Table of Content

10 March 2020, Volume 39 Issue 3

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Fine root traits of hemiepiphytic and non-epiphytic Ficus tree species.

NIU Shan, XIA Shang-wen, WANG Gang, YANG Xiao-dong

2020, 39(3):  715-722. 

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Ficus trees, as a key group in the tropical rainforest ecosystem, play an important role in biodiversity maintenance. In this study, we investigated nine functional traits of fine root of ten Ficus species (5 hemiepiphytic species and 5 non-epiphytic species) grown in the Ficus collection garden of the Xishuangbanna Tropical Botanical Garden of Chinese Academy of Sciences, including root diameter, root length, specific root length, specific surface area, branching intensity, root tissue density, nitrogen content, carbon content and carbon to nitrogen ratio. To explain the role of fine root traits in determining the survival strategy of Ficus species, we analyzed the difference in fine root traits between hemiepiphytic and non-epiphytic Ficus species by comparing the natural habitats of the species. The results showed that root length and root diameter of the hemiepiphytic species were significantly higher than that of the non-epiphytic species (P<0.01). Specific root length and branching intensity were significantly lower in hemiepiphytic species than in non-epiphytic species, while no significant difference was found for other traits (P>0.05). Moreover, morphological traits of fine roots in ten Ficus species showed weak relationships with their nutrient traits. Branching intensity, specific root length, and specific surface area of fine roots showed significant negative correlation with root diameter. Our findings suggest that the differences of structure and functional traits of fine roots between two different life forms of Ficus species are adaptive to the environment. The hemiepiphytic Ficus species that were distributed on mountain ridge with dry environment exhibited thick and long fine root, but lower specific root length and branching intensity as compared to non-epiphytic species. These characteristics of hemiepiphytic species may contribute to their strong water absorption. These species might have a close symbiotic relationship with mycorrhizal fungi, allowing their adaptation to relatively dry environment.

Effects of warming and nitrogen addition on fine root stoichiometry of Chinese fir seedlings.

JIANG Qi, CHEN Guang-shui, GUO Run-quan, SONG Tao-tao, CHEN Ting-ting, CHEN Yu-hui, JIA Lin-qiao, XIONG De-cheng

2020, 39(3):  723-732. 

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Global warming and nitrogen deposition are two main global change drivers, often occurring simultaneously. However, most of related studies referred to only single factor. The concentrations of carbon (C), nitrogen (N) and phosphorus (P) in fine roots affect forest ecosystem productivity and C storage. The effects of climate warming and N deposition on fine root chemical components remain unclear. We conducted a two-factor experiment of warming (W, +4 ℃) and N addition (N, +40 kg N·hm^-2·a^-1) at the Forest Ecosystem and Global Change Research Station of Fujian Normal University in Chenda, Sanming, Fujian Province, to explore the effects of warming and N addition on the concentrations and stoichiometry of C, N and P in fine roots of Chinese fir (Cunninghamia lanceolata) seedlings. The results showed that warming increased the concentration of fine root N in spring, but did not affect fine root C and P concentration. Warming decreased C∶N ratio but not N∶P ratio of fine roots in spring. Nitrogen addition increased the concentration of fine root C and N but not P concentration in spring, N addition decreased the C∶N ratio and increased N∶P ratio of fine roots in spring. The interaction between warming and N addition had a significant effect on C concentration of fine root in 1-2 mm diameter class, but not 0-1 mm diameter class. The effects of the interaction between warming and N addition had no significant effect on the concentration of fine root N and P. Our results suggested that warming and N addition could promote nutrient cycling of subtropical forest ecosystem. Nitrogen addition did not change N limitation status of subtropical Chinese fir plantation. The interaction between warming and N addition had different effects on fine root C, N, P elements, which was regulated by seedling C investment tradeoff and the dilution effect.

The ecological stoichiometric characteristics of Alhagi sparsifolia and Karelinia caspia in different habitats.

JING Rui-xue, ZHANG Bo, GUO Ping-lin, ZHANG Zhi-hao, HUANG Cai-bian, ZENG Fan-jiang

2020, 39(3):  733-740. 

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We investigated carbon (C), nitrogen (N), phosphorus (P) and potassium (K) ecological stoichiometric characteristics in plant and soil of Alhagi sparsifolia population (LTC), Karelinia caspiapopulation (HHC) and A. sparsifolia-K. caspia community (GSQL) in the south rim of the Taklimakan Desert. The results showed that the concentrations of available N (AN), available K (AK), N∶P, and N∶K in GSQL soil were significantly higher than those in HHC soil. The concentrations of total N in GSQL leaves were significantly higher than those in HHC leaves, while the concentrations of total P in GSQL leaves were significantly higher than those in LTC leaves. Results of the correlation analysis showed that soil AK concentrations were positively correlated with N∶P and AN across different habitats, but negatively correlated with SOC concentrations. Across all the habitats, foliar K concentrations were positively correlated with SOC, total N and total P concentrations, respectively; foliar N concentrations were positively correlated with SOC and total P concentrations, while N∶P was negatively correlated with SOC and total P concentrations. The SOC concentrations were positively correlated with foliar P and K concentrations, but negatively correlated with N∶K. Soil AN concentrations were positively correlated with foliar N∶K, but negatively correlated with these four element concentrations in leaves. Soil AK concentrations were negatively correlated with these four element concentrations in leaves and positively correlated with N∶K in leaves. Soil N∶P and N∶K were positively correlated with the foilar total C, total P, total K concentrations, respectively. In brief, A. sparsifolia-K. caspiacommunity can improve nutrient state of soil and plant compared with single-species population, suggesting the significance of leguminous species A. sparsifolia in community succession. Our results could provide scientific basis for the restoration of desert ecosystem in the south rim of the Taklimakan Desert.

Soil carbon, nitrogen and phosphorus stoichiometry of Pinus sylvestris var.mongolica plantations with different densities.

WANG Kai, ZHAO Cheng-jiao, ZHANG Ri-sheng, NA En-hang, LIU Jian-hua, WANG Dong-li

2020, 39(3):  741-748. 

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To understand the relationship between tree density and soil nutrient status, we analyzed the concentrations and stoichiometry of soil carbon, nitrogen and phosphorus in Pinus sylvestris var.mongolica plantations planted in 1980 with different densities (490, 750, 1550, 1930 and 2560 trees·hm^-2) in Horqin sandy land. The results showed that with the increases of tree density, the concentrations of soil organic carbon, total nitrogen, total phosphorus and C∶N increased and then decreased, while soil available phosphorus concentration decreased and then increased at 0-10, 10-20 and 20-40 cm soil layers. Lower soil organic carbon concentration and higher available phosphorus concentration were found in the stand density of 490 trees·hm^-2 than others. Soil C∶P and N∶P at the density of 2560 trees·hm^-2 were significantly higher than that of other densities. The concentrations of soil organic carbon, total nitrogen, total phosphorus and available phosphorus were significantly higher at the depths of 0-10 cm than those at 10-20 and 20-40 cm of P. sylvestris var.mongolica plantations with different densities, suggesting that soil nutrients had surface accumulation characteristics. According to the canonical correspondence analysis, the most important soil nutrient factors affected by stand density were soil organic carbon, total nitrogen and total phosphorus. Higher soil organic carbon, total nitrogen, total phosphorus and available nitrogen concentrations and lower soil C∶P and N∶P were found at the stand density of 1550 trees·hm^-2. Therefore, 1550 trees·hm^-2 was an optimal density for P. sylvestris var.mongolica plantations with higher soil nutrient concentrations and better growth.

Effects of stoichiometric characteristics of soil plantlitter on soil nitrogen components in different forests along an elevational gradient of Qinling Mountains.

MA Huan-fei, XIE Meng-yi, HU Han, GUO Yao-xin, REN Cheng-jie, ZHAO Fa-zhu

2020, 39(3):  749-757. 

