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Saline-alkali land is an important component of terrestrial ecosystems and may serve as a carbon sink but its net contribution to the overall terrestrial carbon sink is unknown. Using methods recommended by the IPCC, this study evaluates the impacts of interconverting saline-alkali and non-saline-alkali land on terrestrial carbon stocks by measuring two major carbon pools (soil organic carbon and vegetation carbon) in the saline-alkali land of China's Songnen Plain. Distinct phases in the evolution of the region's terrestrial carbon stock were delineated, factors contributing to transitions between phases were identified, and the effects of changes in the saline-alkali land carbon stock on the overall terrestrial carbon sink were estimated. Between 2005 and 2020, the region's saline-alkali land carbon stock initially increased, then declined, and finally increased again. However, the overall terrestrial carbon stock decreased by 0.5 Tg (1 Tg = 1012 g), indicating that the increase in the saline-alkali land carbon stock was due primarily to expansion of the saline-alkali land area. The conversion of non-saline-alkali land to saline-alkali land was a carbon-emitting process; consequently, in areas undergoing saline-alkali land change, the lower carbon density bound was equal to the carbon density of unconverted saline-alkali land and the upper bound was equal to the carbon density of unconverted non-saline-alkali land. In general, changes in the carbon stock of saline-alkali land correlated negatively with changes in the overall terrestrial carbon stock. The conversion of saline-alkali land into grassland and cropland through biochar improvement and the planting of saline-tolerant crops (Leymus chinensis, salt-tolerant rice) has a positive effect on promoting the enhancement of terrestrial carbon stocks. [ABSTRACT FROM AUTHOR]

Land-use change is an important factor affecting terrestrial carbon balance, and it is crucial to explore the response of terrestrial carbon stocks to land-use change, especially in the Songnen Plain, which faces a fierce conflict between the rapid growth of production activities and ecosystem degradation. In this study, we measured soil organic carbon and vegetation biocarbon stocks in the Songnen Plain based on IPCC-recommended methodologies, and explored the characteristics of carbon stock changes in land-use trajectories, land-use drivers, and specific land-use change scenarios (cropland cultivation, returning cropland to forests, the expansion of land for construction, deforestation, greening, and land degradation). The results showed that soil organic carbon stock in the Songnen Plain decreased by 1.63 × 105 t, and vegetation biocarbon stock increased by 2.10 × 107 t from 2005 to 2020. Human factors and natural factors jointly contributed to the land-use change, but the extent of the role of human factors was greater than that of natural factors. The increase in land-use trajectory led to the decrease in soil organic carbon stock and the increase in vegetation biocarbon stock. There was no difference in the effects of human-induced and natural-induced land-use changes on vegetation biocarbon stocks, but the effects on soil organic carbon stocks were diametrically opposite, increasing by 43.27 t/km2 and decreasing by 182.02 t/km2, respectively. The reclamation of arable land, returning cropland to forests, and greening led to a net increase in terrestrial carbon stocks (+813,291.84 t), whereas land degradation, deforestation, and land-use expansion led to a decrease in terrestrial carbon stocks (−460,710.2 t). The results of this study can provide a reference for the adjustment of land-use structure and the increase in terrestrial carbon stock in the Songnen Plain. [ABSTRACT FROM AUTHOR]

We assessed the effectiveness of land optimization for controlling non-point source (NPS) pollution by combining a multi-objective dynamic planning approach with the application of the Land Use and its Effects at Small regional extents model and the Soil and Water Assessment Tool. The combined modeling approach showed substantial ability to reduce NPS pollution in Shitoukoumen Reservoir, Changchun City, China, reducing the annual total loads of nitrogen and phosphorus in the study area by 8.7 and 10.12%, respectively. The total nitrogen load decreased significantly and stabilized at less than 8 kg/hm2 from a peak level of over 15 kg/hm2. Higher total phosphorus loads before land use optimization were concentrated in the central parts of the study area, with the highest values exceeding 2.3 kg/hm2, and tended to spread outward but resolved at 1.5 kg/hm2 after optimization. The results showed that from a macro-perspective, optimization of the spatial distribution and quantitative composition of land use can effectively control NPS pollution. The study also demonstrates the potential effectiveness of the coupled multi-model methodology for mitigating NPS in the future. [ABSTRACT FROM AUTHOR]

