Chinese Journal of Applied Ecology

CONTENTS

2022, 33(5): 1152-1152.

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Ecological economics foundation research on ecological values, ecological asset management, and value realization: Scientific concepts, basic theories, and realization paths

YU Gui-rui, YANG Meng

2022, 33(5): 1153-1165. doi:10.13287/j.1001-9332.202205.006

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Ecosystems provide various environmental conditions and natural resources for life, production, and human livelihoods. Ecosystem management based on natural laws is the basic way for human society to recognize the value of nature and ecosystems, protect and utilize the natural environment and resources, create and accumulate ecological assets, and sustainably develop. Taking that as one of the core concepts, regional ecological economics or economic ecology is becoming a frontier in scientific research to evaluate the Anthropocene earth system and sustainable development. From the perspective of macro-ecosystem science, based on the multi-functionality and multi-values of ecosystems, this study expounded the concepts of natural ecological value, ecological assets, ecological products, and some related phrases, analyzed the processes and principles of formation and change of ecological assets, production and consumption of ecological products, ecological investment, and profit and loss of ecological assets based on integrated ecology, sociology, and economics, proposed paths of regional ecological asset management and ecological value realization. It would provide theoretical and methodological references for the evaluation of regional ecosystem value and ecological assets, and the development of ecological industries and ecological value realization systems.

Analysis of carbon concentration and allometric growth model of carbon content for Larix olgensis

ZHANG Yue, XIE Long-fei, DONG Li-hu

2022, 33(5): 1166-1174. doi:10.13287/j.1001-9332.202205.009

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Forest carbon storage accounts for about 45% of terrestrial carbon storage. Accurate assessment of forest carbon storage is of great significance to the scientific management and planning of forests. Based on the data of 77 sampling Larix olgensis trees from Mengjiagang, Shangzhi Maoershan, Xiaojiu Forest Farm and Dongjing, Lin-kou Forestry Bureaus of Jiamusi, Heilongjiang Province from 2015 to 2018, we analyzed the partition of carbon content and variation of carbon concentration for five tree components (i.e., wood, bark, branch, leaf, and root). The mono-element and dual-element additive models of carbon content for each component of L. olgensis were deve-loped. The nonlinear seemly unrelated regression was used to estimate the parameters in the additive models, while the jackknife resampling technique was used to verify and evaluate the developed models. The results showed that the weighted mean carbon concentration of each component differed significantly, branches (49.3%) > bark (48.7%) > foliage (48.5%) > wood (48.2%) > root (47.1%). The aboveground and belowground carbon content accounted for about 80% and 20% of the total carbon content, respectively. The adjusted coefficient of determination (R_a²) of additive models of carbon content was greater than 0.89, the mean absolute error was less than 4.1 kg, and the mean absolute error percentage for most models was less than 30%. Adding tree height in the additive models of carbon content could significantly improve model fitting performance and predicting precision. The additive models of carbon content of total, aboveground, wood and bark were better than that of carbon content of branch, foliage, root and crown.

Effects of mixing proportions on carbon storage and allocation in mixed plantation of Larix olgensis and Fraxinus mandshurica

YAN Jia-jie, LI Feng-ri, XIE Long-fei, MIAO Zheng, DONG Li-hu

2022, 33(5): 1175-1182. doi:10.13287/j.1001-9332.202205.002

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In this study, four types of mixed Larix olgensis and Fraxinus mandshurica plantations were selected according to the rows-mixing proportions (type Ⅰ: 5:3, type Ⅱ: 6:4, type Ⅲ: 5:5, type Ⅳ: 1:1). The see-mingly unrelated biomass models of L. olgensis and F. mandshurica were developed for obtaining biomass values, and the difference and composition of carbon storage in each forest layer and ecosystem were analyzed. The results showed that carbon storage of arbor layer in different stand types was 39.86-50.12 t·hm^-2, the carbon storage of arbor layer inⅠ, Ⅱ and Ⅳ was significantly higher than that in type Ⅲ. The carbon storage of understory was 0.10-0.30 t·hm^-2, with that in type Ⅱ being significantly higher than other types. Carbon storage of litter layer was 4.43-6.96 t·hm^-2, with type Ⅱ and Ⅲ being significantly higher than those of the other types. In the soil layer, carbon storage was 34.97-54.66 t·hm^-2. The carbon storage of soil layer in type Ⅱ was significantly greater than those in the other types. At the whole ecosystem level, carbon storage of type Ⅰ-Ⅳ was 90.43, 108.27, 85.83 and 89.92 t·hm^-2, respectively. Type Ⅱ had significantly greater carbon storage than the other types. The arbor layer and soil layer were the major carbon pools in the ecosystem, which accounted for 43.3%-55.7% and 38.7%-50.5% of the total, respectively. Our results suggested that mixing by six rows of L. olgensis and four rows of F. mandshurica was better for future planting.

Net ecosystem exchange of Pinus sylvestris var. mongolica plantation in the western Liaoning Province, China

GAO Xiang, ZHOU Yu, MENG Ping, PEI Song-yi, ZHANG Jin-song

2022, 33(5): 1183-1190. doi:10.13287/j.1001-9332.202205.001

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Pinus sylvestris var. mongolica is one of the important tree species for afforestation in Three-North Regions of China. Investigating net ecosystem exchange (NEE) and its influencing factors is of significance in understanding carbon balance of P. sylvestris var. mongolica plantation . We used the eddy covariance system and its supporting instruments to measure NEE and environmental factors of P. sylvestris var. mongolica plantation in the western Liaoning Province in 2020. The results showed that, at the half-hour scale, plantation emitted carbon during nighttime and sequestrated carbon over daytime. Carbon sequestration was inhibited by drought stress in the afternoon from May to August. At the daily scale, seasonal dynamics of nighttime NEE were mainly controlled by soil temperature and moisture, while that of daytime NEE were mainly controlled by soil moisture and vapor pressure deficit due to drought stress. When soil was dry, precipitation promoted nighttime and daytime NEE and improved photosynthetic and respiration parameters. At the month scale, there was significant negative linear relationship of daytime NEE with ecosystem apparent quantum yield and ecosystem maximum photosynthetic capacity. When air temperature was lower than 5 ℃, ecosystem respiration rate at 10 ℃ and temperature sensitivity of ecosystem respiration increased linearly with decreasing air temperature. The cumulative NEE of P. sylvestris var. mongolica plantation was -145.17 g C·m^-2, indicating a weak carbon sink in 2020.