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We examined the response of soil N components in forests along an elevational gradient to the stoichiometric characteristics of soilplantlitter with four typical forests Quercus aliena var. acuteserrata (QVA), Quercus liaotungensis (QW), Betula albo sinensis (BA), Betula albo sinensisvar.septentrionalis (BAV) in the range of 1300-2600 m elevation in Taibai Mountain. We measured the contents of organic C, total N, total P in soil, leaves, litter and roots, and soil ammonium N, nitrateN and microbial biomass N. We analyzed the stoichiometric characteristics of soil, plants, and litter in different forests and their effects on soil N components. The results showed that: (1) The variation ranges of soil C, N and P in the four forests were 36.77-59.80, 2.91-4.76 and 0.13-0.80 g·kg^-1, respectively. The changes of soil C and N contents in different forests followed the same trend: BAV>BA>QW>QVA; the trend of change for soil P showed QW>BAV>BA>QVA. (2) The foliar N∶P ratio of QVA was lower than 14, indicating that plant growth in QVA was limited by N availability. Foliar N∶P ratio of QW, BA and BAV was above 16, indicating that plant growth in QW, BA and BAV were all limited by P. (3) Microbial biomass N varied significantly among different forests (P <0.05). There was no significant difference in ammoniumN content. The nitrateN content showed QVA (0.33 mg·kg^-1)>BAV (0.28 mg·kg^-1)>QW (0.27 mg·kg^-1)>BA (0.17 mg·kg^-1). (4) The results of redundancy analysis showed that the N∶P ratio of soilplantlitter was an important factor affecting microbial biomass N. Soil C∶N ratio was an important factor affecting ammonium N and nitrate N contents. Our results provide a basis for the rational management of major tree species and the study of nitrogen cycling in forest ecosystems of Taibai Mountain.

Elevational distribution of soil organic carbon, nitrogen and phosphorus contents and their ecological stoichiometry on Maxian Mountain.

LI Xin-xing, LIU Gui-min, WU Xiao-li, JI Geng-hao, LI Li-sha, MAO Nan, XU Hai-yan, WU Xiao-dong

2020, 39(3):  758-765. 

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The stoichiometric characteristics and spatial patterns of soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP) are useful indicators for understanding their responses to global climate change in semiarid areas. In this study, we collected 0-15 cm and 15-30 cm soil samples from seven plots at five altitudes in Maxian Mountain, which is located in the semiarid area, to determine the physicochemical properties of SOC, TN, TP, pH and soil moisture content. The relationships among soil SOC, TN, TP stoichiometry and soil physical and chemical factors were examined. The results showed that: (1) The contents of SOC, TN, TP in the 0-15 cm soil layer were higher than those in 15-30 cm layer. The SOC and TN contents in the top soils increased with elevation, while the TP content did not change. (2) The C∶N ratios first increased and then decreased, while C∶P and N∶P ratios increased with elevation. (3) Soil pH was significantly negatively correlated with SOC, TN content and C∶P ratio in the 0-15 cm soil layer. In the 15-30 cm soil layer, soil pH had no relationship with SOC, TN, TP contents and their stoichiometric characteristics. Soil moisture content was significantly positively correlated with SOC and TN contents both in 0-15 cm and 15-30 cm soil layers. Soil moisture increased with elevation, coinciding with the increases of SOC, TN contents and C∶P, N∶P ratios. Taken together, our results indicated that soil nutrient contents and stoichiometry in the study area were mainly influenced by soil moisture.

Spatial variation of ecological stoichiometry of soil C, N and P in a small catchment of loess hilly area.

SUN Qian, WANG Bing, ZHOU Huai-ping, WANG Xiao-jun, XIE Wen-yan, YANG Zhen-xing

2020, 39(3):  766-774. 

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As the important sources of nutrients for plants and the ecological factors guaranteeing ecosystem health, the contents and stoichiometry of soil carbon, nitrogen and phosphorus have important impacts on primary productivity. Understanding the spatial variability and driving forces of soil C, N and P content and stoichiometry is significant to soil nutrient management and sustainable land use. We analyzed the spatial variability and driving factors of soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP) contents and stoichiometric characteristics in Sanyanjing catchment on the eastern Loess Plateau, using classical statistics with geostatistics methods. Results showed that: (1) The mean contents of SOC, TN and TP were 3.97, 0.83 and 0.6 g·kg^-1, and the mean value of C∶N, C∶P and N∶P was 4.73, 6.02 and 1.26, respectively. There were moderate spatial variation of soil C, N and P contents and stoichiometry. (2) Land use types and landform types had significant effects on SOC and TN, with higher values in forest and grassland than in terrace and abandoned farmland, and higher at the ridge than at the ravine. TP was mainly affected by land use type, with higher value in terrace than the other three land use types. Land use type had a consistent effect on soil C∶N, C∶P and N∶P, with lowest value in the terrace. Moreover, C∶N was significantly affected by slope gradient and landform type, and C∶P by slope gradient and N∶P by elevation. (3) Predicted maps by regression kriging method demonstrated the effects of environmental factors on ecological stoichiometry of soil C, N and P with better prediction accuracy. There were differences for the spatial patterns of ecological stoichiometry across the catchment. Different approaches of organic dry farming, balanced fertilization, soil and water conservation, and reasonable spatial allocation are beneficial to improving the balance of soil C, N and P in the study area.

Effects of soil arthropod on enzyme activities during leaf litter decomposition of bamboo (Fargesia spathacea).

FENG Rui-fang, LIU Yu-wei, GUO Ke-xin, LAN Li-ying, CHEN Ya, LIU Jing-ru, TAN Bo

2020, 39(3):  775-785. 

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To understand the relationship between soil arthropod and soil enzyme activity during litter decomposition, an experiment on decomposition of bamboo (Fargesia spathacea) leaf litter was conducted in a subalpine forest of western Sichuan. Soil arthropods were repelled by adding naphthalene to the forest floor. The effects of soil arthropod on the enzyme activities related to carbon, nitrogen and phosphorus transformation during litter decomposition were examined from April 2016 to April 2018. The results showed that the individual density and species richness of soil arthropod in litterbags were reduced by 49.7%-66.8% and 19.2%-46.3% with naphthalene addition, respectively. The enzyme activities related to carbon, nitrogen and phosphorus transformation in the treatment (naphthalene addition) and control (no naphthalene addition) litterbags showed similar dynamics. The presence of soil arthropod significantly increased the activities of invertase, β-glucosidase, cellobiohydrolase, polyphenol oxidase, peroxidase Nacetyl-β-D-glucosaminidase and acid phosphatase in decomposing bamboo leaf litter of the control litterbags. The contribution of soil arthropod to enzyme activity deceased rapidly after a peak value during litter decomposition. During the study period, soil temperature and species richness of soil arthropod showed positive correlations with invertase activity but negative correlation with the other enzymes. These results suggest that the stimulating effects of soil arthropods on enzyme activities differ with enzyme types and decomposition time, and have a close correlation with the soil arthropod community structure and decomposition environment.

Effects of canopy openness on seedling regeneration of Machilus bombycina after a snow damage.

FENG Li, CHEN Si, XIA Shang-wen, WANG Bo

2020, 39(3):  786-793. 

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Seedling recruitment is a key process in forest regeneration. Canopy openness plays an important role in seedling establishment, growth and survival, especially after extreme climate events. In this study, we monitored the seedling recruitment dynamics of a dominant tree species Machilus bombycina with 194 plots (1 m×1 m) over four consecutive years after a snow damage event that happened in January 2015, in a mid-mountain moist evergreen broadleaved forest in Ailaoshan, Yunnan Province. The effects of canopy openness on the seedling growth, recruitment rate and mortality rate were analyzed by Linear Mixed Model (LMM) and Generalized Linear Mixed Model (GLMM). Our results showed that: (1) canopy openness decreased quickly especially in the first year after the snow damage, from 20.07% to 9.97%; (2) the relative increase rate of existing seedlings’ height was positively correlated to canopy openness during 2015-2016 (P<0.05), but not in other years; the relative growth rate of existing seedlings’ leaves was positively correlated to canopy openness during 2016-2017, but not in other years; (3) canopy openness did not correlate with either seedling recruitment rate or mortality rate. Overall, our findings indicated that the increases of canopy openness after snow damage benefited the growth of M. bombycina seedlings.

