Table of Content

10 June 2023, Volume 42 Issue 6

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Variations of leaf and fine-root functional traits of five garden tree species across an urban-rural gradient.

CHEN Leiru, MA Ruihao, WANG Fei, XIA Kai, DENG Pengfei, XU Xiaoniu

2023, 42(6):  1281-1289.  doi:10.13292/j.1000-4890.202305.027

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Functional traits are important characteristics that link plants, environment and ecosystems, with a far-reaching significance for indicating environmental changes. In this study, we measured 14 morphological, physiological, and nutrient traits of leaf and fine-root in five garden evergreen tree species, Photinia ×fraseri, Euonymus japonicas ‘Aurea marginatus’, Cinnamomum camphora, Ligustrum lucidum, and Osmanthus fragrans. The differential variations of traits across an urban-rural environmental gradient and the correlation between leaf traits and root traits were analyzed to reveal the survival and adaptation strategies of these species. The results showed that morphological traits of different tree species differed greatly. There were no significant differences in the leaf morphological traits along the urban-rural gradient. The physiological traits showed an increasing trend along the urbanrural gradient, and the similar trend was observed for carbon contents in fine roots and leaves. According to the results of principal component analysis and the theory of plant economic spectrum, the fine roots of the garden tree species tended to adopt a “conservative” strategy, and the survival strategy of tree species as whole appeared “slow investment return” type in the rural sites. This survival strategy was not found in the urban sites. Our findings indicate that urbanization may strengthen the resource acquisition ability of plants for growth and production.





Responses of branch and leaf morphology and structure of Nitraria tangutorum to water conditions

ZHAO Xinghua, ZHANG Ge, HAN Yanlong, GUO Lu, HE Yuting, GAO Yong

2023, 42(6):  1290-1298.  doi:10.13292/j.1000-4890.202306.016

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Soil moisture is an important factor affecting the morphogenesis of branches and leaves and leaf structure. The purpose of this study was to explore the adaptability of Nitraria tangutorum to water conditions and provide theoretical basis for artificial induction of different morphologies of N. tangutorum. An experiment with potted water control method was conducted using one-year-old stem cuttings of N. tangutorum under six levels of water supply. Water supply calculated based on the average precipitation of the cuttings collection site from March to August in recent ten years was used as control (W4). The other five treatments were then designed as reducing water supply by 15%, 30%, and 45% (designated as W3, W2, W1) and increasing water supply by 15%, 30% (W5, W6). After 10, 30, 50, 70, and 90 days of treatment, branch length, number of nodes, internode length, basal diameter, branching angle, branching ratio, leaf length, width, thickness, length to width ratio and leaf anatomical structure were measured. The results showed that the branch growth of N. tangutorum was significantly inhibited while the node formation and branching ratio were promoted under W3 and W2 treatments. Double layers of epidermis and mucous cells appeared in leaves of N. tangutorum under W2 treatment. With the increases of water supply, leaf length, width, thickness, and length to width ratio of N. tangutorum showed an increasing trend. The branch growth of N. tangutorum was promoted under W5 treatment, especially for primary branch angle. The primary branch angle was 43.5° in the later stage of the experiment. Plant clump shape of N. tangutorum transited from “upright” to “semi-upright”. Under W6 treatment, leaf size reached to the maximum, with length of 21.46 mm, width of 4.69 mm, thickness of 0.47 mm, the length to width ratio of 4.62, and the branch showed excessive growth.





Effects of leaf number of woody seedlings on herbivory intensity in a subtropical forest in Ailao Mountain.

YANG Anting, ZHANG Xiang, WANG Bo

2023, 42(6):  1299-1306.  doi:10.13292/j.1000-4890.202305.025

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Investigating the correlation between herbivory intensity and number of leaves of individual seedlings can help us better understand the effects of food abundance on herbivory intensity at small scale. In this study, we compared the correlations between herbivory intensity and the number of leaves among seasons and plant species in a subtropical forest in Ailao Mountain, using linear mixed model and generalized linear mixed model. Across all the species, a significant Ushaped pattern was detected between the number of leaves and herbivory frequency (i.e., the ratio of the number of leaves suffered insect herbivory to the total number of leaves of a target individual) in September and May, but a humpshaped pattern in December. The number of leaves had a minor effect on herbivory intensity (i.e., proportion of leaf area damaged by insect) in all the seasons. At the species level, much more complicated results emerged, including monotonic increasing and decreasing trends, and U-shaped and hump-shaped patterns, although many species did not show a clear trend, indicating that the effect of leaf number on herbivory was species specific. The results would help us further understand the role of herbivorous insects in species coexistence and diversity maintenance of seedling communities in subtropical forests. Future studies of plant-herbivore interactions should consider the role of both species specificity and seasonal variation, as well as different herbivory indices.





Effects of light intensities on leaf morphological structure, stoichiometry and nonstructural carbohydrates of Magnolia sinostellata seedlings.

CHEN Chao, LUO Guangyu, JIN Zexin, YUAN Meng, LI Yueling, SHAN Fangquan

2023, 42(6):  1307-1315.  doi:DOI:10.13292/j.1000-4890.202306.009

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To provide a theoretical basis for field conservation and scientific cultivation of endangered plant Magnolia sinostellata, we investigated its adaptation mechanism to different light environments. The changes of morpholo-gical structures, stoichiometry and non-structural carbohydrates in two-year-old seedlings of M. sinostellata were examined under three light conditions: full light intensity (I₁₀₀), 40% light intensity (I₄₀), and 10% light intensity (I₁₀). The results showed that: (1) Leaf length, leaf width, leaf circumference, and leaf area of M. sinostellata seedlings under I₄₀ were the largest, while leaf water content and specific leaf area significantly increased with decreasing light intensities. (2) The stomatal density and stomatal area percentage of M. sinostellataseedlings under I₁₀₀ were significantly higher than those under I₄₀ and I₁₀. (3) Leaf thickness and palisade tissue of M. sinostellata seedlings under I₁₀₀ and I₄₀ were significantly higher than those under I₁₀. Surface area of mesophyll intercellular space/unit leaf area (S_mes) and chloroplast surface area/unit leaf area (S_c) of M. sinostellata seedlings under I₄₀ were significantly lower than those under I₁₀₀ and I₁₀. Chloroplast number per unit area (n_chr) of M. sinostellata seedlings under I₁₀ were the largest. (4) The N content and N∶P under I₁₀ were significantly higher than those under I₁₀₀ and I₄₀, which suggested that heavy shading could increase enzyme activities and chlorophyll content of photosynthesis. (5) Soluble sugar and non-structural carbohydrate (NSC) in the shading treatments were significantly higher than those under I₁₀₀. In conclusion, M. sinostellata seedlings had higher leaf area, S_mes and S_c, tighter leaf structure, and enhanced CO₂ utilization ability under I₄₀. Shading treatment led to higher NSC content. As a shade-tolerant woody species, moderate shading can alleviate the limitation of high temperature and drought on seedling growth in summer, but the shading intensity should not be too high. The effective light intensity should be kept above 40% of natural light intensity.