Cell characteristics of Larix principis-rupprechtii on the edge of different stand types

WANG Chun-kai, HUANG Xuan-rui, LI Xue, Jiang-yu, WANG Xiao-xue, ZHANG Xian-liang

2022, 33(5): 1191-1198. doi:10.13287/j.1001-9332.202205.010

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To analyze the effects of forest edge on radial growth and cell characteristics in different stand types of Larix principis-rupprechtii, we investigated the differences on radial growth, cell size and numbers between edge trees and inner trees of L. principis-rupprechtii in pure L. principis-rupprechtii forests and mixed forests of L. principis-rupprechtii and Betula platyphylla in Saihanba mechanical forest farm, China. The results showed that radial growth of the edge trees was significantly faster than that of the inner trees in pure forests, with the total ring width, earlywood width and latewood width of edge trees being 48.9%, 58.9% and 29.6% higher than those of inner trees, respectively. However, there was no difference in radial growth between edge trees and inner trees in mixed forest. The total number of earlywood cells, the number of large cells and small cells in earlywood of edge trees were increased by 63.3%, 55.6% and 70.0%, while the total number of latewood cells, the number of large cells and small cells in latewood of edge trees were increased by 35.4%, 37.5% and 28.5% compared with those of inner trees. There was no significant difference in the cell sizes between edge trees and inner trees. The cell numbers of earlywood and latewood of edge trees were not significantly different from those of inner trees in mixed forest, but the cell size in the earlywood of edge trees was 50.0% larger than those of inner trees in mixed forest. The sizes of the largest cells, the smallest cells, the large cells and the small cells in the earlywood of edge trees were increased by 28.6%, 33.3%, 16.6% and 25.0% compared with those of inner trees, respectively. The fast growth of edge trees and slow growth of inner trees in the pure forests could be effectively alleviated by cultivating mixed forests.

Effects of harvest residue management on soil organic nitrogen fractions in young Cunninghamia lanceolata plantation

WANG Hai-zhen, LU Yu-ming, ZHANG Lei, LI Xiao-ling, LIN Wei-sheng, GUO Jian-fen

2022, 33(5): 1199-1206. doi:10.13287/j.1001-9332.202205.007

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Different treatments of harvest residues will change the quantity and quality of soil organic matter, with direct or indirect effects on the composition and content of soil nutrient. Nitrogen is one of the most important soil nutrients. However, the response of soil organic nitrogen fractions to different harvest residue treatments is still unclear. In this study, harvest residue treatments, including harvest residue removed, residue retained and residue burnt, were set up after clear-cutting a 50-year-old mature Cunninghamia lanceolata forest in Sanming City, Fujian, China. The H₂SO₄ hydrolysis method was used to determine soil organic nitrogen fractions and their driving factors in the 0-10 cm and 10-20 cm soil layers after 5 years of harvest residue treatments. The results showed that residue retained treatment significantly enhanced the contents of soil organic nitrogen and its liable fractions. In the 0-10 cm soil layer, soil organic nitrogen content under residue retained treatment (3.36 g·kg^-1) was 1.5 and 1.3 times as those of residue removed and residue burnt treatments, respectively. Residue retained treatment had the highest contents of labile nitrogen Ⅰ and Ⅱ fractions. In 10-20 cm soil layer, the contents of soil organic nitrogen and labile nitrogen Ⅱ fraction were also significantly higher in residue retained treatment (2.20, 0.73 g·kg^-1) than that in residue removed and residue burnt treatments. The labile nitrogen index Ⅱ in residue retained treatment (33.9%) was significantly higher than in residue burnt treatment (26.1%). The contents of total carbon, dissolved organic carbon, dissolved organic nitrogen, microbial biomass under residue retained treatment were the highest in both soil layers. Compared with residue removed treatment, residue retained treatment significantly enhanced the abundance of soil bacteria (Gram-positive bacteria and Gram-negative bacteria) in 0-10 cm soil layer. In 10-20 cm soil layer, residue retained treatment had the highest content of fungi and the lowest content of actinomycetes. Pearson analysis showed that there were significant positive correlations of labile fractions of soil organic nitrogen with total carbon, dissolved organic carbon, dissolved organic nitrogen, microbial biomass carbon, microbial biomass nitrogen, bacteria (Gram-positive bacteria, Gram-negative bacteria), and fungi, and negative correlations with actinomycetes. It was concluded that the retention of harvest residue was beneficial to increase the content of soil organic nitrogen and labile fractions, improve soil biochemical properties and had a positive effect on soil microbial community composition. Retention of harvest residue was an effective management measure to maintain soil fertility and improve forest productivity.

Identification of the potential distribution area of Cunninghamia lanceolata in China under climate change based on the MaxEnt model

CHEN Yu-guang, LE Xin-gui, CHEN Yu-han, CHENG Wu-xue, DU Jin-gui, ZHONG Quan-lin, CHENG Dong-liang

2022, 33(5): 1207-1214. doi:10.13287/j.1001-9332.202205.024

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Based on the distribution records of Cunninghamia lanceolata, we used the maximum Entropy (MaxEnt) model and geographic information system (GIS) methods, combined with environmental factors such as climate and terrain, to predict the potential distribution areas suitable for C. lanceolata under current and future climate scenarios. The results showed that annual precipitation was the most important factor driving the distribution of C. lanceolata. Under the current climate scenario, the total area of suitable for C. lanceolata growth was about 3.28 million km², accounting for about 34.5% of the total land area of China. Among all the suitable areas, the lowly, intermediately, and highly suitable areas accounted for 18.3%, 29.7% and 52.0% of the total, respectively. Under future climate scenarios, the suitable area of C. lanceolata would increase, showing a clear trend of northward expansion in China. A concentrated and contiguous distribution region highly suitable for C. lanceolata would appear in the humid subtropical areas of southern China. The model was tested by the receiver operating characteristic curve (ROC). The average area under the curve of ROC of the training set was 0.91, showing high reliability.

Spatial distribution and correlation of dominant species of karst secondary forest in central Guizhou, China

YANG Wen-song, RONG Li, YE Tian-mu, WANG Meng-jie, LI Xuan, WANG Qi, LI Ting-ting, ZENG zhen

2022, 33(5): 1215-1222. doi:10.13287/j.1001-9332.202205.008

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We analyzed the spatial distribution pattern and correlation of the top four dominant tree species in a 2 hm² karst secondary forest plot of Tianlong Mountain in central Guizhou, using pairwise correlation function g(r) combined with a completely random model (CSR). The results showed that the diameter structure of trees followed an inverted J-shape, and that more trees belonged to diameter class Ⅴ (≥10 cm) driven by the dominant trees of Lithocarpus confinis and Platycarya longipes. L. confinis presented an inverted J-shaped distribution, and the population could renew very well and was in the primary growth stage. The abundance of P. longipes and Itea yunnanensis increased gradually with increasing diameter class. The density of grown and large trees was far more than the young and small individuals, which indicated poor population regeneration, and the population was in the middle and late growth stages. The top dominant tree species, except L. confinis, showed clustering distribution at large scale, which was decreased gradually with scale and trended to distribute randomly. The pattern was particularly prominent in the diameter class for young trees. Different diameter classes of different tree species presented diffe-rent spatial distribution patterns which influenced by many factors. In terms of interspecific associations, the four dominant tree species showed negative or no associations. The higher importance value of tree species, the lower the degree of association with other dominant species. The two negative correlation tree species had the lowest degree of correlation at small scale. With the increase of spatial scale, the degree of negative correlation decreased gradually, and tended to be no correlation.