Altitudinal changes of functional traits and relationships among traits of bracts in dove tree (Davidia involucrata Baill.).

LIU Ting-ting, LIU Qin-song, XU Wen-juan, XU Zhi-bing, LI Zhong-yang, YANG Bao-zhen, XU Xiao

2020, 39(3):  794-802. 

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Bracts of dove tree (Davidia involucrate Baill.) are adaptive to the driving forces of pollinators and abiotic factors, which are sensitive to environmental factors. To reveal the changes of functional traits and their relationships across different altitudes, the independentsample t test and standardized major axis estimation were used to examine the functional traits and relationships of bracts in dove trees at 1400 m and 1800 m in Longcanggou, Sichuan. The results showed that: (1) Length, width and area of large and small bracts, as well as the total area of single flower bract in the population from low altitude (1400 m) were significantly larger than that from high altitude (1800 m) (P<0.05), while area and mass of large and small bracts in high and low altitude populations grew in proportion. (2) The mass of the large and small bracts and the total mass of the single flower bract in the population from low altitude (1400 m) were significantly higher than those from high altitude (1800 m) (P<0.05). (3) There was no significant difference in the length and the mass of inflorescence axis between high and low altitude populations (P=0.446;P=0.791). There was an allometric relationship between the mass of the inflorescence axis and the length at high altitude, but an isometric relationship at low altitude. (4) The relationships between length, width, area and mass of bracts showed isometric relationships at high and low altitudes. The total area and the total mass of single flower bract showed an isometric growth relationship with the mass of inflorescence axis at high and low altitudes, but showed an allometric growth with the length of inflorescence axis. In all, our results highlighted differences in the functional traits and the relationships between traits of bracts in dove tree at different altitudes, which may be an adaptive strategy to resist environmental interference, protect reproductive organs, and improve pollination rate.

Effects of nitrogen addition and precipitation change on non-structural carbohydrates in Reaumuria soongorica seedlings. 

ZHANG Wan-ting, SHAN Li-shan, LI Yi, BAI Ya-mei, MA Jing

2020, 39(3):  803-811. 

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The amount and distribution of non-structural carbohydrates (NSC) is critical for plant growth and survival. Studies on the effects of nitrogen addition and precipitation change on NSC of seedlings will provide basis for revealing the mechanism of seedling death caused by drought and predicting natural regeneration and cultivation of seedlings under the background of climate change. In this study, we measured the contents of NSC and its components in organs of one-yearReaumuria soongorica seedlings under different precipitation conditions \[decreasing precipitation (W-), natural precipitation (W) and increasing precipitation (W+)\] and nitrogen addition levels \[N₀ (0 g N·m^-2·a^-1), N₁ (4.6 g N·m^-2·a^-1), N₂ (9.2 g N·m^-2·a^-1), N₃ (13.8 g N·m^-2·a^-1)\]. The results showed that the content of NSC in organs of R. soongorica seedlings ranged from 28.8 to 71.8 mg·g^-1, with the highest content in leaves and the lowest in stems. Nitrogen addition and precipitation change had significant effects on starch and total NSC contents in leaves and roots, but had no significant effects on starch and total NSC contents in stems. Across all precipitation conditions, nitrogen addition promoted the accumulation of starch and total NSC in leaves of R. soongorica seedlings. The positive effect of nitrogen addition was more significant when precipitation was increased by 30%. The contents of starch and total NSC in leaves under middle and high nitrogen (N₂ and N₃) were significantly higher than that in leaves under low nitrogen (N₁ and N₀). Under the treatment of low nitrogen and precipitation (N₁W^-), the contents of starch and NSC in leaves reached the minimum value, while the roots reached the maximum value, indicating that R. soongorica could adapt to the stress environment through redistributing NSC in different organs under low nitrogen and drought stress. Under natural precipitation and higher precipitation conditions, the contents of starch and NSC in roots decreased with the increasing nitrogen addition level, and the effects of high nitrogen treatments (N₂ and N₃) were significantly lower than that of the control (N₀). Therefore, leaves are the source of NSC of R. soongorica, and nitrogen addition will promote the accumulation of NSC in leaves. Such effect is closely related to water availability, with the effect being more significant when precipitation increased. However, excessive nitrogen can inhibit the accumulation of NSC in roots. Under drought stress and low nitrogen, R. soongorica could transfer NSC from leaves to roots to adapt to stress.

Effects of different tillage measures on soil carbon emission, carbon balance and economic benefits of summer soybean cropland in Ili River valley.

AN Chong-xiao, ZHANG Yong-jie, DU Xiao-jing, FU Xiao-wen, XU Wen-xiu, SHE Run-xiang, FANG Yan-fei

2020, 39(3):  812-821. 

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To get the suitable cultivation measures to increase summer soybean yield as well as efficiency and realize carbon sequestration in cropland under drip irrigation in Yili River valley, northern Xinjiang, we set up four kinds of soil tillage measures including tillage (T), subsoiling tillage (ST), tillage with plastic film (TP), and no-tillage (NT) in 2017 under the drip irrigation condition. We examined the changes of soil respiration, carbon emissions, plant carbon sequestration, economic benefits and yield of summer soybean cropland in northern Xinjiang. The results showed that the peak value of soil respiration in different tillage measures occurred from flowering stage to pod-bearing stage. Soil respiration rate, total respiration rate, total plant carbon sequestration and yield of summer soybean were the highest in tillage with plastic film, followed by subsoiling tillage, which were significantly higher than that in tillage and no-tillage, with the lowest under no-tillage. Carbon balance of summer soybean cropland ecosystem under different tillage measures was positive. Among various inputs of agricultural production means, the irrigation electricity had the highest carbon emission, accounting for 54.33%-65.24% of the total under each treatment. The carbon emission and cost input of the agricultural production means in TP were significantly different from other three treatments due to the increased input of mulching film (P<0.05). The results showed that subsoiling had the highest economic benefits and net carbon absorption, followed by tillage with plastic film. Further, subsoiling had the best carbon productivity, carbon economic benefits and carbon ecological benefits. The overall performance was ST>TP>T>NT. Subsoiling tillage and plastic film with tillage can significantly improve carbon sequestration and production efficiency in cropland ecosystem. Considering the economic benefits, production input and recovery rate of plastic film, subsoiling tillage has the maximum net carbon absorption, optimal economic benefits and carbon efficiency value, and thus it has a priority for application to increase production efficiency and carbon sequestration in this region.

Effects of organic rice-duck farming on soil physicochemical properties and spatial distribution of bacterial community.

ZHANG Jun, LIU Jing, CHEN Chang-qing

2020, 39(3):  822-829. 

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To clarify the effects of organic rice-duck farming on soil physicochemical properties and bacterial community in different depths of tillage layer, field experiments were conducted under three depths of tillage layer (0-6, 6-13 and 13-20 cm) in organic rice-duck farming (ORDF, 12 years) and transition rice-duck farming (TRDF, 3 years) fields. The results showed that after long-term organic rice-duck farming, soil physicochemical properties of 0-6 and 6-13 cm layers was improved to a large extent, but that in 13-20 cm layer changed slightly. Compared with the transitional rice-duck farming, long-term organic riceduck farming significantly changed the bacterial community composition, resulting in a higher proportion of common bacteria in different ploughed soils. Meanwhile, it also improved the richness and diversity of bacterial community and reduced the difference of bacterial community structure in different depths of tillage layer. This was especially evident in 0-6 cm soil layer, which made the structure of bacterial community more stable. Results of correlation analysis showed that pH, soil bulk density, total nitrogen and nitrate concentration were important factors affecting the spatial distribution of soil bacterial community after long-term organic rice-duck farming. In conclusion, long-term organic rice-duck farming affects the spatial distribution of bacterial community mainly by changing soil properties. Therefore, it is an important model to promote the sustainable development of agriculture.

Effects of elevated O₃ concentration and warming on oxidative jury and antioxidant enzyme activities in leaves of Cleome spinosa.