Characteristics of litter decomposition and nutrient release of common tree species at different altitudes in Guizhou karst region.

LI Yuanyuan, REN Shaohua, HUANG Zongsheng, LONG Shilin, FAN Chuanhua, LIU Haiyan

2023, 42(6):  1316-1322.  doi:10.13292/j.1000-4890.202306.013

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To understand the characteristics of litter decomposition and nutrient release of common tree species at different altitudes in Guizhou karst region, we selected Cupressus funebris, Cinnamomum bodinieri, Coriaria nepalensis, and Platycarya longipes as the research objects at two altitudes of 600-700 m and 1300-1400 m. The litterbag method was used to study litter mass loss rates and the changes of N, P, and K contents of litter of various tree species in one year. The results showed that the litter mass loss rates of the four tree species at 600-700 m were higher than those at 1300-1400 m. Results of litter decomposition model showed that the values of t_0.5 (the time required for 50% mass loss) and t_0.95 (the time required for 95% mass loss) of litter of each tree species at 600-700 m were smaller than those at 1300-1400 m, but an opposite pattern of decomposition rate constants (k). Litter decomposition rate of different life-form tree species ranked as deciduous tree species > evergreen broad-leaved tree species > coniferous tree species. During litter decomposition, except for species Cupressus funebris and several nutrient release time periods, the N, P and K releases of litter of each species were generally greater at 600-700 m than those at 1300-1400 m. The nutrient release was mainly characterized by release-accumulation or balance and the annual release rate of each nutrient was 32.90%-48.83%. The changes of nutrient contents were closely related to hydrothermal factors at different altitudes. Our results provided a reference basis for forest stand improvement in Guizhou karst region.





Characteristics and influencing factors of soil organic carbon components under different environmental conditions in Poyang Lake wetland.

YUAN Jihong, REN Qiong, ZHOU Liyin, MIAO Lujun, CHI Yunyang, WAN Fang, WANG Jinping, WAN Songxian

2023, 42(6):  1323-1329. 

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Changes of environmental conditions can affect carbon sink function of wetlands. Understanding the effects of environmental conditions on soil organic carbon and its components in wetlands can provide scientific guidance for soil carbon regulation in wetlands. Here, we investigated the effects of water levels (high and low water level) and vegetation types (Triarrhena lutarioriparia and Polygonum hydropiper) on soil organic carbon and its components in Poyang Lake wetland. We analyzed the relationships between soil physicochemical properties and soil organic carbon components. Results showed that heavy fraction organic carbon was the main component of soil organic carbon, accounting for more than 70% of the total. Water level had significantly stronger effects on soil organic carbon components than the vegetation type. Soil organic carbon, heavy fraction organic carbon, particulate organic, soluble organic carbon and microbial biomass carbon of P. hydropiper community in high water level were 109.2%, 115.5%, 175.8%, 239.4%, and 61.7% higher than those in low water level, respectively. Soil pH was significantly negatively correlated with soil total carbon, heavy fraction organic carbon, and particulate organic carbon. Soil water content and total nitrogen content were significantly positively correlated with organic carbon components. Therefore, increasing water level is beneficial to soil carbon accumulation in wetlands.





Pyrolysis characteristics of surface dead fuel of Pinus massoniana forests with different age groups and slope aspects in Mount Wuyi.

LI Ying, YU Hongbo, XU Qingli, YAN Sixiao, ZHOU Yan, ZHANG Huiguang, HE Dongjin, YOU Weibin

2023, 42(6):  1330-1338.  doi:10.13292/j.1000-4890.202306.010

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Pinus massoniana is a pioneer species in the coniferous forest in southern China, which is one of the flammable forest community types. The knowledge on pyrolysis characteristics of surface fuels in Pinus massoniana forests is of great significance to improve fire behavior model and forest surface fuels management measures. Pyrolysis processes and parameters of both 1 h dead fuel (1 h fuel) and 10 h dead fuel (10 h fuel) for different stand age groups of Pinus massoniana forest in Mount Wuyi were examined by the thermogravimetric analysis. The kinetic analysis of rapid pyrolysis stage was examined using Coats-Redfem integration method. A four-dimensional feature of their combustibility was evaluated based on four pyrolysis parameters (ignition temperature, average weight loss rate of healzocellulose, decomposition time of healzocellulose, and total mass consumed by combustion). The results showed four stages in the pyrolysis process of surface dead fuels in different stand age groups of Pinus massoniana forest. The pyrolysis temperature of holocellulose ranged from 170 ℃ to 371 ℃, and the weight loss was 50%-60%. The pyrolysis temperature of lignin ranged from 358 ℃ to 496 ℃, and the weight loss was 20%-40%. In the pyrolysis stage of dead surface fuels, the activation energy of holocellulose ranged from 50.03 kJ·mol^-1 to 61.83 kJ·mol^-1, and that of lignin ranged from 17.39 kJ·mol^-1 to 64.48 kJ·mol^-1. Across stand age groups, 1 h fuel and 10 h fuel in young Pinus massoniana forest were the most ignitable, with lasting burning duration, high consumption but low intensity. In terms of shady slope and sunny slope, there was relatively consistent ignitability in the 1 h fuel, but quite different for the features of combustibility, sustainability and consumability. There was different for four-dimensional flammability features for 10 h fuel. The results of four-dimensional flammability evaluation showed that the flammability of surface dead fuels in Pinus massoniana forest had distinct heterogeneity among different stand age groups and aspects. Therefore, the effects of heterogeneity characteristics of both aspect and stand age should be fully considered in the construction of fire behavior model for higher simulation accuracy.





Litter accumulation and hydrological effects of common tree species in urban forest of Northeast China.

