Exploring the physical fractions of organic carbon and influencing mechanisms in grassland, forest, and farmland soils in wind erosion area can provide scientific basis for carbon sequestration, land utilization, wind prevention measure making, and fertility restoration of sloping farmland in the region. We examined the differentiation of aggregate organic carbon and density fractionation organic carbon in 0-15 cm soil layer across grassland, forest, and sloping farmland with 350 m long and 5° slope gradient in the wind erosion area of Meilisi District, Qiqihar, Heilongjiang, as well as the sloping farmland in the downhill section, middle section, and uphill section with every 100 m apart from the bottom to the top. The results showed that soil aggregates >2 mm were all destroyed across grassland, forest, and farmland soils, while the percentage of aggregates <0.053 mm was significantly higher than that of other sizes. The percentage of various soil aggregates, organic carbon content from density fractionations, and the proportion of organic carbon in the heavy fraction aggregates in farmland were significantly lower than that in grassland and forest soils. Soil aggregates in the uphill section of farmland were completely destroyed, and organic carbon content in various size aggregates and density fractionations gradually decreased with increasing slope. The proportion of organic carbon in the heavy fraction aggregates decreased, but that in light fraction aggregates increased gradually. Soil organic carbon and available potassium were key factors affecting aggregate stability, aggregate organic carbon content, and organic carbon content in density fractionations, while the loss of organic carbon in aggregate led to a decrease in aggregate stability. In summary, compared with grassland and forest soils, the stability of soil aggregates, the aggregate organic carbon content, the organic carbon content in density fractionations, and the proportion of organic carbon in heavy fraction aggregates in farmland all decreased in the wind erosion area of Northeast China. With the increases of slope, the aggregate organic carbon content, the organic carbon content in density fractionations, and the proportion of organic carbon in the heavy fraction aggregates in sloping farmland all decreased. Planting trees, conserving and expanding grassland area, and increasing the application of organic materials in sloping farmland in wind erosion area are effective approaches to stabilize and increase carbon storage, improve soil structure, and enhance soil quality.
探究风蚀区草地、林地和农田土壤有机碳物理组分及其影响机制,可为风蚀区土地的碳固定与科学利用、防风措施制定以及坡耕地农田肥力修复提供科学依据。本研究在黑龙江省齐齐哈尔市梅里斯区风沙土风蚀区选取相邻近的草地、林地和坡长约350 m、坡度约5°的坡耕地农田(自下而上每100 m分别设为下坡段、中坡段和上坡段),研究0～15 cm土层团聚体有机碳和密度分组有机碳的分异。结果表明: 风蚀区草地、林地和农田土壤>2 mm团聚体均遭到破坏,<0.053 mm团聚体显著高于其他粒级团聚体;与草地和林地土壤相比,农田各粒级土壤团聚体、密度分组有机碳含量以及重组有机碳占比均显著减少。农田上坡段>2 mm团聚体被完全破坏,各粒级团聚体及密度分组有机碳含量均随坡面的上升逐渐下降,重组有机碳占比逐渐减小,轻组有机碳占比逐渐增加。土壤有机碳和速效钾是影响团聚体稳定性、团聚体有机碳含量和密度分组有机碳含量的关键因子,且团聚体有机碳的流失使团聚体稳定性下降。综上,相比草地和林地,东北风蚀区农田土壤团聚体稳定性、团聚体有机碳含量、密度分组有机碳含量以及重组有机碳占比均降低,坡耕地随坡段的上升,团聚体有机碳含量、密度分组有机碳含量以及重组有机碳占比均降低。在风蚀区植树、保护与扩大草原面积、增加坡耕地有机物料施用等是稳固和提高土壤碳储量、改善土壤结构、提升土壤质量的有效途径。.

