Table of Content

15 November 2023, Volume 34 Issue 11

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Root distribution characteristics of monoculture and mixture of Pinus tabuliformis and Robinia pseudoacacia plantation.

GUO Yu, YAO Jiafeng, DONG Yuan, YAN Jue, YANG Nan, FENG Yonghan, WEI Xi, LIANG Wenjun

2023, 34(11):  2881-2888.  doi:10.13287/j.1001-9332.202311.008

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In this study, we analyzed the vertical distribution characteristics of root biomass density, root length density, root surface area density in monoculture and mixture of Pinus tabuliformis and Robinia pseudoacacia plantations in Caijiachuan small watershed of Jixian County, Shanxi. We examined their relationships with soil physical and chemical properties in different stand types. The results showed that the total root biomass density of P. tabuliformis and R. pseudoacacia in mixture was more than 75% higher than that in monoculture. Root system of P. tabuli-formis mainly distributed in shallow layer (0-40 cm), while that of R. pseudoacacia was deeper (40-80 cm). Fine roots were predominant in different diameter classes. Length density and surface area density of fine roots were in the order of R. pseudoacacia in mixture > P. tabuliformis in mixture > R. pseudoacacia stand > P. tabuliformis stand. Root biomass density of fine roots was in the order of P. tabuliformis in mixture ＞ R. pseudoacacia in mixture ＞ P. tabuliformis stand ＞ R. pseudoacacia stand. In vertical profile, the total root and fine root biomass, root length and root surface area density of P. tabuliformis stand, R. pseudoacacia stand, P. tabuliformis in mixture and R. pseudoacacia in mixture showed a rule of decreasing with the increases of soil depth. Under different stand types, fine root length density, root biomass density and total root length density were positively correlated with soil total nitrogen, soil organic carbon, and soil water contents. Total root surface area density was significantly positively correlated with soil organic carbon, soil water content, and soil total nitrogen. The distribution of roots in pure and mixed stands of P. tabuliformis and R. pseudoacacia showed different patterns. Compared with the pure stand, the mixed stand had higher root biomass, soil nutrient contents, and soil water content.

Ecological stoichiometry of leaf-litter-fine roots in mixed plantations in mountainous area of Southern Ningxia, China.

LI Xinyang, ZHANG Juanjuan, ZHOU Jianyun, CHEN Meng, LI Ming, ZHANG Xu, ZHAO Yan, CAO Yang

2023, 34(11):  2889-2897.  doi:10.13287/j.1001-9332.202311.009

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The southern mountainous areas in Ningxia are representative regions of the Loess Plateau, with extremely fragile ecological environment. Large area of pure plantations established during the project of Grain for Green has suffered from poor nutrient availability and biodiversity loss, while planting mixed plantations is commonly consi-dered as an effective way to improve the ecological benefits. We selected Robinia pseudoacacia + Picea asperata mixed plantation, R. pseudoacacia + Armeniaca sibirica mixed plantation, A. sibirica pure plantation and R. pseudoa-cacia pure plantation located ina Ningnan mountainous area as test objects. Based on the theory and method of ecological stoichiometry, we measured the C, N and P contents of leaves, litter and fine roots to understand nutrient cycling characteristics of different plantations. The results showed that there was significant difference in foliar stoichiometry of each tree species within the four plantations. P. asperata leaves had the highest C content in the R. pseudoacacia + P. asperata mixed plantation, and R. pseudoacacia leaves had the highest N and P contents in the R. pseudoacacia + A. sibirica mixed plantation. N content of R. pseudoacacia and A. sibirica leaves was significantly higher in mixed plantation compared with that in pure plantation. There was no significant difference in litter biomass, litter C, N, P contents and stoichiometric ratios between the pure and mixed plantations of R. pseudoacacia. Litter biomass in A. sibirica pure plantation was significantly higher than that in R. pseudoacacia + A. sibirica mixed plantation, while litter C content was significantly lower than that in the mixed plantation. Fine root biomass decreased with increasing soil depth in the four plantations, with total fine root biomass being the highest in the R. pseudoacacia + A. sibirica mixed plantation. N content and N:P of fine roots in the R. pseudoacacia + A. sibirica mixed plantation were higher than those in R. pseudoacacia and A. sibirica pure plantations. There was significant negative correlation between N content in leaves and fine roots of R. pseudoacacia + A. sibirica mixed plantation. There were significant negative correlations between the N content of leaves and litter, as well as between the P content of leaves and fine roots in the R. pseudoacacia + P. asperata mixed plantation. P content between litter and fine roots in A. sibirica pure plantation was significantly negatively correlated. Nutrient status of mixed plantations was better than pure plantations in the Ningnan mountainous area, with the mixed plantation of R. pseudoacacia and A. sibirica being the best. Mixed planting reduced nutrient limitation on plant growth to a certain extent.

Linkages of soil CO₂ emission with plant functional traits in young subtropical plantations.

ZHANG Heng, JIA Hui, CUI Yingying, HE Lulu, XIAO Haoyan, ZOU Bingzhang, WANG Sirong, WAN Xiaohua

2023, 34(11):  2898-2906.  doi:10.13287/j.1001-9332.202311.005

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Soil respiration is a key process in forest biogeochemical cycling. Exploring the relationship between plant functional traits and soil respiration can help understand the effects of tree species conversion on soil carbon cycling. In this study, we selected 15 common subtropical tree species planted in the logging site of second-generation Chinese fir forest to measure soil CO₂ emission fluxes, soil physicochemical properties, leaf and root functional traits of each species, and explored the effects of plant functional traits on soil respiration. The results showed that the annual flux of soil CO₂ emissions varied from 7.93 to 22.52 Mg CO₂·hm^-2, with the highest value under Castanopsis carlesii (22.52 Mg CO₂·hm^-2) and the lowest value under Taxus wallichiana (7.93 Mg CO₂·hm^-2). Results of stepwise regression analysis showed that the annual flux of soil CO₂ emission decreased with the increases of leaf nitrogen content and fine root diameter, and increased with increasing leaf non-structural carbohydrate. In the structural equation model, leaf non-structural carbohydrate had a direct and significant positive effect on soil CO₂ emission fluxes, while leaf nitrogen content and fine root diameter had a direct negative effect by decreasing soil pH and soluble organic nitrogen content. Plantations of different tree species would affect soil CO₂ emission directly by changing functional traits related to water and nutrient acquisition or indirectly through soil properties. When creating plantations, we should select tree species based on the relationship between plant functional traits and ecosystem functions, with a view to improving forest productivity and soil carbon sequestration potential.