QIN Zi-qing, XU Sheng, QI Shu-yan, CHEN Wei, HE Xing-yuan, WANG Yi-jing

2020, 39(3):  830-837. 

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An experiment was conducted to examine the oxidation and anti-oxidizing response in leaves of Cleome spinosa, a garden ornamental plant, exposed to different ozone concentrations (80 and 160 nmol·mol^-1) and increasing temperature treatments (2 ℃ higher than control) in open-top chambers (OTCs). The results showed that: (1) A visible leaf injury was observed after seven days with gas fumigation by elevated O₃ (160 nmol·mol^-1), and a large number of bleaching and chlorotic patches appeared on the leaves, whereas no visible injury was observed under 80 nmol·mol^-1. (2) Under high O₃ concentration (160 nmol·mol^-1), malondialdehyde content (MDA), relative conductivity, peroxidase (POD) activity and superoxide dismutase (SOD) activity of C. spinosa leaves significantly increased by 175.7%, 259.9%, 111.4%,54.3%, respectively (P<0.05), while superoxide radical (O₂^-_·) production rate was significantly reduced by 67% (P<0.05). Under the treatment of ozone concentration of 80 nmol·mol^-1, MDA content increased significantly by 65.5% (P<0.05), catalase (CAT) activity decreased significantly by 65.9% (P<0.05), indicating that C.spinosa had high O₃ tolerance ability at the concentration of 80 nmol·mol^-1 O₃. Under the O₃ concentration of 160 nmol·mol^-1 O₃, plant leaves suffered O₃ stress, and they resisted oxidative damage mainly by increasing antioxidant activity (POD and SOD). (3) Under single increasing temperature (IT), MDA content and relative conductivity of C. spinosa leaves increased significantly by 62.1% and 58.1% (P<0.05) respectively, but the O₂^-_· production rate and CAT activity were 28.8% and 71.1% lower than the control respectively (both P<0.05), POD and SOD activities were not significantly different from the control, which may be attributed to enhanced plant metabolism due to higher temperature. (4) Compared with 80 nmol·mol^-1 O₃ alone, CAT, POD and SOD activities under the combination of increasing temperature and elevated O₃ (80 nmol·mol^-1) significantly increased by 141.7%, 72.1% and 107.9%, respectively (P<0.05); O₂^-_· production rate significantly decreased by 51.0% (P<0.05), indicating that the combined treatment of O₃ and increasing temperature exacerbated the O₃ stress suffered by C. spinosa. These findings will provide a scientific basis for the selection and cultivation of plant species in gardens and urban greening in China under the sudden acute events of high-concentration ozone pollution.

Effects of simulated precipitation pattern changes on seed germination and seedling growth of Achnatherum inebrians.

YUE Yong-huan, JIN Gui-li, GONG Ke, DONG Yi-qiang, HAN Wan-qiang, LIU Wen-hao, WU Xue-er

2020, 39(3):  838-846. 

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Changes in precipitation patterns affect seed germination and seedling renewal. In this study, we examined the responses of seed germination and seedling growth of Achnatherum inebrians, an expanding grassland poisonous weed, to simulated precipitation pattern changes, with the aim to provide scientific basis for exploring the occurrence of A. inebrians and predicting its potential distribution range. Twofactor control experiments of precipitation (W_60%, W_30%, W, W+30%, W+60%) and precipitation interval (T5, T10) were carried out using an environmentally controlled incubator. The results showed that: (1) Under the same precipitation interval, the emergence speed and emergence rate of A. inebrians seeds were enhanced by increasing total precipitation. Wider precipitation interval promoted the emergence of A. inebriansand acce lerated emergence process under W and W+30% conditions. (2) Irrespective of the precipitation interval changes, increasing total precipitation by 60% (W+60%) significantly enhanced emergence energy and emergence index (P<0.05), while prolonging precipitation interval significantly enhanced emergence rate, emergence energy and emergence index under the conditions of W and W+30% (P<0.05). (3) Whether the precipitation interval changes or not, 30% reduction of total precipitation (W_30%) significantly restrained the growth of radicle and seedlings. The growth of seedlings was significantly promoted by 60% increases of total precipitation (P<0.05), but the root seedling ratios were significantly reduced by increasing the total precipitation by 30% (W+30%) and 60% (W+60%) (P<0.05). Therefore, increasing or decreasing precipitation will affect the emergence and growth of A. inebrians. However, in a certain range of precipitation, prolonging precipitation interval will promote the emergence and seedling growth of A. inebrians.

Effects of GA₃ treatment on respiratory metabolism of maize seeds under low temperature stress.

REN Xiao-song, WANG Zi-mu, JIAO Jian, TIAN Li-xin, LIU Zhao-yue, LI Jing

2020, 39(3):  847-854. 

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We examined the effects of GA₃ treatment on soluble sugar and soluble protein content, amylase activity and key enzyme activities in the embryos during germination of maize seeds under low temperature stress for two corn varieties, low temperature sensitive “FH No. 1” and resistant “ZD958”, with the method of GA₃ soaking seeds (20 mg·L^-1 for “FH No. 1”, 5 mg·L^-1 for “ZD958”). The results showed that GA₃ soaking treatment significantly increased the soluble sugar content and soluble protein accumulation in maize embryos, and enhanced the cell osmotic potential under low temperature stress. The activities of α-amylase, β-amylase and total amylase were significantly increased. The activities of malate dehydrogenase (MDH), pyruvate kinase (PK), combined enzymes (G-6-PDH and 6-PGDH) were increased. The efficiency of EMP, TCA and PPP pathways was improved, which facilitates cellular material metabolism and energy supply. GA₃ soaking treatment can significantly improve the resistance of seeds to low temperature, thus promoting their germination under low temperature stress.

Effects of exogenous 2,4-epibrassinolide on the absorption, transportation and allocation of inorganic ions in Avena sativa L. seedlings under NaCl stress.

KOU Jiang-tao

2020, 39(3):  855-864. 

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To investigate the induction effect of exogenous 2,4-epibrassinolide (EBR) on saltresistance of oat seedlings and reveal the potential physiological mechanism, we examined the effects of EBR on the absorption, transportation, and allocation of inorganic ion in oat seedlings under NaCl stress, with Avena sativacv. ‘Qingyin No. 2’ and cv. ‘Jiayan No. 2’ as materials. Results showed that under 100 mmol·L^-1 NaCl stress, the content of Na⁺ and Cl^- in leaf and root of ‘Qingyin No. 2’ and ‘Jiayan No. 2’ seedlings increased significantly. NaCl stress had antagonistic effects on cationic absorption, with reductions of contents of K⁺, Ca²⁺, Mg²⁺, Fe²⁺, Mn²⁺, Cu²⁺, and Zn²⁺ as well as a disordered ion equilibrium in leaf and root of oat seedlings. Under 100 mmol·L^-1 NaCl stress, the addition of 0.01 μmol·L^-1 EBR significantly reduced the content of Na⁺ and Cl^- in leaf and root of ‘Qingyin No. 2’ and ‘Jiayan No. 2’ seedlings, while the absorption of K⁺, Ca²⁺, Mg²⁺, Fe²⁺, Mn²⁺, Cu²⁺, and Zn²⁺ was improved, and the ratios of K⁺/Na⁺, Cl^-/Na⁺, Ca²⁺/Na⁺, Mg²⁺/Na⁺, Fe²⁺/Na⁺, Mn²⁺/Na⁺, Cu²⁺/Na⁺, and Zn²⁺/Na⁺ were increased significantly; the transport ratio of inorganic ions and the transport selectivity ratio of cations were effectively regulated, and the steady state of ion recovered. Our results suggest that exogenous EBR could alleviate the toxicity of Na⁺ and Cl^- to oat seedlings under NaCl stress and effectively regulating the selective absorption, transportation, and allocation of inorganic ions in oat seedlings, with a positive regulatory effect on ion steady-state equilibrium in oat seedlings.

