, goosegrass and pigweed decreased by 19.4%, 17.9%, and 14.7%, and dry weight decreased by 71.7%, 78.0%, and 38.2%, respectively, when the ratio was 3∶1. Under mixtures, the number of tillers of crabgrass and goosegrass was significantly reduced under different mixed ratios. However, side shoot number of pigweed decreased significantly only at the mix ratio of 3∶1 (P<0.05). Under different mixed ratios, the relative biomass of crabgrass, goosegrass and pigweed was lower than 1.0 (P<0.05). Relative biomass of weeds decreased with the increasing mixed ratio of mung bean. Our results indicated that mung bean was strong competitive to the three dominant weeds, and the competitive ability increased with its density. Competitive balance index between mung bean and crabgrass or goosegrass was significantly greater than 0 (P<0.05), but that between mung bean and pigweed was significantly greater than 0 only at the higher mixed ratio (3∶1) (P<0.05), indicating that competitive ability of mung bean to the grass weeds was greater than the broadleaved weeds.
    Effects of nitrogen reduction and humic acid application on yield and nitrogen use efficiency of maize.
    LI Huan, YANG Qing-xia, LI Yang, WU Kai-xian, HE Shu-ran, ZHAO Ping, ZHANG Xiao-zhuo, LONG Guang-qiang
    2021, 40(5):  1331-1339.  doi:10.13292/j.1000-4890.202105.028
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    It is important to maintain crop yield, control nitrogen input, and improve nutrient use efficiency for agricultural green development in China. In this study, we carried out a field experiment with two nitrogen (N) reduction levels (20% and 40%) and N reduction (20% and 40%) + humic acid, with the conventional N application (urea, 250 kg·hm-2) as control. We measured soil N supply, plant N uptake, photosynthetic characteristics, N assimilationrelated enzyme activity and yield components of maize to evaluate the potential and mechanism of nitrogen reduction and efficiency enhancement by humic acid addition in maize cultivation. The results showed that compared with conventional N application, maize yield was not reduced and 20% N use efficiency was improved by 35.8%-48.3% in the treatment with 20% N reduction and humic acid addition, while maize yield was reduced by 20.6%-24.4% and N use efficiency was improved by 20.4%-31.5% under the treatment of 40% N reduction. The 20% N reduction treatment improved root N uptake and photosynthetic N use efficiency and increased the harvest index. Compared with conventional N fertilization, 20% N reduction with humic acid application increased soil nitrate and ammonium content and root N uptake, enhanced leaf photosynthesis, increased total N uptake by 1.2 times and glutamine synthase activity by 19.9%, and reduced barren tip length by 42.9%. Regardless of humic acid application, the 40% N reduction reduced soil nitrate content, total N uptake, net photosynthetic rate, and photosynthetic N use efficiency of maize. The 20% N reduction and combination of 20% N reduction with humic acid application can achieve no reduction in maize yield and improve N fertilizer use efficiency. Compared with urea application alone, urea application with humic acid addition has advantages in improving N uptake and use efficiency.
    Effects of GA3 seed soaking on antioxidant enzymes and endogenous hormones of maize embryo under low temperature.
    ZUO Yue-tao, WANG Zi-mu, JIAO Jian, REN Xiao-song, LIU Zhao-yue, ZUO Shi-yu, LI Jing
    2021, 40(5):  1340-1346.  doi:10.13292/j.1000-4890.202105.026
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    Under low temperature conditions (7 ℃), seed soaking treatment with GA3 solution (GA3 concentration was 5 mg·L-1 for ZD 958, 20 mg·L-1 for FH 1) was carried out to investigate the effects of GA3 on protective enzyme activity, MDA content and endogenous hormone content in seed embryos during seed germination of two maize varieties, ZD 958 (cold resistant type) and FH 1 (low temperature sensitive type), aiming to provide theoretical basis for chemical regulation of seed germination and low temperature tolerance processing before sowing in cold regions. The results showed that under low temperature stress, after soaking seeds in a GA3 solution at an appropriate concentration, the activities of two antioxidant enzymes (SOD, POD) in the embryos were significantly increased; the contents of endogenous hormones IAA, GA, and ZR were increased, while the contents of monochrome display adapter (MDA) and endogenous hormone ABA were significantly reduced. Under low temperature stress during seed germination, GA3 seed soaking could effectively enhance the activities of protective enzymes and increase seed metabolism. The increases of endogenous IAA and GA content promoted seed germination under low temperature, which resulted in stronger resistance to low temperature stress during seed germination.
    Effects of reduced chemical fertilizer with organic fertilizer application on the yield and grain quality of sweet-waxy corn.
