Table of Content

10 September 2022, Volume 41 Issue 9

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Distribution characteristics and influencing factors of soil organic carbon in permafrost regions of the source region of the Yangtze River, China.

ZHANG Chao-fei, MA Su-ping, HE Xiao-bo, WANG Shao-yong

2022, 41(9):  1665-1673.  doi:10.13292/j.1000-4890.202209.002

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Organic carbon in permafrost regions has a rapid and strong response to climate warming. In this study, we analyzed the distribution of soil organic carbon (SOC) and its influencing factors, with 120 soil samples from 40 sampling points in the permafrost source region of the Yangtze River, China. The results showed that SOC contents at 0-10 , 10-20, and 20-30 cm soil depths were 8.00±4.95, 7.65±5.21, and 7.28±5.00 g·kg^-1, respectively. Average SOC contents within 0-30 cm at 4400-4500, 4500-4600, 4600-4700, 4700-4800, 4800-4900, 4900-5000, 5000-5100, 5100-5250 m altitudes were 3.25±0.43, 3.67±1.88, 7.76±4.77, 7.62±3.24, 6.78±3.28, 7.85±4.94, 11.61±4.31, 11.48±4.73 g·kg^-1, respectively. Average SOC contents within 0-30 cm at 33°-34°, 34°-35°, and 35°-36°N latitudes were 9.47±4.44, 3.42±2.04, and 4.21±1.58 g·kg^-1, respectively. SOC content decreased with increasing soil depth and increasing latitude, but increased with increasing altitude. SOC content was positively correlated with the mean annual normalized difference vegetation index, mean annual precipitation, volumetric water content, total nitrogen, and cation exchange capacity (P<0.01), and was negatively correlated with mean annual temperature and pH at all three depths (P<0.01). Soil bulk density had a significant effect on SOC content at 0-10 cm depth (P<0.05). Clay content significantly affected SOC content at the 0-10 and 10-20 cm depths (P<0.05). Mean annual temperature and mean annual precipitation were the main factors affecting the distribution of SOC in the study area. These results provide basic data and theoretical support for accurately simulating and estimating SOC storage in the permafrost regions in the source region of the Yangtze River.





The migration of main tree species lags behind climate change in Changbai Mountains.

ZHANG Peng-yi, LIANG Yu, MA Tian-xiao, LIU Bo, WU Miao-miao

2022, 41(9):  1674-1682.  doi:10.13292/j.1000-4890.202206.012

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The range boundaries of tree species will continually shift in the future for adapting to the changing climate. We developed a model coupling framework which integrates a forest ecosystem model LINKAGES and a forest landscape model LANDIS PRO to simulate the migration process of main tree species in the Changbai Mountains. We calculated the migration velocity of those species in the next 100 years. To explore the migration lag of tree species in response to climate change, we calculated the latitudinal velocity of temperature and precipitation changes across Changbai Mountains in the next 100 years. We then compared the velocity of the shifts in tree species’ ranges with that of climate change to quantify the tree species migration lag. The results showed that the geometric mean velocity of annual mean temperature in latitude was 0.57 km·a^-1 across all of the Changbai Mountains, and that the geometric mean velocity of total annual precipitation in latitude was 1.17 km·a^-1. The northern boundary of Abies nephrolepis, Acer mono, Betula costata, Juglans mandshurica, Larix olgensis, Phellodendron amurense, and Ulmus davidiana var. japonica would migrate northward at a rate of 1.17-9.05 m·a^-1 in the next 100 years. The southern boundary of Betula costata, Betula dahurica, Picea jezoensis var. komarovii, Pinus koraiensis, Tilia amurensis, and Ulmus davidiana var. japonica would migrate southward by 0.97-10.03 m·a^-1. These results suggest that the migration of the examined tree species may lag behind climate change in Changbai Mountains.





Vertical distribution pattern and seasonal dynamics of photosynthetically active radiation in a tropical seasonal rain forest, Xishuangbanna.

LI Yuan, SONG Liang, MO Yu-xuan, TAN Zheng-hong

2022, 41(9):  1683-1690.  doi:10.13292/j.1000-4890.202207.007

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Photosynthetically active radiation (PAR) is a main factor controlling primary productivity, which influences the structure, function and dynamics of forest ecosystems. Here, we analyzed the variations of PAR in different community layers (77.7 m of above canopy, 61.3 m of upper canopy, 24.3 m of middle canopy, 16 m of lower canopy, and 2 m of shrub layer) and different seasons (rainy season and dry season) in a tropical seasonal rain forest of Xishuangbanna. The key factors affecting the distribution of PAR were determined using linear mixed model. Results showed that: (1) The diurnal dynamic trends of PAR in various vertical layers were generally similar in both seasons, with the maximum value appearing around noon, and PAR in the dry season was slightly higher than that in the rainy season. (2) The maximum monthly PAR in various vertical layers usually appeared in the dry-hot period (March to April) of the dry season, while the minimum mostly appeared in the fog-cool period of the dry season (November to December). (3) The annual total amount of PAR in the above canopy, upper canopy, middle canopy, lower canopy, and shrub layer were 7533.63, 5327.93, 1346.69, 1036.87 and 58.63 mol·m^-2, respectively, which was roughly equally distributed between dry season and rainy season. Due to different degrees of shading, the annual total amount of PAR in upper canopy, middle canopy, lower canopy and shrub layer accounted for 70.72%, 17.88%, 13.76% and 0.78% of the total, respectively. (4) The results of mixed linear model showed that both temporal factor (hour, season) and spatial factor (PAR of the upper canopy) affected the PAR of each subsequent layer in the community. PAR gradually decreased toward the forest floor, which subsequently created a complex light environment and sustained diverse groups of organisms in the tropical seasonal rain forest in Xishuangbanna.