CHEN Jiaqi, ZHAI Chang, BAO Guangdao, LIU Ting, SHA Yinghu

2023, 42(6):  1339-1347.  doi:10.13292/j.1000-4890.202306.012

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Litter of urban forest plays an important role in dispersing precipitation and mitigating surface runoff to address urban waterlogging. In this study, we explored litter accumulation and hydrological effect in each decomposition layer in Nanhu Park of Changchun City through field investigation and laboratory experiments, with litter of five common tree species including Mongolian oak (Quercus mongolica), Asian white birch (Betula platyphylla), Mongolian pine (Pinus sylvestris var. mongolica), Chinese pine (Pinus tabuliformis), and Manchurian fir (Abies holophylla). The results showed that the thickness of litter layer had a positive correlation with the accumulated amount of litter. Litter thickness of Mongolian oak was significantly higher than that of the other species  in the un-decomposed layer (P<0.05), while that of Mongolian pine and Chinese pine were significantly higher than that of the other species in the semi-decomposed layer (P<0.05). Litter accumulation of the undecomposed layer ranged from 2.44 to 9.06 t·hm^-2, and that of semi-decomposed layer ranged from 3.85 to 11.79 t·hm^-2, with higher values in Chinese pine and Mongolian pine forests. With increasing soaking time, water-holding capacity of litter firstly increased, then tended to be stable and finally reached saturation. The fitting curve of water-holding capacity (both proportion and content) of the two decomposition layers of different forest stands with soaking time showed a power function relationship (Y=at^b). The maximum water-holding capacity of the undecomposed layer was 4.52 to 18.72 t·hm^-2 across different species, with Mongolian oak being significantly higher than the other four species (P<0.05), while the maximum water holding-capacity of the semi-decomposed layer was 6.00 to 27.51 t·hm^-2. The water-holding capacity of broad-leaved forests was significantly better than that of coniferous forests in un-decomposed litter layer, while the semi-decomposed litter layer of coniferous forests performed better in water-holding capacity. Stand age was one of the important factors regulating the hydrological characteristics of litter. The maximum water loss ranged from 2.58 to 8.00 t·hm^-2 in the un-decomposed layer, and from 2.39 to 13.78 t·hm^-2 in the semidecomposed layer. Chinese pine litter had significantly higher maximum water loss than other species (P<0.05). Our results suggested that Mongolian oak pure forest, or Mongolian oak, Chinese pine and Mongolian pine mixed forest could be considered in future urban park planning for urban waterlogging mitigation in Changchun and other cities with similar site conditions, since they can maximize the hydrological ecological function of urban forests, solve the problems of urban waterlogging and groundwater level decline, and help construct sponge cities in China.





Characteristics of soil organic matter and aggregates in Artemisia sacrorum community with different restoration modes.

QIN Li, WANG Ning, CHEN Jiamin, GAO Hongtu

2023, 42(6):  1348-1354.  doi:10.13292/j.1000-4890.202306.011

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With Artemisia sacrorum community on old field in a loess hilly region as the control, we investigated the characteristics of A. sacrorum community under artificial restoration and natural restoration after returning farmland and the effects of artificial restoration and natural restoration on soil organic matter and aggregates. The results showed that: (1) After about 20 years restoration, species number and diversity of A. sacrorum community had no significant differences between artificial restoration and natural restoration, but they were lower than those of A. sacrorum community in old field. (2) The content of soil organic matter in artificial restoration (29.68 g·kg^-1) was similar to that of old field (29.25 g·kg^-1), but significantly higher than that of natural restoration (14.34 g·kg^-1). (3) Soil aggregate indicators (water-stable large aggregates, mean weight diameter and geometric mean diameter) were all in the order as old field > artificial restoration > natural restoration. (4) Soil organic matter and aggregate indicators were positively correlated with species diversity, total number of species, the number of Compositae species, and the number of Gramineae species. In summary, after 20 years restoration, artificial restoration accelerated the improvement of aggregates and organic matter. However, taking the old field as a reference, natural restoration could result in a richer species composition and higher species diversity, and have positive effects on soil aggregates with the extension of restoration duration.





Effects of fire disturbance on soil bacterial community in Pinus tabuliformis forest.

LI Bingyi, LIU Guanhong, GU Ze, LIU Xiaodong, SHU Lifu

2023, 42(6):  1355-1364.  doi:10.13292/j.1000-4890.202306.025

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High-throughput sequencing technology (16S rRNA) was used to measure OTU of soil bacterial community in plots with different fire intensities (no fire (control), light intensity, moderate intensity, and high intensity) in a secondary Pinus tabuliformis forest in Pingquan City, Hebei Province. OTUs were annotated at different taxonomic levels, which were used to analyze the quantitative changes of dominant soil bacterial groups under different fire intensities. Soil physicochemical properties (soil organic carbon, NH₄⁺-N, NO₃^--N, available phosphorus, water content, pH) and soil enzyme activity (urease, protease, catalase, and dehydrogenase) were used to analyze the relationship between soil microenvironment changes and soil bacterial communities after fire disturbance. The results showed that the composition of bacterial community varied across different fire intensities. At the phylum level, Proteobacteria, Acidobacteria, Actinobacteria, Verrucomicrobia, Chloroflexi dominated the communities. At the genus level, Candidatus_Udaeobacter (Verrucomicrobia, Chthoniobacterales), Bradyrhizobium (Proteobacteria, Rhizobiales), RB41(Acidobacteria, Pyrinomonadales), uncultured_Acidobacteria_bacterium (Acidobacteria, Vicinamibacterales), Mycobacterium (Actinobacteria, Corynebacteriales) dominated the communities. Fire disturbance had a significant effect on the distribution of bacterial communities, with significant differences among different fire intensities (P<0.05). Among the alpha diversity indices, the value of Chao1 was the highest in the moderate fire intensity plots, and Observed_species was the highest in the light fire intensity plots. PD_whole_tree and Shannon index were generally higher in the light, moderate, and high fire intensity plots than in the control plots. Moderateintensity fire maintained a high diversity of soil bacterial community, while high-intensity fire increased community heterogeneity and led to habitat fragmentation, which a legacy effect after many years. Urease and dehydrogenase activities had the greatest degree of interpretation for bacterial community composition in different fire intensity plots. Urease activity was highly positively correlated with Candidatus_Udaeobacter, uncultured_Acidobacteria_Bacteria, RB41. Dehydrogenase activity was highly positively correlated with Candidatus_Solibacter, Bryobacterium, Bradyrhizobia and uncultured_Acidobacteria_Bacteria.





Responses of negative air ion concentration to temperature in urban forests of Beijing.