Construction of universal equations for knot attributes of three coniferous species

LI Zelin, JIA Weiwei, GUO Haotian, AO Ziqi, ZHAO Yang

2023, 34(11):  2907-2918.  doi:10.13287/j.1001-9332.202311.001

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We constructed base model, dummy variable model, and mixture model with three variables including knot diameter, loose knot length, and sound knot length with three typical coniferous species, Pinus koraiensis, Larix olgensis, and Pinus sylvestris var. mongolica, from the Linkou Forestry Bureau and Mengjiagang forest farm in Heilongjiang Province in 2020. We analyzed the differences in knot properties among different tree species and simplified the modeling work. Firstly, we collected relevant knot property data through the sectioning method based on relevant literature, transformation of the model form and substitution of related variables to conduct a base model. We transformed the species into dummy variables as qualitative factors, and introduced the dummy variable model of the relevant attributes into the base model. We introduced the random effects of sample trees and sample plots when constructing the mixture model. By comparing evaluation indicators, such as Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC), the mixture model with the best fitting effect was selected. We selected the optimal universal equation by comparing the fitting accuracy of the base model, dummy variable model and mixture model. The fitting accuracy of the dummy variable model and mixture model was higher than that of the basic model. The evaluation indicators (AIC and BIC) showed that the mixture model had a better fitting effect on knot properties than the dummy variable model. In the model comparison results, R² of mixture models for sound knot length, the loose knot length, and knot diameter increased by 13.2%, 84.8% and 40.3%, respectively. The predictive accuracy of the three base models for different tree species’ knot attributes was above 90%, and both the prediction accuracy of the dummy variable model and mixture model were above 94%, indicating that the constructed models could well predict knot-related properties. From the perspective of tree species, the sound knot length, knot diameter, and loose knot length was in order of P. sylvestris var. mongolica > P. koraiensis > L. olgensis. Fitted results of the dummy variable model and the mixture model were superior to the basic model, with higher accuracy.

Spatiotemporal variation and driving factor of vegetation coverage from 2000 to 2020 in southern Jiangxi Province, China.

LIU Dongdong, PAN Ping, FU Jia, OUYANG Xunzhi

2023, 34(11):  2919-2928.  doi:10.13287/j.1001-9332.202311.023

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Vegetation plays a critical role in the water and carbon cycling and energy flow, serving as an indicator for regulating land carbon balance and reflecting climate change and human activities. We analyzed the spatiotemporal variations of normalized difference vegetation index (NDVI) during the growing season in southern Jiangxi from 2000 to 2020, using statistical methods, including the Mann-Kendall test, Theil-Sen Median analysis, Hurst index, and coefficient of variation. We employed the geodetector model to comprehensively assess the impacts of climate, topography, soil and human factors on spatial differentiation of vegetation NDVI. The results showed NDVI exhibited an upward fluctuating trend with a rate of 0.003 per year from 2000 to 2020. The proportion of high-grade and medium-high-grade NDVI areas were 55.8% and 41.9%, respectively, while the areas with low and relatively low fluctuations accounted for 92.3%. The proportions of areas showing extremely significant improvement and significant improvement were 40.4% and 19.4%, respectively. In contrast, the combined proportion of areas displaying extremely significant degradation and significant degradation was only 2.2%. The proportions of areas demonstrating continuous improvement and future improvement were 28.0% and 60.2%, respectively. Elevation, precipitation, relative humidity, temperature, landform type, land use type, population density, and nighttime light were identified as the major factors for the vairations of NDVI in the study area, followed by slope, soil type, and GDP, while slope aspect and vegetation type had indirect influence. Throughout the study period, NDVI in southern Jiangxi was overall stable, with future changes primarily indicating improvement. Notably, human factors such as land use type, population density, and nighttime light index exhibited an upward trend in their impacts on NDVI.

Ecological drought monitoring of Inner Mongolia vegetation growing season based on kernel temperature vegetation drought index (kTVDI).

ZHAO Jiapei, GUO Enliang, WANG Yongfang, KANG Yao, GU Xiling

2023, 34(11):  2929-2937.  doi:10.13287/j.1001-9332.202311.024

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Ecological drought monitoring is important for regional status assessment and protection of water resources. In this study, we constructed a new ecological drought index, the kernel temperature vegetation drought index (kTVDI), by using the kernel normalized vegetation index (kNDVI) to improve the temperature vegetation drought index (TVDI) in Inner Mongolia. We further analyzed the spatial and temporal distribution of ecological drought in Inner Mongolia during 2000-2022 and the future trend of ecological drought by using segmented linear regression model, Theil-Sen median, Mann-Kendall test, and Hurst index. The results showed that kTVDI performed better in monitoring ecological drought than TVDI. From 2000 to 2022, kTVDI showed a decreasing trend in the growing season in Inner Mongolia, but the change was not significant, and a sudden change occurred in 2016, and the wetting trend after the sudden change was more obvious. During the study period, ecological drought in 23.6% of the areas of Inner Mongolia showed an aggravating trend, and ecological drought was alleviated in 46.5% of the area. In the future, ecological drought would be exacerbated in the eastern part but alleviated in the central and western parts of Inner Mongolia.

Characteristics of herbaceous plant community composition, niche and stability under different main-tenance measures at Sanxingdui City Wall, Sichuan, China.

ZHONG Xinyi, ZHAO Fan, YAO Xue, WU Yuru, XU Yin, YU Shunyao, LIN Jingyun, HAO Jianfeng

2023, 34(11):  2938-2946.  doi:10.13287/j.1001-9332.202311.007

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To understand the distribution characteristics and restoration status of vegetation at Sanxingdui City Wall, we sampled five typical communities of the city wall at the Sanxingdui site and explored the stability and niche characteristics of herbaceous plant communities under different maintenance measures (natural regeneration, planting, abandoned field, shrub removal, and pruning) following the niche theory and the improved contribution law method. A total of 87 herbaceous species belonging to 73 genera and 31 families were recorded. Compositae and Gramineae were dominant, and perennial herbs were the majority. There were differences in the niche breadth of major herbaceous species under different maintenance measures. The niche breadth of annual plants was higher under natural regeneration and shrub removal, and that of perennial plants was higher under planting, abandoned field, and pruning measures. The niche overlap and similarity of herbaceous plants were higher under natural regene-ration, shrub removal and pruning measures, and were the lowest under planting measure. The importance values were positively correlated with the niche breadth, but the ranking was not completely consistent. Species with higher niche breadth usually had higher probability of niche overlap and higher niche similarity. Combined with the M-Godron’s stability analysis, community stability was comparable among shrub removal, pruning, and natural regeneration measures whereas the abandoned field and planting showed lower community stability. We recommended the implementation of in situ conservation measures based on natural regeneration, supplemented by scientific artificial maintenance (shrub removal, pruning, etc.) when necessary, so as to achieve a stable species composition and promote the sustainable development and vegetation landscape restoration at Sanxingdui City Wall.