    FANG Cheng, DAI Zi-wen, LI Wei-ming, WANG Dong-sheng, JIAO Jia-guo, CHEN Xiao-yun, XU Li
    2021, 40(5):  1347-1355.  doi:10.13292/j.1000-4890.202105.003
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    We examined the effects of 30% reduction of chemical fertilizer replaced by adding different organic fertilizers (chicken manure organic fertilizer, vermicompost from pig manure, and vermicompost from kitchen waste) on the growth, yield and grain quality of sweet-waxy corn, aiming to choose proper strategy of using organic fertilizer to replace chemical fertilizer in sweet-waxy corn planting. Sweet-waxy corn Nongkeyu 368 was used as test crop. There were six treatments, including no fertilizer treatment (CK), fullquantity fertilizer application (CF), reduced fertilizer application (RF), reduced fertilizer combined with chicken manure organic fertilizer (RF+OF), reduced fertilizer combined with vermicompost from pig manure (RF+PF), andreduced fertilizer combined with vermicompost from kitchen waste (RF+KF). The growth and photosynthetic characteristics of corn were measured at the jointing stage and tasseling stage respectively, while the yield and quality (including heavy metal content) of the grain were measured during the harvest period. The corn yield under the treatments of RF+KF and RF+PF was similar to that under CF treatment. Compared with CF treatment, the number of spikes of RF treatment was significantly decreased while the yield was not significantly different. The plant height, stem diameter and leaf chlorophyll content followed the sequence of CF ≥RF+KF > RF > RF+OF > (RF+PF). Compared with CF treatment, photosynthetic rate was significantly lower under RF+PF treatment, and intercellular CO2 concentration of RF+KF was significantly higher. Fertilizer application significantly increased the contents of vitamin C, soluble protein, and starch in corn grains. Compared with CF treatment, reduced fertilization with application of organic fertilizer significantly increased vitamin C content, with the maximum under RF+KF treatment. The soluble protein content was significantly higher under RF+PF treatment. The soluble sugar contents were significantly higher under RF+OF and RF+KF treatments, with an enhancement of42.07% and 69.01%, respectively. The starch content was significantly higher under RF+KF treatment. Fertilization treatment significantly increased Zn content in the corn grains, but did not affect Cd and Pb contents. The maximum accumulation of Zn, Cu, and Cr was found under RF+OF treatment. In conclusion, corn yield under RF+PF and RF+KF treatments was similar to that under full-quantity fertilizer treatment. RF+KF treatment improved fruit quality, and thus is a feasible strategy for fertilizer reduction in corn production.
    Effects of population structure on soil water consumption and dry matter production of dryland wheat.
    YANG Lei, SUN Min, LIN Wen, REN Ai-xia, DING Peng-cheng, YU Shao-bo, GAO Zhi-qiang
    2021, 40(5):  1356-1365.  doi:10.13292/j.1000-4890.202105.030
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    We carried out an experiment with two sowing dates \[early sowing (September 20, EB) and late sowing (October 10, LB)\] and three sowing rates \[low sowing rate (67.5 kg·hm-2, LD), medium sowing rate (90 kg·hm-2, MD) and high sowing rate (112.5 kg·hm-2, HD). According to the number of tillers at the jointing stage of wheat, the populations were divided into three levels: class I (> 12 million plants·hm-2, G1), class II (9-12 million plants·hm-2, G2) and class Ш (< 9 million plants·hm-2, G3). We examined water consumption, dry matter accumulation and transportation, yield and its components, and water use efficiency under different population levels. The results showed that compared with class II and Ш, soil water consumption under class I after anthesis was increased by 3-11 and 16-32 mm respectively, while the dry matter mass at maturity was increased by 664-1122 and 2072-2300 kg·hm-2 respectively. Dry matter accumulation was the highest in each growth stage of class I, with the dry matter transport before flowering being increased by 42-60 and 17-179 kg·hm-2 respectively. The contribution of dry matter allocation to grain after anthesis was increased by 306-403 and 681-926 kg·hm-2, with a growth rate of 7.45%-8.40% and 18.97%-20.83%, respectively. Water use efficiency was increased by 7.93%-10.94% and 14.69%-18.94%, respectively. Under class I, soil water consumption (especially after anthesis) was significantly correlated with dry matter mass and yield at maturity. Early sowing with low sowing rate (EB+LD) was important for the formation of class I population. When population density reached class I at jointing stage, soil water consumption after anthesis, dry matter accumulation during growth period, dry matter transport before flowering, yield and water use efficiency were significantly increased. In conclusion, the class I population formed under a sowing rate of 67.5 kg·hm-2 and sowing date on September 20 could increase the absorption and utilization of soil water by grain filling after anthesis as well as dry matter accumulation, which is conducive to its transport and contribution to grain and finally increased the yield and water use efficiency of dryland wheat in the southern Shanxi Province.
    Effects of panicle fertilizer reduction on nitrogen use efficiency of rice under side deep application of basal fertilizer.