SHI Cong, LU Shaowei, ZHAO Na, XU Xiaotian, LI Shaoning

2023, 42(6):  1365-1372.  doi:10.13292/j.1000-4890.202306.018

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To clarify the responses of negative air ion (NAI) concentration in urban forests to temperature changes, four urban forest parks in Beijing were used as the research objects, including Beijing Chaoyang Park (central urban area), Nanhaizi Country Park (suburban wetland area), Xishan National Forest Park (suburban shallow mountain forest area), and Songshan National Nature Reserve (outer suburban mountain forest area). The responses of NAI concentration to temperature during 2017-2020 were analyzed using continuous dynamic observation data from NAI monitors and automatic weather stations in forest ecological environment monitoring stations. The results showed that NAI concentration in the central urban area was negatively correlated with the changes of hourly temperature in each season during the four years, with NAI concentration and temperature reaching the lowest and highest values at 14:00-15:00, respectively. In suburban shallow mountain forest area and suburban wetland area, there was a positive correlation between NAI concentration and temperature in spring, autumn, and winter, but a negative correlation between NAI concentration and temperature in summer. At the month scale, NAI concentration in each urban forest area was positively correlated with temperature, but the response of NAI concentration to temperature in the outer suburban mountain forest area had a hysteresis. At the annual scale, NAI concentration was significantly positively correlated with temperature (P<0.01). In 2020, when temperature was 0-10 ℃, the negative correlation between NAI concentration and temperature in the suburban shallow mountain forest area was the strongest (r=-0.441). At 10-20 ℃, there was a very significant negative correlation between NAI concentration and temperature in the suburban shallow mountain forest area (r=-0.253), while a positive correlation in the outer suburban mountain forest area. When temperature was between 20-30 ℃, there was a significant negative correlation between NAI concentration and temperature in the suburban wetland area and the outer suburban mountain forest area. The correlations between NAI concentration and other meteorological factors (wind speed and solar radiation) in different urban forest areas in 2020 showed seasonal variations. In spring, the NAI concentration in the suburban wetland area was significantly positively correlated with solar radiation. In summer, there was a negative correlation between NAI concentration and wind speed in the suburban shallow mountain forest area, and a negative and positive correlation between NAI concentration and solar radiation in the suburban shallow mountain forest area and the outer suburban mountain forest area. In autumn, NAI concentration was significantly positively correlated with solar radiation in the outer suburban mountain forest area. In winter, NAI concentration was significantly positively correlated with solar radiation in the central urban area and negatively correlated with solar radiation in the outer suburban mountain forest area.





Relationship between nutrients of sheath blades and taste quality of bamboo shoots across 22 bamboo species from 6 genera.

XU Sen, DONG Yawen, CHEN Shuanglin, GUO Ziwu, YANG Liting, XIE Yanyan

2023, 42(6):  1373-1380.  doi:10.13292/j.1000-4890.202306.020

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Sheath blade is the unique organ of bamboo shoot, which is located at the apex of the sheath. It is unclear whether the nutrient content of sheath blades differs among species and affects the formation of bamboo shoots’ taste quality. Here, we analyze the nutrient contents of sheath blades, and the contents of flavor compounds and roughness substances of bamboo shoots across 22 bamboo species (or forms) from 6 genera growing in the same site and under the same artificial interference measures. The results showed that the coefficients of variation of N, P, and soluble sugar contents in sheath blades ranged from 23.66% to 35.30%, belonging to medium variations. The coefficients of variation of C, starch and nonstructural carbohydrates were all less than 20%, which were weak variations. The coefficients of variation of oxalic acid, tannin, lignin, bitter amino acids, aromatic amino acids and delicious amino acids in bamboo shoots were more than 54%, which were strong variations. The coefficients of variation of other taste quality indices ranged from 22.95% to 49.31%, which were medium variations. The results of redundancy analysis showed that the contents of N and P in sheath blades were positively correlated with the contents of oxalic acid, total acid, tannin, bitterness and aromatic amino acids in bamboo shoots, but negatively correlated with cellulose content and the content and proportion of sweet and delicious amino acids. The contents of C and soluble sugar were positively correlated with soluble sugar contents, sugar-acid ratio, and the content and proportion of delicious amino acids, but negatively correlated with the contents of oxalic acid, total acid, and sweet amino acid. There was a significant negative correlation between starch content of sheath blades and lignin content of bamboo shoots. Nitrogen content of sheath blade was the main nutrient index affecting taste quality. Our results indicated that there were significant differences in nutrient content of sheath blades and taste quality of bamboo shoots among different bamboo species and forms, and that nutrient content of sheath blades had a significant effect on the taste quality. High N content promoted the synthesis of bitter, sour and aromatic substances in bamboo shoots, while inhibited the synthesis of sweet and fresh substances.





Photosynthetic physiological response of rice seedlings to water stress and high CO₂ concentration.

CUI Jinghui, WANG Yidan, QI Xiufen, WANG Xuhao, TIAN Lu, WANG Lanlan

2023, 42(6):  1381-1388. 

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In this study, rice (Oryza sativa L.) cultivar “Liao Star 1” was used as the material to examine the effects of high CO₂ concentration and drought stress on photosynthetic physiology of rice seedlings under CO₂ concentrations of 380±10 and 760±20 μmol·mol^-1, aiming to provide a theoretical basis for explaining how plants cope with complex environmental changes. PEG-6000 (0, 5%, 10%, and 15%) was used to simulate rhizosphere drought stress. Single drought stress inhibited the growth of rice seedlings, decreased plant height, root length, fresh weight and dry weight, with stronger inhibitory effect on aboveground part than that on underground part, and on fresh weight than on dry weight. Under drought stress, net photosynthetic rate (P_n), stomatal conductance (G_s) and transpiration rate (T_r) were significantly decreased compared with the control. Under light (5%) and moderate (10%) drought stress, intercellular CO₂ concentration (C_i) decreased, and the decrease of P_n was largely due to stomatal factors. Under severe (15%) drought stress, C_i increased, and the decrease of P_n was largely due to non-stomatal factors. The chloroplast pigment contents, initial fluorescence yield (F_o), largest PSII photo-chemical quantum yield (F_v/F_m), and potential photochemical efficiency (F_v/F_o) did not change significantly under mild drought stress. F_o did not change significantly under moderate drought stress, but significantly increased under severe drought stress. Under moderate and severe drought stress, F_v/F_m, F_v/F_o and Chla, Chlb, Car contents were significantly decreased. Compared with the control, high CO₂ concentration alone promoted the growth of rice seedlings, plant height and root length, with stronger promotion effect on root than plant height. The dry weight of underground part increased significantly due to its promoting effect on dry weight than fresh weight. High CO₂ concentration significantly increased P_n, and decreased G_s, T_r and C_i. Photosynthesis was also increased by the increases of F_v/F_m, F_v/F_o and Chla, Chlb, Car contents. Under high CO₂ and water stress, high CO₂ promoted the growth of rice seedlings compared with water stress alone, P_n, G_s and T_r were also significantly increased. Photosynthesis was promoted by the increases of F_v/F_m, F_v/F_o and contents of chlorophyll and decrease of F_o, and thus reduced damage induced by water stress. The decrease of P_n under severe water stress transformed from non-stomatal factors to stomatal factors.





Edge effect of artificially reconstructed vegetation on slope of Baishan quarry in Zhoushan City, East China.