Mechanical effects of litter cover on seedling survival and early growth of Cunninghamia lanceolata.

LUO Hang, ZHAO Chong, WANG Zheng-ning, LI Meng-qi, CHEN Hang, CHEN Wen-wen, CHENG Hua, LIU Bo

2022, 41(9):  1691-1699.  doi:10.13292/j.1000-4890.202209.011

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Compared with the physical and allelopathic mechanisms of litter mulching on seed germination and seedling growth, the mechanical mechanism remains relatively unknown. In this study, we examined the mechanical effects of litter on seedling survival and early growth of Cunninghamia lanceolata. Three litter types (C. lanceolata, Schima superba, mixture of C. lanceolata and S. superba with litter mass ratio of 1∶1 (Referred to as mixed litter hereafter)) and four litter amounts (control, 0 g·m^-2; shallow layer, 200 g·m^-2; moderate layer, 400 g·m^-2; deep layer, 800 g·m^-2) were simulated in an indoor control experiment. The results showed that: (1) Litter mulching had negative effects on the emergence rate of germinated seeds. The 30day survival rate showed a promotion response in the shallow layer but an inhibition in the deep layer. Ninety days after emergence, no seedlings survived under the deep mulching of mixed litter and the moderate and deep mulching of S. superba litter. The 90 day survival rates under moderate and deep cover of C. lanceolata litter was significantly lower than that under the control. (2) Ground diameter growth was promoted in shallow layer and inhibited in deep layer under C. lanceolata and mixed litter cover. Root growth decreased and stem length increased with increasing litter cover thickness. Compared with the control, C. lanceolata litter cover had a promoting effect on seedling height, while S. superba and mixed litter cover did not affect seedling height. (3) The effect of C. lanceolata litter on total biomass was positive under shallow layer, neutral under moderate layer, but negative under deep layer. The mixed litter had no significant effect on total biomass under shallow layer, negative effect under the moderate layer. The S. superba litter of shallow layer had significant negative effect on total biomass. (4) The root biomass proportion and root/shoot ratio decreased gradually with increasing litter layer thickness. Compared with the control, the proportions of leaf biomass, photosynthetic and non-photosynthetic tissue biomass increased significantly under the cover of the three types of litter, but without difference between different cover thicknesses. Compared with the control, the robustness (ratio of aboveground biomass to seedling height) of C. lanceolata seedlings was not significantly affected by shallow cover of C. lanceolata litter, but was significantly inhibited by moderate and deep cover. The robustness of C. lanceolata seedlings was inhibited by shallow mulching of S. superba litter. In general, the mechanical effect of litter on the growth of C. lanceolata seedlings was as follows: S. superba litter > mixed litter > C. lanceolata litter, indicating stronger impacts of broadleaf litter.





Effects of controlledrelease compound fertilizer application and seeding rate on growth and yield of mechanically dry direct-seeded rice.

YUAN Man-man, SUN Yi-xiang, ZHONG Cheng-hu, WANG Jia-bao, WU Gang, HU Peng, ZHANG Xiang-ming, WANG Wen-jun, JING Yu-dan

2022, 41(9):  1700-1707.  doi:10.13292/j.1000-4890.202207.022

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A field experiment was carried out over three years to clarify the effects of mechanized direct dry seeding in drill with controlled-release formula fertilizer and seeding rate on growth and yield of rice, with indica and japonica rice varieties being used. There were three treatments with a one-time application of controlled-release compound fertilizer (OTA), one-time application of controlled-release compound fertilizer with increased seeding rate (OTA+S), and three-time fertilization, representing typical farmer fertilization practices (FFP). The results showed that the yields of indica and japonica were 8.9% and 8.8% higher on average, respectively, under the two controlled-release compound fertilizer treatments (OTA, OTA+S) than that under FFP over the three years, but with no significant difference between OTA and OTA+S treatments. In addition, the effective tiller percentage, shoot and root biomass, root-shoot ratio, and harvest index of the population and the biomass per individual of Indica and Japonica were improved under the two controlled-release compound fertilizer treatments. There were no significant differences in the above parameters between the two controlled-release compound fertilizer treatments for the same variety. Both indica and japonica under FFP treatment had higher total N accumulation but lower fertilizer partial productivity than that under the two controlled-release compound fertilizer treatments. The net benefits of both varieties under the two controlled-release compound fertilizer treatments were higher than those under FFP. The net benefit of indica under OTA was 41.1% higher than that under FFP, while that of japonica under OTA was 57.0% higher than that under FFP. Therefore, mechanicaldirect seeding through drilling combined with one-time application of controlled-release compound fertilizer could increase rice yields, reduce fertilizer and labor costs, and increase the economic benefits of rice production, with wide application prospects.





Influences of simulated nitrogen deposition on mixing effects of litter decomposition at early stage.