Effects of exogenous melatonin on growth and physiological characteristics of Agropyron mongolicum seedlings under drought stress

WANG Jing, FU Bingzhe, LI Shuxia, WANG Xing, SONG Wenxue, YE Yunong, HU Pengfei, WANG Tongrui

2023, 34(11):  2947-2957.  doi:10.13287/j.1001-9332.202311.004

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To clarify the alleviation effect of exogenous melatonin (MT) on Agropyron mongolicum under drought stress, we examined the response of A. mongolicum ‘Yanchi’ seedlings to simulated drought stress with polyethylene glycol 6000 (PEG-6000), by investigating the effects of exogenous addition of different concentrations (0, 1, 10, 50, 100, 150 and 200 mg·L^-1) of MT on seedlings growth and physiological characteristics under drought stress. The results showed that drought stress significantly inhibited the growth of A. mongolicum seedlings, and that exogenous addition of different concentrations of MT could alleviate the growth inhibition caused by drought stress, with the strongest mitigation effect observed at MT concentration of 100 mg·L^-1. Compared with the drought stress treatment alone, exogenous addition of 100 mg·L^-1 MT under drought stress increased plant height, aboveground dry weight, and leaf relative water content by 58.2%, 121.2% and 48.1%. The contents of chlorophyll a, chlorophyll b, carotenoids increased by 48.7%, 80.8% and 38.3%, superoxide dismutase, peroxidase and root activity increased by 12.6%, 33.9% and 39.1%, and the contents of ascorbic acid and glutathione increased by 19.5% and 18.3%, respectively. The contents of proline, soluble sugar and soluble protein were increased by 16.2%, 32.6% and 14.3%, while that of malondialdehyde, hydrogen peroxide and superoxide anion radical were decreased by 45.8%, 65.8% and 30.8%, respectively. In summary, exogenous addition of 100 mg·L^-1 MT could improve drought tolerance of A. mongolicum seedlings by promoting growth, enhancing antioxidant capacity, increasing the content of osmoregulation substances, inhibiting the excessive production of reactive oxygen, and reducing membrane peroxide level.

Methane emissions partially offset carbon sink function in global wetlands: An analysis based on global data.

ZHAN Pengfei, TONG Chuan

2023, 34(11):  2958-2968.  doi:10.13287/j.1001-9332.202311.006

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Wetlands serve as atmospheric carbon dioxide (CO₂) sinks, as well as atmospheric methane (CH₄) source due to the anaerobic soil environment. Although some studies report that the CH₄ emission from wetlands partially offset their net CO₂ uptake, there is no global data analysis on the offset of net ecosystem exchange of CO₂ (NEE) by CH₄ emission in wetland ecosystems. In this study, we collected the data sets of NEE and CH₄ flux which were simultaneously measured in the inland wetlands (peatland and non-peatland wetland) and coastal wetlands (seagrass beds, salt marshes and mangroves) around the world. The results showed that all types of wetlands were atmospheric CO₂ sink, with the NEE values ranking as follows: mangrove (-2011.0 g CO₂·m^-2·a^-1) < salt marsh (-1636.6 g CO₂·m^-2·a^-1) < non-peatland wetland (-870.8 g CO₂·m^-2·a^-1) < peatland (-510.7 g CO₂·m^-2·a^-1) < seagrass bed (-61.6 g CO₂·m^-2·a^-1). When CH₄ flux being converted into CO₂-equivalent flux (CO₂-eq flux) based on the 100-year scale global warming potentials, we found that the CH₄ emissions partially offset 19.4%, 14.0%, 36.1%, 64.9% and 60.1% of the net CO₂ uptake in seagrass beds, salt marshes, mangroves, non-peatland wetland and peatland, respectively. Over the 20-year scale, CH₄ emissions partially offset 57.3%, 41.4%, 107.0%, 192.0% and 177.3% of the net CO₂ uptake, respectively. Some mangroves, peatlands, and non-peatland wetlands acted as net CO₂ equivalent source. Over the 100-year scale, the net greenhouse gas balance of each wetland ecosystem was negative value, which indicated that even accounting CH₄ emission, wetland ecosystem was still an atmospheric carbon sink. Our results indicated that clarifying the main regulation mechanism of CH₄ emission from wetland ecosystems and proposing reasonable CH₄ reduction measures are crucial to maintain the carbon sink function in wetland ecosystems, and to mitigate the trend of climate warming.

Effects of biochar application on nitrogen transformation and N₂O emission in a coastal saline-alkali soil

XIANG Jian, SUN Xi, WANG Cheng, Zhaxiyangzong, SHI Wenzhu, WANG Genmei, ZHANG Huanchao

2023, 34(11):  2969-2977.  doi:10.13287/j.1001-9332.202311.014

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The application of biochar can improve soil fertility and benefit sustainable agricultural development and carbon neutrality simultaneously. To better understand the effects of biochar addition on nitrogen transformation and N₂O emission in a coastal saline-alkali soil and its potential mechanisms, we conducted a 60-day laboratory incubation experiment with six treatments, i.e., ammonium sulfate (N 150 mg·kg^-1), ammonium sulfate + 0.4% (weight/weight) biochar, ammonium sulfate + 0.6% biochar, ammonium sulfate + 0.8% biochar, ammonium sulfate + 1.6% biochar, and ammonium sulfate + 0.2% biochar and 0.2% organic fertilizer (based on equivalent N basis). The results showed that soil nitrogen transformation was mainly affected by biochar addition at the early stage of incubation. Biochar addition significantly increased the contents of nitrate and ammonium. Biochar addition significantly increased soil net nitrification rate, but the magnitude of such increases decreased with increasing biochar addition level. Similar temporal change patterns of N₂O emissions were observed in all treatments, and the N₂O emissions mainly occurred in the first 30 days of incubation. Compared with the CK, biochar addition significantly reduced the cumulative N₂O emission, and the decrement increased with increasing biochar addition levels. In conclusion, the effects of biochar and nitrogen fertilizer addition on soil nitrogen transformation and N₂O emission varied with the application rate. Biochar addition with a rate of 0.8% (W/W) increased soil inorganic nitrogen content and decreased soil N₂O emission. It could provide theoretical basis and reference for the formulation of reasonable plans for the improvement and utilization of biochar in coastal saline-alkali soil.

Distribution characteristics and influencing factors of soil organic carbon in tidal flat wetland of central Jiangsu, China.