Effects of elevated atmospheric CO₂ concentration on biogenic volatile organic compound emission from woody plants.

LAI Jin-mei, PAN Ruo-qi, LIU Yan-fei, HUANG Xing-ran, FANG Xiong, JIN Shao-fei, YI Zhi-gang

2020, 39(3):  865-871. 

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Biogenic volatile organic compounds (BVOCs) play an important role in the formation of near-surface ozone and secondary organic aerosols. Elevated atmospheric CO₂ concentration can significantly affect the BVOCs emission from plants. We carried out a meta-analysis with the related published data. Our results showed that: (1) BVOCs emission from different woody plants (evergreen vs. deciduous) significantly decreased with elevated atmospheric CO₂ concentration. (2) In terms of different functional types, increased atmospheric CO₂ concentration mainlyreduced the BVOCs emission from deciduous plants but increased that from evergreen plants. (3) For BVOCs species from plants, elevated atmospheric CO₂ concentration significantly reduced isoprene emissions from deciduous and evergreen plants, while it had no effect on monoterpene emissions. Our results can provide a basis for clarifying the response of BVOCs emission from terrestrial ecosystems to the elevated atmospheric CO₂ concentration.

Effects of dissolved oxygen on tolerance of juvenile Hippocampus erectus to ammonia-N and histopathology of gill and liver under ammonia-N stress.

LUO Hui-yu, WU Shui-qing, ZHENG Le-yun, LIN Jin-bo, WANG Quan-yang

2020, 39(3):  872-879. 

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We investigated the toxic effects of ammonia-N on juvenile lined seahorse (Hippocampus erectus). The half lethal concentration of ammonia-N to lined seahorses for 96 hours (96 h LC₅₀) was evaluated under normal oxygen level (4.32-5.12 mg·L^-1) and high oxygen level (8.22-9.46 mg·L^-1), respectively. We examined the histopathological changes of gill and liver of juvenile lined seahorses under ammonia-N stress (control, 6, 9, 12 mg·L^-1). The results showed that the 96h LC₅₀ of ammonia-N and non-ionic ammonia to juvenile lined seahorses at normal oxygen level was 10.22 and 0.16 mg·L^-1, with a safe concentration of 1.02 and 0.016 mg·L^-1, respectively. When treated with high dissolved oxygen, the 96h LC₅₀ of ammonia-N and nonionic ammonia to juvenile lined seahorses increased to 12.68 and 0.2 mg·L^-1, with a safety upper limit of 1.27 and 0.02 mg·L^-1, respectively. The juvenile lined seahorses exposed to ammonia displayed histopathologic abnormalities in gill and liver, which were dependent on dose and duration. AmmoniaN stress caused gill lesions, including telangiectasis, vascular congestion and fracture, necrosis of epithelial cell and hyperplasia of chloride cells. Nucleomegaly, hepatocytes swelling, sinusoids dilatation and blurred cell contour were observed in liver. The enhancement of ammonia-N stress increased liver lesions, causing hydropic degeneration, dissolution and vacuolation of hepatocytes, resulting in loose organization of hepatic tissue. In summary, ammonia nitrogen stress above threshold to juvenile lined seahorse would damage the structure of gill and liver tissue. Appropriately increasing the concentration of dissolved oxygen could effectively alleviate the toxicity of ammonia N on juvenile lined seahorse.

Distribution characteristics and influencing factors of the benthic macroinvertebrate functional groups in the salt marshes of Chongming Dongtan.

WANG Yan, TONG Chun-fu, TANG Lin, WU A-na, WU Feng-run

2020, 39(3):  880-892. 

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Based on monthly surveys in the salt marshes of Chongming Dongtan in the Yangtze Estuary, we analyzed the distribution characteristics of macroinvertebrate functional groups and driving factors, especially exotic plants, along an elevation gradient. The results showed that dominant species varied across different elevations. Both omnivores and herbivores were dominant functional groups in the middle tiddal zone, while omnivores were dominant in the other sites. Both the abundance and biomass of each functional group significantly varied along the elevation gradient (P<0.01), and such variations differed for different functional groups. The abundance and biomass of carnivores in the lowest mudflat were significantly higher than those in the vegetated zones (P<0.05), while those of herbivores in the middle tidal zone, occupied by Scirpus mariqueter, were significantly higher than that in the other sites (P<0.05). Main habitat factors (including total phosphorus, total nitrogen, organic matter, available phosphorus, nitrate nitrogen, ammonium nitrogen contents and median-sized grain of the sediment), and shoot height and aboveground biomass of the vegetation, varied significantly along the elevation gradient (P<0.05), and the characteristics of those variations changed among different factors. The invasion of Spartina alterniflora did not change the dominant functional group in the high tidal zone, but increased the abundance and biomass of omnivores (P<0.05). Some environmental factors, including available phosphorus, nitrate nitrogen, ammonium nitrogen and organic matter of the sediment, were significantly different between invasive S. alterniflora and natural Phragmites australis zones (P<0.05). The variations of the composition and distribution of the benthic macroinvertebrate functional groups were determined by the combination of multiple environmental factors, while the main factors varied with groups. Nutrient content and salinity of the sediment were the most important factors driving the abundance and biomass of the functional groups, respectively. Therefore, it is necessary to consider the comprehensive effects of various environmental variables including hydrology, vegetation and sediment when we examine the distribution characteristics and underlying mechanism of functional groups of benthic macroinvertebrate.

Status of early fish resources of drifting egg fishes in the estuary of the Yalong River.

WANG Dao-qun, TIAN Hui-wu, TANG Xi-liang, XU Huo-qing, DUAN Xin-bin, LIU Shao-ping, XIANG Peng, CHEN Da-qing

2020, 39(3):  893-899. 

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To understand the status of early resources of drifting egg fishes, we carried out surveys on the fishes at early life history stage in the Yalong River estuary located in Yanbian County from June to July in 2016-2018. The results showed that five species of drifting egg fishes were identified, belonging to two families and one order. Three endemic fishes of the upper Yangtze River were identified among the five species, namely Leptobotia elongata, Jinshaia sinensisand Jinshaia abbreviata. The abundance of fish eggs flowed through the Yalong River estuary was 3.5×10⁶, 13.78×10⁶ and 3.87×10⁶ ind from 2016 to 2018, respectively. There were eight spawning peaks during surveys (2, 4, and 2 times in 2016, 2017 and 2018 respectively). The main spawning period of fishes was in the middle and late June. It was estimated that Yanbian County and Deshi Town of Miyi County in Panzhihua were the main spawning grounds for drifting eggs in the Yalong River estuary.

Photoammonification of typical low-molecular-weight dissolved organic nitrogen in surface water system.

ZHANG Yu-tong, ZHANG Ruo-chun, LI Cai, SUN Pei-zhe, YANG Yan-wen, JI Hao-dong, LIU Wen3, LI Si-liang

2020, 39(3):  900-908. 

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Phototransformation, a process from dissolved organic nitrogen (DON) to dissolved inorganic nitrogen (DIN), is an important component of nitrogen cycle in surface aquatic system. In this study, we measured photoammonification rates of typical low-molecular-weight DON (e.g., amino acids, nucleotides, and urea) under different conditions to elucidate the potential role of DON structures, light sources and water matrices during photoammonification. Results showed that under simulated sunlight, amino acids with aromatic moieties produced differentamounts of NH₄⁺. L-tyrosine and L-tryptophan exhibited the highest ammonification rates, up to 50% transformation within 6 hours, whereas there was negligible photoammonification rate of urea, adenine and cytosine. Under natural sunlight, L-tyrosine and L-tryptophan produced NH₄⁺ by phototransformation in both buffer solution and natural water sample, while all aromatic amino acids and L-histidine produced NH₄⁺ only in natural water sample by phototransformation. Visible light did not contribute to photoammonification of the low molecular weight DON. These results indicated that photoammonification was affected by light sources and matrix constituents. Meanwhile, the structures of DON affected photoammonification. For example, at optimal conditions of irradiation, all nitrogen atoms of L-histidine could be converted into NH₄⁺ by photoammonification, whereas only one of N atoms in L-tryptophan was transformed into NH₄⁺. Based on density functional theory calculation, there was significantly negative correlation between photoammonification rates and E_LUMO-E_HOMO of amino acids. Our results demonstrated the complex of DON photoammonification in surface water system. The significant role of photoammonification of low-molecular-weight DON in surface water system should be considered in nitrogen cycle, water quality evolution and the assessment of eco-environment.

