Ecological Stoichiometry Homeostasis of Six Microelements in Leymus chinensis Growing in Soda Saline-Alkali Soil

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.

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 (H_Cu) 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.