The increased frequency and intensity of heavy rainfall events due to climate change could potentially influence the movement of nutrients from land-based regions into recipient rivers. However, little information is available on how the rainfall affect nutrient dynamics in subtropical montane rivers with complex land use. This study conducted high-frequency monitoring to study the effects of rainfall on nutrients dynamics in an agricultural river draining to Lake Qiandaohu, a montane reservoir of southeast China. The results showed that riverine total nitrogen (TN) and total phosphorus (TP) concentrations increased continuously with increasing rainfall intensity, while TN:TP decreased. The heavy rainfall and rainstorm drove more than 30% of the annual N and P loading in only 5.20% of the total rainfall period, indicating that increased storm runoff is likely to exacerbate eutrophication in montane reservoirs. NO3--N is the primary nitrogen form lost, while particulate phosphorus (PP) dominated phosphorus loss. The main source of N is cropland, and the main source of P is residential area. Spatially, forested watersheds have better drainage quality, while it is still a potential source of nonpoint pollution during rainfall events. TN and TP concentrations were significantly higher at sites dominated by cropland and residential area, indicating their substantial contributions to deteriorating river water quality. Temporally, TN and TP concentrations reached high values in May-August when rainfall was most intense, while they were lower in autumn and winter than that in spring and summer under the same rainfall intensities. The results emphasize the influence of rainfall-runoff and land use on dynamics of riverine N and P loads, providing guidance for nutrient load reduction planning for Lake Qiandaohu.

The swift proliferation of forests converted into monoculture plantations has profound impacts on soil nutrients, microbial communities, and many ecological processes and functions. Nematodes are soil microfauna that play a pivotal role in biogeochemical cycling and in soil food web, whereas the response of soil nematode communities and energy flows to forest conversion remains unknown. Here, we assessed the community composition and the energy flows of the nematode food webs as a function of soil chemistry after conversion from natural forests (Forest) to four plantations (8-year-old): Amygdalus persica (Peach), Myrica rubra (Berry), Camellia oleifera (Oil), and Cunninghamia lanceolata (Fir). After forest conversion, soil organic carbon (SOC) and total nitrogen (TN) contents decreased by 65 % and 55 %, respectively. Forest conversion strongly reduced the abundance (particularly large-bodied omnivorous-predatory nematodes), diversity, maturity, and stability of the soil nematode community. The shifts in composition and structure of nematode communities after forest conversion are reflected in changes in the abundance of predominant genera and trophic taxa, especially bacterivorous, fungivorous, and omnivorous-predatory nematodes. Acrobeloides notably increased, whereas Plectus, Prismatolaimus, Tylencholaimus, and Tripyla decreased. Accordingly, the abundances of r-strategy nematodes (cp value = 1-2) increased, but that of the K-strategists (cp value = 3-5) declined. Additionally, the energy flow across the soil nematode food web was reduced by 36 % and flow uniformity declined by 24 % after forest conversion. These changes in nematode diversity and abundance were triggered by diminishing soil C and N contents, thereby affecting the energy flows via the nematode food webs. Thus, forest conversion affects soil biotas and multi-functions from the perspective of nematode food web structure and energy flows, and underlines the interconnections between ecosystem and energy dynamics across multi-trophic levels, which is crucial for sustainable forest management.

Phthalate esters (PAEs) are widely prevalent in agricultural soil and pose potential risks to crop growth and food safety. However, the current understanding of factors influencing the behavior and fate of PAEs is limited. This study conducted a large-scale investigation (106 sites in 18 counties with 44 crop types) of 16 types of PAEs on a tropical island. Special attention was given to the impacts of land use type, soil environmental conditions, agricultural activity intensity, and urbanization level. The health risks to adults and children from soil PAEs via multiple routes of exposure were also evaluated. The results showed that the mean concentration of PAEs was 451.87 ± 284.08 μg kg-1 in the agricultural soil. Elevated agricultural and urbanization activities contributed to more pronounced contamination by PAEs in the northern and southern regions. Land use type strongly affected the concentration and composition of PAEs in agricultural soils, and the soil PAE concentration decreased in the order of vegetable fields, orchards, paddy fields, and woodlands. In paddy fields, di-isobutyl phthalate and di-n-butyl phthalate made more substantial contributions to the process through which the overlying water inhibited volatilization. Soil microplastic abundance, pesticide usage, crop yield, gross domestic product, and distance to the nearest city were calculated to be the major factors influencing the concentration and distribution of PAEs. Soil pH, organic matter content, microplastic abundance and the fertilizer application rate can affect the adsorption of PAEs by changing the soil environment. A greater risk was detected in the northern region and paddy fields due to the higher soil PAE concentrations and the dietary structure of the population. This study reveals important pathways influencing the sources and fate of PAE pollution in agricultural soils, providing fundamental data for controlling PAE contamination.