    LIU Hong-jiang, ZHANG Hui, SHENG Jing, ZHANG Yue-fang, GUO Zhi, ZHENG Jian-chu, CHEN Liu-gen
    2021, 40(5):  1366-1374.  doi:10.13292/j.1000-4890.202105.025
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    A field experiment was conducted to explore the effects of reduced application of nitrogen fertilizer on yield formation and nitrogen uptake and use efficiency of rice (cultivar Wuyunjing 31), by setting different nitrogen application treatments and deep application of basal fertilizer with machine at root side. The results showed that, during two seasons of rice in 2017 and 2018, compared with spraying application of basal fertilizer (N1), deep application of basal fertilizer at root side and 10% reduction in nitrogen application (N3) significantly reduced the number of panicles per unit area and increased the spikelets per panicle and filled grain percentage, which ensured the high yield of rice. Compared with the N1 treatment, N3 treatment significantly reduced the biomass of rice; however, its yield was not decreased due to the higher economic coefficient. There were no differences in rice nitrogen accumulation, nitrogen use efficiency of biomass and nitrogen use efficiency of grain yield between N3 and N1 treatments. Under deep application of basal fertilizer at root side, with the decreasing nitrogen application level, N use efficiency of biomass and grain yield of rice gradually improved. Compared with the N1 treatment, N3 treatment increased rice agronomic efficiency, average recovery efficiency, physiological efficiency and partial factor productivity of nitrogen fertilizer by 8.9%, 8.3%, 0.6% and 10.5%，respectively. There was no difference between N3 and N1 treatment in soil available nitrogen content at rice maturity stage. Our results indicated that, in comparison with artificial application of basal fertilizer, deep application of basal fertilizer at root side and 10% reduction in nitrogen application could ensure high rice yield, improve both the efficiency and rate of nitrogen uptake and use, and maintain soil fertility.
    Effects of machine-transplanted densities on yield and quality of middle-seasonindica hybrid rice and its relationships with photosynthetically active radiation inside canopy.
    HE Hai-bing, REN Hao-jie, SHI Qiang-qiang, LI Gang-hua, WU Xiao-wen, YOU Cui-cui, KE Jian, ZHU De-quan, WU Li-quan
    2021, 40(5):  1375-1385.  doi:10.13292/j.1000-4890.202105.009
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    We explored the effects of machineplantation densities on yield and quality formation of indica hybrid rice based on the distribution characteristics of photosynthetically active radiation (PAR) inside the canopy. A field experiment was conducted in 2017 and 2018 with three rice cultivars, Huiliangyou-898, Fengliangyouxiang-1, and Y-Liangyou-900. There were six density treatments, including 17 ×104 hills·hm-2 (D17), 19 ×104 hills·hm-2(D19), 21 ×104 hills·hm-2 (D21), 23 ×104 hills·hm-2 (D23), 24 ×104 hills·hm-2 (D24), and 25 ×104 hills·hm-2 (D25). The results showed that the densities significantly affected yield. Generally, the maximum value of grain yield was observed in the D19 treatment in 2018 and in the D21 treatment in 2017, and then followed by high density treatments (D24 and D25) and low density treatment (D17) across both cultivars each year. The fitted equation indicated that the highest grain yield of middle-seasonindicahybrid rice was 9.91×103 kg·hm-2 when the density was 20.52×104 hills·hm-2 in machine transplanted condition in this region. Higher daily crop growth rate during grain filling, greater PAR interception, and larger PAR use efficiency were key factors driving higher grain yield in medium density treatments than that in high density treatments and low density treatment across cultivars. For the three tested cultivars, both processing qualities and appearance qualities were continuously deteriorated with increasing planting density. There was no significant difference among D17 treatment, D19 treatment, and D21 treatment (P>0.05). Meanwhile, there was little difference among the D19, D23, and D24 treatments for eating quality of cultivar Huiliangyou-898 and cultivar Y-Liangyou-900. Densities mainly affected the PAR of 20-40 cm and 40-60 cm from top of canopy, with PAR at 20-60 cm from top of canopy being negatively correlated with planting density. The PAR inside of 20-60 cm canopy was positively correlated with processing qualities, but negatively correlated with appearance qualities (P<0.05). However, only 40-60 cm of PAR was significantly negatively related to grain yield (P<0.05). Theseresultssuggest that the optimum density harvested the highest yield and good qualities should be recommended for 19×104-21×104 hills·hm-2. Improving 20-40 cm PAR from the canopy top coordinating moderately lower canopy PAR 40-60 cm may be the crucial point for the formation of good quality and high yield of indica hybrid rice.
    Evaluation of climate resource utilization rate of main grain crops in Shanxi Province.