GONG Zheng, WEN Tianyi, JIN Chuang, ZHAO Kun, SU Min

2023, 34(11):  2978-2984.  doi:10.13287/j.1001-9332.202311.030

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We measured winter and summer soil organic carbon (SOC) contents in two typical coastal wetlands, the Spartina alterniflora salt marsh and the non-vegetation mudflat, on the south side of the Chuandong River Estuary in Yancheng, Jiangsu Province. We investigated the spatiotemporal variations of soil organic carbon contents and its driving factors. The results showed that SOC content ranged from 0.75 to 2.38 g·kg^-1 in the mudflat area and from 2.07 to 18.59 g·kg^-1 in the S. alterniflora salt marsh area, showing a decreasing trend towards the sea. The SOC content in the S. alterniflora salt marsh area was approximately 2.5 to 3.5 times of that in the mudflat area. Within a depth range of 1 m, there was no vertical variation in SOC content in the mudflat area, but an increasing and then decreasing pattern in the S. alterniflora marsh area with the peak occurring in the depth range of 20 to 30 cm. Soil organic carbon content exhibited significant seasonal difference, with higher value in summer than in winter. The summer SOC content was 5% to 10% higher than that in winter in the S. alterniflora marsh area, while it was 43% higher in summer than in winter in the mudflat area. In the S. alterniflora marsh area, soil organic carbon content was positively correlated with soil moisture and salinity, but negatively correlated with sediment particle size. In contrast, there was no significant correlation between soil organic carbon content and soil physicochemi-cal factors in the mudflat area. Those results indicated that the correlation between various soil physicochemical factors and SOC is established on the basis of vegetation cover in coastal wetlands. Our findings could provide valuable insights for the conservation of blue carbon ecosystems in coastal wetlands in China.

Effect of electron acceptor addition on the temperature sensitivity of soil anaerobic carbon mineralization in the Yellow River Estuary wetland, China

ZHANG Jiapeng, YANG Jisong, LIU Yue, NING Kai, YU Junbao, WANG Zhikang, WANG Xuehong

2023, 34(11):  2985-2992.  doi:10.13287/j.1001-9332.202311.029

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The temperature sensitivity of soil carbon mineralization (Q₁₀) is an important index to evaluate the responses of ecosystem carbon cycling to climate change. We examined the effects of three electron acceptors [SO₄^2-, NO₃^- and Fe(Ⅲ)] addition on the Q₁₀ value of anaerobic carbon mineralization of Phragmites australis community soil (0-10 cm) in the Yellow River Estuary wetland with the closed culture-gas chromatography method. The results showed that the three electron acceptors addition inhibited the production of CO₂ and CH₄ during the 48-day culture period, with a decrease of 17.3%-20.8% for CO₂ and 29.2%-36.2% for CH₄. Generally, the CO₂ production differed with the concentrations of electron acceptors, while CH₄ production differed with the type of electron acceptors. The CO₂:CH₄ ratios were significantly different with temperature, indicating an obvious temperature dependence for the anaerobic carbon mineralization pathway. The Q₁₀ values of CO₂ and CH₄ production under three electron acceptor additions ranged from 1.08 to 1.11 and from 1.19 to 1.37, respectively, showing an increasing trend compared with the control. The type and concentration of electron acceptors affected the temperature dependence of CO₂ production, while electron acceptors affected that of CH₄ production. It is suggested that the input of reducing salts would retard the mineralization loss of organic carbon in estuary freshwater wetlands under the background of climate change, but enhance the sensitivity of carbon mineralization to increasing temperature.

Effects of slope aspect on soil enzyme activity and microbial nutrient limitation in subalpine region of wes-tern Sichuan, China.

LIU Shun, XU Gexi, CHEN Miao, CHEN Jian, FENG Qiuhong, SHI Zuomin

2023, 34(11):  2993-3002.  doi:10.13287/j.1001-9332.202311.003

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Exploring the resource limitation of soil microbial metabolism is essential to understand ecosystem functions and processes. However, the spatially divergent patterns and drivers of soil microbial nutrient limitation cha-racteristics in montane ecosystems at small scales, especially at the slope aspect scale, are still unclear. In this study, we measured soil enzyme activities involved in carbon (C), nitrogen (N) and phosphorus (P) cycle and quantified the microbial nutrient limitations by enzyme stoichiometry in two representative mountain sites in subalpine region of western Sichuan, including the sunny and shady slopes with different vegetation types (shrubland and forest, respectively) in Miyaluo of Lixian County, and with the same vegetation type (shrubland) in Yakexia of Heishui County. The results showed that soil enzyme activities and their stoichiometric ratios were significantly different between slope aspects in Miyaluo, while the differences were not significant in Yakexia. The stoichiometry ratio of C-, N- and P-acquiring enzymes on the sunny slope of Miyaluo was 1:0.96:0.92, approaching the 1:1:1 ratio at the global scale, but deviated from 1:1:1 on the shady slope of Miyaluo (1:1.39:0.75) and the different slopes of Yakexia (1:1.09:1.35). There was no significant difference in vector length between slope aspects at both sites, indicating no significant effect of slope aspect on the microbial C limitation. The vector angle was significantly higher on the sunny slope (43.6°) than that on the shady slope (28.7°) in Miyaluo, suggesting that the microorganisms were mainly N-limited. Partial least squares path model showed that the vector angle was mainly directly influenced by the soil nutrient ratios. The vector angle ranged from 50.3° to 51.4°, and did not differ between slope aspects in Yakexia. Therefore, differences in vegetation types between slope aspects drove variations in soil enzyme activity and microbial nutrient limitation through soil properties. It would provide a scientific basis for predicting the spatial pattern of soil enzyme activity and microbial nutrient limitation.

Response of soil stoichiometric characteristics to climatic factors in temperate steppe of Longzhong region, China

XU Heguang, LI Yali, HE Guoxing, LIU Xiaoni, JI Tong, XIAO Rong

2023, 34(11):  3003-3010.  doi:10.13287/j.1001-9332.202311.002

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We explored the relationship between climate factors (mean annual precipitation and mean annual temperature) and the contents and stoichiometry of soil carbon (C), nitrogen (N), and phosphorus (P) at different soil depths (0-5, 5-10, 10-20, 20-30, 30-50, 50-70, and 70-100 cm) temperate steppe of Longzhong. The results showed with the increases of soil depth, soil C, N contents, C:P, and N:P gradually decreased from 21.88 g·kg^-1, 1.84 g·kg^-1, 33.6 and 3.1 to 7.67 g·kg^-1, 0.59 g·kg^-1, 12.5 and 1.0, respectively. Soil C:N showed an increasing trend from 12.2 to 13.9, while soil P content remained stable with an average of 0.61 g·kg^-1. Soil C, N, C:P, and N:P were significantly positively correlated with mean annual precipitation and negatively correlated with mean annual temperature. Soil P content and C:N were not correlated with mean annual precipita-tion and mean annual temperature. With the increases of soil depth, the total explanatory power of the changes in soil C, N and P contents by mean annual precipitation and mean annual temperature decreased and then increased, and that in soil C:P, N:P and C:N did not change significantly. The changes of soil C, N and P contents on the temperature steppe were mainly influenced by mean annual precipitation. The effects and relative contributions of mean annual precipitation and mean annual temperature on the variations of soil nutrient contents and stoichiometry of C, N and P differed at different soil depths.

Estimation of soil water and organic matter content in medium and low yield fields of Ningxia Yellow River Irrigation area based on hyperspectral information.