Understanding the spatial distribution of soil properties is essential for comprehending soil fertility, predicting ecosystem productivity, enhancing environmental quality, promoting sustainable agriculture, and addressing global climate change. This study focuses on investigating the spatial distribution and influencing factors of soil carbon (C) and nitrogen (N) in the Danjiangkou Reservoir area, a vital water source for the South-to-North Water Transfer Project. Utilizing both geostatistical and traditional statistical methods, this research explores the impact of various land-use types—such as orchards, drylands, paddy fields, and Hydro-Fluctuation Belts (HF belts)—on soil C and N content. The findings reveal predominantly low levels of soil organic carbon (SOC) (ranging from 2.95 to 21.50 g·kg−1), total nitrogen (TN) (ranging from 0.27 to 2.44 g·kg−1), and available nitrogen (AN) (ranging from 18.20 to 170.45 mg·kg−1), mostly falling into deficient categories. Notably, spatial variability is observed, especially in agriculturally developed regions, leading to areas of enrichment. Paddy fields and HF belts are identified as influential contributors to increased SOC and nitrogen content compared to orchards and drylands. Correlation and stepwise regression analyses unveil intricate interactions among SOC, TN, AN, and environmental factors, underscoring the necessity for a holistic approach to soil management. This study emphasizes the critical role of adopting rational land-use types and sustainable agricultural practices for effective soil management in the Danjiangkou Reservoir area. [ABSTRACT FROM AUTHOR]

As an important part of soil and water conservation, ecological stability, and climate regulation, vegetation is sensitive to climate change and human disturbance. At present, there is a lack of research on the dynamic changes to vegetation in river basins and sub-basins from a holistic and partial perspective, which limits our ability to understand the spatial heterogeneity of vegetation changes and their influencing factors. In this study, the spatial and temporal variations of vegetation and their influencing factors in the Songliao River Basin (SLB) from 2000 to 2020 were analyzed using Sen's trend method, the Mann–Kendall test, the coefficient of variation method, and the Geodetector method. The results showed that the NDVI (normalized difference vegetation index) in the SLB exhibited an increasing trend of 0.003 yr−1, indicating that the vegetation was greening. In general, climatic factors and soil type were the dominant factors affecting the spatial differentiation of the NDVI in the SLB and sub-basin units. The interactions between the influencing factors were all enhanced, and the population density highlighted its influence on reflected vegetation changes. We also focused on analyzing the spatial differentiation of vegetation changes and influencing factors in the sub-basins. The research results provide a basis for the ecological restoration and stability of the basin. [ABSTRACT FROM AUTHOR]