WANG Ying, WEI Boliang, WU Yannan, XU Hui, YU Mingjian, XU Ligen

2023, 42(6):  1389-1401.  doi:10.13292/j.1000-4890.202306.005

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Quadrats were set up in the revegetated area on a rock slope of a quarry with artificial revegetation for 16 years and in adjacent original vegetation areas (mainly natural vegetation) in Zhoushan, Zhejiang Province. We examined community structure, species composition, and species diversity under different edge gradients, and then explored the influence of edge effects on artificial vegetation. The results showed that: (1) The similarity between plant communities in the revegetated area near the edge and the adjacent natural vegetation was higher than that between plant communities in the revegetated area far to the edge and the adjacent natural vegetation. The former was also closer to natural vegetation in species composition of trees and shrubs. (2) There were still great differences in plant species composition between the revegetated area and the natural vegetation area. Tree species richness of the former was much lower than that of the latter, while the dominant species of each layer of the artificial vegetation were more prominent. Compared with natural plant community, the artificial vegetation on the slope was still at the early stage of succession. (3) Species composition of the artificial vegetation was affected by adjacent natural vegetation. Species initially sprayingseeded or planted were gradually replaced by local native species. Species diversity of shrub layer, herb layer, and vine layer in the revegetated area was close to that of adjacent natural vegetation. Meanwhile, there was no biological invasion or biodiversity loss of adjacent natural vegetation caused by artificial seeding or planting of alien species. Our results demonstrated that the edge effect of the ecotone between the artificial vegetation on the quarry slope and the adjacent natural vegetation had a certain effect on the positive succession of plant community in the artificial vegetation and reducing the degree of forest fragmentation.





Effects of photoperiod on feeding habit and hepatopancreatic enzyme activity of button-sized Eriocheir sinensis.

LI Chunbo, FENG Guangpeng, ZHUANG Ping, ZHANG Tao, SONG Chao, WU Yeling

2023, 42(6):  1402-1408.  doi:10.13292/j.1000-4890.202306.019

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We analyzed the effects of photoperiod on the food intake, feeding rhythm and hepatopancreatic enzyme activity in the button-sized crabs by considering three photoperiods, including full light group (24L), full darkness group (24D) and simulated natural light group (10D:14L). A total of 360 button-sized Chinese mitten crab (Eriocheir sinensis) with the weight of (10.04 ± 1.03) g were used in this study. The results showed that food intake of crabs in 10D:14L group was significantly higher than that in 24D treatment, but without difference between 24L group and the other groups. There were significant differences in food intake between 24D group and 10D:14L group during day and night. In 24L group, there was no significant difference in food intake at various time points, with the highest food intake at 10:00-13:00 and 22:00-01:00. In 24D group, there were significant differences in food intake at various time points, with the highest food intake at 01:00-04:00. In 10D:14L group, there were significant differences in food intake at various time points, and the food intake was also highest at 01:00-04:00. For hepatopancreatic enzyme activity, in 24L group, the activity of amylase and alkaline phosphatase reached the peak at 01:00 and 13:00; the activity of lipase reached the peak at 01:00; the activity of Na⁺/K⁺-ATPase reached the peak at 04:00. The activity of amylase, lipase, Na⁺/K⁺-ATPase and alkaline phosphatase in 24D group reached the peak at 04:00. The amylase activity in 10D:14L group reached the peak at 07:00, while that of lipase, Na⁺/K⁺ ATPase and alkaline phosphatase reached the peak at 04:00. There was no significant difference in hepatopancreatic enzyme activity under different photoperiods. In conclusion, photoperiod affected the food intake of button-sized crabs. The button-sized crabs had an obvious feeding rhythm under the full darkness and simulated natural light. The button-sized crabs under full light had the same feeding peak as the other groups, but there was no obvious feeding rhythm, implying that the photoperiod might have no effect on the feeding rhythm of button-sized E. sinensis.





Effects of nutrient input by foraging wintering waterbirds on the distribution of nitrogen and phosphorus in shoal soil of Shengjin Lake, China.

FENG Jiawei, ZHOU Lizhi, XU Wenbin

2023, 42(6):  1409-1416.  doi:10.13292/j.1000-4890.202306.003

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Flocks of migratory waterbirds gather frequently in wetland stopovers and wintering grounds. The foraging and excreting activities of waterbirds affect nutrient contents in their habitats, with their excreta as a crucial external nutrient sources. Nitrogen and phosphorus are important indicators of nutrient levels in lakes. Therefore, it is important to understand the effects of nutrient input by waterbirds on soil nitrogen and phosphorus. Here, we investigated waterbird population and soil nitrogen and phosphorus contents at 0-10 cm layer in the shoal of Shengjin Lake in China. The effects of the waterbird’s migratory visits on the nutrient status of the shoal soil were analyzed by the means of variance, correlation, and stepwise regression analyses. We identified the main waterbird species that affected the soil nitrogen and phosphorus levels. The results showed that, compared to the control shoal without waterbird visits, the total nitrogen, total phosphorus, nitrate, and ammonium contents were significantly higher in the habitats that harbored the flocks. Due to the large amounts of organic nitrogen and phosphate introduced by waterbirds droppings, the correlations of total nitrogen vs. nitrate nitrogen, total phosphorus vs. nitrate nitrogen, and total phosphorus vs. pH in the shoal soils were significantly affected by bird activities. Soil nitrogen and phosphorus contents increased with waterbird population, among which geese were the main waterbirds that caused the increases of soil nitrogen and phosphorus contents. Our results are of great significance for understanding the environmental behaviors of nitrogen and phosphorus in lake shoals.





Oxidative stress and metabolic adaptations of liver to hibernating and non-hibernating states in Eremias multiocellata.

ZHANG Xiujing, ZHONG Qiumei, ZHENG Yanghui, WANG Jianli

2023, 42(6):  1417-1425. 

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Studies of oxidative stress contribute to understanding relationships between animal life history and habitat. Oxidative stress in animals is closely related to their metabolism. To explore the effects of habitat and hibernation on oxidative and metabolic responses in lizards, we compared the basal activities of key antioxidant enzymes and metabolic enzymes and liver glycogen content in Eremias multiocellata from a low-altitude desert with those in Scincella tsinlingensis from a high-altitude mountainous region. We assessed these parameters and the expression of the genes encoding glycogen synthase-2 (GYS2), phosphorylase (PYGL) and xanthine dehydrogenase (XDH) in E. multiocellata during summer active period (July), hibernating period (December), and spring arousal period (April). The activities of superoxide dismutase (SOD), glutathione peroxidase (GPX), catalase (CAT), and citrate synthase (CS) were significantly lower in E. multiocellata than in S. tsinlingensis, while malondialdehyde (MDA) displayed an opposite trend. There were no significant differences in liver glycogen content between the two species. Liver SOD, GPX, and CAT activities in E. multiocellata were significantly higher during arousal period than those during active and hibernating periods, while MDA content was significantly lower in hibernating and arousal periods than that in the active period. CS activity was significantly higher during hibernation than that during the other periods. Liver glycogen was significantly reduced during arousal period relative to active and hibernating periods. Expression of GYS2, PYGL, and XDH genes in the liver was lower during hibernation than that during the other periods. These results indicate that E. multiocellata living in low-altitude desert areas displays a reduced dependence upon oxidative metabolism relative to S. tsinlingensis living in high-altitude mountain areas. The oxidative stress resistance and metabolic levels of E. multiocellata showed an adaptive response to seasons. Antioxidant enzyme activities in the liver were broadly up-regulated during the arousal period but not during the hibernating period, which may be associated with restored metabolism during the arousal period. These results enrich our understanding of lizards’ adaptabilities to oxidative stress.