ZHANG Xiao-xi, ZHOU Wen-xing, WANG Li-jie, LIU Chu-bo, MI Hao-hao

2022, 41(9):  1708-1716.  doi:10.13292/j.1000-4890.202206.011

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During the decomposition of plant litter mixture, interactions might cause significant nonadditive effects, which could lead to unpredictable variations in decomposition when compared to those predicted from single litter decomposition. Such variations would affect decomposition rate and nutrient release. This will also be relevant when considering  how increasing environmental nitrogen concentrations affect such interactions in the decomposition of litter mixture. In this study, the decomposition of litter from Pinus tabuliformis, Robinia pseudoacacia, and their mixture were examined in a 150day indoor experiment under 0, 4, 8, and 12 g N·m^-2·a^-1 nitrogen addition. At the end of the experiment, different litters were separated according to morphological differences. Then, their decomposition processes were compared with the corresponding monospecific decomposition processes, in order to investigate the effects of nitrogen deposition on the interaction of litter types during mixed decomposition. The results showed that (1) when there was no nitrogen deposition, P. tabuliformis litter significantly inhibited the decomposition and C release of R. pseudoacacia litter during mixed decomposition (P<0.05). Such inhibition effect was eliminated by 4 g·m^-2·a^-1 nitrogen deposition, but stimulated by 8 and 12 g·m^-2·a^-1 nitrogen deposition (P<0.05). (2) R. pseudoacacia litter significantly inhibited the N release of P. tabuliformis lit ter during the first 1-2 months of decomposition in all treatments, whereas N release of R. pseudoacacia litter was only inhibited by P. tabuliformis litter under 8 g·m^-2·a^-1 nitrogen deposition (P<0.05). (3) Under no nitrogen deposition, P. tabuliformis litter significantly inhibited P release of R. pseudoacacia litter (P<0.05), and such effects were eliminated by all nitrogen treatments. (4) In general, during early decomposition, slight nitrogen deposition tended to alleviate the inhibition of P. tabuliformis litter on the decomposition and nutrient release of R. pseudoacacia. However, moderate and heavy nitrogen deposition tended to intensify the inhibitory effects and thus hinder nutrient cycling in mixed forests.





Effects of urea added with humic acid and biochemical inhibitors on rice cultivation in loess.

XIAO Fu-rong, LI Dong-po, XUE Yan, SONG Yu-chao, ZHANG Ke, ZHANG Yi-ji, LI Yong-hua, ZHENG Ye, ZHANG Jin-ming, CUI Yong-kun

2022, 41(9):  1717-1725.  doi:10.13292/j.1000-4890.202209.001

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Understanding the effects of urea addition with humic acid and biochemical inhibitors in rice cultivation in loess can provide a theoretical basis for developing new types of high-efficiency and stable urea fertilizer for loess rice paddy field. In a pot experiment, blank (CK) and urea (N) were set as controls, and humic acid (H), N-butyl thiophosphate-triamine (NBPT), 3,4-dimethyl-pyrazolate phosphate (DMPP), 2vchloro-6-trimethyl-pyridine (CP), and humic acid combined respectively with three biochemical inhibitors were added into urea to form seven types of fertilizers. Compared with the application of urea alone, the addition of humic acid inhibited soil nitrification, promoted rice growth, and significantly increased grain yield by 13.3% and grain N uptake by 21.7%, with an increased nitrogen use efficiency (NUE) (P<0.05). Addition of humic acid with NBPT did not affect the transformation characteristics of urea nitrogen compared with NBPT alone, but significantly increased total N uptake and NUE by 8.0% and 9.3%, respectively. Compared with the DMPP treatment, the addition of humic acid inhibited soil nitrification in the early growth stage and significantly increased the total biomass of rice by 7.3%. Compared with the CP treatment, the addition of humic acid inhibited soil nitrification, but significantly decreased grain yield, partial factor productivity and agronomic efficiency of applied nitrogen by 11.3%, 11.3%, and 13.2% (P<0.05), respectively. Our results suggest that the combination of humic acid and DMPP should be the first choice for developing new type of high-efficiency and stable urea fertilizer for rice cultivation in loess areas, followed by NBPT + humic acid. The combination of CP and humic acid had negative effects, which was less effective than adding CP alone.





Effects of crude toxin of Lecanicillium lecanii JMC-01 on the activities of four enzymes in Myzus persicae and Plutella xylostella.

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CHAI Jun-fa, ZHAO Xue-yi, ZHANG Xuan-yi, HONG Bo, JIA Yan-xia

2022, 41(9):  1726-1730.  doi:10.13292/j.1000-4890.202207.016

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In order to develop a new agent of Lecanicillium lecanii to control pests on vegetable, the crude toxin of Lecanicillium lecanii JMC-01 fermented for eight days was extracted by ethyl acetate, with which the apterous Myzus persicae and 3rd instar larvae of diamondback moth (Plutella xylostella) were treated. We measured the indoor virulence of the test insects and the changes of glutathione S-transferase (GST), carboxylesterase (CarE), acetyl cholinesterase (AchE) and peroxidase (POD) activities of the test insects. The results showed that the toxicity of JMC-01 crude toxin to M. persicae and P. xylostella reached 94.25% and 85.41%, and the LC₅₀ values were 37.62 and 43.42 mg·L^-1, respectively. After being treated with JMC-01 crude toxin, the activities of CarE, AchE, GST, and POD in M. persicae increased to 0.81, 0.1173, 22.52, and 5.29 U·mg^-1 prot, respectively, while those of P. xylostella increased to 0.85, 0.1176, 27.5, and 13.25 U·mg^-1 prot, respectively. Our results demonstrated that the JMC-01 crude toxin contained natural insecticidal active substances by examining the virulence of the crude toxin to M. persicae and P. xylostella, as well as the changes of detoxification enzyme and protective enzyme activities, which provided basis for the further development of fungal biocontrol agents.





The effects of low temperature and weak light on the photosynthetic characteristics of chrysanthemum and the determination of its disaster index.