Soil erosion and surface pollution near reservoirs can adversely affect water quality and safety. Soil aggregate stability is an important predictor of soil water loss and erosion resistance that is strongly influenced by land use. This study therefore aimed to identify factors affecting soil aggregate stability near reservoirs to provide empirical and theoretical insights that could guide the development of management measures to increase land quality, optimize land use, and maximize sustainability. This study focuses on the land around the Shitoukoumen Reservoir in China and examines the effects of six land use types, eleven soil physicochemical properties, and five environmental factors. Ninety-four sets of soil samples were collected in 2021 for analysis of soil aggregates and properties. Particle size classification of soil aggregates was carried out using the wet sieve method and four indicators were calculated to evaluate the effects of land use, soil physicochemical properties, and environmental factors on soil aggregate stability: water stable aggregates (WSA), mean weight diameter (MWD), geometric mean diameter (GMD), and fractal dimension (D). Descriptive statistics and geostatistics were used to explore the spatial distributions of soil aggregate stability around the reservoir and the influence of soil properties was studied using correlation analysis and path analysis. The conclusion indicates that land use type significantly affects aggregate stability. The most stable aggregates were found in paddy fields (WSA = 0.77, MWD = 0.76, GMD = 0.57) and forests (WSA = 0.75, MWD = 0.76, GMD = 0.55), followed by an orchard, irrigated land, and grassland. Aggregate stability was worst in upland sites (WSA = 0.61, D = 2.28), where soil aggregates were highly fragmented. There were clear spatial correlations between all four stability indicators. The environmental factors and soil physicochemical characteristics with the strongest influence on aggregate stability were soil organic matter, pH, soil clay content, total nitrogen, and temperature changes. Path analysis revealed that some soil properties affect aggregate stability indirectly, with particularly complex relationships between clay, soil organic matter, and pH. In conclusion, land use type, soil organic matter, pH, soil clay content, total nitrogen, these soil physicochemical properties, and environmental factors, especially temperature, significantly affect soil aggregate stability around reservoirs. In the future, it is necessary to appropriately change upland into paddy land, increase forest land, and appropriately add organic fertilizer to improve soil quality. [ABSTRACT FROM AUTHOR]

Rapid urbanization is intensifying land use transitions in China by shrinking cropland and increasing land development, exacerbating land abuse, and causing environmental degradation. There are clear needs to improve land use and address these problems; however, most previous studies focused on either structural or layout optimization. In contrast, this paper proposed a method for comprehensive optimization of land use areas, layout, and structure. This involved coupling multiobjective dynamic planning (MODP), Conversion of Land Use and its Effects at Small regional extent (CLUE-S), and minimal cumulative resistance (MCR) models. In this approach, the MODP model predicted future changes that were based on areas of current land use, and the CLUE-S model simulated various future types that were based on the analysis of geographic land use and economic data. In addition, the MODP and CLUE-S models optimized the amounts and spatial distributions of land use types, respectively. The MCR model could then partition the simulation results for ecological optimization. In this paper, an illustrative application was presented that partitioned Changchun City, Jilin Province, China into construction-prohibited, restricted construction, suitable for construction, and key construction areas (which accounted for 17.41%, 30.24%, 25.32%, and 27.04%, respectively of the total area). The optimization result met expectations and provided potentially valuable reference data for spatial land use planning and ecological protection in the focal region. The proposed method to optimize the ecological layout of land use that was based on multimodel coupling considered operability and objectivity; therefore, facilitating practical applications of the results in Changchun and the presented methodology elsewhere. [ABSTRACT FROM AUTHOR]

Saline-alkali stress is a serious abiotic factor which negatively impacts agricultural production and the ecological environment. Thus, improving the development of saline-alkali soil and reducing the effects of saline-alkali stress is a key issue for sustainable agricultural development and environmental protection. As such, it is unsurprising that researchers have lately focused on how to improve saline-alkali soil, increase the agricultural yield of saline-alkali land, and promote the adaptive growth of plants in saline-alkali soil. This paper reviews the latest research concerning nutrient content changes in saline-alkali soil, along with the associated changes in key nutrients in plants, to summarize which methods are most effective for improving the plant growth under saline-alkali stress. Finally, the prospects for alleviating saline-alkali stress and improving saline-alkali soil are put forward as a theoretical foundation for the stabilization of plant growth in saline-alkali soil, expansion of arable land area, crop yield improvement, and effective environmental protection. [ABSTRACT FROM AUTHOR]

