Microplastics sequestered in the soil affect the turnover and stability of soil aggregates: A review.

Plastic products have become ubiquitous in society, and entered various ecosystems due to the massive scale of production. The United Nations Environment Program (UNEP) has listed microplastics (MPs), which form when plastic remnants degrade, as a global emerging pollutant, and the association between soil pollution and MPs has become a popular research topic. This paper systematically reviews research focusing on MP-related soil pollution from the past 10 years (2012-2022), with the identified papers demonstrating that interactions between MPs and soil aggregates has become a research frontier in the field. The presented research provides evidence that soil aggregates are important storage sites for MPs, and that storage patterns of MPs within soil aggregates are influenced by MP characteristics. In addition, MPs affect the formation, turnover, and stability of soil aggregates through the introduction of fracture points along with diverse physicochemical characteristics such as composition and specific surface area. The current knowledge base includes certain issues and challenges that could be addressed in future research by extending the spatial and temporal scales over which microplastic-soil aggregate interactions are studied, unifying quantitative and qualitative methods, and tracing the fates of MPs in the soil matrix. This review contributes to enriching our understanding of how terrestrial MPs interact with soil aggregates, and whether they pose a risk to soil health.

Advances and future research in ecological stoichiometry under saline-alkali stress.

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.

Challenges and Potential to Revamp the Normative Framework on the Right to Development.

The world is currently at an ebb for realizing the Right to Development. Weakening multilateralism, de-globalization, the COVID-19 pandemic and inertia to reform international governance are among the multitude of reasons for this phenomenon. However, the need for a better, more inclusive and greener recovery, and the efforts necessary to attain the 2030 Agenda have provided the international community an opportunity to reinvigorate its realization. This article reviews the international discourse on the Right to Development and provides recommendations on the way forward to revitalize its implementation at the 35th anniversary of the related Declaration.

Mechanisms of straw biochar's improvement of phosphorus bioavailability in soda saline-alkali soil.

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.

Quantifying the Ecosystem Services of Soda Saline-Alkali Grasslands in Western Jilin Province, NE China.

This study aimed to quantitatively describe the ecosystem services of soda saline-alkali grasslands based on literature research, the InVEST model, a transition matrix, and Spearman's correlation analysis. The chosen methodology could provide insight into the relationships between different services to provide empirical evidence for decision-making concerning the protection and restoration of saline-alkali grasslands. The research provided several insights into the ecological situation in western Jilin Province. First, the area of saline-alkali grassland in western Jilin Province had noticeably decreased from 1990 to 2018. Moreover, the threat of grassland degradation in western Jilin Province has increased year by year, and has become the main problem facing the ecological environment of this region. Second, the results demonstrated how the amount of grassland area, and coverage, are intricately linked to the provided ecosystem services, and maintaining the stability of ecosystem services is the basis for future efforts to increase grassland area and coverage. A trade-off relationship exists between water supply services and other ecosystem services, which indirectly confirms a climatic cause for grassland salinization in western Jilin Province. The analyses identified various types of grassland ecosystem service hotspots, but the share of hotspots representing all four assessed ecosystem services was small; this indicates that the grassland ecosystem of western Jilin Province is of generally poor quality. In conclusion, increasing grassland salinization has reduced vegetation coverage, which leads to the degradation of the grassland ecosystem and, in turn, affects the relationships between various ecosystem services.

Soil moisture determines nitrous oxide emission and uptake.

Soils are major sources and sinks of nitrous oxide (N2O). The main pathway of N2O emission is performed through soil denitrification; however, the uptake phenomenon in denitrification is overlooked, leading to an underestimation of N2O production. Soil moisture strongly influences denitrification rates, but exact quantifications coupled with nosZ, nirK, and nirS gene analysis remain inadequately unaccounted for. In this study, a 15N-N2O pool dilution (15N2OPD) method was used to measure N2O production rates under different soil moisture levels. Therefore, 20%, 40%, 60%, 80% and 100% soil water holding capacity (WHC) were used. The results revealed that N2O uptake rates increased proportionally with soil moisture content and peaked at 80% WHC with 4.17 ± 2.74 µg N kg-1 soil h-1. The N2O production and net emission rates similarly peaked at 80% WHC, reading at 32.50 ± 4.86 and 27.63 ± 3.09 µg N kg-1 soil h-1 during the incubation period (18 days). Soil moisture content increased the gene copy number of the nosZ, NH4+ content, and denitrification potential in soil. N2O uptake at WHC 80-100% was significantly greater than that at WHC 20-60%. It was attributed to a decrease in O2 and the high NO3- concentration inhibition (> 50 mg N kg-1 of soil NO3--N content). Principal components analysis (PCA) indicated that the number of nosZ genes was the major driver of N2O uptake, especially nosZ clade II. Thus, the results of this study deepen our understanding of the mechanisms underpinning N2O sources and sinks in soils and provide a useful gene-based indicator to estimate N2O uptake.