    2021, 40(5):  1386-1396.  doi:10.13292/j.1000-4890.202105.006
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    It is of great significance for promoting agricultural production to evaluate the status of regional agricultural climate resources, find out the factors limiting the effective matching of agricultural climate resources, and improve the utilization rate of agricultural climate resources. Based on the meteorological data of daily temperature, precipitation and sunshine hours from 108 surface meteorological stations in Shanxi Province during 1981-2018 and the observation data of growth period of spring maize, summer maize and winter wheat from 31 agricultural meteorological stations, we analyzed the suitability degree, matching status and utilization rate of climate resources in different crop growing areas of Shanxi Province, using average resource suitability index, average efficacy suitability index, and average resource utilization index. The results showed that: (1) The suitability degree, matching degree and utilization rate of climate resources were high in most of the planting areas of spring maize in Shanxi Province, with a trend of increasing in the west and decreasing in the middle and eastern planting areas in Shanxi Province from 1981 to 2018. The low temperature restricted the reasonable matching of light, temperature and water to spring maize in the middle and western regions of Shuozhou and Xinzhou Prefecture, resulting in lower utilization rate. (2) The climate resource suitability was high in most of the planting areas of summer maize, but with low matching degree of climate resource. The utilization rate of climate resource to summer maize was low in western parts of Yuncheng Prefecture due to the low precipitation. The climate resource degree, matching status and utilization rate were lower in most of the summer maize planting areas. (3) The spatial distribution pattern of the average resource suitability index, average efficacy suitability index and average resource utilization index in the planting areas of winter wheat in Shanxi Province was low in the northwest and high in the southeast. The low precipitation in the northwest led to the poor matching of light, temperature, and water. The average resource utilization was lower in the northwest. The utilization rate of climate resources was higher in Changzhi, Jincheng, central Linfen and eastern Yuncheng, and lower in Lüliang, Taiyuan, Jinzhong and western Yuncheng. Thus, the effective way to improve the utilization rate of climate resources is to increase the utilization rate of heat resources in Northern Shanxi, and to increase the utilization rate of water resources in the Central and Southern Shanxi. It should consider the adverse effects of continuous temperature increase on crop growth and development in Yuncheng and Linfen basin of Southern Shanxi.
    Spatiotemporal changes of supply and demand risk of soil conservation services in Bailongjiang watershed, Gansu Province.  
    XU Cai-xian, GONG Jie, YAN Ling-ling, GAO Bing-li, LI Yan
    2021, 40(5):  1397-1408.  doi:10.13292/j.1000-4890.202105.008
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    Compared with the quantification of service supply and the degradation risk assessment of supply capacity, research on the balance of supply and demand of ecosystem services and the risk of supply and demand is relatively weak. It is important to clarify the relationship between supply and demand of ecosystem services, spatial matching and the temporal and spatial evolution of supply and demand risks for the management of watershed ecosystem and the effective allocation of resources. With Bailongjiang watershed in Gansu Province as an example, based on InVEST model, ArcGIS and GeoDa, we evaluated the supply and demand of soil conservation services, and revealed the temporal and spatial change characteristics of supply and demand risks under the research framework of supply and demand risks of ecosystem services at the basin scale. The results showed that: (1) From 1990 to 2016, the spatiotemporal variations of soil conservation service supply and demand in Bailongjiang watershed were significantly different. The total supply of soil conservation services in the basin showed a trend of decreasing first and then increasing. It decreased from 8.79×108 t in 1990 to 7.74×108 t in 2002, and then increased to 2016. The total demand showed a decreasing trend, from 7.06×108 t in 1990 to 5.69×108 t in 2016. However, there was a trend of increasing risk in some areas. (2) In terms of spatial matching of supply and demand, the supplydemand ratio was less than 0 in some areas of the northern mountainous Diebu, Wudu, and Wenxian, indicating that the supply exceeded demand. Other areas basically maintained a balance. The main spatial matching types of watershed soil conservation services were highhigh and lowlow types. (3) In the aspect of supply and demand risk, the risk levels of supply and demand of soil conservation services in the basin were mainly fragile (V) and safe (VI) low risk, accounting for 21% and 64% of the total area of the basin respectively. The medium risk (IV and III) areas accounted for 15%. There was no high risk area (II and I). The ecological environment of the river basin in 2002-2016 was better than that in 1990-2002, with the level of supply and demand risk being reduced. The proportion of high-risk areas had been reduced from 8% to 0. Our results would provide theoretical support for the research and management of ecosystem service risk assessment.

     

    Variation of cool island effect for urban forest patches across an urban-rural gradient in Shanghai.
    QIU Kuan-biao, ZHANG Hui, GAO Ji-xi, PEI Wen-ming, ZHANG Biao, WANG Min, WANG Qing
    2021, 40(5):  1409-1418.  doi:10.13292/j.1000-4890.202105.018
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    Vegetation is a key factor to mitigate the urban heat island effect because it can form the local cool island. Previous studies focused on the local cooling effect of vegetation and water bodies in urbanized regions. However, few studies have figured out whether such effect would vary along the urbanrural gradient, as well as the relationship between such variations and the geometry characteristics of urban forest patches. In this study, we first retrieved the land surface temperature (LST) and the land use from Landsat 8 TIRS and GF-2 PMS imagery, respectively, and then analyzed the cooling effects of urban forest patches in Shanghai via buffer analysis method. Different urban development zones with various urbanization levels were used to represent the urban-rural gradient. Results showed that LST of the urban forest patches was 0.55 ℃ lower than the mean LST in Shanghai, indicating the role of forest patches as cool island in urban thermal environment during the daytime in summer. However, such effect of forest patches was not consistent along the urban-rural gradient. Strong cooling island effect was found for those in the downtown, with a reduction of LST up to 1.67 ℃. Forest patches did not serve as the cool island in the outskirt, such as in Chongming District. In each region, the area and shape characteristics of forest patches exerted great influences on the cool island effect. The patches with large size and regular shape had stronger cool island effect compared with those with small size and irregular shape. Compared to those in the region with low urbanization level, the small and irregular shape forest patches in the region with high urbanization level were apt to serve as cool islands. These findings can provide scientific support for future urban greening and ecological construction.