LONG Yu-yun, SU Ze-yang, JIANG Yu-han, ZHANG Yao, XU Ruo-han, YANG Zai-qiang

2022, 41(9):  1731-1739.  doi:10.13292/j.1000-4890.202207.017

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To clarify the effects of low temperature and weak light on photosynthetic characteristics and fluorescence parameters of chrysanthemum, a greenhouse experiment was carried out with chrysanthemum ‘Hongman’ as experimental material, following an orthogonal experiment design of L₁₆(2¹×4²). There were four levels of low temperature: 13 ℃ (day temperature)/3 ℃ (night temperature), 16 ℃/6 ℃, 19 ℃/9 ℃, 22 ℃/12 ℃, and two levels of low light: 200 and 400 μmol·m^-2·s^-1, with 28 ℃/18 ℃ and 800 μmol·m^-2·s^-1 as a control (CK). The duration was set up at 3, 6, 9, and 12 d. The cytochrome, photosynthetic parameters and chlorophyll fluorescence dynamic parameters of leaves with different treatments were measured. The results showed that the cytochrome content of leaves decreased with the intensity of low temperature and weak light stress and duration extension. The contents of chlorophyll a, chlorophyll b and carotenoid decreased by 23.17%, 42.39% and 47.04% in T₄ compared with CK, respectively. The maximum net photosynthetic rate (P_n max), light saturation point (LSP), and stomatal limit value (L_s) were decreased by 70.11%, 60.31% and 60.61% under T₄ treatment compared to the CK. With increasing intensity of low temperature and weak light stress and duration extension, light compensation point (LCP) and dark respiration rate (R_d) increased by 162.27% and 211.95% in T₄, compared to CK, respectively. With increasing intensity of low temperature and weak light stress and duration extension, maximum quantum efficiency (F_v/F_m), photochemical quenching coefficient (q_P) and PSⅡ actual photochemical efficiency (Φ_PSII) decreased significantly by 48.85%, 27.17% and 41.10%, respectively, compared with CK. The non-photochemical quenching coefficient (NPQ) increased by 88.77% compared with CK. The results indicated that the structure and function of photosystem were irreversibly damaged with increasing intensity of low temperature and weak light stress and duration extension. The low temperature and weak light stress index was established based on photosynthetic parameters, and the meteorological index of low temperature and weak light stress during the flowering period of chrysanthemum was determined. This study provides scientific basis for meteorological disaster prevention and facility environment optimization of chrysanthemum under low temperature and weak light.





Habitat characteristics and main factors influencing habitat selection of Rana hanluica during breeding period.

XIA Xin, LI Yuan, YANG Dao-de, PI Yang-yan

2022, 41(9):  1740-1745.  doi:10.13292/j.1000-4890.202206.014

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Understanding habitat characteristics and habitat selectivity of wildlife play a significant role in designing effective strategies for the conservation of wildlife populations and habitats. Rana hanluica is an endemic frog species in China. Habitat selection of R. hanluica during the breeding period was examined in Hunan Yangmingshan National Nature Reserve (where the specimen collected) from September to October, 2020. A total of 72 quadrats were investigated and 13 habitat factors including vegetation type, land use type, slope, aspect and water temperature were recorded from these quadrats. Habitat preference coefficient analysis and principal component analysis were performed to explore habitat selectivity of R. hanluica. The results showed that R. hanluica prefers gentle semi-shady and semi-sunny slopes with high surface temperature and relative humidity. The vegetation type for R. hanluica habitat was mainly cropland (mainly rice Oryza sativa). R. hanluica preferred to spawn in water fields far from roads and settlements, with shallow water depth, high water temperature, high oxygen content, and neutral pH. The main factors affecting habitat selection of the frogs included geographical factors, temperature factors, and water body factors. Further studies should be conducted to explore population ecology. Habitat protection and restoration measures should be implemented. The level of protection should be increased.





Phylogenetic and functional diversity of  bird communities in Funing, Jiangsu.

CHEN Wan, YUAN Si-jia, LIU Wei, CHEN Ming-jie, LI Peng, HU Chao-chao, CHANG Qing

2022, 41(9):  1746-1754.  doi:10.13292/j.1000-4890.202207.008

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The effect of habitat type on community diversity is a fundamental concern in ecology. In this study, we estimated taxonomic, functional, and phylogenetic diversity of bird community in four habitats (farmland, woodland, wetland, and urban area) in Funing County, Jiangsu Province in 2018-2019. A total of 115 species belonging to 15 orders and 40 families were recorded. Woodland had the highest value of taxonomic diversity, followed by farmland, wetland, and urban area. However, farmland showed the highest values of phylogenetic and functional diversity. There was no seasonal variation in bird diversity. Habitat type was more important than season in shaping bird community diversity. Standard effect size of each phylogenetic and functional diversity metrics in different habitats was significantly less than zero, indicating that environmental filtering was the main driver of bird community assembly. With comprehensive multi-dimensional diversity analysis, our results indicated that environmental heterogeneity help maintain high bird diversity and the diverse habitats provide strong support for high bird community diversity.





The dependence of daily activity rhythms of Reeves’s pheasant (Syrmaticus reevesii) on age and sex.