Temporal and spatial variations of intestinal microbiota of Exopalaemon modestus in Anhui section of Huai River.

ZHANG Ning, YING Congping, LIU Silei, WANG Yinping, LUO Junyi, LIU Kai

2023, 42(6):  1426-1433.  doi:10.13292/j.1000-4890.202305.012

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To explore the temporal and spatial variations of the intestinal microbiota of benthic community in Anhui section of Huai River, 16S rDNA amplicon sequencing technology was used to compare the intestinal microbiota characteristics of Exopalaemon modestus, one dominant shrimp species of the region. A total of 37 phylum and 855 genera of microbes were detected from E. modestus intestines, with Pseudomonas, Brevundimonas, Ralstonia, Caulobacter, Lactococcus and Sphingomonas as the dominant genera. There were significant differences in the intestinal microbiota richness of E. modestus (P<0.05) among low-water period (March), mean-flow period (June) and high-flow period (September). The β diversity index showed the intestinal microbiota composition in all sub-sections tended to be similar from March to September. The common ASVs in intestines of E. modestus increased gradually from low-water period to high-flow period. There were significant divergences of intestinal microbiota both in the low-water and mean-flow period (P<0.05), but not in the high-flow period. Due to the different habitats and hydrological regimes of different water bodies, the intestinal microbiota of E. modestus in Anhui section of Huai River (main stream) generally exhibited temporal and spatial variations. The intestinal microbiota composition of E. modestus in each sub-section showed the maximum divergence in low-water period, followed by mean-flow period, but no significant divergence in high-flow period.





Spatial and temporal variations of shrimp community diversity at the lower reaches of the Yangtze River.

ZHAO Xing, WANG Yinping, LIU Silei, LI Peijie, LIU Kai

2023, 42(6):  1434-1442.  doi:10.13292/j.1000-4890.202306.021

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To explore the spatiotemporal variations of shrimp community diversity at the lower reaches of the Yangtze River, we investigated seasonal variations of shrimp community from September 2020 to August 2021. We collected 62.57 kg and 34922 individuals of shrimps, belonging to 10 species, 6 genera and 3 families. Macrobrachium was the dominant genus, containing 5 species, whereas the other five genera contained only one species each. Among them, there were two exotic species, Macrobrachium rosenbergii and Procambarus clarkii. A significant difference of shrimp community was observed among seasons and sites. Species number, quantity, and weight of shrimp in Anqing section were 10, 17815 individuals, and 32.55 kg, respectively, which were significantly higher than those of the other sections (P<0.05). There was no significant difference of richness index among different sections (P>0.05), but differences of diversity index and evenness index among different sections (P<0.05). Species number, quantity, and weight of shrimp in summer were 9, 15748 individuals, and 26.23 kg, respectively, which were significantly higher than those in the other seasons (P<0.05). Evenness index in spring was significantly higher than that in the other seasons (P<0.05), while there was no difference in diversity index and richness index among seasons. According to cluster analysis, the lowest shrimp community similarity was observed in Changshu section and in winter, respectively. The abundance/biomass curves of shrimp communities in Anqing and Zhenjiang sections crossed, indicating that these two sections were severely disturbed, while Dangtu and Changshu sections were hardly disturbed. In general, shrimp diversity was relatively low at the lower reaches of the Yangtze River, and the community was disturbed to a certain extent. Attention should thus be paid to the dynamics and protection measures of the shrimp community.





Effects of phenanthrene stress on aminotransferase and liver tissue structure of loach (Misgurnus anguillicaudatus).

YANG Chaochao, TAN Ting, YANG Na, WANG Jia, WU Hangli, LEI Xin

2023, 42(6):  1443-1448.  doi:10.13292/j.1000-4890.202305.009

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To clarify the toxic effects of low-molecular-weight polycyclic aromatic hydrocarbons on aquatic organisms, we examined the effects of phenanthrene (Phe) on the liver structure and related enzyme activities of female and male loach (Misgurnus anguillicaudatus). Loaches were exposed to different concentrations of Phe aqueous solution (1.29, 1.67, 2.16, and 2.79 mg·L^-1, respectively) in hydrostatic water. Loaches that were kept in an acetone solvent were used as control, while those in deionized water were used as the blank control group. Loach samples were harvested on day 7, 14, 21, and 28 after the treatments respectively. Rie’s colorimetric method was employed to determine the changes of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities in the liver of loach. The liver tissue slices of loaches under Phe stress for 14 and 28 days were prepared, stained with hematoxylin-eosin (HE) and observed. The results showed that compared with the control groups, the activities of AST and ALT exhibited a trend of significant increase and then decrease with the increases of Phe stress concentrations and treatment duration, showing a certain dose effect and time accumulation effect. In addition, the activities of AST and ALT of female loaches were significantly higher than those of males. Liver histological results showed that when loaches were treated by 1.29 mg·L^-1 Phe for 14 days, their hepatocytes were slightly swelled, and a few hepatocytes appeared nuclear lysis, deformation and vacuolization. When loaches were treated by 2.79 mg·L^-1 Phe for 28 days, their liver tissue was severely damaged, and the liver structure of the male was more severely damaged. Our results indicated that Phe can induce firstly and then inhibit AST and ALT in the liver of loach, and such effect is stronger in female loaches. Continuous stress of high-concentration Phe can cause significant damage to liver tissue, and the magnitude is more significant in male than female loaches.





Growth adaptability of 13 Rhododendron varieties in complex polluted cropland in a plateau lead-zinc mining area.

CHANG Linxi, LIU Fengshuo, ZHAN Fangdong, LI Bo, CHEN Jianjun, ZU Yanqun, LI Yuan, HE Yongmei

2023, 42(6):  1449-1456.  doi:DOI:10.13292/j.1000-4890.202306.008

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Soil heavy metal pollution is a serious problem in mining areas. A field experiment was conducted to select the Rhododendron varieties suitable for planting in a lead-zinc polluted mining area on the Yunnan Plateau. The traits screened among 13 varieties included seedling height, growth rate, chlorophyll content, nutrient content, and characteristics of heavy metal accumulation. The results showed that: (1) Compared with non-rhizosphere soil, rhizosphere soil of Rhododendron had significantly lower pH value, available potassium and alkali-hydrolyzable nitrogen concentrations, but higher available phosphorus concentration. (2) There were differences in growth factors and mineral nutrient concentrations among Rhododendron varieties. Varieties ‘Hongyang’ and ‘Hongyunlai’ had the greatest increase in plant height and biomass; Variety ‘Azalea’ had the highest chlorophyll content; Varieties ‘Huolieniao’, ‘Yangzhizhu’ and ‘Hongyang’ had the highest N, P, and K concentrations, while variety Duanyang’ had the lowest nutrient concentrations. (3) There were significant differences in the capacity to accumulate and transport heavy metals among different varieties. Variety ‘Hongyang’ had the greatest capacity to absorb heavy metals, whereas variety ‘Yangzhizhu’ had the lowest. In conclusion, all the 13 Rhododendron varieties screened could grow in lead-zinc polluted mining area. ‘Azalea’ had the highest score after an evaluation of growth adaptability factors, followed by ‘Huolieniao’. These two varieties should be considered as the primary varieties for alternative planting in lead-zinc polluted mining areas of the Yunnan Plateau.