High pH and exchangeable sodium percentage, structural deterioration due to alkalinity, and nutrient deficiencies are typical characteristics of soda saline-alkali soil. In addition, phosphorus is typically the main limiting nutrient. Thus, there have been intense efforts to counter the salinity and improve the phosphorus availability of these soils (which cover large and growing areas). A promising approach is long-term application of straw biochar, which can significantly reduce soil salinity and promote the transformation of soil phosphorus. However, the mechanisms involved remain unclear. Thus, major aims of this review are to systematically address the mechanisms whereby biochar improves phosphorus bioavailability in soda saline-alkali soil through changes in the soil's physico-chemical properties, aggregate stability, contents of organic acids, enzyme activities, key functional genes, and microbial community structure. Another is to provide theoretical foundations for establishing effective methods for applying straw biochar to improve soda saline-alkali land and optimize phosphorus fertilizer applications. [ABSTRACT FROM AUTHOR]

Cultivated-land multi-functionality has become an important way to achieve sustainable cultivated-land protection, and it has become a hot spot in the field of land-management policy. Taking the cultivated black soils in the grain-producing area of Jilin Province, Northeast China, as a case study, this paper assessed the multi-functions of cultivated land over the past 30 years by applying the improved TOPSIS model. Furthermore, the key limiting factors and influencing factors of the multi-functions of cultivated land were identified through the obstacle-degree model and the Geo-detector. The results show that the level of multi-functionality rose from 1990 to 2020, but an increase in both economic and social functions hindered improvements in the ecological function of cultivated land. There were obvious spatial differences in the functions of cultivated land in different counties, with ecological functions showing the highest degree of differentiation, followed by social and economic functions. The per capita agricultural output, the degree of agricultural mechanization, the average output from cultivated land, and the agricultural-labor productivity had the most restrictive effects on the functions of cultivated land, with barrier-degree values of 15.90, 13.90, 11.76, and 10.30, respectively. Coupling–coordination in the multi-functions and sub-functions of cultivated land showed an upward trend, from "low coupling coordination–antagonistic coupling coordination" to "high coupling coordination-optimal coupling coordination". The government should include the level of multi-functional utilization in future policies for the management and utilization of cultivated land and take measures to reduce the differences in the functions of cultivated land among regions. Quantifying the multi-functional value of cultivated land and subsidizing land cultivation should encourage farmers to protect the land and help to strengthen multi-functional planning and functional design, improve ecological utilization, and promote the sustainable use of cultivated land. [ABSTRACT FROM AUTHOR]

To purchase or authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1467-9701.2008.01128.x Byline: Yuefen Li (1), Bin Zhang (2) Abstract: The segmentation of global manufacturing and services provided China and subsequently India with a golden opportunity to make full use of their absolute advantage - low-cost, yet educated labour - to integrate into the world economy within a comparatively shorter period of time than some earlier industrialisers. Though international trade functioned as a vent of surplus in view of the narrowness of their domestic markets at the beginning of their economic catch-up, the label of export-led model may not reflect the real picture as imports underwent dramatic increases during their respective growth periods, in particular for China. Foreign direct investment has played a pivotal role in their economic growth and has major presence in international trade and investment in leading sectors of both countries, giving rise to certain special features and weak links for their economic expansion and sustainability of fast economic growth. To maintain more broad-based, fast and balanced growth, it seems that both countries have to redress sectoral imbalances, encourage technology upgrading and cope with future changes in demographic profiles which constituted a trigger to fast economic growth at the time of their respective economic reform. Author Affiliation: (1)UNCTAD, Geneva, and (2)Chinese Academy of Social Sciences, Beijing

