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Soil salinization affects more than 25% of land globally. Subsurface pipe drainage is known for its effectiveness in improving saline–alkali land. The red clay layer (RCL) hinders soil improvement in the Hetao Irrigation District of Inner Mongolia, China. The soil water and salt migration rules at different buried depths and RCL were studied based on the field subsurface pipe drainage test and simulation using the DRAINMOD-S model (Version 6.1). The following implications can be drawn from the results: (1) Although the RCL affected the accuracy of the model, the calibrated statistical results met the application requirements, and the DRAINMOD-S model can be used to analyze subsurface pipe drainage under different distribution conditions of the RCL. (2) The RCL can reduce the drainage efficiency of the subsurface pipe, specifically when the distribution is shallow. (3) The soil desalting rate increased with an increase in the buried depth of the subsurface pipe. The desalination effect of shallow soil was better than that of deep soil. The RCL reduced the drainage and salt removal efficiency of the subsurface pipe. Burying the subsurface pipe as far above the RCL as possible should be considered. Thus, it is feasible to apply the DRAINMOD-S model to relevant studies. [ABSTRACT FROM AUTHOR]

Soil moisture content (SWC) can change the diversity and composition of soil fungal communities by affecting soil texture and soil nutrients. To explore the response of soil fungal communities to moisture in the grassland ecosystem on the south shore of Hulun Lake, we set up a natural moisture gradient that was subdivided into high (HW), medium (MW), and low (LW) water contents. Vegetation was investigated by quadrat method, and aboveground biomass was collected by the mowing method. Soil physicochemical properties were obtained by internal experiments. The composition of the soil fungal community was determined using high-throughput sequencing technology. The results showed significant differences in soil texture, nutrients, and fungal species diversity under the moisture gradients. Although there was significant clustering of fungal communities in different treatments, the fungal community composition was not significantly different. According to the phylogenetic tree, the Ascomycota and Basidiomycota were the most important branches. The fungal species diversity was smaller when SWC was higher, and in this environment (HW), the fungal-dominant species were significantly related to SWC and soil nutrients. At this time, soil clay formed a protective barrier for the survival of the dominant classes Sordariomycetes and Dothideomycetes and increased their relative abundance. In summary, the fungal community responded significantly to SWC on the southern shore of the Hulun Lake ecosystem in Inner Mongolia, China, and the fungal community composition of the HW group was stable and easier to survive. [ABSTRACT FROM AUTHOR]

Purpose: Soil organic carbon (SOC) dynamics are central to understanding the effects of environmental change on the carbon cycle of ecosystems. Vegetation and soil stable carbon isotope composition (δ13C), especially the difference of δ13C between surface soils and source vegetation (Δδ13C), can provide useful information about the SOC dynamics. The variations and patterns of vegetation and soil δ13C and Δδ13C along climatic and edaphic gradients were analyzed to improve the understanding of SOC dynamics in temperate grassland ecosystems. Materials and methods: Soil and plant samples were collected along climatic and edaphic gradients. Meteorological data were extracted from a regional climate database, which was spatially interpolated based on the records at 107 climatic stations located in Inner Mongolia. δ13C, carbon and nitrogen contents of soil and plant, soil pH, soil clay, silt, and sand contents were determined. Δδ13C and soil C:N were calculated. The integrative effects of these factors were further estimated using stepwise regression, redundancy analysis (RDA) and T value biplots. Results and discussion: As expected, soil δ13C was positively related to vegetation δ13C, and higher than the vegetation δ13C. Vegetation and soil δ13C and Δδ13C were all related to growing season precipitation (GSP) and growing season temperature (GST). However, when climatic and edaphic factors were considered together, vegetation δ13C was positively related to GST and soil C:N, soil δ13C was positively related only to GST, and Δδ13C was negatively related only to soil C:N. Unlike previous research conducted at the species level which only included C3 species, GST, instead of precipitation, was the dominant controlling factor of vegetation δ13C. Conclusions: GST influences vegetation δ13C mainly through its effect on relative abundance of C4 plants. Soil C:N rather than climatic factors is the dominant controlling factor of SOC decomposition, and the effects of climatic factors on SOC decomposition are indirect and induced by their effects on soil C:N through influencing species composition and plant C:N. Measuring vegetation δ13C, soil δ13C, and △δ13C simultaneously is necessary to comprehensively understand how environmental changes influence ecosystem carbon cycles. [ABSTRACT FROM AUTHOR]