Effects of microplastics on transports of tetracycline and triclosan in saturated porous media.

WANG Chu, ZHANG Qiaoyan, HU Enzhu

2023, 42(6):  1457-1463.  doi:10.13292/j.1000-4890.202306.002

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Microplastics in soil and sediment may affect the transport of contaminants in the environment. In this study, we examined the transport behaviors of tetracycline and triclosan in saturated quartz sand with an addition of 5% newly made or aged polypropylene microplastics. The breakthrough curves were fitted with a convection-dispersion model coupled with a two-site sorption (chemical nonequilibrium) model. The results showed that the transport dynamics of tetracycline and triclosan at different pH conditions were closely associated with their dissociation status. The transport of tetracycline was prohibited at neutral condition, but was almost unaffected at acid and alkaline conditions due to the electrical repulsion between tetracycline and porous media. Triclosan was least able to migrate in its molecular form under acidic conditions, but its transport ability was increased with increasing solution pH. The presence of microplastics in the media restrained the transport of tetracycline and triclosan by increasing kinetics sorption sites and reducing sorption rate. Particularly, the degree of nonequilibrium adsorption was promoted, and the retardation factor was increased when the aged microplastics existed in the porous media. As a consequence, the sorption and retention of tetracycline and triclosan were intensified due to the generation of oxygen functional groups in aged microplastics.





Spatiotemporal patterns of ecological quality across the Qinghai-Tibet Plateau during 2000-2020.

ZHANG Yunxia, WANG Shimei, LI Yan, GAO Bingli, GONG Jie

2023, 42(6):  1464-1473.  doi:10.13292/j.1000-4890.202306.033

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The Qinghai-Tibet Plateau has a unique location, complex landform, and rich resources, with essential climatic regulation, ecological security, and special geographical significance for China and even the world. The assessment of ecological quality changes on the Qinghai-Tibet Plateau is of great significance for regional ecological protection and global change research. Based on the Google Earth Engine, we constructed a remote sensing ecological index (RSEI) by combining regional characteristics. We further analyzed the spatiotemporal variations of ecological quality in the plateau from 2000 to 2020, and examined the responses of ecological quality to climate changes and land use changes. The results showed that ecological quality had been generally improved and partially deteriorated, of which 68.33% had increased significantly, mainly distributed in Qinghai and Tibet, and 4.39% had decreased significantly, mainly located in Xinjiang and some parts of southern Tibet over the past 20 years. The RSEI was relatively low, with an average of 0.40, and showing an upward trend from the northwest to the southeast. The coefficient of variation of RSEI was dominated by weak and relatively weak grades, accounting for 89.33% of the total area, indicating that its variability could be negligible. The mean value of Hurst index was 0.45, indicating that the future change trend of ecological quality is stronger in reverse than in same direction, showing a weak deterioration trend in the plateau. Among them, 0.28% of the area with significant continuous deterioration was located in the northwestern plateau. Only 12.40% of the plateau that will begin to deteriorate was mainly distributed in the central and northern plateau. The impacts of precipitation on RSEI were greater than that of temperature. The area with significant correlation between RSEI and temperature only accounted for 10.68%, while that with significant correlation between RSEI and precipitation accounted for 25.73%. The improvement and expansion of forest and grassland promoted the improvement of ecological quality, while the reduction of permanent glaciers and snow led to the deterioration of regional ecological quality. Our results can provide a theoretical basis for regional ecological restoration and promoting ecosystem balance of Qinghai-Tibet Plateau.





Impacts of climate change and human activities on the NPP of vertical natural belts in arid zones.

CHEN Bingming, ZHAO Shanchao, SUN Fenghua, WANG Yugang

2023, 42(6):  1474-1483.  doi:10.13292/j.1000-4890.202306.004

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Clarifying the impacts of climate change and human activities on net primary productivity (NPP) is important for regional environmental management and sustainable development. Based on data of NPP, land use type and meteorology, we analyzed the spatial and temporal variations of actual NPP (NPPA) in Fukang from 2001 to 2019, and further distinguished the impacts of climate change and human activities on NPPA in altitudinal natural belts. The results showed that the multi-year average of NPPA in Fukang was 100.56 g C·m^-2·a^-1, with a significant increasing trend (P<0.05). The areas with high and rapidly rising NPPA were located in farmlands and forests. The multi-year average of NPPA of different land use types differed significantly (P<0.05), with the highest in forests (335.77 g C·m^-2·a^-1) and the lowest in deserts (19.27 g C·m^-2·a^-1). NPPA of forests, grasslands, and built-up lands showed a significant increasing trend (P<0.05). After subdividing NPPA into potential NPP (NPPP) and NPP caused by human activities (NPPH), we found that the multi-year average of NPPP in Fukang was 284.06 g C·m^-2·a^-1, with insignificant interannual variation (P>0.05). In contrast, the multi-year average of NPPH was 183.50 g C·m^-2·a^-1, with a trend of significant decline (P<0.05). There were differences in the impacts of climate change and human activities on different natural belts, with climate change contributing most to NPPA in the steppe belt (NPPP=353.05 g C·m^-2·a^-1) and NPPA in the desert belt being most influenced by human activities (NPPH=201.94 g C·m^-2·a^-1). For the impact factors of NPP_A, precipitation and temperature can indirectly contribute to NPP_A by enhancing NPP_P, while beneficial human activities indirectly contribute to NPP_A by reducing NPP_H.





Research progress on net carbon sequestration capacity of plants under the background of carbon neutra-lization.