    Spatial-temporal variations of habitat quality in Qilian Mountain National Park.  
    ZHANG Hua, HAN Wu-hong, SONG Jin-yue, LI Ming
    2021, 40(5):  1419-1430.  doi:10.13292/j.1000-4890.202105.029
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    Qilian Mountain National Park is an important ecological protection area in western China, with important ecological core function. Understanding the temporal and spatial variations of habitat quality of Qilian Mountain National Park is of practical significance for ecological environmental protection and sustainable development. Based on land use data from four periods (1990, 2000, 2010, and 2018), we used the InVEST model to quantitatively assess the spatial and temporal variations of habitat quality and habitat degradation in Qilian Mountain National Park. The results show that, from 1990 to 2018, land use in Qilian Mountain National Park was generally stable, manifested as the expansion of both forests and water bodies, along with the decreases of grassland and unused land. The changes were mainly contributed by the mutual transformation among grassland, forest land, and unused land. Overall, the habitat quality of Qilian Mountain National Park had been increased, with high quality in the east and low quality in the west. From the perspective of land types, forest land had the highest habitat quality, while unused land had the lowest. The habitat quality varied across different altitudes and slope grades. With the increases of altitude, habitat quality showed an upward but fluctuating trend, with the lowest habitat quality in altitude grade IV. With the increases of slope grade, the habitat quality presented a downward trend, which was the highest in slope grade I. At the same altitude and slope grade, habitat quality varied across different periods. The cold and hot spots of habitat quality were exhibited as “cold in west and hot in east”. The hot spots were mainly distributed in the central and eastern regions, while the cold spots were primarily distributed in the west. Thedegree of habitat degradation of Qilian Mountain National Park from 1990 to 2018 had a characteristic of first increasing and then decreasing. The degree of habitat degradation was spatially distributed in points, with a ring-shaped structure distributed along the edges of the middle and east of the study area.
    The cooling effect of parks and influencing factors during the construction of a new town.
    WANG Ya-nan, XIE Miao-miao, LIU Shi-zhe, WU Rong-rong, LIU Qi, LI Xin-yu
    2021, 40(5):  1431-1439.  doi:10.13292/j.1000-4890.202105.027
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    The land surface temperature in the Tongzhou District, Beijing’s sub-center, was retrieved by a singlechannel algorithm. Seven cooling indicators, from the aspects of local environmental temperature difference of the park, comparison of cooling effect before and after completion of the park, and cooling stability, were used to evaluate the cooling effects of overall and individual parks during the construction of the new city from 2000 to 2017. We analyzed the impacts of park characteristic parameters and internal surface parameters on the cooling effects. The results showed that, from 2000 to 2017, 16 new parks were constructed in Tongzhou District, 62.5% of which had cooling effect and cooling stability, with a maximum reduction of 2.40 ℃ compared with the preconstruction. The overall cooling area and temperature difference of the parks increased significantly, whereas the cooling distance reduced. The maximum cooling distance of single park was 210 m, the maximum cooling area was 284.79 hm2, the maximum cooling amplitude was 3.80 ℃, and the maximum cooling rate was 0.33 ℃·m-1. The cooling amplitude was positively correlated with park area, while the cooling stability was positively correlated with vegetation coverage. There was a positive correlation between the cooling area and the normalized differential water index (NDWI) and park area, respectively. The impervious surface ratio (ISA) and the construction year were weakly correlated with the various cooling indicators. Our results provide a basis for the layout of parks to alleviate the overall heat island effect of the city.
    Spatiotemporal variation of wind speed in Shibei District of Qingdao from 2003 to 2018.
    ZHANG Pei-feng, LIU Jun, GAO Yu-jia, CHENG Zheng, QI Xiao-lin, LI Xin
    2021, 40(5):  1440-1448.  doi:10.13292/j.1000-4890.202105.032
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    Studies of the spatiotemporal variations of wind environment during urban three-dimensional development are important for solving the problems of heat island and air pollution. In this study, we simulated the wind environment of Shibei District, Qingdao from 2003 to 2018 by PHOENICS software based on the buildings’ 3D information obtained from high-resolution satellite images and analyzed the spatiotemporal variations of wind environment in 3D space. The results showed that the wind speed in summer and winter decreased, the area ratio of low wind speed increased, and the area ratio of high wind speed decreased year by year. The spatiotemporal variation of wind speed was consistent at the heights of 1.5, 10, and 30 m. The distribution of wind speed was uneven, with wind speed being high in the area with sparse buildings and low in the area with dense buildings. The area of calm wind zone at the height of 1.5 m increased significantly year by year. From 1.5 m to 30 m, wind speed decreased yearly, with the deceleration rate increased with the increases of height. The average building height, building coverage ratio and floor area ratio were negatively correlated with the average wind speed and the area ratio of comfort zone, and positively correlated with the area ratio of calm and strong wind zone.