Optimization for the determination of phenol oxidase activity in subtropical forest soils developed on sandstone

XIA Yun, SHI Jia-qi, XIAO Hua-cui, WANG Quan-cheng, YANG Liu-ming, FAN Yue-xin

2022, 33(5): 1223-1232. doi:10.13287/j.1001-9332.202205.016

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Phenol oxidase plays an important role in the degradation of soil organic matter. There was no standard method to determine soil phenol oxidase activity. To fill such knowledge gap, we investigated the effects of substrate type, pH, soil storage conditions, storage time, substrate concentration, water-soil ratio, incubation time and incubation temperature on soil phenol oxidase activity in three different subtropical forest soils developed on sandstone. The pH of extraction buffers significantly affected the phenol oxidase activity. Using 2,2′-azinobis-(-3-ethylbenzo-thiazoline-6-sulfononic acid)-diammonium salt (ABTS) as substrate acquired higher oxidase activity and was applicable to wider pH range than using 3-(3,4-Dihydroxyphenyl)-L-alanine (L-DOPA) as substrate, indicating that ABTS was more suitable as a substrate for measuring phenol oxidase activity in acidic soils of subtropical forests. The storage condition significantly affected phenol oxidase activity. The phenol oxidase activity declined with time in all the three types of soil. The decreasing rate was air-dried > 4 ℃ refrigerated > -20 ℃ frozen > -80 ℃ frozen, suggesting that the frozen storage method was better than others in maintaining soil phenol oxidase activity if the determination of phenol oxidase activity in fresh soil samples cannot be immediately done. Substrate concentration, water-soil ratio, and incubation time and temperature all affected the activity of soil phenol oxidase. The condition of soil: buffer ratio of 1:100, 2 mmol·L^-1 concentration of ABTS with an incubation time of 4 h at 25-30 ℃ was optimal for measuring phenol oxidase activity in acidic soils of subtropical forests, with high repeatability and sensitivity.

Effects of the removal of invasive Moso bamboo on soil microbial biomass and enzyme activities in subtropical forests

WANG Ya-fang, LIU Zong-yue, ZHANG Bao-gang, YU Shu-quan, CAI Yan-jiang

2022, 33(5): 1233-1239. doi:10.13287/j.1001-9332.202205.015

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Removal of invasive plant species is the first step to restoring the invaded ecosystems. The soil microbial biomass and extracellular enzyme activities were measured in Moso bamboo (Phyllostachys edulis) pure forest (completely invasion), invasive P. edulis removal forest (secondary succession 5 years after clear cutting), and the evergreen broadleaved forest (no invasion) in Tianmu Mountain. The results showed that compared with P. edulis pure forest, invasive P. edulis removal significantly increased the contents of soil organic carbon (SOC), nitrate nitrogen, available phosphorus and potassium, as well as microbial biomass carbon (MBC) and microbial biomass phosphorus (MBP), while significantly decreased microbial biomass nitrogen (MBN). The activities of α-glucosidase (AG), β-glucosidase (BG), leucine aminopeptidase (LAP) and phenol oxidase (POX) in the forest with removal of invasive P. edulis were significantly higher than those in P. edulis pure forest, while invasive P. edulis removal did not change the activities of cellodisaccharide hydrolase (CBH), β-N-acetyl-glucosaminopeptidase (NAG), acid phosphatase (ACP) and peroxidase (PER). Furthermore, the activities of AG, BG and LAP were positively correlated with SOC and MBC, while the increase in POX activity was positively correlated with soil nitrate content. In addition, MBC, MBN and MBP, and activities of AG, BG, NAG, LAP and ACP in P. edulis removal forest forest were significantly higher than those in evergreen broadleaved forests. Taken together, the removal of invasive P. edulis could increase soil nutrient contents, microbial biomass and extracellular enzyme activities, thus could be considered as an effective way to restore the invaded forests. Our results provide important theoretical basis for controlling P. edulis invasion in subtropical forests.

Characteristics and driving forces of vegetation dynamics in Inner Mongolia Autonomous Region from 1992 to 2018

LYU Ji-xin, LAI Yong, GENG Shou-bao, CHEN Sheng-zhong

2022, 33(5): 1240-1250. doi:10.13287/j.1001-9332.202202.020

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Human activities related with construction and destruction are one of the important drivers for vegetation dynamics. Using remote sensing to explore the quantitative monitoring process and driving force of vegetation succession can well reveal the impacts of human activities on ecological background. Based on the vegetation formation group and vegetation formation scales, this study used the European Space Agency's annual land cover data and geo-information TUPU analysis to investigate vegetation succession direction, succession speed, and succession sequence in the Inner Mongolia from 1992 to 2018. The vegetation succession characteristics and its driving forces were then clarified. Results showed that vegetation structure changed dramatically with increasing vegetation and decreasing barren during the study period. The specific annual growth rate was cultivated land (353.10 km²) > grassland (243.92 km²) > forest (-16.22 km²) > shrubland (-120.37 km²) > desert (-556.31 km²). There was a trade-off between the area changes of adjacent grasslands, deserts, and shrublands. Vegetation succession presented a spatial pattern of vegetation expansion and desert reduction, with the succession hotspots concentrated in the West Liaohe River Plain, the desert-grassland junction of central Inner Mongolia, and along the Yellow River. The structure of vegetation succession sequence was complex with progressive succession and regressive succession intermixed. The retention rate of succession flow differed among different communities. Most of the succession flow was intercepted by the grassland and shrubland community of vegetation formation group and the grassland and cropland rainfed community of vegetation formation. The core driving forces of vegetation dynamic succession are agriculture and animal husbandry production, economic development level, population size, ecological engineering, and climate change. As a case study of plantsociology and landscape ecology, our results could provide scientific guidance for optimizing vegetation patterns and enhancing the spatial division and succession level of ecological measures.

Effects of livestock grazing on the C:N:P stoichiometry in global grassland ecosystems: A meta analysis

LIU Yu-zhen, LIU Wen-ting, YANG Xiao-xia, LI Cai-di, FENG Bin, YU Yang, ZHANG Chun-ping, DONG Quan-min

2022, 33(5): 1251-1259. doi:10.13287/j.1001-9332.202205.011

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In order to clarify the influence of livestock grazing managements on C:N:P stoichiometry of grassland ecosystem and improve grassland management ability at global scale, 83 Chinese and English papers were selected for meta-analysis in this study. We explored the effects of grazing herbivore assemblage (sheep alone, cattle alone, and mixed cattle and sheep) and grazing intensity (light grazing, moderate grazing and heavy grazing) on leaf, litter, root and soil C, N and P stoichiometry of grassland ecosystems. The results showed that grazing significantly decreased C content, C/N and C/P, and increased N, P content and N/P in leaf and litter. C content, N content, C/P and N/P were significantly reduced, and P content and C/N were increased in root and soil. Leaf and litter stoichiometry were more sensitive to cattle and sheep grazing alone, while root and soil stoichiometry were more sensitive to mixed grazing. Heavy grazing had a greater impact on the stoichiometry of grassland ecosystems. Grazing reduced soil N content and increased P content, indicating that grazing had different pathways of influence on grassland N and P content. Further research on the mechanisms of N and P content changes in response to unbalanced grazing activities and the incorporation of the effects of grazing herbivore assemblage and intensity into models for predicting and managing grassland ecosystems could effectively improve grassland ecosystem management.