Pathways of soil N2O uptake, consumption, and its driving factors: a review.

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.

Homeostatic responses and growth of Leymus chinensis under incrementally increasing saline-alkali stress.

Despite considerable tolerance to salt and alkali stress, Leymus chinensis populations on the southwestern Songnen Plain in northern China are threatened by increasing soil salinity and alkalinity. To explore the species' responses to saline-alkali stress, we grew it in substrates with varying concentrations of nitrogen (N) and phosphorus (P) while applying varying levels of saline-alkali stress (increasing in 14-, 17- or 23 -day intervals). We measured the plants' contents of N and P, and the N:P ratio, and calculated their homeostasis indices (HN , HP and HN:P ) under each nutrient and saline-alkali stress treatment. The N content was found to be more sensitive to saline-alkali stress than the P content. The N and P contents were highest and the N:P ratio was stable at pH 8.4. At both pH 8.1 and 8.4, H N:P> H N > H P, but the indices and their relations differed at other pH values. Exposure to saline-alkali stress for the 14-day incremental interval had weaker effects on the plants. Rapid changes in salinity-alkalinity weakened both the positive effects of the weakly alkaline conditions (pH 7.5-8.4) and the negative effects of more strongly alkaline conditions (pH 8.7 or 9.3) on L. chinensis. When L. chinensis plants lack N, applying N fertilizer will be extremely efficient. The optimal concentrations of N and P appeared to be 16 and 1.2 mmol/L, respectively. When the L. chinensis plants were N- and P-limited, the specific growth rate correlated positively with N:P, when limited by N it correlated positively with the environmental N concentration, and when limited by P it was weakly positively correlated with the environmental P concentration.

Cu and Na contents regulate N uptake of Leymus chinensis growing in soda saline-alkali soil.

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.

A multi-faceted, location-specific assessment of land degradation threats to peri-urban agriculture at a traditional grain base in northeastern China.

Urbanization-induced cultivated land degradation can hamper the ability of peri-urban agriculture (PUA) to deliver clean food and agroecosystem services. Detailed geo-information about which cultivated lands are being influenced by urbanization will be important to designing future measures for the conservation of PUA. This information will be especially relevant for traditional grain bases because PUA is often underappreciated in these regions. For this reason, we performed a multi-faceted and location-specific assessment, including soil pollution, soil fertility, basic tillage conditions and land fragmentation, of cultivated land in a rural-urban transition zone outside of a city in northeast China. We also illustrated the combined risks in different urbanized environments via GIS-based two-step spatial clustering. The results indicated that, in general, cultivated lands were more polluted and fragmented, as well as less fertile and tillable, the closer they were to the urban area. Most of the affected cultivated lands were located within 8 km of the urban periphery. Furthermore, certain urban environments exposed the surrounding cultivated lands to specific degradation in relation to different combined risks. PUA in long-standing industrial areas mainly faced risks of polluted agricultural production, underutilization and impaired landscape ecological security (LES), whereas cultivated lands close to a recently developed residential area were characterized by risks of supplying service disruption, unsustainable agricultural production, underutilization and impaired LES. The present study highlighted that PUA associated with traditional grain bases must be preserved to enhance urban sustainability and resilience, and suggests that measures which can adapt to multi-faceted local degradation issues will be the most effective protection for peri-urban areas. Furthermore, the results also suggest that multi-functional and profitable agriculture will contribute to breaking the vicious circle of land degradation in peri-urban cultivated areas of traditional grain bases.

Ecological stoichiometry-based study of the influence of soil saline-alkali stress on nutrient homeostasis in L. chinensis.