We systematically elaborated and compared the spatial scope and landscape changes of Horqin Grassland and Horqin Sand Land from their definitions and ranges. Horqin Grassland is an area with geographical units named after Mongolian tribes, but the boundary is unclear. Horqin Sand Land is also an area that borrows tribal names, but has independent topographic and geomorphic units, and clear boundaries. Horqin Grassland and Horqin Sand Land belong to two spatial regions that are both cross and different. The area and range of Horqin Grassland are larger than that of Horqin Sand Land which has obvious regional characteristics, and is a typical and research object area to study the development and restoration of aeolian desertification. Based on those cognition, we summarized the technologies and example models of comprehensive land management and desertification controlling over the years, and finally sorted out what should be focused on in the future to serve the annihilation war against desertification for Horqin Sand Land.
本文首先从定义、空间范围以及土地退化演变等方面对科尔沁草原与科尔沁沙地进行了较为系统的阐述和分析对比,科尔沁草原是一个以蒙古族部落名称命名兼具地理单元特征的区域,但边界不清晰;科尔沁沙地是借用部落名称但具有独立地形地貌单元的区域,边界明确。科尔沁草原与科尔沁沙地既有交叉又有不同的两个空间区域。科尔沁草原区域大、范围广,而科尔沁沙地范围小但区域特色明显,已成为研究土地沙漠化发展与恢复的典型区域。以此为基础, 回顾和总结了多年来科尔沁草原和科尔沁沙地相关的综合治理技术、模式以及取得的成效,整理归纳了今后沙地综合治理的焦点及亟待解决的问题,以期为当前科尔沁沙地歼灭战服务。.

Soil microbiota are significantly influenced by their microenvironments. Therefore, to understand the impacts of various land use patterns on the diversity and composition of soil bacterial communities, this study focused on three typical land use types-NF (natural forest), AF (artificial forests), and FL (farmland)-in the Heilongjiang Central Station Black-billed Capercaillie National Nature Reserve, located in the southwestern part of Heihe City, Heilongjiang Province, China. Using high-throughput sequencing of the 16S rRNA gene, we examined the soil bacterial community structures in these different land use types and explored their correlation with soil environmental factors. The following were our main observations: (1) Significant variations in soil chemical properties among different land use patterns were observed. In artificial forests, total nitrogen (TN), alkali hydrolyzed nitrogen (AN), total phosphorus (TP), and available phosphorus (AP) were higher compared to farmland and significantly higher than those in natural forests. Furthermore, the organic carbon content (SOC) in natural forests was higher than in artificial forests and significantly higher than in farmland. (2) Comparative analysis using the Shannon and Simpson indices revealed that bacterial community diversity was higher in artificial forests than in natural forests, which was significantly higher than in farmland. (3) The effect of different land use types on soil bacterial community structure was not significant. The three land types were dominated by Proteobacteria, Acidobacteria, and Actinobacteria. Proteobacteria exhibited a higher relative abundance in farmland and artificial forests compared to natural forests, whereas Actinobacteria exhibited the lowest relative abundance in natural forests. (4) Redundancy analysis (RDA) revealed that SOC, TN, AN, and AP were key environmental factors influencing the microbial communities of soil. Collectively, our findings demonstrated that land use practices can significantly alter soil nutrient levels, thereby influencing the structure of bacterial communities.