Effects of hydrodynamic disturbance on algal toxins in eutrophic lakes.

ZHANG Hong-liang, XIE Meng-ping, TIAN Wei, TANG Xiang-ming

2020, 39(3):  909-919. 

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Taihu Lake is a typical shallow large lake, which is disturbed by wind wave all the year round due to the monsoon. To understand the effect of disturbance from wind and wave on the release of microcystin (MC) by Microcystis spp. in Taihu Lake, water samples containing Microcystis bloom were collected in July 2018. Three treatments including control, intermittent disturbance and continuous disturbance were set up at Taihu Laboratory for Lake Ecosystem Research, Chinese Academy of Sciences to investigate the changes of MC during 19 days. Ourresults showed that the changes of MC concentration under the three treatments were consistent, which increased during 1-13 d and decreased with different margins. The average concentration of MC in control was 1.69 μg·L^-1, which is significantly lower (P<0.05) than those in the intermittent(1.81 μg·L^-1) and continuous disturbance group (1.86 μg·L^-1). The differences of MC concentration between the two disturbance groups were not statistically significant. During 1-7 d, the contents of MC per unit decreased in all the three treatments, with no significant differences among them (P>0.05). During 10-19 d, the contents of MC per unit in all treatments increased and then decreased, with significant differences among groups (P<0.05). The average contents of MC per unit in control, intermittent and continuous disturbance groups were 0.55, 1.20 and 1.98 μg·10⁸ cells^-1, respectively. Under this experiment condition, the concentration of MC was significantly negatively correlated with nitrogen and phosphorus, and positively correlated with water temperature, SS and Chla. Our results indicated that hydrodynamic disturbance could increase the MC concentration and MC content per unit in lake waters.

Spatial distribution and pollution characteristics of heavy metals in sediments of the upper reaches of Ganjiang River.

LI Feng-guo, CHEN Ming, SHI Yan-li, ZHENG Xiao-jun, LIU Yan, LIU You-cun, TAO Mei-xia, HU Lan-wen

2020, 39(3):  920-927. 

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We collected 38 samples from the upper reaches of the Ganjiang River, Jiangxi, China, with the aim to clarify the characteristics of heavy metal pollution in the surface sediments The contents of heavy metals in sediments were analyzed by inductively coupled plasma mass spectrometer (ICP-MS, Agilent 8800). The Nemerov comprehensive pollution index, geoaccumulation index, principal component analysis and sediment quality benchmarks were used to investigate the pollution degree of heavy metals and their possible sources, and to evaluate the ecological risks. The results showed that the average contents of nine heavy metals including W, Cr, Mn, Cu, Zn, As, Cd, Hg and Pb were 12.30, 4.40, 999.84, 9.72, 293.81, 47.66, 2.85 and 1.34, 63.68 mg·kg^-1, respectively. Except for Cr and Cu, the average of heavy metals exceeded the soil background value of Jiangxi Province. The results of Nemerov comprehensive pollution index assessment showed that 47.37% of the sampling points in the surface sediments were seriously polluted, and 28.95% of the sampling points were obviously polluted. The pollution degree was in the order of Zhangshui section > Taojiang section > Gongshui section. According to the results of geoaccumulation index assessment, Mn, As, W and Pb were mildly polluted, while Cd and Hg were moderately or heavily polluted. Results of principal component analysis showed that As, W, Hg and Pb had similar pollution sources, while Cr and Mn had similar pollution sources. The results of sediment quality baseline analysis showed that Cd and Hg were the major heavy metals that might have toxic effects on benthos, mainly distributed in Zhangshui section and Taojiang section.  

Ecological risk assessment of heavy metal pollution in soil of a lead-zinc mine area in Danzhai County, Guizhou Province, China.

GAO Yue, SUN Rong-guo, YE Cai, LIU Chao-shu, DAI Guang-qian, FAN Li

2020, 39(3):  928-936. 

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The ecological risks of heavy metals (Pb, Zn, Mn, Cu, Hg, and Cd) in soil wereevaluated in a lead-zinc mine area located in Danzhai County, Guizhou Province, China. We analyzed concentrations and chemical species of heavy metals and assessed ecological risk using potential ecological risk index (RI) and the ratio of secondary phase to primary phase. The results showed that concentrations of Pb, Zn, Mn, Cu, Hg, and Cd in 0-10 cm soil layer were 5.69,3.91, 0.80, 0.58, 9.64 and 1.50 times higher than background values of Guizhou Province, respectively. Compared with the risk screening values of heavy metals in Risk Control Standard for Soil Contamination of Agriculture Land in China (GB 15168-2018), concentrations of Pb, Zn and Cd were high in the tailings accumulation area. For 10-20 cm soil layer, concentrations of Pb, Zn, Hg, and Cd were higher than the background values of Guizhou Province. The concentrations of Zn and Cd exceeded the risk screening value of heavy metals in the tailings accumulation area, the cropland in the tailings accumulation area, and the downstream of the river near the tailings. Residual fraction was the predominant species for all heavy metals. Exc-Pb(20.9%), CARB-Zn (26.2%), RED-Mn (31.8%) and OM-Mn (48.7%) accounted for the highest proportion in the exchangeable fraction, carbonate bound fraction, iron-manganese bound fraction and oxide bound fraction, respectively. The bioavailability of heavy metals was characterized by the order of Zn>Pb>Hg>Cd>Cu>Mn. The potential bioavailability heavy metals was characterized by the order of Mn>Pb>Cd>Hg>Zn>Cu. Results of potential ecological index assessment showed that there were high ecological risk in the cropland in tailings accumulation area, village of downstream of the tailings accumulation area and the downstream of the river near the tailings. Contribution rate of Hg to the potential ecological hazard index was 60.9%. Soil Mn and Cd had the greatest ecological risk as indicated by the ratio of secondary phase to primary phase.

Effects of road on diurnal group pattern and vigilance behavior in goitered gazelle.

WANG Mu-yang, JI Sheng-nan， CHEN Chen, XU Wen-xuan, HAN Lei, YANG Wei-kang

2020, 39(3):  937-943. 

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Understanding the effects of road on behavior pattern of endangered ungulates and expounding their behavior response and adaptation mechanism to the road effects are important to making comprehensive measures and schemes for effective conservation of endangered species under the disturbance of road projects. From June to August in both 2015 and 2016, we investigated the effects of national highway G216 on the group patterns and vigilance behaviors of goitered gazelle (Gazella subgutturosa) in Kalamaili Mountain Nature Reserve. Our results showed that the disturbance from G216 forced goitered gazelles to increase their group size, and that goitered gazelles invested much more time in vigilance when they were closer to G216. A distance of 500 m to G216 may be a threshold on the group pattern and vigilance behavior. Similar to the predation risk, disturbance of G216 forced goitered gazelles to adjust their group size and vigilance level. In the future, researches on behavioral response and adaptation mechanism under road project disturbances should be conducted, the results of which would help produce management measures to reduce the negative impacts on the wildlife in this area.

Assessment of eco-environment vulnerability in the proposed construction area of the Selincuo-Puruogangri National Park.

LIU Xiao-na, LIU Chun-lan, ZHANG Cong-lin, CHEN Long, HUANG Bao-rong

2020, 39(3):  944-955. 