WANG Jia-yu, HUA Jun-qin, LU Shuai, ZHAO Yu-ze, LI Jian-qiang, XU Ji-liang

2022, 41(9):  1755-1761.  doi:10.13292/j.1000-4890.202209.008

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With 25 infrared cameras in Pingjingguan Village, Guangshui City, Suizhou, Hubei Province, China, we recorded the activity rhythms of the Reeves’s pheasants (Syrmaticus reevesii) from January 2018 to December 2019. We conducted a comparative analysis of the activity rhythms of Reeves’s pheasants across different age groups and different sexes. The results showed that the daily activity rhythms of the Reeves’s pheasants differed among different age groups and between sexes, showing staggered peaks. From May to July when chicks appeared, there were two peak activity periods for brooding females, three peak periods for non-brooding females, and no peak periods for male adults. From July to September when subadults appeared, there were three peak periods for subadults, female adults and male adults, presenting in the early morning, noon, and evening. The daily activity rhythms of Reeves’s pheasants from May to July differed significantly between the sexes. The degree of overlaps between different ages and sexes was high from July to September, with the highest overlap between subadults and concurrent female adults (overlap coefficient=0.96). The results highlight the differences in the daily activity rhythms of Reeves’s pheasants of different ages and sexes. Life history stages may account for their differences in daily activity rhythms. We also make recommendations for the conservation of the Reeves’s pheasants.





Phytoplankton community structure and its relationship with environmental factors in different vegetation zones of a landscape lake.

LI Tao, CHEN Ru, WANG Hai-yan, MAO Wen-jing, LIU Zhang-yong, YANG Jun

2022, 41(9):  1762-1768.  doi:10.13292/j.1000-4890.202206.017

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We investigated the phytoplankton community of three aquatic vegetation zones in a landscape lake in July 2019 (wet season), October 2019 (normal season), and January 2020 (dry season). The three vegetation zones included Nymphaea tetragona (Nt), Potamogeton crispus (Pc), and Nelumbo nucifera (Nn). We analyzed the spatial and temporal variation of phytoplankton communities and their relationship with environmental factors. The results showed that a total of 41, 46 and 35 phytoplankton species were identified in Nt, Pc and Nn zones, respectively. Most species were belonged to Chlorophyta in three vegetation zones, which accounted for 39.02%, 36.96% and 34.29% of total species number in Nt, Pc and Nn zones, respectively. During the sampling period, the abundance of phytoplankton in Nt, Pc, and Nn zones were (0.59-16.06)×10⁷, (0.59-8.83)×10⁷, and (0.20-1.79)×10⁷ cells·L^-1, respectively. Phytoplankton abundance in Nt and Pc zones followed the order of wet season > normal season > dry season, while Nn zone followed the order of wet season > dry season > normal season. Chlorella sp., Pseudanabaena sp. and Cryptomonas ovata were the most dominant species in each vegetation zone. The Pielou index and Shannon index in three vegetation zones were 0.77-0.86 and 2.08-2.86, respectively, indicating that water quality of the landscape lake belonged to low to medium pollution. Spatially, the main environmental factors affecting phytoplankton abundance in Nt and Nn zones were dissolved oxygen and total nitrogen, while Pc zone was mainly affected by water temperature and total nitrogen. Temporally, the main environmental factor affecting phytoplankton abundance in wet season was total nitrogen, which was changed to dissolved oxygen in dry season. Therefore, the alternation of hydrological periods and vegetation types were the main factors influencing phytoplankton community structure in the three vegetation zones.





Phytoplankton community structure and its relationship with environmental factors in the Tibet reaches of the Lancang River.

DU Hong-chun, ZHU Ting-bing, GONG Jin-ling, HU Fei-fei, ZHU Yong-jiu, YANG De-guo

2022, 41(9):  1769-1777.  doi:10.13292/j.1000-4890.202206.013

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In this study, phytoplankton community structure were surveyed in eight sampling stations in both the main stream and the tributaries (Maiqu, Jinhe, Angqu, Requ) in the Tibet reaches of the Lancang River from 2017 to 2019, aiming to explore the relationship among phytoplankton and environmental factors. The results showed that there were 119 species of phytoplankton, belonging to 6 phyla and 49 genera. Bacillariophyta (87 species) were the dominant phytoplankton, accounting for 73.1% of the total species. Phytoplankton species diversity was higher in the tributaries than that in the main stream. The ranges of phytoplankton density and biomass were 1.11×10⁴-1.78×10⁷ cells·L^-1 and 0.01-6.44 mg·L^-1, with mean values of 1.57×10⁶ cells·L^-1 and 0.88 mg·L^-1, respectively. The average density and biomass of phytoplankton in tributaries except Jinhe were higher than that in the main stream (8.71×10⁵ cells·L^-1, 0.50 mg·L^-1). The average density and biomass of phytoplankton in spring (2.73×10⁶ cells·L^-1, 1.51 mg·L^-1) were higher than in autumn (4.18×10⁵ cells·L^-1, 0.24 mg·L^-1). The mean values of the Shannon diversity index and Pielou evenness index of the phytoplankton community in the Tibet reaches of the Lancang River were 2.83 and 0.74, respectively. The results of the community similarity analysis in different times showed substantial spatial and temporal variations of phytoplankton community. Results of Pearson correlation analysis and redundancy analysis showed that CODcr, pH, dissolved oxygen and watertemperature were the key factors affecting phytoplankton in the Tibet reaches of Lancang River. We recommend regular monitoring of phytoplankton in order to provide a reference for water ecological protection and management in the Tibet reaches of Lancang River.





Assemblage structure of larvae and juvenile fish of Changqingsha and Minzhusha in Rugao Section at the lower reaches of the Yangtze River.