Effects of simulated precipitation changes on plant community characteristics of wetland in the Yellow River Delta, China

HOU Ya-lin, HAN Guang-xuan, ZHU Lian-qi, LI Xin-ge, ZHOU Ying-feng, XU Jing-wei

2022, 33(5): 1260-1266. doi:10.13287/j.1001-9332.202205.012

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Under the changing climate scenario, changes in precipitation regimes are expected to alter soil water and salinity conditions, with consequences on the characteristics of plant community in estuarine wetland. Here, we used a six-year (2015-2020) precipitation manipulation experiment to examine how plant community characteristics responded to precipitation changes in the Yellow River Delta. The results showed that soil electrical conductivity significantly decreased, while soil moisture significantly increased with increasing precipitation. Precipitation changes altered plant community composition. Increased precipitation reduced the absolute dominance of Suaeda glauca and Suaeda salsa, but increased that of Triarrhena sacchariflora and Imperata cylindrica. Shannon index and Margalef richness index of plant community significantly increased with increasing precipitation. Compared with the control, both decreased and increased precipitation decreased the plant community abundance, frequency and coverage. The treatment of 60% increased precipitation significantly decreased plant community frequency by 54.9%, while the 60% decreased precipitation, 40% decreased precipitation, 40% increased precipitation and 60% increased precipitation treatment significantly decreased plant abundance by 38.9%, 33.8%, 35.8% and 45.7%, respectively. The aboveground biomass significantly increased with increasing precipitation, but aboveground plant biomass under 60% increased precipitation treatment being lower than that reducing under 40% increased precipitation treatment, probably due to the negative effects of flooding stress. In addition, Margalef richness index had a significantly positive relationship with aboveground biomass. Aboveground biomass, Shannon diversity index, Margalef richness index, and Simpson diversity index were negatively related to soil electrical conductivity, and aboveground plant biomass was positively related to soil moisture. Our results revealed that precipitation changes regulate growth characteristics, species composition, and diversity of plant community by altering soil water and salinity conditions in a coastal wetland.

Effects of aridity on carbon, nitrogen, and phosphorus contents in soils and plants of mountain swamps, Zhejiang, China

YANG Le, HE Ying, LI Dong-bin, YUE Chun-lei, ZHU Hong, ZHANG Fei-ying, LI He-peng

2022, 33(5): 1267-1274. doi:10.13287/j.1001-9332.202205.029

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Mountain swamps in Zhejiang Province have been suffered from severe drouhgt threats because of climate change and artificial interruption. Sphagnum bogs and swamps were gradually degraded into arid swamps. However, the effects of arid processes on the C, N, P contents of soils and their stoichiometry in mountain swamps are still unclear. We measured C, N and P concentrations, pH values, and bulk density in the upper 0-60 cm soil layers in the stands of five mountain swamps with the different arid levels. Moreover, the aboveground biomass and the C, N, P concentrations in the crushed plant mixture were also measured. The results showed that the soils of mountain swamps in Zhejiang Province were rich in soil organic carbon (SOC), total nitrogen (TN), but infertile in phosphorus (TP). Aboveground biomass, soil pH, bulk density increased, while SOC, TN, TP, C:N, C:P, N:P decreased with aridity. Soil pH and bulk density had significant negative correlations with SOC, TN, and TP in soils, respectively. The differences in the C, N, P accumulation in the soils were probably associated with litterfall production, the oxygen condition of wetlands, and the degree of plant decomposition at the different types of mountain swamps. In all, arid trends were obvious at the mountain swamps in Zhejiang Province. Soil nutrients, such as C, N, P, deceased, while plant community succeeded from the wet swamp to the mesophyte vegetation with the arid processes. The contents of C, N and P in the plants varied across species, and were not coupled with those in the soils.

Cumulative effects of K-function in the research of point patterns

WANG Xin-ting, WANG Dian-jie, LI Hai-bing, TAI Yang, JIANG Chao, LIU Fang, LI Su-ying, MIAO Bai-ling

2022, 33(5): 1275-1282. doi:10.13287/j.1001-9332.202205.005

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The spatial pattern of plant population is one of primary issues in ecological research. Point pattern analy-sis is considered as an important method to study the spatial pattern of plant population. Ripley's K function has been commonly used for point pattern analysis. However, the cumulative effect of Ripley's K function may lead to specific spatial pattern charcteristics. To explore how the cumulative effect of Ripley's K function affects population pattern, the data of clumped distribution, random distribution and regular distribution of Stipa grandis were simulated by R software. All data generated by R software were analyzed by Ripley's K function and the non-cumulative pairwise correlation function g(r). The results showed that for clumped distribution (or regular distribution), the cumulative effect of Ripley's K function was manifested in two aspects. On the one hand, the scale of clumped distribution (or regular distribution) was increased due to Ripley's K function. On the other hand, Ripley's K function could detect the difference of the distribution of cluster (or negative interaction range) in the sampling space, exhibiting different pattern characteristics. For random distribution, Ripley's K function had no cumulative effect. In conclusion, the combination of Ripley's K function and pairwise correlation function by collecting replicate samples could better reveal the essential characteristics of the pattern in the study of population pattern.

Effects of combined application of biochar with organic amendments on enzyme activity and microbial metabolic function of carbon sources in infertile red soil

BAI Mei-xia, SITU Gao-ming, LI Song-hao, WU Qi-feng, LIANG Chen-fei, QIN Hua, CHEN Jun-hui

2022, 33(5): 1283-1290. doi:10.13287/j.1001-9332.202205.017

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To improve carbon (C) sequestration and soil fertility of red soil, a two-year (2017 and 2018) field experiment was conducted to investigate the effects of two organic amendments (i.e., corn straw and sheep manure) applied alone or combined with biochar on soil nutrient content, enzyme activities involved in C cycling, and microbial substrate utilization rate in infertile red soil. There were six treatments, including control (non-amendment), corn straw, sheep manure and across biochar treatments (without and with biochar amendment, respectively). The organic amendments and biochar were applied in 2017 and 2018. The results showed that, compared with the control, organic amendments significantly increased soil pH, organic C, total nitrogen, available phosphorus and potassium contents. Compared with straw and manure alone, the biochar co-application with straw or manure significantly increased the contents of soil organic C, available potassium, and available nitrogen, without any significant interactive effects. Application of organic amendments significantly increased the activities of soil β-glucosidase (BG), cellobiohydrolase (CB), β-xylosidase (XYL), and peroxidase (PERO). The combined application of biochar and straw significantly reduced the activity of phenol oxidase (PHOX) by 28.6% and PERO by 22.2% in comparison with straw addition alone, respectively, while the combined application of biochar and manure significantly reduced the activities of α-glucosidase (AG) by 46.1%, BG by 50.9%, XYL by 41.6%, and PERO by 31.3% compared with manure addition alone, respectively. Compared with the control, the application of organic amendments significantly enhanced soil basal respiration and microbial utilization rates of carbohydrates, whereas biochar co-application significantly decreased microbial utilization rates of carbohydrates and carboxylic acids. Microbial C source utilization rates were significantly and positively correlated with the activities of BG and PERO. Thus, biochar co-application with organic amendments can enhance nutrient content and reduce enzymatic and microbial metabolic activities, thereby may facilitate C sequestration and fertility of infertile red soil.