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The proposed construction area of the Selincuo-Puruogangri National Park (Se-Pu National Park) is endowed with the most abundant rare and endangered species in the alpine grassland ecosystem, and is the centralized distribution area of lots of high-quality natural landscapes and cultural heritages. The local fragile eco-environment is the primary issue that should be considered during the establishment of the Selincuo-Puruogangri National Park. Based on the research scheme of “factor identification, index construction, single factor assessment, integrated assessment”, we evaluated single-factor sensitivity of freeze-thaw erosion, soil erosion, land desertification, soil wind erosion, and habitat environment respectively, after identifying eco-environment vulnerability factors. Combined with the limiting factors of elevation, slope and important ecosystems, comprehensive assessments of the eco-environment vulnerability of the study area were conducted to provide scientific basis for the delineation of spatial extent, the function division of national park, and moderate development of eco-tourism. The results showed that: (1) There are serious eco-environmental problems, including freeze-thaw erosion, soil erosion, grassland degradation and biodiversity loss in this area. (2) From the perspective of different single factor sensitivity, the area mainly had moderate and high sensitivity of habitat environment, moderate sensitivity of soil erosion, mild and moderate sensitivity of freezethaw erosion, insensitivity and mild sensitivity of soil wind erosion. (3) The comprehensive assessment showed that the eco-environment of the study area is highly fragile, with a proportion of 57.60% of highly vulnerable areas, mainly distributed in the west and north parts. The lowly vulnerable areasaccount for 7.38% of the total area, mainly distributed in the eastern region. Nima County has the smallest distribution area of low vulnerability, while Anduo County has the most. The area with high vulnerability is widely distributed in Shuanghu County. (4) It is suggested that the future human activities and tourism development should be mainly allocated in low vulnerable areas in the national park. Meanwhile, the protection of ecosystem integrity and authenticity in the highly vulnerable areas should be strengthened.

Temporal and spatial evolution of greenspace system and evaluation of ecosystem services in the core area of the Yangtze River Delta.

2020, 39(3):  956-968. 

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Under the background of prominent contradiction between economic construction and environmental protection, it is of great significance to examine the spatiotemporal evolution characteristics of regional greenspace system and analyze the effects of human factors on ecological services of greenspace system, which would facilitate the improvement of greenspace resource management and the promotion of sustainable and coordinated development of the region. Based on the methods of landscape ecology and the equivalent factor evaluation of ecological service value, using the spatial analysis function of software ArcGIS 10.2, we analyzed the spatiotemporal evolution characteristics and ecological service value of the greenspace system in the core area of the Yangtze River Delta from 1990 to 2015. The results showed that: (1) The temporal changes of greenspace landscape area in the core area of the Yangtze River Delta had the stage characteristics, with a trend of first expanding and then decreasing. The transformation between greenspace landscape and other land use types had the characteristics of stage and directionality. As a whole, the landscape pattern of greenspace was homogeneous in the initial stage and heterogeneous in the later stage. (2) The value of greenspace ecosystem services in the core area of the Yangtze River Delta showed significant temporal changes, with different greenspace landscape types having different stage characteristics. Among all the types of ecosystem services, regulation services contributed most to the overall ecological service value of the greenspace system. (3) The value of greenspace ecosystem services exhibited imbalance between the north and the south of the region, being higher in the south and lower in the north. Among them, the value of greenspace ecosystem services in Hangzhou was the highest at different stages. Regional topography and geomorphology were important factors affecting the value of regional ecological services.

Evaluation of regional eco-environmental quality before and after earthquake in Jiuzhaigou County, Sichuan Province.

HU Xiang, BAI Wen-ke, DONG Xin

2020, 39(3):  969-978. 

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Based on remote sensing data and the geographic information system processing software platform, we analyzed the eco-environmental quality of Aba Tibetan and Qiang Autonomous Prefecture in Sichuan Province before and after the 2017 8·8 earthquake. We used the Landsat 8 OLI satellite sensor to obtain remote sensing image data of December 31, 2016 (before the earthquake) and December 18, 2017 (after the earthquake), and extracted the normalized vegetation index, humidity component, surface temperature, and normalized soil index as four indices of green degree, humidity, heat degree and dryness, respectively. We used principal component analysis to obtain the Remote Sensing Ecological Index (RSEI) from these four indices. According to the RSEI, the eco-environmental quality of Jiuzhaigou County was categorized as excellent, good, medium, poor and worse. In 2016, 24.8% of Jiuzhaigou County areas were in an excellent eco-environment level, which fell to 19.84% after the earthquake in 2017. In 2017, area proportions of the eco-environment quality at poor and medium levels showed an upward trend, accounting for 17.99% and 33.93%, respectively. The proportion of the area with excellent eco-environment quality in the buffer zone of 15.5 km from the epicenter of the earthquake decreased most, accounting for 5.01%. In summary, the Jiuzhaigou earthquake in 2017 had significant impacts on the eco-environment quality, particularly in the buffer zone of 15.5 km. The Jiuzhaigou National Nature Reserve was most impacted among the three nature reserves of Jiuzhaigou County. Our results provide scientific basis for ecological monitoring, disaster assessment, and restoration in Jiuzhaigou area.

Ecological vulnerability assessment   of coral reef: A case study of Si Chang Island, Thailand.

HU Wen-jia, CHEN Bin, Arnupap Panichpol, ZHANG Dian, LIU Xin-ming, GU Hai-feng, Ajcharaporn Piumsomboon, CHAO Bi-xiao, ZHENG Xin-qing

2020, 39(3):  979-989. 

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Coral reef ecosystems are seriously threatened by environmental changes and human activities. Protecting coral reef ecosystems is a hotspot in global marine ecosystem conservation. Quantitative assessment of ecological vulnerability of coral reefs would provide important scientific basis for coral reef conservation management. Taking Si Chang Island, Thailand as the study area, a versatile vulnerability assessment approach was developed combined with spatial analysis technology. Based on the ESA model, a comprehensive vulnerability index and related indicators were built for coral reefs. The source and composition of coral reef vulnerability were identified using the established model, while the spatial distribution of vulnerability was visually displayed. The results showed that the vulnerability of coral reef on northeast side was greater than that on the southwest side of the Si Chang Island. The key impact factors of local coral reefs were tug sewage, harbors and piers, water transparency, etc. The zoning management countermeasures were proposed for the conservation and restoration of coral reefs based on our findings. This study provided a feasible example for the ecological vulnerability assessment of Indo-Pacific reefs, and can also be taken as a reference for the sustainable management of coral reefs in China.

Spatial-temporal changes and tradeoff/synergy relationship of ecosystem services in Xinjiang.

WANG Xiao-feng, CHENG Chang-wu, YIN Li-chang, FENG Xiao-ming, WEI Xin-dong

2020, 39(3):  990-1000. 

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We quantitatively estimated net primary productivity (NPP), soil conservation and water yield from 1982 to 2015 in Xinjiang based on CASA model, RUSLE model, and InVEST model. The spatial analysis and hot spot analysis were used to characterize the regional variation of ecosystem services. The Sen’s method was used to analyze the temporal and spatial variations of ecosystem services. The tradeoffs and synergies among three ecosystem services were explored based on partial correlation analysis. From 1982 to 2015, the variation of annual NPP in Xinjiang was relatively stable with an increasing trend, whereas the inter-annual variation of soil conservation and water yield fluctuated greatly. Both soil conservation and water yield were positively correlated with NPP. The changes of soil conservation and water yield were synergistic, and the strong synergies being dominant. Over the whole examined period, the synergistic interaction-between NPP and soil conservation tended to weaken in the whole province. The relationship between NPP and water yield transferred from tradeoffs to synergies. The synergies between soil conservation and water yield were strengthened first and then weakened.

Modeling spatial distribution of potential vegetation NPP in China.

PAN Jing-hu, XU Bai-cui

2020, 39(3):  1001-1012. 