DING Qidong, WANG Yijing, ZHANG Junhua, CHEN Ruihua, JIA Keli, LI Xiaolin

2023, 34(11):  3011-3020.  doi:10.13287/j.1001-9332.202311.013

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Accurately obtaining soil water and organic matter content is of great significance for improving soil qua-lity in croplands with medium to low yield. We explored the estimation effect of fractional order differentiation (FOD) combined with different spectral indices on soil water and organic matter content in medium and low yield croplands of Ningxia Yellow River Irrigation Area. After root mean square transformation of field measured hyperspectral reflectance, we used 0-2 FOD (with a step length of 0.25) to construct difference index (DI), ratio index (RI), product index (PI), sum index (SI), generalized difference index (GDI), and nitrogen planar domain index (NPDI) and to select the optimal spectral index based on the correlation coefficients between six spectral indices with soil water and organic matter contents. We constructed a model for estimating soil water and organic matter content based on partial least squares regression (PLSR) and support vector machine (SVM). The results showed that the correlation between soil water and organic matter content and spectral information was effectively improved after FOD transformation compared with the original spectrum, with maximum increases of 0.1785 and 0.1713, respectively. The soil water content sensitive bands were mainly in the range of 400-630 and 1350-1940 nm, while the sensitive bands of organic matter content were mainly at 460-850, 1530-1910, and 2060-2310 nm. The accuracy of SVM model was significantly higher than that of PLSR, and the soil water content estimation model based on 1.75-order NPDI-SVM reached the highest precision, with a validation determination coefficient (R_p²) of 0.970, root mean square error (RMSE) of 1.615, and relative percent deviation (RPD) of 4.211. The organic matter content estimation model based on 0.5 order DI-SVM had the best performance, with R_p², RMSE and RPD of 0.983, 0.701 and 5.307, respectively. Our results could provide data and technological support for soil water and nutrient monitoring, quality improvement, and graphics creating in similar area with medium to low yield fields.

Effects of exogenous trehalose on filling characteristics and sugar component content of wheat under high temperature stress during the filling period.

CUI Guoji, WANG Chuanwei, HE Wei, LI Yuxing, HUANG Zhenglai, ZHANG Wenjing, MA Shangyu, FAN Yonghui

2023, 34(11):  3021-3029.  doi:10.13287/j.1001-9332.202311.016

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Taking the heat-sensitive wheat variety ‘Fanmai 5’ (FM5) and the heat-tolerant variety ‘Huaimai 33’ (HM33), which were screened out in the previous experiments, as experimental materials, we conducted a field experiment with passive heat-enhancing shelters to simulate post-flowering high-temperature environment (average temperature increase of 5.13 ℃) during 2021-2022. During the filling period, we analyzed the effects of exogenous trehalose (10, 15 and 20 mmol·L^-1) on the filling characteristics and sugar fraction under high temperature, with no spraying at ordinary temperature as control (CK). The results showed that treating without spraying exogenous trehalose at high temperature (H) significantly reduced wheat grain yield and grain weight during the filling period, and spraying exogenous trehalose alleviated the reduction of grain yield and grain weight at the filling stage under high temperature stress. Compared with the H treatment, grain yield and grain weight of HM33 and FM5 wheat varie-ties increased by 3.5%, 6.7% and 4.2%, 5.4%, respectively. High temperature stress significantly increased the trehalose content and trehalase (THL) activity in flag leaves of both wheat varieties, and decreased the fructose and glucose contents. Spraying exogenous trehalose increased the contents of trehalose, fructose, and glucose in flag leaves, and decreased the trehalase activity in flag leaves compared with H treatment, which could improve the glucose metabolism capacity of wheat at filling stage. The increasing effect of FM5 was higher than that of HM33. High temperature stress significantly reduced starch content of flag leaves and grains, while spraying exogenous trehalose alleviated the decrease of starch content of flag leaves and grains under high temperature stress, which was profit able for the substance accumulation of wheat grains under high temperature stress. Under the conditions of this experiment, spraying 15 mmol·L^-1 trehalose at flowering stage was the best treatment for the two wheat varieties.

Effects of maize and soybean intercropping on soil phosphorus bioavailability and microbial community structure in rhizosphere.

GU Jiacheng, WANG Wenmin, WANG Zhen, LI Luhua, JIANG Guiju, WANG Jiaping, CHENG Zhibo

2023, 34(11):  3030-3038.  doi:10.13287/j.1001-9332.202311.015

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To investigate the effect of maize/soybean intercropping on rhizosphere soil microbial communities and phosphorus (P) bioavailability, we examined the changes of soil bioavailable P fractions and microbial community characteristics in the monoculture and intercropping systems based on high-throughput sequencing. The results showed that maize/soybean intercropping increased the contents of rhizosphere soil organic matter (SOM), available phosphorus (AP), microbial biomass phosphorus (MBP), and aboveground biomass. The increase of AP was mainly related to the increasing enzyme extracted phosphorus (Enzyme-P) and hydrochloric acid extracted phosphorus (HCl-P) contents. The dominant bacterial phyla under each treatment were Proteobacteria, Actinobacteria, Acidobacteria and Chloroflexi, while the dominant bacterial genera were Nocardioides, Solirubacter, Sphingomonas and Arthrobacter, with Proteobacteria and Sphingomonas having the highest relative abundance. The relative abundance of Proteobacteria and Sphingomonas in intercropping maize rhizosphere soil was significantly higher than that in monoculture, and that of Proteobacteria in intercropping soybean rhizosphere soil was significantly higher than monoculture. Soil properties and P fractions were closely related to the rhizosphere soil microbial composition. In all, maize/soybean intercropping could affect the rhizosphere soil P bioavailability by altering the structure of rhizosphere microbial communities.

Effects of microbial agents and corn protein ferment on physiological characteristics in leaves and yield of tomato

LIU Xigang, LI Nan, JI Tuo, ZHOU Bo, WEI Min, LI Jing, YANG Fengjuan

2023, 34(11):  3039-3044.  doi:10.13287/j.1001-9332.202311.017

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Premature senescence in greenhouse tomato is a significant challenge under long-season cultivation, due to suboptimal nutrient management during growth periods. We investigated the effects of microbial agents (T₁), corn protein ferment (T₂), and their combined application (T₃) on photosynthetic characteristics and antioxidant enzyme activities in ‘Saint Laurent 3689’ tomato leaves, normal management served as the control (CK). We explored the physiological mechanism of delaying leaf senescence. Results showed that applying microbial agents or corn protein ferment individually led to improvements in leaf photosynthetic characteristics and antioxidant enzyme activities. The combined application yielded superior outcomes. Eighty days post the combined application of microbial agents and corn protein ferment (T₃), chlorophyll (a+b) content, net photosynthetic rate, and the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in leaves increased by 16.4%, 30.9%, 23.4%, 33.0% and 40.3%, respectively, compared with the CK. Furthermore, plant height and stem diameter increased by 8.2% and 7.0%, while the total yield exhibited a significant increase of 9.9% compared with the CK 210 days post-treatment. In conclusion, the combined application of microbial agents and corn protein ferment has promising potential in enhancing chlorophyll content, net photosynthetic rate, and the activities of SOD, POD and CAT in tomato leaves. This approach effectively delayed leaf senescence, thereby promoting tomato growth and remarkably increasing the yield.