Expressway construction has caused a significant threat to the ecological environment in developing countries, and therefore the variation characteristics of ecological resilience along the expressway in developing countries are of major importance. This empirical study focuses on a typical area within a 2-km range of the Phnom Penh-Sihanoukville Expressway in Cambodia and uses remote sensing and geographic information systems (GIS) technology to analyze the variation characteristics of ecological resilience along the expressway. The results of the study reveal that due to the construction of expressways, the land use types transferred into or out of the land use types increase and furthermore the land use types show a trend of decreasing natural attributes and increasing human attributes. It is found that expressway construction has an observed effect on the transfer rate of the center of gravity of land use type, and the direction of the center of gravity shifts in the direction of expressway construction. The impact of construction on the ecological resilience of the western region with higher vegetation coverage was higher than that of the eastern region with higher urbanization. The research develops a theoretical evaluation model based on land use type of the variation characteristics of ecological resilience along the expressway, which can be used to enable the sustainability of expressway construction and maintain the regional ecological environment.

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.
青藏高原作为全球最大的关键生态热点区域,具有丰富的生态系统服务,但其广阔而独特的高寒生态系统正受到如土地利用集约化等日益严重的人为干扰。本研究旨在探讨1980—2020年青藏高原土地利用规模、时空格局及其变化过程,分析其对主要生态系统服务的影响。采用生态系统服务与权衡综合评价模型模拟研究了生境质量、碳储存、产水量3种生态系统服务的时空变化趋势,分析了土地利用演变对生态系统服务的影响。结果表明: 1980—2020年间,研究区土地利用格局较为稳定,以高寒草地和荒漠为主。生境质量整体提高,碳储量和产水量先升高后降低。3种服务整体呈现从西北向东南逐渐提升的空间格局,与土地利用由荒漠、草地到林地过渡的空间格局相对应。土地利用强度与生态系统服务的相关性呈现明显的空间分异特征,受土地利用强度影响较大的县域主要集中在青藏高原中西部、南部和中东部等区域。本研究结果对制定土地利用政策、调控青藏高原独特的高寒生态系统土地利用格局具有一定的指导意义。.

Groundwater vulnerability can partially reflect the possibility of groundwater contamination, which is crucial for ensuring human health and a good ecological environment. The current study seeks to assess the groundwater vulnerability of Zhengzhou City by adopting an amended version of the traditional DRASTIC model, i.e., the DRASTICL model, which incorporates land use type indicators. More specifically, the AHP-DRASTICL, entropy-DRASTICL, and AE-DRASTICL models were established by optimizing weights using the analytic hierarchy process (AHP) and entropy weight method. The evaluation results for these five models were divided into five levels: very low, low, medium, high, and very high. Using Spearman\'s rank correlation coefficient, the nitrate concentration was used to verify the groundwater vulnerability assessment results. The AE-DRASTICL model was found to perform the best, with a Spearman correlation coefficient of 0.78. However, the AHP and entropy weight method effectively improved the accuracy of vulnerability assessment results, making it more suitable for the study area. This study provides important insights to inform the design of strategies to protect groundwater in Zhengzhou.

Dissolved organic matter (DOM) transported by inflowing rivers can considerably contribute to the organic loadings of lakes. The current study characterized the DOM properties and source apportionment in the inflowing rivers of Dianchi Lake, the sixth largest freshwater lake in China suffering from organic pollution, during the rainy season by using spectroscopic and carbon stable isotope techniques, and the regulation role of land use was assessed. The results showed that land use (urbanized, agricultural, or mixed) largely affected DOM properties. Greater concentrations and fluorescence intensities of DOM with low aromaticity and dominant autochthonous sources were observed in the urban rivers than in the agricultural rivers. The proportion of humic-like substances increased, while that of tryptophan-like matter decreased from upstream to downstream of two main urban rivers. DOM in the agricultural rivers was characterized by more amounts of aromatic humic-like substances with dominant allochthonous sources compared to that in the urban rivers. Stable isotope analysis showed that the decomposition of macrophytes and input of terrestrial sources from C3 plant-dominated soil and sewage were the major DOM origins in the rivers. The positive linear relationship between the chemical oxygen demand (COD) concentration and fluorescence intensities of terrigenous DOM components implied the necessity of controlling exogenous inputs to alleviate organic pollution in the Dianchi Lake.