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 (HN) was greater than that of P (HP) in the aboveground part, whereas HN was less than HP 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, HN and HN: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.

Modelling field scale spatial variation in water run-off, soil moisture, N2O emissions and herbage biomass of a grazed pasture using the SPACSYS model.

In this study, we evaluated the ability of the SPACSYS model to simulate water run-off, soil moisture, N2O fluxes and grass growth using data generated from a field of the North Wyke Farm Platform. The field-scale model is adapted via a linked and grid-based approach (grid-to-grid) to account for not only temporal dynamics but also the within-field spatial variation in these key ecosystem indicators. Spatial variability in nutrient and water presence at the field-scale is a key source of uncertainty when quantifying nutrient cycling and water movement in an agricultural system. Results demonstrated that the new spatially distributed version of SPACSYS provided a worthy improvement in accuracy over the standard (single-point) version for biomass productivity. No difference in model prediction performance was observed for water run-off, reflecting the closed-system nature of this variable. Similarly, no difference in model prediction performance was found for N2O fluxes, but here the N2O predictions were noticeably poor in both cases. Further developmental work, informed by this study's findings, is proposed to improve model predictions for N2O. Soil moisture results with the spatially distributed version appeared promising but this promise could not be objectively verified.

Assessment of soil water, carbon and nitrogen cycling in reseeded grassland on the North Wyke Farm Platform using a process-based model.

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.

Machine learning for the prediction of L. chinensis carbon, nitrogen and phosphorus contents and understanding of mechanisms underlying grassland degradation.

The grasslands of Western Jilin Province in China have experienced severe degradation during the last 50 years. Radial basis function neural networks (RBFNN) and support vector machines (SVM) were used to predict the carbon, nitrogen, and phosphorus contents of Leymus chinensis (L. chinensis) and explore the degree of grassland degradation using the matter-element extension model. Both RBFNN and SVM demonstrated good prediction accuracy. The results indicated that there was severe degradation, as samples were mainly concentrated in the 3rd and 4th levels. The growth of L. chinensis was shown to be limited by either nitrogen, phosphorus, or both during different stages of degradation. The soil chemistry changed noticeably as degradation aggravated, which represents a destabilization of L. chinensis community homeostasis. Soil salinization aggravates soil nutrient loss and decreases the bioavailability of soil nutrients. This, along with the destabilization of C/N, C/P and N/P ratios, weakens the photosynthetic ability and productivity of L. chinensis. This conclusion was supported by observations that L. chinensis is gradually being replaced by a Chloris virgata, Puccinellia tenuiflora and Suaeda acuminate mixed community.

Effects of Ginkgo biloba extract on acute cerebral ischemia in rats analyzed by magnetic resonance spectroscopy.

AIM: To study the effect of Ginkgo biloba extract (GbE) on acute cerebral ischemia in rats. METHODS: The rats were randomly divided into four groups: sham-operated group (group I as control), ischemic group (group II), the prophylactic (GbE premedication) group (group III) and GbE-treatment group (group IV). Magnetic resonance spectroscopy (MRS) was carried out to dynamically monitor the changes in biochemical metabolic variations 48 h after cerebral ischemia and effects of GbE (100 mg/kg, ip, qd). RESULTS: (1) Lactate (Lac) peak could be detectable at the infarction area 90 min after acute cerebral ischemia and increased with time. Lac peak in the prophylactic group was elevated slightly (P<0.01, n=6), whereas in the treatment group the elevation of Lac was more remarkable than that in the prophylactic group (P<0.05, n=6). (2) In the ischemic group, the level of N-acetyl aspartate (NAA) was decreased within 4 h after ischemia (P<0.05, n=6), and the decline persisted (P<0.01, n=6). In the treatment group and prophylactic group, NAA was decreased slightly after 24 h (P<0.05, n=6). (3)Twenty-four hours after ischemia, in both ischemic group and treatment group, choline (Cho) was elevated slightly (P<0.05, n=6) and creatine (Cr) was decreased slightly (P<0.05, n=6), but in the prophylactic group these changes occurred only after 48 h. CONCLUSION: GbE could prevent and treat acute cerebral ischemia. The effectiveness was more satisfactory when GbE was used preventively.