2022, 41(9):  1778-1786.  doi:10.13292/j.1000-4890.202207.015

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Rugao section at the lower reaches of the Yangtze River is located near estuaries and strongly affected by tides. Changqingsha and Minzhusha located in Rugao section have a typical stream-sandbank habitat with special hydrological condition. In order to understand the assemblage characteristics of larval and juvenile fish and the influencing factors in this special habitat, we conducted ichthyoplankton surveys in Changqingsha and Minzhusha from May to August each year between 2018 and 2020. A total of 17776 larval and juvenile fish were collected during the survey, belonging to 6 orders, 8 families and 34 species, with Cyprinidae being absolutely dominant. Hemiculter leucisculus, Hemiculter bleekeri and Coilia nasus were the predominant species in Changqingsha and Minzhusha. The mean abundance of larval and juvenile fish in June and July at each section was significantly higher (P<0.05) than other months, with the highest abundance in July 2019 and H. leucisculus as the most dominant species (S3#, 204.75 ind·100 m^-3). The total abundance of larval and juvenile fish in the north branch was higher than the south branch in Rugao section. The clustering analysis based on the abundance of dominant and common species at 14 sites showed that they could be divided into three groups at a similarity level of 84.60, showing significant differences in assemblage structure of larval and juvenile fish in different groups (R=0.76, P<0.05). Results of MDS analysis showed stress=0.14<0.2, indicating a meaningful interpretation of the clustering results for each site. Results of RDA analysis showed that the abundance of larval and juvenile fish was positively correlated with temperature and turbidity and negatively correlated with transparency. Overall, our results indicated that the stream-sandbank habitat affects the assemblage structure of larval and juvenile fish. The north branch with a weaker diversion effect in the surveyed section is more suitable for reproduction of most fish species, and the survival and development of larval and juvenile fish. It is recommended to strengthen protection and monitoring in the branch waters of Yangtze River, which would play an important role in the replenishment of fish resources.





Dynamics of phosphorus concentration and bacterial community structure in sediment of Qinhu Lake as influenced by Vallisneria natans.

WANG Juan-juan, XIE Tao, QUE Tian-yang, ZHANG Si-wen, QIAN Xiao-qing, LYU Shi-peng

2022, 41(9):  1787-1795.  doi:10.13292/j.1000-4890.202206.005

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Restoring submerged macrophytes is of significant importance for the remediation of water eutrophication. Sediment samples with or without Vallisneria natans were collected at Qinhu Lake, Taizhou in January, May and September of 2019. We analyzed phosphorus content and examined bacterial community structure in sediments by high-throughput sequencing of the 16S rRNA gene. The environmental factors were also investigated. The results showed that the growth of V. natans reduced the concentrations of total phosphorus (TP) and available nitrogen contents in sediments, but increased bioavailable iron, organic matter contents and Fe-P/TP ratio. The dominant bacterial phyla in the sediments included Proteobacteria, Chloroflexi, Acidobacteria, Actinobacteriota and Desulfobacterota, with seasaonal variations of bacterial community structure. With the presence of V. natans, the relative abundance of Proteobacteria and Desulfobacterota increased and the relative abundance of Chloroflexi and Acidobacteria decreased. Results of the redundancy analysis showed that water pH and TP in sediments had the most significant influence on the spatial distribution of bacterial community, followed by dissolved oxygen. Overall, our results indicated that the growth of V. natans affected bacterial community composition in sediments by changing the physical and chemical properties of lake water and sediments, and thus increased phosphorus fixation efficiency in sediments and improved water quality of the lake.





Ecological risk assessment and driving force analysis of landscape in the compound mine-urban area of the northern Peixian County.

CHEN Xin-qu, DING Zhong-yi, YANG Jun, CHEN Xiao-dong, CHEN Mei-nan

2022, 41(9):  1796-1803.  doi:10.13292/j.1000-4890.202209.007

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Resource development and utilization are followed by landscape changes and lower ecosystem stability in the compound mineurban area. Assessment of landscape ecological risk is becoming a hot topic. We assessed the landscape ecological risk of the northern coal mining area of Peixian County in Xuzhou City. The ecosystem services were used to reveal the shifts of landscape vulnerability. The unbalance index and inconsistent index were introduced to represent the distribution of landscape ecological risk. Further, the drivers of ecological risk dynamics during 2000 to 2019 were analyzed. Results showed that: (1) the areas with high landscape disturbance degree were mainly distributed in the adjacent areas of Weishan and Zhaoyang lakes and construction land; the vulnerability of the whole landscape decreased first and then increased; (2) the landscape ecological risk increased as a whole, while the middle and high-risk areas had transferred from coal mining areas to towns; (3) the spatial variation of ecological quality and human population in different towns tended to be similar; (4) With a 1% increases of urbanization rate and raw coal output, the ecological risk value would increase by 1.081% and 0.091%, respectively. Our results can provide reference for the ecological protection and rational development in the mining area of eastern plain with high groundwater level.





The connectivity and accessibility of Guangzhou greenway network and their response to urbanization.