Under the "double carbon" target, it is important to reduce carbon emissions in each region. Using exploratory spatial data analysis (ESDA), the center of gravity method, and spatial econometric models, we analyzed the characteristics and spatial spillover effects of carbon emission intensity in counties in Northeast China from 2000 to 2020 and made recommendations to the government for more reasonable carbon reduction strategies in order to achieve sustainable development. The results were as follows: (1) Since 2000, the carbon emission intensity in Northeast China has increased after first declining, and the carbon emission intensity in the western and northern regions of Northeast China has increased faster than Northeast China's average. (2) After 2000, the spatial aggregation of carbon emission intensity has improved in Northeast China. (3) Northeast China's carbon emission intensity has a positive spatial spillover effect. Through the feedback mechanism, the growth in population size, the rise in economic development level, the level of industrialization as well as the rise in living standard, the land use structure dominated by arable land and construction land, and the increase in urbanization level in the region will cause the carbon emission intensity in the surrounding areas to increase. An increase in public expenditures leads to a decrease in carbon emission intensity in the adjacent area. (4) When the vegetation cover exceeds its threshold value, it can have a larger inhibitory influence on carbon emission intensity. To summarize, each county in Northeast China is a carbon emission reduction community, and policymakers must consider the spatial spillover effect of carbon emission intensity when developing policies. [ABSTRACT FROM AUTHOR]

Nitrous oxide (N2O) is an important greenhouse gas that plays a significant role in atmospheric photochemical reactions and contributes to stratospheric ozone depletion. Soils are the main sources of N2O emissions. In recent years, it has been demonstrated that soil is not only a source but also a sink of N2O uptake and consumption. N2O emissions at the soil surface are the result of gross N2O production, uptake, and consumption, which are co-occurring processes. Soil N2O uptake and consumption are complex biological processes, and their mechanisms are still worth an in-depth systematic study. This paper aimed to systematically address the current research progress on soil N2O uptake and consumption. Based on a bibliometric perspective, this study has highlighted the pathways of soil N2O uptake and consumption and their driving factors and measurement techniques. This systematic review of N2O uptake and consumption will help to further understand N transformations and soil N2O emissions. [ABSTRACT FROM AUTHOR]

Recent reforms in the distribution of incremental land revenue in China aimed to establish an optimal scheme for the rational and equitable allocation of appreciation revenue from land that has been expropriated from peasant collectives, which effectively enables development and protects the interests of the peasants. First, the Shapley value method will be used to formulate a preliminary scheme for the equitable distribution of incremental land revenue between the government and peasant collectives, then a risk assessment procedure will be applied to adjust the allocations following both stakeholders' risks and contributions. The rationality of the resulting allocation scheme will be verified by comparing the theoretical results with the actual allocation of benefits accrued from transfers of rural collectives' operational construction land over 3 years in Jiutai District, Changchun City, Jilin Province, China. A questionnaire survey will be used to clarify peasants' opinions of land expropriation. The results obtained with the Shapley value method indicated that the government and relevant peasant collective were entitled to 93.19% and 6.81%, respectively, of the incremental land revenue based on their contributions. However, the corresponding allocations following risk adjustment were 90.83% and 9.17%, because the peasants have higher risks than the government. The peasants could generate CNY 38.38 × 104/ha by directly marketing their rural collectives' operational construction land. This is similar to the amount (CNY 37.99 × 104/ha) that they could obtain from the modified land expropriation system proposed in this study, which includes a share of the incremental land revenue. In addition, it agrees with the results of two pilot studies and meets the objectives of the reform. However, the questionnaire results showed that the peasants were in a weak position following land expropriation, and the current land expropriation system should include measures that safeguard their long-term well-being, which includes the dissemination of land expropriation information, strengthening of capital supervision, and the establishment of diversified, long-term security mechanisms. [ABSTRACT FROM AUTHOR]