Inversion of soil water and salt information based on UAV hyperspectral remote sensing and machine lear-ning.

WANG Yijing, DING Qidong, ZHANG Junhua, CHEN Ruihua, JIA Keli, LI Xiaolin

2023, 34(11):  3045-3052.  doi:10.13287/j.1001-9332.202311.012

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Accurate diagnosis of water and salt information in saline agricultural lands is crucial for long-term soil quality improvement and arable land conservation. In this study, we extracted field-scale vegetation canopy spectral information by UAV hyperspectral information, transforming the reflectance (R) to standard normal variate transformation (SNV), multiplicative scatter correction (MSC), first derivative of reflectance (FDR) and second derivative of reflectance (SDR). We determined the optimal spectral transformation forms of soil water content (SWC), soil pH, and soil salt content (SSC) by the maximum absolute correlation coefficient (MACC), and extracted the feature bands by competitive adaptive reweighted sampling (CARS). We constructed an inversion model of soil water and salt information by partial least squares regression (PLSR), random forest (RF), and extreme gradient boosting (XGBoost). The results showed that R, FDR and MSC were the best spectral transformation types for soil water content, soil pH, and soil salt content, and the corresponding MACC were 0.730, 0.472 and 0.654, respectively. The CARS algorithm effectively eliminated the irrelevant variables, optimally selecting 16-17 feature bands from 150 spectral bands. Both soil water content and soil pH performed best with XGBoost model, achieving determination coefficient of validation (R_p²) 0.927 and 0.743, and the relative percentage difference (RPD) amounted to 3.93 and 2.45. For soil salt content, the RF model emerged as the best inversion method with R_p² and RPD of 0.427 and 1.64, respectively. The study could provide a reference solution for the integrated remote sensing monitoring of soil water and salt information in space and sky, serving as a scientific guide for the amelioration and sustainable management of saline lands.

Temporal and spatial variations and the relationships of land use pattern and ecosystem services in Qinghai-Tibet Plateau, China.

HAO Jiayuan, ZHI Liehui, LI Xiaowen, DONG Shikui, LI Wei

2023, 34(11):  3053-3063.  doi:10.13287/j.1001-9332.202311.019

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The Qinghai-Tibet Plateau is the key and largest ecological hotspot globally with enormous multiple ecosystem services. The vast and unique alpine ecosystems in this area have been subjected to the increased human disturbances, such as intensified land use. To explore the magnitude, spatiotemporal pattern and transformation process of land use in the Qinghai-Tibet Plateau and their impacts on the major ecosystem services during 1980-2020, we used the Integrated Valuation of Ecosystem Services and Trade-offs model to simulate the spatiotemporal variations of three types of ecosystem services, including habitat quality, carbon storage, and water yield. We analyzed the impacts of land use change on ecosystem services. The findings revealed that land use pattern remained generally stable from 1980 to 2020, with alpine grassland and desert as the dominant land use types. Habitat quality had generally enhanced, while carbon storage and water yield increased firstly and then declined. The magnitudes of three services gradually increased from the northwest to the southeast, corresponding to the spatial transformation pattern from desert via grassland to forest. The correlation between land use intensity and ecosystem services showed significant spatial heterogeneity, particulaly in counties greatly affected by land use intensity which concentrated predominantly in the mid-west, southern, and mid-east regions of the Qinghai-Tibet Plateau. The results have certain guiding significance for formulating land use policy and regulating land use pattern of alpine ecosystems in the Qinghai-Tibet Plateau.

Assessment of ecosystem quality changes based on optimizing key indicators in Nanwenghe National Nature Reserve, Heilongjiang, China.

ZENG Haowei, LING Chengxing, LIU Hua, ZHAO Feng, WANG Xinmiao, ZHANG Yutong

2023, 34(11):  3064-3072.  doi:10.13287/j.1001-9332.202311.022

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Net primary productivity (NPP) is an indicator to reflect the production capacity of terrestrial ecosystems, as well as a key indicator for ecological quality. NPP at large scale is difficult to be measured. At present, most of the assessment of ecosystem quality uses NPP products with low resolution, which cannot capture the detailed characteristics of the ecosystem and is not conducive to the assessment of ecosystem quality at small-scale. The establishment of a rapid and efficient assessment method for small-scale ecosystem quality will greatly promote the protection and restoration of ecosystems in China. We focused on the calculation method of ecosystem quality assessment and NPP, and optimized the calculation process of the NPP, and obtained NPP by remote sensing without ground observation data. We established a regression model for remote sensing inversion of leaf area index, and estimated the vegetation coverage by using dimidiate pixel model, developed a set of methods for rapid assessment of ecosystem quality by remote sensing. Taking Nanwenghe National Nature Reserve as an example, we evaluated the change of ecosystem quality from 2001 to 2022. The results showed that from 2001 to 2022, the ecosystem qua-lity of the reserve was good as a whole, and that the area with good and excellent quality accounted for more than 85% in 2022. High vegetation coverage was the backbone of the sustainable good ecosystem quality of the reserve. From 2001 to 2022, ecosystem quality of the reserve showed a trend of first decreasing and then increasing, with the lowest point of ecosystem quality in 2013. This method had achieved good results in the evaluation of ecosystem quality in Nanwenghe National Nature Reserve. The index optimization method proposed in this study could facilitate the rapid and accurate assessment of ecosystem quality in small-scale regions, and thus provides technical reference for the precise improvement of ecosystem quality.

Trade-offs and synergies relationships of ecosystem services and their socio-ecological driving factors under different spatial scales in Shaoguan City, Guangdong, China.

DENG Yuyue, WANG Dan, XU Han

2023, 34(11):  3073-3084.  doi:10.13287/j.1001-9332.202311.025

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Ecosystem services refer to the benefits that human obtain from natural ecosystems. Different ecosystem services are generated by the combination of social-ecological driving factors, and exhibit different spatial patterns across scales. The complex relationships and driving mechanisms among ecosystem services under different spatial scales remain unclear. With Shaoguan City from Guangdong Province as the study area, we analyzed the spatial patterns and relationships of four ecosystem services and their trade-offs/synergies (TOSs), quantified their responses to seven social-ecological drivers at the kilometer grid scale and sub-watershed scale, and proposed regional ecologi-cal management and planning strategies for cross-scale sustainable development. The results showed that the spatial distribution of ecosystem services in Shaoguan City exhibited spatial clustering and cross-scale variations. Habitat quality, water yield, and carbon storage exhibited similar spatial distribution pattern. High supply was mainly distributed in mountainous areas in the east, north, west, and south, while weak supply was distributed in plain areas in the central, northwest, south and northeast. In addition, the spatial clustering of these services intensified with increasing spatial scale. Ecosystem services displayed synergistic relationships at both spatial scales, and the intensity of the synergy changed with scale. At both the kilometer grid and sub-watershed scale, the primary drivers for ecosystem services were the normalized vegetation index and digital elevation model. The main driver for TOSs was the mean annual temperature at the kilometer grid scale, while it was the mean annual evapotranspiration at the sub-watershed scale. Based on the supply levels of ecosystem services, the study area could be divided into five distinct ecosystem service bundles, i.e., mountain ecological balance zone, forest ecological conservation zone, urban forest maintenance zone, ecologically sensitive zone, and ecological risk zone. All bundles exhibited both spatial heterogeneity and cross-scale variations. We integrated the cross-scale variations of four representative ecosystem services and their complex interactions and driving mechanisms in Shaoguan City into spatial planning to facilitate the sustainable ecosystem management across multiple scales, which could offer valuable references for the construction of ecological civilization in other regions.