TANG Yi-jia, PEI Nan-cai, SHI Zhao-wan, LUO Shui-xing, LUO Yan-hua, LIU Xiao-tian, XIE Ya-ting, HE Ji-hong, TANG Pin-chuan, YANG Chao, SUN Qian, SUN Bing

2022, 41(9):  1804-1812.  doi:10.13292/j.1000-4890.202206.004

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The distribution characteristics, connectivity, and accessibility of Guangzhou greenway were quantified by density analysis method, network structure index method, morphological space pattern analysis method, and network analysis method. Furthermore, correlation analyses between greenway density and four socioeconomic indicators (i.e., economic development level, road network density, urbanization rate, and population density) were carried out to detect key factors influencing the construction of Guangzhou greenway. The results showed that the average greenway density in Guangzhou was 0.44 km·km^-2, and the per capita greenway length was 0.21 m. The construction center of greenway was located in “the-Four-Old-Districts” (Yuexiu, Liwan, Haizhu, Tianhe) and gradually weakened outward in the form of circles. The greenway network structure indices α, β, and γ was 0.149, 1.297, and 0.65, respectively. The network closure degree was relatively low but the complexity and the connectivity were high. 95.82% of the ecological source patches were connected in Guangzhou. The districts with excellent accessibility included the greenway network in Yuexiu, Haizhu, Liwan, Tianhe. The districts with normal accessibility included the greenway network in Baiyun, Huangpu, Panyu, Zengcheng. The districts with relatively poor accessibility included the greenway network in Nansha, Huadu, Conghua. Urbanization rate, population density, and road network density had a positive impact on the greenway construction in Guangzhou, with the value of R² being 0.749, 0.634, and 0.715, respectively. Guangzhou greenways were densely distributed in “the-Four-Old Districts”, where the network structure was relatively complete and the accessibility was generally convenient, and there was a downward trend for various indicators. To comprehensively promote the formation of a sustainable and ecological space network in Guangzhou as soon as possible, more efforts are needed to construct high-quality greenways on peripheral urban areas, optimizing the spatial structure, improving ecosystem functions, and realizing the goal of shared greenways by all citizens.

Landscape ecological risk analysis of urban agglomeration in the central basin of Shanxi from the perspective of “production-living-ecological spaces”.

GUO Yan-jun, GUO Wen-jiong

2022, 41(9):  1813-1824.  doi:10.13292/j.1000-4890.202206.015

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The urban agglomeration in the central basin of Shanxi is a densely populated and economic area. The spatial pattern of the “production-living-ecological spaces” of the agglomeration is significantly influenced by humans and trigger changes in landscape ecological risks, which deserves more attention. Based on the land use data in 1980, 2000, 2010 and 2018, the whole region was divided into production-living-ecological spaces according to their dominant functions, aiming to analyze the increase and decrease of the area and the situation of land type transformation in three types of space. An ecological risk evaluation model was constructed by the landscape index to quantitatively measure the degree of regional risk. Using the methods of grid GIS, spatial autocorrelation, and Kriging interpolation, we comprehensively explored the distribution and clustering characteristics and the spatial-temporal pattern evolution of landscape ecological risks, as well as the driving factors. The area of the region was dominated by agricultural production space, which was decreasing year by year and mostly transferred to urban-rural living and industrial mining production spaces. Woodland and grassland ecological spaces took high proportions and were frequently transferred to each other. The area of urban, rural living and industrial mining production spaces transferred from other types were significantly expanded, with 1216.75 km²enhancement compared with the initial period. The production-living-ecological spaces in this region were correlated with the landscape ecological risk. Urban living space was at a low risk. Woodland was at a lower risk. Grassland was at medium risk level. Rural living, agricultural production and industrial mining production spaces formed a higher risk area in the basin. Waters and other ecological spaces had the highest risk. The spatial autocorrelation of landscape ecological risk was strong, with obvious highhigh and low-low clustering patterns. The overall trend of landscape ecological risk in the region from 1980 to 2018 was upward, as indicated by the facts that the proportion of area with higher and high risk was totally increased by 6.47% and that each risk area mostly shifted to a higher level. In the period of rapid urbanization from 2000 to 2010, there was a large change in the transformation of production-living-ecological spaces, and the average value of landscape ecological risk index increased from 0.3042 to 0.3140.





The potential distribution of main Sciaenidae species in coastal China based on MaxEnt model.

YANG Wen, HU Wen-jia, CHEN Bin, TAN Hong-jian, DONG Peng, YU Wei-wei, DU Jian-guo

2022, 41(9):  1825-1834.  doi:10.13292/j.1000-4890.202206.016

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Sciaenidae species are one of the traditional economic fishes in China. To understand the potential distribution and the influence of marine environmental factors on their distribution, the MaxEnt model combined with 10 environmental factors was used to predict the potential distribution of 12 Sciaenidae species in the coastal China. The receiver operating characteristic curve (ROC) was used to verify the accuracy of the model, while the Jackknife method was used to assess the importance of environmental factors. The potential distributions were mapped and the dominant environmental factors were identified. The results showed that the average AUC value of the model reached 0.943, indicating that the accuracy of the model was good and the results were reliable. Most of the 12 Sciaenidae species are distributed in the Bohai Bay, the south-central Yellow Sea, the Yangtze River estuary, and the coast of Fujian and the Pearl River estuary, with the highest richness of Sciaenidae species appearing in the Pearl River estuary. Dissolved oxygen concentration, offshore distance and primary productivity are the dominant environmental factors driving the potential distribution of Sciaenidae fishes. The genus Pennahia is distributed in coastal China, with the common potential distribution for more than two species being mainly distributed in the south of the Yangtze River estuary, and concentrated in the Taiwan Strait, the coast of Guangdong and the northern Hainan Island. The genus of Johnius is also distributed in coastal China, with the potential distribution of most of the species being in the Yellow Sea, the East China Sea, the Taiwan Strait and the Pearl River Estuary. The common potential distribution for two species of genus Larimichthys are continuously distributed from the south of the Yangtze River estuary to the north of the Minzhong fishing ground, and the sea off the Yangtze River estuary is the most concentrated distribution area. The common potential distribution for the two species of genus Collichthys is distributed in large patchy areas in the south of Lianyungang, Jiangsu and north of the Yangtze River estuary.