Leymus chinensis (L. chinensis) is the dominant plant in the eastern margins of the Eurasian temperate grasslands. It is a very robust species, exhibiting good saline-alkali resistance and stabilizing soil. In this study, 67 soil samples and L. chinensis were collected in western Jilin province, China. The contents of N, P, K, S, Mn, Fe, Zn, Cu and Na were measured, revealing that the growth of L. chinensis was mainly restricted by N based on the stoichiometric N: P ratios of plant. Furthermore, path analysis indicated that N was significantly correlated with K, S, Cu, and Zn. Imbalances in the homeostasis of these four elements may thus constrain N. The homeostasis index of Cu (HCu) in sites with 100%-70% of vegetation cover was only 0.79, it was classified as a sensitive element. However, K, S and Zn, whose concentrations in L. chinensis were significantly related to those of N, exhibited no homeostatic characteristics. These results suggest that when seeking to treat saline-alkali stress, it is important to add fertilizers containing K, S, and Zn to avoid growth limitation. Na+, an ion associated with high soil alkalinity, exhibited weak homeostasis in L. chinensis even in sites with only 40%-10% of vegetation cover. When soil Na exceeded 16000 mg/kg, the homeostasis mechanism of L. chinensis appeared to be overwhelmed, resulting in rapid and probably harmful accumulation of Na. Proper control of N content can alleviate the toxicity of Na stress in L. chinensis and enhance its Na tolerance. Together, these results suggest that combined fertilization with N, K, S, Zn and Cu should be applied to improve grasslands growth. The results of this study can provide a reference basis for sustainable grassland management. [ABSTRACT FROM AUTHOR]

Abstract Soil salinization is a major cause of land degradation and hinders the effective utilization of agricultural land resources. Leymus chinensis (L. chinensis), as a dominant species with wide ecological amplitude, plays an important role in improving saline-alkali grasslands and indicating the degree of salinization. In this study, a sand culture experiment (nitrogen and phosphorus addition accompanied by saline-alkali stress) was designed to investigate the impact of different saline-alkali environments on the ecological stoichiometric homeostasis of L. chinensis with the aim of elucidating the saline-alkali resistance mechanisms. The results showed that the homeostasis indexes of N, P and N:P in the aboveground part of L. chinensis were generally higher than those in the belowground part under different saline-alkali conditions. Furthermore, the homeostasis index of N (H N) was greater than that of P (H P) in the aboveground part, whereas H N was less than H P in the belowground part. This indicates that the growth aboveground of L. chinensis was mainly dependent on N, whereas the growth belowground was mainly affected by P. The homeostasis index of the aboveground organs was 4.45–12.93 under pH 7–9.8. In contrast, H N and H N:P(+N) in the belowground organs did not conform to a homeostasis model when pH > 9.1. Consequently, when L. chinensis is subjected to high saline-alkali stress, the homeostasis reaction of the roots is more sensitive than that of the aboveground organs. Graphical abstract fx1 Highlights • N and P addition accompanied by saline-alkali stress was studied in L. chinensis. • H N , H P , H N:P were higher in the overground than underground part under different pH. • The homeostasis model did not apply to H N and H N:P(+N) of roots when pH > 9.1. • The homeostasis response in the underground part was most sensitive under high pH. [ABSTRACT FROM AUTHOR]

The North Wyke Farm Platform (NWFP) generates large volumes of temporally-indexed data that provides a valuable test-bed for agricultural mathematical models in temperate grasslands. In our study, we used the primary datasets generated from the NWFP ( https://nwfp.rothamsted.ac.uk/ ) to validate the SPACSYS model in terms of the dynamics of water loss and forage dry matter yield estimated through cutting. The SPACSYS model is capable of simulating soil water, carbon (C) and nitrogen (N) balance in the soil-plant-atmosphere system. The validated model was then used to simulate the responses of soil water, C and N to reseeding grass cultivars with either high sugar ( Lolium perenne L. cv. AberMagic) or deep rooting ( Festulolium cv. Prior) traits. Simulation results demonstrated that the SPACSYS model could predict reliably soil water, C and N cycling in reseeded grassland. Compared to AberMagic, the Prior grass could fix more C in the second year following reseeding, whereas less C was lost through soil respiration in the first transition year. In comparison to the grass cultivar of the permanent pasture that existed before reseeding, both grasses reduced N losses through runoff and contributed to reducing water loss, especially Prior in relation to the latter. The SPACSYS model could predict these differences as supported by the rich dataset from the NWFP, providing a tool for future predictions on less characterized pasture. [ABSTRACT FROM AUTHOR]