    Ethogram and PAE coding system for Tibetan antelope (Pantholops hodgsonii).
    WU Tong, LIAN Xin-ming, MIAO Zi-yan, LI Hong-qi, CHEN Jia-ping, WANG Dong, ZHANG Tong-zuo
    2021, 40(5):  1449-1457.  doi:10.13292/j.1000-4890.202105.017
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    Three key elements of behaviors for Tibetan antelope Pantholops hodgsonii, posture, act, and environment (PAE), were recorded in the Kekexili area of Sanjiangyuan National Park and Chang Tang National Nature Reserve from 2017 to 2019. Using the recorded behaviors, we established a PAE coding system for Tibetan antelope, including 12 postures, 79 acts, 10 environmental categories, and 89 behaviors. According to the behavioral functions, those behaviors were divided into 13 categories: ingestion, elimination, thermo-regulation, rutting and estrus, mating, parturition, parental behaviors, conflict, communication, aggregation, resting, locomotion, and miscellaneous. Behaviors varied across season, sex, and age. For example, Tibetan antelope used different behaviors to regulate body temperature and to obtain food and water in different seasons. There were differences in foraging and mating behaviors among male Tibetan antelope with different ages. The occurrence of Tibetan antelope behavior was closely related to their inhabiting environment and physiological condition. In previous studies, the classification of behaviors was largely dependent on body posture, with the potential differences between the function of acts in the same posture being overlooked. The PAE coding system established here could eliminate such uncertainties and provide a robust framework for effectively studying behaviors of Tibetan antelope by accurately recording behavioral functions and conducting long-term population monitoring.
    Soil microarthropod diversity in six subtropical forest plantations.
    LI Xiao-han, LIU Shi-rong, WEI Xue, WU Peng-fei
    2021, 40(5):  1458-1468.  doi:10.13292/j.1000-4890.202105.010
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    We analyzed the differences in taxonomic composition and diversity of soil microarthropod communities among six tree plantations (two coniferous plantations ofCunnighamia lanceolata and Pinus massoniana, and four broad-leaved plantations of Mytilaria laosensis, Castanopsis hicklii, Michelia macclurei andBetuia alnoides) in Pingxiang City, Guangxi Zhuang Autonomous Region, China. A total of 575 soil microarthropod individuals were extracted and identified into three classes, 10 orders, 58 families and 79 genera. The compositional structure of soil microarthropod communities differed among the six plantations, with Oribatida, Prostigmata and Hymenoptera being the dominant orders. The Pielou evenness index of soil microarthropod in the P. massonianaplantation was relatively higher than that in the M. laosensis and C. lanceolata plantations (P<0.05). The abundance of Prostigmata (P<0.05) in theM. laosensisplantation was significantly higher than that in other plantations. The transmission coefficient for diffuse penetration, mean leaf angle, total phosphorus, and soil pH were the main environmental factors driving soil microarthropod communities. The abundance and diversity of soil microarthropods were relatively higher in the C. hickliiplantation and lower in the C. lanceolata plantation, and abundance of Oribatida, Prostigmata and Hymenoptera were also higher in the C. hickliiand M. laosensis plantations. Our results indicated that M. laosensisor C. hickliican be planted to transform theC. lanceolataplantation forests, with the aim to regulate the compositional structure and diversity of soil microarthropod communities.
    Community structure and functional traits of the rocky intertidal macrobenthos in Jiushan Islands, Zhejiang Province.
    FENG Ming, HAN Qing-xi, YAN Run-xuan
    2021, 40(5):  1469-1477.  doi:10.13292/j.1000-4890.202105.007
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    Based on an investigation in Jiushan Islands in September 2017 and September 2018, we analyzed the rocky intertidal macrobenthic composition and community structure, including community composition, abundance, biomass, dominant species, and functional traits, using the methods of clustering and ordination. The results showed that a total of 25 macrobenthic species were recorded, including 18 Mollusca species, 6 Crustacean species, and 1 Cnidaria species. The mean biomass was 1228.40 g·m-2, and the mean abundance was 676.00 ind·m-2. The crustacean Tetraclita squamosawas the major contributor to total biomass, accounting for 42.39%. Mytilus unguiculatus, Littorina brevicula, Mytilisepta virgata and Tetraclita squamosa were the major contributors to total abundance, accounting for 59.96%. The spatial variation of community structure was much greater than temporal variation. Biological zonation was described, including upper Littorinids zonation and lower mussel-barnacle algae zonation. Compared with other rocky intertidal zones in Zhejiang, the species richness, total abundance and total biomass in Jiushan Islands were lower. Our results can provide basic data for future ecological environment assessment of the reserve, marine biological conservation, and scientific research.