Research progress on distribution characteristics and environmental behaviors of microplastics in mangrove forests.

LI Yi-fan, BI Ran, ZHAO Pu-hui, LIU Wen-hua, LI Ping

2022, 41(9):  1835-1844.  doi:10.13292/j.1000-4890.202209.025

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Microplastics as emerging pollutants have been detected in many environmental media and organisms. Their potential environmental risks have attracted wide attention in recent years. Mangrove forest is an essential ecosystem in the transition zone from land to ocean and an essential habitat for fishery resources. While a few studies addressed the abundance and distribution of microplastics in the mangrove forests, the toxicities of microplastics to those ecosystems remained largely unknown. Here, we review the source and distribution pattern of microplastics in the mangrove forest and evaluate the potential threats of microplastics to the mangrove health, and the possible degradation pathway of microplastics. We analyzed the problems during microplastic pollution prevention in the mangrove forests and proposed perspectives on microplastics pollution prevention, aiming to provide scientific support for mangrove ecosystem management.





Research progress of using plant growth promoting rhizobacteria to alleviate continuous cropping obstacles of horticultural crops.

ZHOU Qian-yi, LI Yi, HAN Rui, TIAN Jie

2022, 41(9):  1845-1852.  doi:10.13292/j.1000-4890.202209.018

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Continuous cropping obstacle is one problem affecting the development of horticultural industry in China. Plant growth promoting rhizobacteria (PGPR) is of great significance in improving soil properties and plant growth as well as in alleviating continuous cropping obstacles. Although PGPR has been widely used in the production of horticultural crops, the comprehensive understanding of its mechanisms is still lacking. In this review, we summarized the effects of PGPR on soil health and plant growth. For soil health, we focused on the role of PGPR in improving soil physical structure, chemical properties, and biological characteristics. For plant growth, we focused on the regulatory effects of PGPR on plant hormone secretion, root growth and development, adversity stress defense, and “rootsoilmicrobiome” interaction network. We proposed the current research shortcomings and future research directions to lay a theoretical foundation for the scientific application of PGPR in the production of horticultural crops and the sustainable development of the horticultural industry.





Repellency of electric barrier with different parameters on three fish species.

LI Yang-xi, HOU Yi-qun, JIN Yao, WAN Fan, SHI Xiao-tao, ZHU Zheng-qiang, ZHOU Chao-yan, ZENG Yu-hong

2022, 41(9):  1853-1861.  doi:10.13292/j.1000-4890.202209.017

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We investigated the repellency of electric barriers with different electrical parameters in still water and flowing water of 0.3 and 0.7 m·s^-1 on three protected species from the Dadu River, Schizothorax prenanti, Schizopygopsis malacanthus, and Euchiloglanis kishinouyei. Twelve treatments, including three pulse voltages (26, 30 and 36 V) and four pulse frequencies (3, 5, 8 and 12 Hz), were conducted at each velocity at 18-20.5 ℃ of water temperature and 248-270 μS·cm^-1 of water conductivity. The results showed that the barrier had the best repellent effect harmlessly on the three fish species with the pulse voltage of 36 V and pulse frequency of 5 Hz in all the three flow conditions. Despite the declined interception rate and the sensing distance of all the three fish species with higher flow velocity, there was no significant difference. The escaping response of the three fish species at given electric settings can serve as the basis for electric barriers design of fish and lay a foundation for their conservation.





Systematic planning of micropriority areas in the Southeast Himalaya Biodiversity Priority Conservation Area.

YE Jin, HU Jin-ming, WU Rui-dong, WANG Heng-ying, WANG Jun-jun, ZHOU Jian, WANG Yi-ting, YANG Fei-ling

2022, 41(9):  1862-1872.  doi:10.13292/j.1000-4890.202209.005

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Global biodiversity loss seriously threatens the multiple functions and services of ecosystems. Identifying micro-priority areas cost-effectively and representatively at the fine scale is an effective way to promote successful regional biodiversity conservation. This study selected the endangered, endemic and national protected plant species in the southeastern Himalayas priority area as surrogate taxa to represent community biodiversity of the region. Systematic conservation planning model (Zonation) was used along with data on habitat suitability (Maxent) of each plant species to systematically identify the biodiversity micro-priority areas and analyze its ecological representativeness. The conservation gaps in the study area were identified. Our results showed that: (1) The species distribution model accurately predicts that these representative plant species are mainly concentrated in southeastern Tibet; (2) The identified micropriority areas are mainly distributed in the high mountains and valleys in southeastern Tibet, the original lake basins and valleys in southern Tibet, and the middle section of the Himalayas in southwestern Tibet; (3) The micropriority areas identified based on endangered species surrogate has better ecological representation for ecosystem and its services, but it is necessary to combine species, ecosystem and its services to identify micro-priority areas in conservation planning in the future; (4) There are some differences in the geographical distribution between the micro-priority areas and the in situ protected areas. The conservation gaps were mainly located in Zayü, northern Mêdog, northern Lhozhag, southern Nagrze, Kamba, Yadong, Kangmar, and central Saga. The future optimization work in the national park planning in the southeastern Himalayas should focus on those gap areas. This study can provide methodological support to improve the effectiveness of biodiversity conservation at the fine scale and provide decision support for local administration to integrate and optimize the protected areas system.