The natural Leymus chinensis grassland in western Jilin Province of NE China has been extensively degraded, thereby restricting the development of animal husbandry. Using theory of ecological stoichiometry homeostasis, this study investigated the homeostasis of L. chinensis at different degradation stages in the research area using a homeostasis model. Results showed that the degraded grassland generally had lower soil carbon (C), nitrogen (N) and phosphorus (P) compared with normal L. chinensis grassland. In particular, the degraded grassland exhibited severe shortage of P, but L. chinensis showed strong homeostasis. Except for C in the roots and leaves and P in stems, the N, P and corresponding ratios had higher homeostasis than 1, between 1.53 and 15.92. The homeostasis of N in L. chinensis was higher than that of P, and the homeostasis of C/P was higher than that of C/N and N/P. L. chinensis absorbs and uses nutritive elements in a conservative manner, which enables it to remain productive during changes in the external environment. Therefore, grassland degradation control should prioritize the protection of dominant species. Appropriate use of N and P fertilizers is suggested for the recovery of the seriously degraded L. chinensis grassland ecosystem. [ABSTRACT FROM AUTHOR]

Ecological stoichiometry is an emerging discipline started in China in recent years. It is the science of studying the balance of energy and elements (i.e. carbon, nitrogen and phosphorus) in ecological processes and ecological interaction, providing an integrative approach to investigate the stoichiometric relationships and rules in the biogeochemical cycling and ecological processes. It has been one of the hotly-discussed issues in ecological research. The contents of carbon, nitrogen, and phosphorus is a core issue in ecological stoichiometry studies. It is necessary to choose a method that can simulate and accurately predict the contents of plant carbon, nitrogen, and phosphorus in order to avoid destructive sampling. There is a complex nonlinear relationship between plant carbon, nitrogen, phosphorus, and soil physical and chemical properties. It is difficult to accurately predict plant carbon, nitrogen, and phosphorus by using traditional methods and models such as linear regression and a BP neural network. As a new artificial neural network model, a RBF (radial basis function) neural network has some advantages of fast learning, getting in the local minimum, and approximating any arbitrary accuracy of the global nonlinear relationship. Therefore, a RBF neural network can show an ability to handle a complex nonlinear relationship. Currently, a RBF neural network is one of the most accepted prediction methods. Taking the prediction of 38 samples as a research sample, this paper established a prediction model based on a RBF Neural network from seven impact indexes including pH, the total soluble salt, total carton, total nitrogen, total phosphorus, available nitrogen, and available phosphorus. Taking the prediction of five samples as a test sample, the results indicated that the relative errors of carbon, nitrogen, and phosphorus contents were only 1.39%, 4.69%, and 7.65%, respectively, and the correlation coefficients were 0.5, 0.93, and 0.94 respectively. Therefore, a RBF neural network had higher prediction accuracy. The statistical results showed that the average contents of carbon, nitrogen, and phosphorus in Leymus chinensis (103 samples) were 411.46, 18.25, and 1.11 mg/g, respectively. They are all lower than the global average contents of carbon, nitrogen, and phosphorus in a terrestrial plant. The values of C/N, C/P, and N/P were 24.70, 429.24, and 17.92, respectively in Leymus chinensis. They were all higher than those in a global terrestrial plant. The N/P was 17.92 in Leymus chinensis. The growth of Leymus chinensis in the research area was limited by phosphorus. [ABSTRACT FROM AUTHOR]