Relationship between functional diversity and ecosystem multifunctionality of alpine meadow along an altitude gradient in Gannan, China

LIU Min-xia, ZHANG Guo-juan, LI Liang, MU Ruo-lan, XU Lu, YU Rui-xin

2022, 33(5): 1291-1299. doi:10.13287/j.1001-9332.202205.003

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Relationship between plant community functional diversity and ecosystem multifunctionality (EMF) was a new area of ecological research in recent years. Previous studies had mostly focused on the relationship between plant community functional diversity and individual ecosystem function, and lack of understanding of the EMF. In this study, six functional indices of aboveground biomass, soil organic carbon, soil total nitrogen, soil total phosphorus, soil available nitrogen and soil available phosphorus of Gannan alpine meadow were selected to analyze the relationship between plant community functional diversity and EMF on the altitude gradient of Gannan alpine mea-dow by using Bartlett sphericity test and multi-threshold method. The results showed that there was significant altitudinal difference in plant community composition, with species richness and plant coverage at 3500 m were significantly higher than those at other altitudes. Single and multi-functional diversity decreased with the increases of altitude, with significant difference among altitudes. Redundancy analysis showed that single and multi-functional richness, functional evenness and Rao's quadratic entropy were significantly positively correlated with soil temperature, soil water content and soil bulk density, and significantly negatively correlated with soil pH and soil conductivity. In a large threshold range (6%-89%), functional diversity had a significant positive effect on EMF. Based on correlation analysis, optimal regression model and random forest model, it was found that multi-functional richness index had a significant positive relationship with EMF, and that multi-functional richness was also the main driving factor of EMF. Overall, functional richness had the most significant impact on the EMF of alpine meadow in the Qinghai-Tibet Plateau.

Effects of fulvic acid on photosynthetic characteristics, yield and quality of cucumber under drought stress

LIU Cai-juan, LYU Chun-yu, AI Xi-zhen, BI Huan-gai

2022, 33(5): 1300-1310. doi:10.13287/j.1001-9332.202205.014

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Fulvic acid (FA) participates in the regulation of drought stress tolerance in plants, but the underlying mechanisms remain unclear. We carried out an experiment with cucumber cultivar ‘Jinyou 35' as the test material and the polyethylene glycol (PEG-6000) being used to simulate drought stress. The concentration effect of FA on drought alleviation of cucumber as well as the effect of FA on photosynthetic enzymes activities, chloroplast ultrastructure, fluorescence parameters, water use efficiency, yield and quality of cucumber plants were studied through spraying FA with different concentrations (0, 100, 300, 500, 700 and 900 mg·L^-1). The results showed that FA with different concentrations significantly promoted the relative water content and leaf area and decreased drought injure index as well as the electrolyte leakage and malondialdehyde (MDA) content, compared with the control (0 mg·L^-1) under drought stress. The mitigative effect of FA increased first and then decreased with the increases of FA concentration, with 700 mg·L^-1 FA showing the best effect. FA significantly enhanced the chlorophyll content, Rubiasco and Rubisco activase (RCA) activities and gene expression, net photosynthesis (P_n), maximal photochemical efficiency of PSⅡin darkness, actual photochemical efficiency, absorbed light energy per unit area, captured light energy per unit area, quantum yield of electron transport and PSⅠ activity, decreased the increase of K point and maintained chloroplast ultrastructure. The experiment in solar-greenhouse showed that FA obviously increased water use efficiency, promoted dry matter accumulation as well as the contents of Vc, soluble sugar, soluble protein and free amino acid, and decreased tannin content. Our results suggested that FA could improve the yield and quality of cucumber in solar greenhouse under drought stress.

Effects of exogenous melatonin on antioxidant capacity and nutrient uptake of Lolium perenne and Medicago sativa under drought stress

WANG Hui, WANG Dong-mei, ZHANG Ze-zhou, REN Huai-xin, HUANG Wei, XIE Zheng-feng

2022, 33(5): 1311-1319. doi:10.13287/j.1001-9332.202205.004

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To explore the effects of exogenous melatonin on antioxidant capacity and nutrient uptake of plants under drought stress, we used Lolium perenne and Medicago sativa potted seedlings for foliar spraying and root application of 100 μmol·L^-1 melatonin, respectively. We measured the biomass, malondialdehyde (MDA) content, relative conductivity, superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities, as well as nutrient contents (organic carbon, total nitrogen, total phosphorus) under drought stress. The results showed that the biomass of L. perenne and M. sativa decreased significantly under drought stress, and that external melatonin application could effectively alleviate the inhibitory effect of drought stress on L. perenne and M. sativa. Foliar spray and root application of melatonin under drought stress enhanced L. perenne biomass by 14.5% and 29.6%, and that of M. sativa by 36.6% and 49.1%, respectively. The SOD and POD activities in L. perenne and SOD activity in M. sativa significantly decreased under drought stress, and exogenous melatonin significantly increased SOD, POD and CAT activities in L. perenne and M. sativa, reduced the accumulation of MDA in leaves, caused a significant decrease in the relative conductivity of leaves, and significantly increased antioxidant capacity. Drought stress and exogenous melatonin did not affect organic carbon content of L. perenne and M. sativa. Under drought stress, the contents of N and P in L. perenne leaves and roots and the content of N in M. sativa roots decreased, while the application of melatonin increased the contents of N and P in roots and leaves of L. perenne and M. sativa, indicating that melatonin could regulate the nutrient absorption of L. perenne and M. sativa under drought stress. In conclusion, the melatonin application not only improved the antioxidant capacity of plants, but also regulated nutrient uptake to enhance plant resilience to drought stress. Foliar spraying of melatonin was more effective than root application.

Effects of moisture and humic acid on the metabolism of oat fructans

LI Ying-hao, WANG Qi, ZHAO Bao-ping, MI Jun-zhen, LIU Yan-di, ZHANG Zhi-fen, LIU Jing-hui

2022, 33(5): 1320-1330. doi:10.13287/j.1001-9332.202205.018

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To provide theoretical guidance and technical support for oat production in dry farming area, we exa-mined the effects of moisture and humic acid (HA) on the accumulation and distribution of non-structural carbohydrates (NSC) in different organs of oat, as well as the mechanism of sugar metabolism and grain weight formation of oat. Two oat cultivars, ‘Mengnong Dayan 1' and ‘Neiyan 5', were used as experimental material. HA and clean water (CK) were foliar sprayed under dry framing (without irrigation) and limited irrigation (irrigated twice at jointing and heading stage). The dynamics of NSC components in stems, leaves and panicles, as well as the changes of carbon metabolism-related enzyme activities at different growth stages of oats after flowering were measured. Results showed that the trend of the contents of NSC in stems, leaves and panicles, in both two oat cultivars increased firstly and then decreased with the prolong of post-anthesis time. The contents of NSC in different organs were similar between two oat cultivars. Under irrigation treatment, the fructan content in panicle for Mengnong Dayan 1 of HA was higher than that of CK, with magnitude of enhancement being significantly greater than that corresponding treatment under dry farming. Under irrigation condition, the fructan, invertase activities in leaves and grain weight per panicle for Mengnong Dayan 1 of HA were increased by 27.1%, 30.6% and 55.9% compared with CK, respectively. Further, the increase trend under irrigation was stronger than that under dry farming condition. For Mengnong Dayan 1, the 1000-grain weight and grain weight per panicle were positively correlated with the content of fructan in leaves. In conclusion, the synergistic effect of moisture and humic acid could effectively regulate the accumulation of oat fructans and the activities of carbon metabolic enzymes, consequently promoting the formation of yield.