     Structure and diversity of butterfly community in the Shiwandashan National Forest Park district of Guangxi.
    HU Jin, LI Jun, WU Hai-pan, HUANG Zong-you, ZHENG Xia-lin
    2021, 40(5):  1478-1490.  doi:10.13292/j.1000-4890.202105.013
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    To explore community structure and diversity of butterfly in the Shiwandashan National Forest Park district of Guangxi, five different habitat types were selected in this region, and a2 km transect was set for each habitat. We investigated butterfly species and abundance fromApril to September in 2016-2018, and analyzed the diversity and compositional similarity of different habitats. A total of 3734 individuals from 155 species belonging to 88 genera and 5 families were collected. Eurema blanda and Stichophthalma howgua were the most abundant species, which accounted for 16.60% and 25.98% of the total abundance, respectively. The number of rare butterfly species was 75. The numbers of genus and species of butterfly in the habitat of mixed farming and forestry area were significantly higher than those in the shrub, lakeside area, conifer and hardwood mixed forest, and rain forest. Butterfly richness in the habitat of mixed farming and forestry area and shrub was significantly higher than those in other habitat types. The highest similarity coefficient was found between the habitats of shrub and lakeside area (0.42), while the lowest was between the habitats of shrub and rain forest (0.29). There was no difference of number of genus, species and individual, and diversity index, evenness index, dominance index and richness index among different months. Therefore, environmental protection of butterflies is recommended in Shiwandashan National Forest Park district due to the high richness of rare butterfly species.
    The characteristics of nearshore fish community in the lower reaches of Yangtze River in autumn.
    DENG Chao, WANG Yin-ping, YAN Yuan-jie, YANG Yan-ping, YOU Yang, LIU Kai
    2021, 40(5):  1491-1498.  doi:10.13292/j.1000-4890.202105.033
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    To understand the characteristics of nearshore fish community in the lower reaches of the Yangtze River in autumn, a survey in different sections was conducted in September 2016. The results showed that a total of 38 species of fish were collected, belonging to 6 orders, 11 families and 31 genera. Cyprinidae was the predominant family, accounting for 63.2% of the total species richness. The community composition was dominated by smallsized fish, which accounted for 81.6% of total species and 98.0% of total catch. The dominant species were Hemiculter bleekeri, Hyporhamphus intermedius, Pseudolaubuca sinensis, and Coilia nasus, accounting for 68.3% of the total catch and 40.6% of the total weight. Among the four feeding functional groups, species from omnivorous and carnivorous groups accounted for a relatively high proportion (47.4% vs. 39.5%). Freshwater sedentary fish was the most common one in four ecological groups (81.6%). Among the three habitats, the pelagic fish accounted for highest proportion (36.8%). The diversity values based on the catch number were as follows: Margalef richness index 4.03, Shannon index 2.18, Simpson dominance index 0.18, and Pielou evenness index 0.60. In conclusion, the diversity of nearshore fish community in Anhui section of Yangtze River was higher than that in Jiangsu section, which is related to the differences in river channel type and human activity intensity.
    Fish resources status in Heishui River, a tributary of the lower reaches of Jinsha River.
    TENG Hang, TIAN Hui-wu, LIU Han-wen, CHENG Bi-xin, YANG Shao-rong, LIU Shao-ping, CHEN Da-qing, DUAN Xin-bin
    2021, 40(5):  1499-1511.  doi:10.13292/j.1000-4890.202105.016
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    Heishui River, located in the lower reaches of the Jinsha River, is an important habitat and a priority tributary for fish conservation in the mainstream of the Baihetan Reservoir area. The structure of fish communities in Heishui River has been changed due to human activities, such as hydropower station construction, overfishing, and sand excavation from river channels. The aim of this study was to understand the status of fish resources and to provide a scientific basis for fish resources protection and ecological restoration in Heishui River. Quarterly samples were collected at 23 sampling sites in Heishui River from November 2018 to September 2019. Fish samples were collected by gill nets (outer mesh 7 cm, inner mesh 2-3 cm, net height 2 m, net length 80 m) and cages (12 m×0.4 m×0.4 m). Species identity, body weight and body length of all fish collected at each sampling site were determined. During the surveys, a total of 44 fish species were identified belonging to 4 orders, 10 families, and 33 genera, with 11 species being endemic species of the upper Yangtze River. Paracobitis varigatus, Schizothorax wangchiachii, Triplophysa daqiaoensis, Zacco platypus, Paracobitis potanini and Glyptothorax sinense were the dominant fish species in Heishui River, which accounted for 28.44%, 28.01%, 16.66%, 7.18%, 5.09% and 3.36% of the total weight of captures, respectively. The similarity of fish community composition between the upper reaches of Sujiawan Dam and the lower reaches of backwater point 765 in Heishui River was the lowest (24.32%), whereas the upper reaches of the Sujiawan dam and the reaches from Songxin dam site to Laomuhe dam site was the highest (61.90%). The results of autecology matrix analysis showed that the fish community in Heishui River was mainly composed of riffle, with lower mouth, and omnivore group. The fish diversity index showed an increasing tendency from upstream to downstream of Heishui River, with no variation of diversity index among different seasons (P>0.05). Abundance biomass comparison (ABC) curve showed that the structure of the fish community in Heishui River was moderately disturbed. Our results suggested that the fish in Heishui River exhibited a trend of miniaturization compared with historical data, and consequently the protection measures should be strengthened.