Soil samples from T (0~20 cm) and S (20~40 cm) layers of four saline-alkali rice fields (R5, R15, R20, and R35) with different reclamation years were selected to study the distribution of soil aggregates and the contents of readily oxidizable organic carbon (ROC), dissolved organic carbon (DOC), microbial biomass carbon (MBC), potentially mineralizable carbon (PMC), and soil organic carbon (SOC). The effects of large macroaggregate (>2 mm, LMA), small macroaggregate (0.25 to 2 mm, SMA), and microaggregate (<0.25 mm, MA) particle size, soil layer, and soil physicochemical properties on SOC fractions were also analyzed. The results showed that the LMA size in saline-alkali paddy fields were easily decomposed and was unstable due to the influence of the external environment. With the increase in reclamation years, the proportion of LMA in the S layer decreased gradually. The ROC, DOC, MBC and TOC contents of aggregates in the T and S layers gradually increased with the increase in reclamation years, and SOC fractions contents of aggregates in different grain sizes were SMA > LMA > MA. An effective way to increase carbon sink and improve the ecological environment in western Jilin Province is to change the soil environment by planting rice in saline-alkali land. [ABSTRACT FROM AUTHOR]

Dynamic change in vegetation is an integral component of terrestrial ecosystems, which has become a significant research area in the current context of global climate warming. Jilin Province in northeast China is an ecologically fragile area, and there is an urgent need to understand its vegetation changes and responses to both climatic factors and human activities. The normalized difference vegetation index (NDVI) was used to analyze trends in vegetation growth, and indicated significant growth overall. The NDVI of different vegetation cover types is increasing, indicating that the vegetation is continuously greening, and in descending order, the growth trends were grassland (0.0035/year) > permanent wetland (0.0028/year) > cropland (0.0027/year) > forest land (0.0022/year) > barren land (−0.0001/year). Grassland and cropland vegetation types included the most severely degraded areas, with fluctuating NDVI values. Precipitation was the main positive controlling climatic factor of NDVI in the western regions of the study area, while average temperature was the main factor in the eastern regions. Precipitation was the main climatic control factor for grassland and cropland, while forest land was limited by precipitation and average temperature. Barren land and permanent wetland were slightly negatively correlated with precipitation. From 2000 to 2019, the residual values for NDVI increased from −0.0121 to 0.0116, and the impact of human activities on vegetation changed from negative to positive. By 2019, the proportion of positively affected zones was as high as 94.01%, and the negatively affected zones were mainly distributed across transitional areas of cropland and grassland, and urban and built-up land and forest land. [ABSTRACT FROM AUTHOR]

Soil salinization poses severe threats to grassland ecosystems in various parts of the world, including the Songnen Plain in northeast China. Severe impairment of plant growth in this soil is generally attributed to high soil pH, total alkalinity, and sodium (Na) contents. This paper focuses on the ecological stoichiometry of microelements, which has received much less attention than relations of macroelements, in the soil and plants (specifically Leymus chinensis) growing in it. The results show that the soil's manganese (Mn), zinc (Zn), iron (Fe), copper (Cu), nickel (Ni) and molybdenum (Mo) contents are lower than average in Chinese soils, but only Mn and Zn are severely deficient in L. chinensis. With increases in soil pH, total alkalinity, and Na, the Mo contents in both soil and L. chinensis slightly increase, while contents of the other microelements decline. Homeostasis indices obtained for the six microelements—and Fe/Zn, Fe/Ni, Fe/Cu, and Cu/Zn ratios—were all between 0.82 and 3.34 (ranging from just below the "plastic" threshold to "weakly homeostatic"). Despite Zn deficiency in the soil, Zn appears to have the highest homeostasis of the six elements in L. chinensis (homeostasis indices of Zn, Cu, Ni, Mn, Fe and Mo were 3.34, 2.54, 1.86, 1.76, 1.52, and 1.33, respectively). In addition, the Cu/Zn ratio had the highest homeostasis index (1.85), followed by Fe/Zn (1.02), Fe/Cu (0.95) and Fe/Ni (0.82). Appropriate application of Mn and Zn fertilizers is recommended to promote the growth and development of L. chinensis in soda saline-alkali soil. [ABSTRACT FROM AUTHOR]