Driving factors and decoupling effects of agricultural carbon emissions in Jiangxi Province based on time-varying parameter C-D production function

ZHU Jiaqing, QIN Huiyan, ZHANG Mengchun

2023, 34(11):  3085-3094.  doi:10.13287/j.1001-9332.202311.011

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The reduction of agricultural emission plays an important role in realizing the dual-carbon goals. It is thus of great significance to examine the characteristics and drivers of regional agricultural carbon emission. We measured agricultural carbon emission in Jiangxi Province from the perspective of input-output and production processes, and explored the drivers and decoupling dynamics of agricultural carbon emission by using the LMDI decomposition method together with the Tapio decoupling model modified by time-varying parameter C-D production function. The results showed that agricultural carbon emission in Jiangxi increased by 26.4% from 2010 to 2021, and the carbon emission intensity decreased year by year with an average annual rate of 4.9%. Factors such as agricultural carbon intensity, labor input, and capital stock collectively reduced carbon emission by a total of 61.05 Mt, with a contribution of 27.0%, 44.5% and 28.5%, respectively. Level of agricultural economic development, agricultural structure, and technological progress had strong driving effects, which accounted for 75.7%, 5.6% and 18.8%, respectively. Agricultural carbon emission in Jiangxi was weakly decoupled from economic development, capital stock, and technological progress factors, but was negatively decoupled from labor input. Moreover, the decoupling state was more desirable in the later period than in the earlier period. Our results suggested that the application of the time-varying parameter C-D production function is innovative and applicable by incorporating technology, labor, and capital factors in the examination of carbon emission drivers and decoupling effects.

Evolution and interaction relationship of “eco-economy” dual grid pattern in Lingwu City, Ningxia, China

MA Caihong, LIU Yuanyuan, YANG Hang, LI Conghui, YANG Zhonghua

2023, 34(11):  3095-3104.  doi:10.13287/j.1001-9332.202311.020

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Strengthening ecological network construction is an important measure to improve urban ecological environment and protect biodiversity. With Lingwu City of Ningxia as an example, based on remote sensing and social and economic data, we comprehensively analyzed the “double network” (ecological network and social and economic landscape) pattern and their relationship by using morphological spatial pattern analysis, Linkage Mapper, and improved gravity model. The results showed that land use/cover changed dramatically from 2000 to 2020 in Lingwu City. The area of sandy land and grassland decreased sharply, that of forest and construction land increased, and industrial zones expanded rapidly. The connectivity and stability of “dual network” were improved. The intensive areas of human activities were distributed in urban area, oasis agricultural areas, and Ningdong energy industrial zone. The ecological source areas and ecological corridors were mainly distributed in the middle of the nature reserve, while some extended to the other three functional areas. The transportation corridor presented an “H” pattern that was dense in oasis agricultural area and Ningdong energy industrial zone, and connected between the two regions. The “double network” were centered around their respective functional area spaces and had interwoven distributions. The trend of the “double network” changed from conflict to coordinated situation, with obvious zoning and interaction in space. The oasis agricultural area and Ningdong energy industrial area destroyed the eco-logy in the early stage and improved that in the later stage. In the future, it is necessary to strengthen the coordination between ecological protection and social and economic development, which could improve ecological quality by combining measures such as improving the quality of ecological sources and corridors, constructing ecological nodes, and repairing ecological disturbance points.

Variations of pollen concentration in urban alleys of park city and the transmission pattern during the period of high allergenic risk: Taking Qingyang District of Chengdu City as an example

LIU Jiahui, YIN Rui, TANG Yuqian, TANG Qi, ZONG Hua

2023, 34(11):  3105-3113.  doi:10.13287/j.1001-9332.202311.021

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Pollen (spores and pollen) allergy caused by green areas is one of the most serious environmental epidemics endangering urban public health. The pollen allergy rate in China reached 17.8% in 2022, characterized by a wide age range of onset, severity and diversity of symptoms. The aims of this study were to verify the consistency of the prediction results of pollen concentration and the index of allergenicity of urban green zones (I_UGZA) equation, and to clarify the dispersal pattern of tree pollen in the urban alleys of cities with high density of static wind. We selected representative high, medium and low allergenic areas based on the allergenic stress in urban alleys of Qingyang District, Chengdu calculated by I_UGZA equation, and monitored the pollen concentrations by selecting points and indicator species within the three allergenic areas. There was a consistency in the variation of pollen concentration in urban alleys of the three areas, with the highest pollen concentration in March. Mean pollen concentration showed a pattern of spring > autumn > summer > winter. The main pollen sources belonged to Ginkgo, Platanus, Firmiana and Cedrus, accounting for 42.4%, 16.3%, 9.0% and 6.5% of the total pollen, respectively. Wind speed had the greatest effect on pollen concentration and its dispersal distance in the urban alley. The horizontal dispersal distance of pollen was up to 260 m, and the number of pollen showed a significant negative linear correlation with the distance away from the pollen sources. The concentration of exotic pollen collected at the high site (4.5 m above ground) was much lower than that at the near-ground site (1.5 m above ground), but without difference in the types of pollen. The results of allergenic risk predicted by the I_UGZA equation were consistent with the actual measured pollen concentration, which could be used in high-density static wind city.

Environmental pollution of fluoroquinolones and its relationship with nitrogen cycling mediated by microorganisms.