YANG Qianmin, YUAN Danping, DENG Cunbao, WANG Yansheng, QIAO Ling

2023, 42(6):  1484-1496.  doi:10.13292/j.1000-4890.202306.015

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Plants play a key role in regulating the balance of atmospheric CO₂ concentrations, improving carbon sequestration capacity and ecosystem carbon stocks, and contributing to the mitigation of global warming. It is therefore of great significance to further understand the factors affecting the net carbon sequestration capacity of plants in order to achieve the targets of carbon peak and carbon neutralization in China. We summarized the recent progresses in carbon fixation pathways in photosynthesis, carbon release processes through litter decomposition, and factors (CO₂ concentration, temperature, water content, litter addition and removal) affecting carbon sequestration and carbon release through CO₂ and CH₄ emissions. The results showed that there was a threshold for the promotion of water, temperature, and CO₂ concentration on plant carbon sequestration and the promotion of water and temperature on the CO₂ emission from litter decomposition. When the threshold exceeds a certain range, an inhibitory effect exists on the aforementioned process. Litter removal is beneficial to reducing CO₂ emission, but the response of CH₄ emission through litter decomposition to the above environmental factors has been inconclusive. We propose to strengthen studies on the carbon sequestration ability of plants in different stages of life cycles by the combined action of multiple environmental factors; and on carbon emission mechanisms of tree residues, belowground litter, root exudates, and their responses to environmental factors, which will provide a reference for improving plant carbon sequestration and carbon neutrality.





Review on the pathways of soil nitrous oxide production and its research methods.

HE Meixia, DUAN Pengpeng, LI Dejun

2023, 42(6):  1497-1508.  doi:10.13292/j.1000-4890.202306.001

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Nitrous oxide (N₂O) is a greenhouse gas in the troposphere and contributes to ozone depletion in the stratosphere. Soil N₂O production involves biotic (autotrophic nitrification, heterotrophic nitrification, nitrifier denitrification, nitrification-coupled denitrification, heterotrophic denitrification, codenitrification, dissimilatory nitrate reduction to ammonium) and abiotic pathways. A couple of N₂O production pathways may occur simultaneously, it is thus difficult to quantify the contribution of a single pathway to N₂O production. However, quantifying the contribution of individual pathways to total N₂O production is necessary to mitigate soil N₂O emission, or to simulate soil N₂O production and its responses to global change using Earth system models. Some methods have been developed to decipher N₂O production pathways, including molecular methods, inhibition techniques, and stable isotope methods. Here, we review current status of soil N₂O production pathways and their research methods. We pointed out the advantages and disadvantages of each method and the knowledge gaps. The information is useful for researchers to carry out relevant researches, or can help understand the major sources of soil N₂O emission and thus make effective measures to mitigate soil N₂O emission.





Macroalgal consumption by two herbivorous coral-reef fish species from Jinqing Island, Xisha.

WU Peng, WANG Teng, LIU Yong, LI Chunhou, LING Juan, XIAO Yayuan, LIN Lin

2023, 42(6):  1509-1516.  doi:10.13292/j.1000-4890.202305.013

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Herbivorous fish plays an important role in controlling macroalgal overgrowth on coral reefs. Here, we used 18S rRNA high-throughput sequencing to investigate the diet composition and macroalgae consumption of two herbivorous fish (Acanthurus triostegus and Siganus punctatissimus), the common herbivores species on reefs of Jinqing Island, Xisha, China. The two species differed in food composition pattern. A. triostegus fed more on Rhodophyta, Ochrophyta, and Bacillariophyta, whereas S. punctatissimus preferred Porifera, Ochrophyta, and Streptophyta. The dominant operational taxonomic unit (OTU) in the intestines also varied between the two species. Moreover, the two species showed different feeding preferences for macroalgae. The grazer A. triostegus consumed eight species of macroalgae and fed mostly on turf algae, whereas S. punctatissimus consumed 16 macroalgae species and preferred fleshy macroalgae. Our findings indicated that both A. triostegus and S. punctatissimus are important for preserving the health of coral reefs, by removing macroalgae and consuming predators of corals, namely sponges.





Analysis of urban river pollution characteristics of Fuxi River, a tributary of Tuojiang River by multivariate statistical model.

ZHANG Wanping, FAN Min, YANG Yuankun, LI Jian, SU Min, CHEN Shu

2023, 42(6):  1517-1526.  doi:10.13292/j.1000-4890.202306.007

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Small sized rivers in towns are facing the problems such as complex pollution sources, serious water pollution, and lack of hydrological monitoring data. It is thus of great significance to accurately analyze pollution source for watershed water pollution control. Based on water quality monitoring data of each monitoring section of the Fuxi River, a primary tributary of Tuojiang River from 2018 to 2020, we comprehensively evaluated water pollution using the Nemerow pollution index and analyzed pollution sources using the absolute principal component score-multiple linear regression model. Results showed that water quality of Fuxi River basin was mainly in moderate pollution level in 2018, while in mild-moderate pollution level in 2019 and 2020. Water quality of the basin was mainly in light to moderate pollution level in wet season and normal season, while in moderate pollution level in dry season. Water quality of the main stream was better than that of the tributaries. Agricultural-livestock and poultry breeding mixed sources, domestic-livestock and poultry breeding mixed sources, natural sources, and organic pollutant sources were main pollution sources in the basin. The agricultural-livestock and poultry breeding mixed sources contributed greatly to chemical oxygen demand (COD_Mn) and total phosphorus concentrations, with a contribution rate of 7.8% and 11.8%, respectively. As for ammonia and total nitrogen, the main pollution sources were domestic-livestock and poultry breeding mixed sources, with a contribution rate of 59.4% and 23.8%, respectively. For five-day biochemical oxygen demand, the main contributor was organic pollutants, with a contribution rate of 12.1%. The framework of watershed pollution analysis based on multivariate statistical technology proposed in this study can be used to quickly and accurately analyze the pollution sources and their contribution rates in river basins with hydrological data lacking and complex pollution sources, which provides a scientific basis for water environmental management in tributaries of Tuojiang River basin and a reference for the analysis of water pollution characteristics and pollution sources in other rivers with small towns similar to the tributaries of Tuojiang River basin.





Optimization of urban green space ecological network in Chengdu based on morphological spatial pattern analysis and graph theory.

ZHOU Yuan, TANG Mi, CHEN Juan, LI Bei

2023, 42(6):  1527-1536.  doi:10.13292/j.1000-4890.202306.014

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The construction of green space ecological network is a key point for urban and rural green space to play its compound ecological efficiency, which is of great significance for promoting the sustainable development of urban and rural ecological environment. In this study, we extracted the spatial distribution information of green space in the central urban area of Chengdu to quantify the spatial connectivity characteristics of green space ecological network, and examined the optimal structure of urban green space ecological network by using morphological spatial pattern analysis (MSPA) and graph theory. The results showed that MSPA method could effectively identify the systemically important core areas and connecting-bridge areas. The green space ecological network constructed by graph theory presented the following characteristics: (1) The south and north parts of Chengdu were dominated by river corridors, with complex network structure. (2) The west part of Chengdu was dominated by isolated island green patches, with relatively less corridors. (3) The connectivity of green space network had obvious spatial differences, with a decreasing trend from west to east and from periphery to center. Finally, based on the graph metrics, important ecological sources, stepping-stone patches and important connected ecological corridors were selected in the central Chengdu to optimize the structure of green space ecological network. The optimization of green space ecological network based on MSPA and graph theory has crucial theoretical reference and method support for urban green space system planning.