Contribution of straw disposal to carbon source and sink under the framework of carbon neutrality

MA Ming-jing, XI Feng-ming, YIN Yan, BING Long-fei, WANG Jiao-yue, ZHANG Wen-feng, NIU Le

2022, 33(5): 1331-1339. doi:10.13287/j.1001-9332.202205.025

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Exploring the spatio-temporal variation characteristics of carbon source and carbon sink under different disposal methods of crop straw is of great significance for optimizing the utilization policy of crop straw resources in China and realizing the goal of maximizing carbon emission reduction and carbon neutralization. Based on data from National Statistical Yearbook, we examined the changing trends of both the amount and value of carbon emission, carbon emission reduction, carbon sink enhancement under different crop straw disposal methods in 31 provinces of Chinese mainland. The results showed that the mean annual carbon emissions of straw burning in China from 2008 to 2019 were 8.74 million tons of CO₂e. Since 2014, the mean annual reduction rate of carbon emissions was 17.3%. The mean annual carbon emission reduction of energy utilization was 39.82 million tons of CO₂e, with solid briquette fuel produced by straw contributing the most with a contribution of about 98%. The amount of carbon sequestration of straw returning to field was increasing annually, with an average annual value of 271 million tons of CO₂e. There was a carbon ecological surplus in straw disposal in China. The annual growth rate of net carbon emission reduction was 9.8%. The net carbon emission reduction intensity and its value were increasing, reaching 2.62 t·hm^-2 and 76.19 yuan·hm^-2 in 2019, respectively. A spatial pattern of ‘high in the east and low in the west' was observed for the mean annual carbon emissions of straw, energy carbon emission reduction, carbon sink of straw returning to the field, and net carbon emission reduction in China, with main external characteristics of the regional differences and spatial aggregation.

Field greenhouse gas emission characteristics and carbon footprint of ratoon rice

LIN Zhi-min, LI Zhou, WENG Pei-ying, WU Dong-qing, ZOU Jing-nan, PANG Zi-qin, LIN Wen-xiong

2022, 33(5): 1340-1351. doi:10.13287/j.1001-9332.202205.013

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It is of great significance to understand the effects of different rice cultivation methods in southeast China on greenhouse gas emission characteristics and carbon footprint of paddy fields during rice cultivation for rice sustainable production. In this study, the popular conventional rice ‘Jiafuzhan' and hybrid rice ‘Yongyou 2640' were used as materials to establish four rice cultivation patterns suitable for different ecological types in Fujian Province: 1) double-cropping system, early rice and late rice with Jiafuzhan (D-J); 2) early maturing ratooning system, first season rice and ratooning season rice with Jiafuzhan (R-J); 3) middle-maturing ratooning system, first season rice and ratooning season with Yongyou 2640 (R-Y); and 4) single cropping system with Yongyou 2640 (S-Y), which should be synchronized in heading time with the counterpart (the ratooning season rice). Greenhouse gas emissions from paddy soil were measured by the closed static black box observation method and the gas chromatography method, respectively. The total direct and indirect greenhouse gas emissions (carbon footprints) from different rice farming patterns were evaluated by using the life cycle analysis. The results showed that greenhouse gas emissions in different rice cropping systems were lower in the early growth stage, then decreased after reaching the peak at the booting stage, demonstrating a double peak curve in the whole growth stage, in which the first peak was higher in early season or first season than the second peak in the late season or ratooning season in the cropping patterns. Moreover, the total greenhouse gas emissions were significantly different among cropping systems. The global warming potential (GWP) of different cropping patterns was in order of R-Y>D-J>S-Y>R-J, while the annual greenhouse gas emission intensity (GHGI) was D-J>S-Y>R-Y>R-J. GWP and GHGI of the ratooning system decreased by 26.1% and 14.1%, respectively, compared with those of the double-cropping system. The same pattern was observed in the ratooning rice of Yongyou 2640, which were decreased by 74.3% and 56.7%, respectively, compared with the counterpart, Yongyou 2640 in a single-cropping system synchronized heading. Carbon footprint of rice per unit yield ranged from 0.38-1.08 kg CO₂-eq.·kg^-1 under the different cropping systems, of which the carbon footprint of rice per unit yield was the highest under the double cropping system compared with that under other cropping systems. The reverse was true in the case of carbon footprint of rice per unit yield under the ratooning system with Yongyou 2640. Additionally, the main source of carbon footprint of different rice cropping patterns was CH₄, contributing 44.2%-71.5%, suggesting that rice ratooning system could significantly reduce global warming potential and carbon emission intensity of rice in comparison with other cropping patterns. Therefore, it is key to select rice varieties with high yield and low carbon emission and to establish the supporting scientific cultivation techniques for effective reduction of CH₄ emission and carbon footprint of paddy fields and promotion of ratooning rice production.

Responses of soil moisture at different slope positions to rainfall in dry-hot valley

SHI Chun-mao, LUO Ya, YANG Sheng-tian, ZHOU Qiu-wen, YU Jun-lin, LIU Yang

2022, 33(5): 1352-1362. doi:10.13287/j.1001-9332.202202.018

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The study of short-term dynamics of soil moisture in the dry-hot valley area during rainfall process will help identify soil hydrological function. In this study, we analyzed the short-term responses of soil moisture to rainfall in Huajiang dry-hot valley of Guizhou, using in-situ monitoring method to yield high-frequency soil moisture monitoring data of different slope positions. The results showed that, during the whole monitoring period, soil moisture at each layer was at a moderate variation level (15.2%≤coefficient of variation CV≤29.7%), for both upper slope and middle slope. The fluctuation range of soil moisture of the upper slope (CV=21.1%) was greater than that of the middle slope (CV=19.1%), and that of the 0-5 cm soil layer (CV=26.2%) was greater than 20-40 cm layer (CV=16.5%). Compared with the middle slope, soil moisture of the upper slope had a faster response to rainfall. The supplement amount of rainfall was bigger and the supplement speed of rainfall was faster at the upper slope than that at the middle slope. The difference between the supplement speed and the depletion speed of soil moisture of the upper slope (2.3%·h^-1) was greater than that of the middle slope (1.8%·h^-1). With the increase of soil depth, the responses of soil moisture to rainfall in subsoil layer was earlier or synchronous with that in topsoil layer. When the supplement amount of soil moisture decreased and the supplement speed slowed down, the depletion speed slowed down. Compared with the middle slope, soil at the upper slope had greater water infiltration capacity and better water retention capacity. The responses of soil moisture to rainfall in dry-hot valley were influenced by micro-environment and microclimate, and the rapid recharge of dominant flow at rock-soil interface accelerated the response speed of subsoil moisture to rainfall, which made the slopes in this area easier to form mixed runoff generation mechanism.