WEN Lilian, SONG Jinming, LI Xuegang, MA Jun, DAI Jiajia, YUAN Huamao, DUAN Liqin, WANG Qidong

2023, 34(11):  3114-3126.  doi:10.13287/j.1001-9332.202311.032

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Fluoroquinolone antibiotics (FQs) are one of the most widely used antibiotics, which are new pollutants with ‘pseudo persistence’ in the environment, causing great ecological risks. FQs could change the structure and function of microbial communities and affect nitrogen cycling mediated by microorganisms. Consequently, FQs would change the composition of various types of nitrogen in the environment and exert a significant impact on the global nitrogen cycling. We encapsulated the distribution of FQs in the environment and its impacts on nitrogen cycling mediated by microorganisms, explained the role of FQs in each key process of nitrogen cycling, aiming to provide an important reference for revealing the ecological effects of FQs. Generally, FQs could be detected in various environmental media, with significant differences in the concentration and types of FQs in different environments. Ofloxacin, norfloxacin, ciprofloxacin, and enrofloxacin are the four types of FQs with the highest detection frequency and concentration. The effect of FQs on nitrogen cycling deeply depends on typical characteristics of concentration and species. FQs mainly inhibit nitrification by reducing the abundance of amoA gene related to ammoxidation process and the abundance and composition of ammoxidation bacteria. FQs inhibits nitrification by reducing the abundance and composition of microbial communities. The denitrification process is mainly inhibited due to the reduction of the activity of related enzymes and the abundance of genes such as narG, nirS, norB, and nosZ genes, as well as the abundance and composition of denitrifying functional microorganisms. The process of anammox is restricted due to the reduction of the abundance, composition and hzo gene abundance of anaerobic anammox bacteria. FQs lead to the reduction of active nitrogen removal and the increase of N₂O release in the environment, with further environmental problems such as water eutrophication and greenhouse effect. In the future, we should pay attention to the effects of low concentration FQs and complex antibiotics on the nitrogen cycling, and focus on the effects of FQs on the changes of nitrogen cycle-related microbial monomers and communities.

Effects of yak and Tibetan sheep grazing on soil arthropods community in an alpine meadow on the Qinghai-Tibet Plateau, China.

SUN Caicai, DONG Quanmin, YANG Xiaoxia, FENG Bin, SHI Guang, LYU Weidong

2023, 34(11):  3127-3134.  doi:10.13287/j.1001-9332.202311.031

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We investigated the responses of community structure of soil arthropods to yak and Tibetan sheep grazing based on a manipulated grazing experiment at the alpine meadow livestock Adaptive Management Platform, which locates in Haiyan County, Qinghai Province. The results showed that the obtained soil arthropods belonged to 26 families, 8 orders, and 4 classes, with Acaroidae and Oribatida as the dominant groups. Yak and Tibetan sheep grazing decreased the abundance but increased Shannon index, Margalef index and Pielou index of soil arthropods. Yak grazing significantly increased the quantity of the predatory soil arthropod groups. Yak and Tibetan sheep gra-zing significantly increased the quantity of the detritivore soil arthropod groups, but did not affect the quantity of the omnivorous and phytophagous soil arthropod groups. Yak and Tibetan sheep grazing significantly reduced the abundance of soil mites. Soil bulk density, available potassium, and available nitrogen were the main abiotic factors affecting soil arthropods community composition.

Research progress on productivity of mixed forest.

YIN Zaifang, SUN Honggang, TAN Zifeng, LIU Wei

2023, 34(11):  3135-3143.  doi:10.13287/j.1001-9332.202311.027

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One of the effective ways to improve the productivity of mixed forests is enhancing resource use efficiency based on the biological characteristics of afforestation tree species. Resource use efficiency is affected by tree species interactions and environmental conditions through applying appropriate cultivation patterns. In this study, we evaluated two estimating methods for the productivity of mixed forest, analyzed the internal mechanism of interspecific tree competition and complementary effects on mixed forest productivity, clarified external factors of growth space and habitat factors control over productivity of mixed forest, discussed the effects of tree species composition, stand density and site quality on productivity, and illustrated the productivity trajectory during the development of mixed forests. Finally, based on the knowledge of the internal mechanism and habitat factors affecting the formation of mixed forest productivity, we focused on the key scientific issues that urgently need to be solved in the construction of the current mixed forests cultivation patterns, and put forward future research directions, including improving the productivity estimation system, establishing long-term mixed forest observation field, enhancing the research on the comprehensive effect of various cultivation measures, and reinforcing research of the growth and development dynamics in mixed forests.

Research progress on plant functional traits in agroecosystems.

YE Junlong, GUO Liang, ZHAO Lufeng, TANG Jianjun, HU Liangliang, CHEN Xin

2023, 34(11):  3144-3156.  doi:10.13287/j.1001-9332.202311.010

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Plant functional traits have an essential role in community formation and ecosystem function. Unlike natu-ral ecosystems, agroecosystems are affected by natural conditions and human management. Plant (i.e., crop)functional traits in the agroecosystems are thus shaped by natural and human selection. We reviewed the development of functional trait research, focusing on crop functional traits, research methods of agroecosystems based on traits, and the application of functional traits in agriculture. We then elaborated on the effect of domestication on crop trait trade-offs, the relationship between community functional structure and agroecosystem services, and the application of functional traits in weed management, cover cropping, and intercropping systems. Future research directions of crop functional traits include enriching the types of agroecosystems and crop species in studies, buil-ding up a crop functional trait database, and focusing on agroecosystem multifunctionality.

Research progress on the interference effects of plasticizers on maternal behavior and its potential mechanisms.

HAN Chengquan, WANG Hui, WANG Jianwei, LI Fukuan, WANG Zhennan, HU Xiyi, YANG Yan, LYU Shenjin

2023, 34(11):  3157-3168.  doi:10.13287/j.1001-9332.202311.028

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Environmental endocrine disrupting chemicals (EDCs), known as environmental hormones, are exogenous chemicals that can disrupt hormone levels and cause dysfunction of the secretory system in humans and animals. Plasticizers, which are widely used EDCs, are commonly used to enhance the flexibility of plastic products. As plastics age and wear, however, they can leach into the environment and enter the bodies of animals through various pathways such as the digestive tract and skin. They can lead to estrogen-like effects and have substantial reproductive toxicity. Residual plasticizer concentrations in the environment are typically low. Unlike high doses that induce acute damage to the reproductive system, low doses of plasticizers do not cause macroscopic harm and thus its reproductive toxicity is often overlooked for extended periods. An increasing number of studies conducted on humans and mice in recent years have demonstrated that low doses of plasticizers can induce reproductive toxicity by interfering with maternal behavior. Prenatal exposure to plasticizers can result in abnormal postnatal maternal behavior. Female offspring also exhibit significantly low maternal care, lactation, and other behaviors in adulthood, which may persist for multiple generations, significantly disrupting the animal breeding process and impacting the health and well-being of newborn pups. The underlying mechanisms have not been systematically summarized. The risk of continuous exposure to low-dose plasticizers in humans and animals has increased due to the extensive utilization of plastic and rubber products in modern production and lifestyle patterns. It is thus crucial to conduct a systematic review on the effects of low-dose plasticizers on maternal behavior. We reviewed the research progress on the disruptive effects of plasticizers on animals’ maternal behavior and concluded that these effects are primarily caused by inducing oxidative stress damage and DNA methylation reprogramming in the hypothalamic-pituitary-ovarian axis, as well as disrupting the balance of the thyroid system and causing intestinal microbial disorders. It would offer a novel perspective for future studies about the influence of plasticizers and other environmental hormones on maternal behavior in domesticated animals.