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Potential NPP refers to the NPP that is generated in the natural state when the impacts of human beings on the ecological environment are excluded. The study of spatial pattern of potential vegetation productivity has become basic work toward the ecological environment rehabilitation and reconstruction in China. Data from 592 meteorological stations were used to build climate models, while regression trees were applied to estimate potential NDVI based on climate variables and training data of actual NDVI. Then, potential NPP of China was simulated using CASA model and potential NDVI data. The results showed that China’s potential NDVI and potential NPP show a pattern of high in the south and low in the north and high in the east and low in the west. The lower potential NPP occurred at desert, Gobi and other arid areas, and the higher potential NPP are mostly distributed in low and middle plain. In particular, the spatial pattern can be divided into relatively higher and lower parts in 400 mm equivalent precipitation line. The average potential NDVI and potential NPP of China were 0.396 and 319.31 g C·m^-2 respectively. The mean value of potential NPP in summer was the highest, followed by spring and the lowest in winter. According to the difference between potential NPP and actual NPP in 2015, the national vegetation restoration area can be divided into three parts: high potential area in the west, low potential area in the north, and non-potential area in the south. Spatial simulation of potential NDVI and potential NPP can separate the direct impact of human activities on natural ecosystems from the impact of climate change and quantify the differences between real and potential ecological conditions under external pressures, and thus could provide scientific basis for formulating differentiated ecological restoration strategies.

Paternal behavior of birds and the associated endocrine regulation mechanism.

GONG Da-jie, CAO Rui-dong, CHEN Zhuo, ZHANG Ming-yu, MIAO Fei, YANG Min-na, YU Peng

2020, 39(3):  1013-1021. 

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Flight ability greatly expands the distribution range of birds, allowing for a rapid response to local environmental changes. In the early stages of ontogenesis, chicks are unable to adapt to changes due to lacking flight ability, and thus require much parental care. Parental behavior of birds is different from that of mammals, which mainly relies on maternal care. Male birds have many paternal behaviors, such as nesting, brooding, and rearing fledglings. We summarized related studies on paternal behaviors and underlying mechanisms. (1) Nesting behavior is often accompanied by male courtship behavior. Testosterone promotes both nesting behavior and courtship behavior, while vasopressin promotes nesting behavior. (2) Incubation could transfer heat and thus could protect and support the development of offspring. Meanwhile, it stimulates the release of prolactin, which further promotes the incubation behavior. During this process, testosterone is reduced to a basic level. (3) The breeding behavior is related to the growth rate of young birds, with altricial birds needing more paternal care. Similar to the regulation of incubation behavior, prolactin increases and testosterone decreases. Progesterone is involved in regulating paternal behavior. (4) Environmental stress regulates the paternal behavior by changing corticosterone and prolactin levels. In conclusion, testosterone and prolactin could regulate the development and expression of paternal behavior of birds, which are affected by environmental pressure. Studies on the neuroendocrine mechanisms are limited and the mechanisms require further investigation.

Research advances and applications on oxygen isotope anomaly in atmospheric nitrate.

DONG Xin-yuan, GUO Qing-jun, WEI Rong-fei, TAO Zheng-hua, TIAN Li-yan

2020, 39(3):  1022-1032. 

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In recent years, increasing atmospheric nitrate resulted from anthropogenic activities negatively affects human health and ecological environment. It is important to identify the sources and formation mechanisms of nitrate. As a powerful tracer, the multi-oxygen stable isotopes in nitrate are widely used for investigations of aerosol, aquatic ecosystems, soils, forests, and paleoclimate. In this review, experimental methods and causes of oxygen isotope anomaly (Δ¹⁷O) in atmospheric nitrate are introduced, and the tracing mechanisms of Δ¹⁷O are discussed according to the differences of nitrate formation processes. Finally, the applications of Δ¹⁷O are reviewed in the studies of atmospheric chemical reaction mechanism. According to the progress and problems in literature, we proposed the future directions of the researches on Δ¹⁷O in nitrate.

Advances in microbial mediated anaerobic oxidation of methane and its influencing factors.

LIU Jun-xia, CHEN Huai, XUE Dan, GAO Yong-heng, LIU Jian-liang, YANG Jun

2020, 39(3):  1033-1044. 

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Reduction of methane emission is a research hotspot in the field of climate change. The anaerobic methane oxidation (AOM) process has been neglected as a methane sink, but in fact plays an important role in regulating global methane balance and mitigating greenhouse effect. AOM microorganisms could utilize methane as electron donors to reduce sulfate (SO₄^2-)^, nitrite (NO₂^-), nitrate (NO₃^-) and metal ions (Fe³⁺, Mn⁴⁺, Cr⁶⁺). AOM process is the key for the coupling of carbon, nitrogen, and sulfur cycles. We systematically analyzed the progress in research of AOM types, underlying mechanisms, related functional microbial groups (ANME-1, ANME-2, ANME-3, NC10, MBG-D) and key regulatory factors affecting the AOM process. We found that more than 80% of the studies focused on the AOMrelated processes of the most common electron acceptor types (SO₄^2-, NO₃^-, NO₂^-, Fe³⁺, Mn⁴⁺), ignoring the coupling process with potential new electron acceptors (AQDS, HAsO₄^2-, Cr⁶⁺, ClO₄^-, etc.), the corresponding microbial types, and the underlying mechanism. We proposed future direction of AOM research with the aim to provide new ideas for finding out the ecological distribution of methane anaerobic oxidizing bacteria in different ecosystems and mitigating global greenhouse gas emissions.

Integrated identification and classification of rural ecological land.

FEI Jian-bo, XIA Jian-guo, OU Ding-hua, SHU Xiang-yang, HU Jia

2020, 39(3):  1045-1055. 

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Urban land has long been the hotspot of ecological land research, while rural ecological land has gradually been valued in recent years. In this study, 10 indicators including ecological sensitivity and habitat quality were selected from three aspects: resource characteristics, morphological characteristics and functional characteristics of rural ecological land to construct a rural ecological land identification index system, and to make comprehensive identification and classification of rural ecological land in the hilly area of central Sichuan Province. The identification index system comprehensively reflects the characteristics of rural ecological land use, and can identify ecological land with strong ecological function as well as high habitat quality and nonecological land that is not suitable for inclusion in the category of ecological land. Core, auxiliary and baseline ecological land accounted for 20.48%, 34.41% and 41.16% of the study area, respectively. The core ecological land was mainly consisted of forest land, grassland and waterarea, while the auxiliary and baseline ecological land were mainly consisted of cultivated land. The spatial distribution of ecological land in the study area is characterized by auxiliary ecological land > baseline ecological land > core ecological land > non-ecological land, and the spatial distribution difference is basically consistent with the terrain (high in the northeast, and low in the southwest). There is a one to many relationship between land use/cover type and rural ecological land type, which is mainly caused by the degree of human activity, spatial distribution of geological hazards and differences in topography. Our results can provide references for constructing regional pattern for ecological security, optimizing land use mode, coordinating the contradiction between regional production development and ecological protection, enriching the contents of spatial planning and rural geography.

Comparison of extraction methods and the distribution characteristics of cluster bamboo forest information based on Sentinel-2.

YAN Xin-rong, ZHANG Mei-man, ZHENG Ya-xiong, YIN Zi-xu, HUANG Lan-ying, JIANG Xiao-yu, GUAN Feng-ying

2020, 39(3):  1056-1066. 

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Southwest Yunnan is enriched in landscapes of cluster bamboo forests and rare but unique resources of bamboo species. The development and utilization of bamboo resources are greatly limited by the uninformed distribution and growing stock of bamboo forests and the lack of proper monitoring techniques. Based on Sentinel2A image data, we compared three machine learning methods: back-propagation neural network, support vector machine, and random forest, for classifying cluster bamboo forests and other land use types in Cangyuan County. Google Earth images and DEM data were used to analyze the spatial and topographic characteristics of the distribution of bamboo forests. The results showed that random forest achieved the best accuracy in classification, with overall accuracy of 90%, Kappa coefficient of 0.87, and user accuracy of 81%. With a total bamboo forest of 138.07 km², bamboo forests in Cangyuan are mainly located in towns and villages, along roads, rivers and cultivated lands. At a resolution of 10 m, Sentinel-2A data is good at characterizing spatially dispersed cluster bamboo forests. Cangyuan’s bamboo forests are mainly located at gentle slopes or incline at altitudes from 900 to 2000 m. Our results provided basis for the development and utilization of bamboo resources in Cangyuan County. The methods used here provided reference for monitoring cluster bamboo forests.