Canopy interception and water harvesting function of shrubs in urban green spaces of semi-humid region and their influencing factors

LI Hai-fang, YU Jie-lei, SHAO Xi-ning, ZHOU Chun-ling

2022, 33(5): 1363-1369. doi:10.13287/j.1001-9332.202205.023

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In the semi-humid region, developing innovative water conservation urban green space design and facilitating urban greening projects from high water consumption to water conservation are hot topics in research and practice. Using the simulated rainfall method, we explored the water interception and collection functions and their influencing factors of six shrub species (Ligustrum ×vicaryi, Euonymus japonicas, Buxus sinica var. parvifolia, Photinia ×fraseri, Juniperus chinensis and Platycladus orientalis) in urban green space in the semi-humid region. The results showed that canopy interception and water harvesting were two stages in hydrological processes. The canopy interception of coniferous shrubs was high, while their stemflow was low. When the rainfall intensity increased, throughfall rates and stem-flow rates of all shrub species increased significantly, while the interception rate relatively decreased. The throughfall and stem-flow rates of broad-leaved shrubs were significantly higher than those of coniferous shrubs. The canopy interception was significantly lower in broad-leaved shrub species than in coniferous ones. At the center of canopy projection, the throughfall rate was the lowest. The leaf area index (LAI) and throughfall rate decreased gradually from the center of the canopy projection area. When the rainfall intensity was small, the throughfall rate at the center of canopy projection area was low, and thus the interception rate and the stem-flow rate were higher. When the rainfall intensity was more elevated, throughfall at the center of canopy projection area was large, and thus the interception rate and the stem-flow rate were low. With increasing rainfall intensity, the funnel-shaped water collection system tended to shrink due to the increases of throughfall rate at the edge of canopy. Rainfall intensity and LAI were the most critical factors affecting water harvesting function. Planting broad-leaved shrubs under the forest may be more effective in water harvesting than planting coniferous shrubs.

Benggang (collapsing hill) erosion hazard zoning based on the minimum cumulative resistance model: A case study of a small watershed in Anxi County, Fujian, China

YAO Ying-ying, HUANG Yan-he, LIN Jin-shi, JIANG Fang-shi, GUAN Jia-lin, JI Xiang

2022, 33(5): 1370-1376. doi:10.13287/j.1001-9332.202205.020

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In order to understand the possibility and spatial pattern of Benggang (collapsing hill) erosion in risk assessment and distinguish the primary and secondary areas in Benggang prevention, we took a small watershed in Anxi County (Fujian, China) as the study area and Benggang as the source, and constructed the Benggang expansion resistance surface using the minimum cumulative resistance (MCR) model and divided the risk zoning. The results showed that the area around Benggang displayed a low resistance value, while the northwest and southeast areas displayed a high resistance value. The Benggang expansion resistance surface had an island type form. Based on resistance surface, the research region was divided into very high-risk, high-risk, medium risk, low-risk and very low-risk zones. We proposed corresponding Benggang management suggestions for those zones. A total of 21 strategic saddle points were extracted based on the resistance surface morphology. The strategic points in the lower safety zone were considered as the priority areas for Benggang prevention. We compared the hazard results based on the MCR model and the information quantity method. These results were consistent in spatial distribution, indicating the reliability of the results of hazard zoning by the MCR model.

Simulation of water and carbon coupling of the Pearl River basin based on the WaSSI model

WANG Xiao-la, DUAN Kai, WEI Lin

2022, 33(5): 1377-1386. doi:10.13287/j.1001-9332.202205.022

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Watershed water and carbon cycles are closely linked through plant photosynthesis and evapotranspiration (ET). Simulation of coupled water-carbon cycles at the watershed scale is important for the comprehensive management of water and carbon resources. By improving the WaSSI (water supply stress index) eco-hydrological model, we established and verified a water-carbon coupling simulation model for the Pearl River Basin in south China (WaSSI-PRB). The Pearl River Basin was divided into 1715 watersheds. The simulations of three water-carbon flux parameters, such as runoff, ET and gross primary productivity (GPP), were verified with 1980-2004 as the calibration period and 2005-2016 as the validation period. The Nash-Sutcliffe efficiency coefficient (NSE) and the coefficient of determination (R²) of the simulated runoff at the controlling hydrological stations of Xijiang, Beijiang and Dongjiang were greater than 0.80 during calibration period and greater than 0.75 during validation period. Compared with MODIS, PML, SSEBop, VPM and other large-scale remote sensing data products, WASSI-PRB showed a better performance in capturing the spatiotemporal variations of ET and GPP. In general, WaSSI-PRB model had good applicability in the study area, and could be used as an effective tool to quantitatively analyze water-carbon balance and their responses to environmental changes in the Pearl River Basin.

Village-level landscape succession and its driving mechanism in the agro-pastoral ecotone of Ningxia, China

SONG Nai-ping, CHEN Xiao-ying, WANG Lei, PAN Ya-qing, YANG Xin-guo, CHEN Juan, CHEN Lin, MENG Chen

2022, 33(5): 1387-1394. doi:10.13287/j.1001-9332.202205.019

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The relationship between human activities and landscape patterns and its regulation are one of the core fields in landscape ecology. The ecological conditions and local cultures of agro-pastoral ecotone are gradually wea-kening due to environmental fluctuations, land-use characteristics (suitable for both farming and grazing), and unstable policy. Therefore, protecting and restoring this semi-natural landscape and the resulting biological, ecolo-gical and cultural functions are becoming increasingly urgent. Here, by combing remote sensing data with interview survey and geographic investigation, we characterized the landscape changes (1964 to 2019) of Wanjigou Village in Yanchi County of Ningxia Hui Autonomous Region, which lay within the agro-pastoral ecotone. We further explored the rules of landscape succession and the underlying natural and social mechanism, as well as the interactions between landscape types. Results showed that Wanjigou Village had been subjected to a succession from the landscape characterized by grassland, arable land and sandy land to that characterized by grassland, shrub land, sandy land and arable land. The change from the competition of landscape function separation to the preliminary integration had formed a definite succession path for grassland-arable land-sandy land-shrub land. The main driving factors were a synthesis of policy, human needs, and environment. Policy often promoted landscape change through large-scale and intensified human activities, while environment promoted landscape succession through internal driving force of ecosystem toward a mutual adaption between landscape and the innate conditions. The driving factors of landscape succession were soil moisture variations caused by the change of soil physical structure, and vegetation change in adapting to new environment. In agro-pastoral ecotone with low resource density, the separation of landscape functions was one of the main reasons for land desertification. The integration and coordination of landscape functions greatly alleviated the situation of ecological deterioration. The critical path to maintain sustainable development of agro-pastoral ecotone was to achieve complementation among landscape types and even integrating with external resources by transforming landscape separation competition into landscape symbiosis.

Impact of provincial infrastructure investment on the vulnerability of social-ecological system in China

XIONG Chang-sheng, HU Yu-yao, ZHOU Tian-xiao, TAN Rong, ZHANG Yong-lei

2022, 33(5): 1395-1404. doi:10.13287/j.1001-9332.202205.021

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The impact of infrastructure investment on social-economic system or ecological system has been widely discussed, yet, the overall impact of infrastructure investment on social-ecological system (SES) is still unknown. This study summarized the impact mechanism of infrastructure investment on social ecosystem vulnerability. We first sorted out the impact mechanism of infrastructure investment on SES vulnerability, and then empirically analyzed the effect of provincial infrastructure investment on SES vulnerability by using spatial autocorrelation and spatial econometric models on the basis of accounting provincial per capita infrastructure capital stock and comprehensive evaluation of SES vulnerability. The results showed that the infrastructure capital stock per capita at provincial level increased significantly during 2004-2017, with a spatial pattern that the north was higher than the south and the east/west was higher than the middle in China. The provincial SES vulnerability was improved, with spatial distribution characteristics of gradually getting worse from east to west in China. There was positive spatial correlation between provincial infrastructure investment and SES vulnerability, with aggregation distribution characteristics. There was inverted U-shaped relationship between infrastructure investment and SES vulnerability in China, that was, the appropriate investment of infrastructure at early could decrease SES vulnerability, while over-investment would increase it. Our results revealed the overall impact mechanism and dynamic characteristics of infrastructure investment on SES vulnerability, and could provide theoretical and policy-making support for the coordination of infrastructure construction and SES vulnerability governance at the macro level for China.