    Effects of freshwater bivalveCorbicula fluminea on the growth of submerged macrophytes Vallisneria natans.
    GU Jiao, HAN Yan-qing, HE Hu, DAI Yan-yan, ZHANG Peng-fei, LI Kuan-yi
    2021, 40(5):  1512-1520.  doi:10.13292/j.1000-4890.202105.011
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    In the ecological restoration engineering of eutrophic water body, high coverage or biomass of submerged vegetation is the key to shift water body from turbid to clear. Filter feeding bivalves are always used to improve the light condition of water body and to promote the expansion and restoration of submerged vegetation. We conducted a controlled experiment to investigate the effects of different densities (control, low, medium, and high) of Corbicula fluminea on the growth of the submerged macrophytes Vallisneria natans. Compared with the control, the relative growth rate of V. natans in the low, medium and high density treatments increased significantly by 29.1%, 41.5% and 69.3%, respectively, while the abundance of tubers increased by 53.0%, 88.3% and 141.0%. Moreover, the root:leaf ratios of V. natans in the medium and high density treatments were 43.9% and 71.6% higher than that in the control, but no significant difference between the low density and the control. C. fluminea can filter-feed on phytoplankton and suspended materials, promote the growth of benthic algae, improve light conditions, change plant biomass allocation, resulting in a higher root:leaf ratio. Moreover, by biodeposition, C. flumineacan increase N and P concentrations in sediments and leaves, decrease C∶N and C∶P in leaves, and consequently enhance plant growth. Thus, the presence of the bivalve C. fluminea could facilitate the restoration of submerged macrophytes in shallow eutrophic lakes.
    Research advance on the key factors affecting the migration of alpine grassland plants to high altitude or high latitude in Qinghai-Tibet Plateau.
    Awang, ZHANG Li-rong, SUN Jian-ping, ZHANG Su-ren, XIA Lu, WANG Shi-ping
    2021, 40(5):  1521-1529.  doi:10.13292/j.1000-4890.202105.001
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    In response to rapid climate warming, plants in the alpine grasslands of the Qinghai-Tibet Plateau are increasingly migrating to high altitude or high latitude. However, few studies have addressed the processes and mechanisms of species migration, which limits our comprehensive understanding the responses and adaptation of alpine plants to climate warming. In this review, we summarized related studies on plant migration and analyzed the key processes and mechanisms restricting plant migration to high altitude or high latitude in Qinghai-Tibet Plateau from the perspective of life history, including seed dispersal, seed germination, seedling establishment, and plant competition. Generally, seed dispersal is the main factor limiting the migration of alpine grassland plants to high altitude or high latitude. Seed germination and seedling establishment also play a role. The competition among mature plants may have limited influence on plant migration. Currently, many studies on QinghaiTibet Plateau focus on model simulation. In the future, long-term in situ observations and field manipulative experiments should be strengthened to clarify the processes and mechanisms underlying species migration in alpine grassland, which would provide theoretical basis for model simulation, biodiversity conservation, and ecosystem function maintenance.
    Research progress on Pseudanabaenasp. and its metabolite 2-methylisoborneol (2-MIB).
    PANG Yi-ming, CHEN Shu-hua, XU Hang-zhou, LI Yi-zhen, PEI Hai-yan
    2021, 40(5):  1530-1548.  doi:10.13292/j.1000-4890.202105.002
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    Due to global warming and eutrophication, Pseudanabaena sp. has become the main dominant species of cyanobacterial blooms in many water bodies around the world. During the growth of Pseudanabaenasp., a large amount of 2-methylisoborneol (2-MIB) is produced, which severely degrades the aquatic environment and threatens the safety of drinking water. Here, we provide an up-to-date review ofPseudanabaenasp., including its taxonomic rank, morphological features, global distribution, growth and physiological characteristics, as well as the production and removal of its metabolite 2-MIB. Pseudanabaenasp. could adapt to a wide range of temperature, pH and phosphorus concentration, which may explain its wide distribution in the world and its dominant status in many water bodies. In addition, we introduced the synthesis of 2-MIB in Pseudanabaenasp. and pointed out the controversy on the relationship between the growth of Pseudanabaenasp. and its production of 2-MIB. We also compared the removal efficiency of Pseudanabaenasp. and 2-MIB resulted from different drinking water treatments, and summarized the advantages and disadvantages of current technologies. Based on the current state of Pseudanabaena sp. research, we proposed the potential advancement of basic science research and technical development in this field. This review provides reference for future studies on the effective control and removal of Pseudanabaenasp. and 2-MIB.