Effects of freeze-thaw cycles on soil arthropod in the permafrost region of the Great Hing'an Mountains, Northeast China

DOU Yong-jing, WANG Rang-hu, WU Dong-hui

2022, 33(5): 1405-1412. doi:10.13287/j.1001-9332.202208.032

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A laboratory experiment was conducted to investigate the impacts of freeze-thaw intensity (-5-5 ℃, -10-5 ℃) and frequency (1, 5, 10, 15 times) on the community structure of soil arthropod in permafrost zone, Great Hing'an Mountains with the 5 ℃ as control. A total of 4198 individuals of soil arthropod were extracted, belonging to 4 classes, 9 orders, 24 families and 33 genera. The results showed that the number of individuals and groups of soil arthropod decreased significantly in the treatment with high frost intensity (-10-5 ℃), while the individuals of some taxa increased in the treatment with low frost intensity (-5-5 ℃) after the first freeze-thaw incubation. The group number, Margalef index and Shannon index decreased with the increases of freeze-thaw cycling times in low frost intensity treatment, while did not change regularly in high frost intensity treatment. Larva stage was a kind of survival strategy for arthropod to resist low temperature stress, with Acari showing stronger cold tolerance. Different responses of soil arthropod to freeze-thaw cycles, synergistic effect among species and soil environment were factors affecting the structure of soil arthropod community. This study could provide scientific data and theoretical basis for the research and conservation of soil arthropod diversity in the permafrost zone in mid-high latitudes.

Population characteristics of Collichthys lucidus in the Pearl River Estuary during 2017 and 2020

LAI Li-hua, ZHANG Shen-zeng, LU Li-yi, LIN Kun, LYU Shao-liang, ZENG Jia-wei, CHEN Hai-gang, WANG Xue-feng

2022, 33(5): 1413-1419. doi:10.13287/j.1001-9332.202205.031

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To understand the population characteristics of Collichthys lucidus, an important economic fish in the Pearl River Estuary, the biological characteristics and resource density distribution characteristics of C. lucidus were preliminarily analyzed using bottom trawling by cruises conducted in each spring and autumn during 2017 and 2020. The results showed that the body length and weight of C. lucidus ranged between 22-168 mm and 0.23-103.11 g, respectively. Female individuals were larger than the male ones. The length of sexually mature individuals intensively ranged between 90 mm and 140 mm. Neither of them evidenced the earlier of sexually maturity nor the minimizer of dominant group. The population of C. lucidus in Pearl River estuary still developed in safe status in all, but its habitat downgraded than in 1988, as indicated by the fact that the allometric growth factor (b=2.9057) of the body length to body weight had no significant annual variations, but the conditional factor (a=3.029×10^-5) was drama-tically decreased than in 1988. The population was at a state of overexploitation due to the estimated exploitation rate of 0.67. The resource density averaged 77.73 kg·km^-2, showing a pattern of higher in the middle and west than in the east and relatively uniform of latitudinal distribution. The four high densities of sampling zones suggested that the zone around Nansha Port was probably the core of spawning ground of C. lucidus. Considering the annual average resource density in 2017-2020 sharply decreased by 93.5% than in 1980 to 1982, it was pressing to establish the protection zone in spawning ground in spring to protect the recruiting and spawning stocks of C. lucidus population.

Analysis of the underlying mechanisms of green tide with a perspective of algae ecophysiology

MA Wen-fei, LI Jing-yu

2022, 33(5): 1420-1428. doi:10.13287/j.1001-9332.202205.028

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Green tide in the sea is an abnormal ecological phenomenon caused by the explosive proliferation or high aggregation of some green macroalgae under particular environmental conditions. Since 2007, green tides have occurred in the Yellow Sea for 15 consecutive years, resulting in extremely serious damage to coastal ecological environment, social development, and economic construction. Therefore, it is urgent to solve the green tide problem, which is driven by external and internal factors. Global researchers have scientifically recognized the external causes (environmental factors) of the green tide blooms, and have carried out a series of studies on the physiological response of green tide algae to some environmental factors and obtained some achievements. However, the internal causes of green tide blooms, which is the intense ecophysiological adaptability of green tide algae in response to drastic fluctuation of environmental factors, has not yet been sufficiently addressed. From the perspective of algae ecophysiology, we reviewed the response mechanisms of green tide forming species to the fluctuations of various ecological factors, including light intensity, carbon dioxide, temperature, salinity, desiccation, nutrient, heavy metals, and biotic factors. Moreover, we summarized the adaptive regulation mechanisms of green tide algae dealing with fluctuating environmental factors from the aspects of photosynthetic and growth physiology, nutritional physio-logy, and reproductive physiology, which help reveal the internal mechanisms of green tide blooming.

Review on the effects of heavy metal accumulation in flowers on the mutual benefit relationship between plant and insect pollinators

WU Lei, SUN Qi, ZHAO Ji-min, WANG De-li, ZHANG Yan-wen

2022, 33(5): 1429-1434. doi:10.13287/j.1001-9332.202205.032

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The global sharp decline of pollinators is one of the hot issues concerned by ecologists, mainly driven by global climate change, land use change, habitat fragmentation and harmful substances such as pesticides brought by industrial and agricultural production. In contrast, the potential impact of soil heavy metal pollution on pollinators is lack of in-depth evaluation. Heavy metals in soil would enter plant tissues, such as flowers, etc., and be transmitted to pollinators during pollination. By affecting pollinators' behavior, they can change plant fitness for male and female. This review aimed to comprehensively sort out the status of research and existing problems, which would deepen our understanding on the ecological consequences caused by heavy metal pollution as well as the plant-animal relationship in response to environmental change. Summarizing previous researches, we reviewed findings on the pattern of heavy metal accumulation in flowers, the impacts of flower heavy metal accumulation on plant male and female fitnesses in addition to pollination behavior and the key aspects of life history of bees, to help understand the interrelationship between flower heavy metal accumulation and pollinators, and further expand the scientific understanding on the internal connection between soil heavy metal pollution and the decline of pollinators.

Research advances in ecological risk of antibiotic resistance genes

CAI Tian-gui, ZHANG Long, ZHANG Jin-dong

2022, 33(5): 1435-1440. doi:10.13287/j.1001-9332.202205.030

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Antibiotics have played an important role in the prevention and treatment of human and animal diseases as well as the improvement of animal products. However, the mass products and application of antibiotics, especially the abuse in animal industry and clinical medicine, led to the widespread of antibiotic resistance genes (ARGs) in the environment. They spread widely through conjugation, transposition, and transformation with the help of movable elements such as plasmid, transposon and integrons, resulting in the continuous enhancement of microbial medicinal properties and posing a serious threat to human health and ecological security. At present, great attention has been paid to the impacts of ARGs on human health, but limited research on the ecological risk of ARGs in the environment. Here, the status quo and ecological risks of ARGs pollution were summarized, and the future research priorities in this field were prospected. We hope it could pave the way for further studies and give references for the ecological control and prevention of ARGs pollution.

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