International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.6, 267-276 http://ecoevopublisher.com/index.php/ijmec 268 soil organic matter input (Yang et al., 2019). Furthermore, the role of grassland ecosystems in carbon storage and greenhouse gas emissions has also been intensified by global change, making the study of their nutrient cycles have more prominent Earth system significance. This study will conduct a comprehensive discussion from four aspects: the cycling pathways of nutrient elements, the decomposition mechanisms of litter and soil organic matter, the functions of microorganisms and soil animals, and the impact of global change, with the aim of revealing the functional maintenance mechanisms of grassland ecosystems in dynamic environments. A systematic review of the grassland nutrient cycle model, decompression functions, and multi-scale regulatory mechanisms from the perspective of ecological processes not only helps to deepen the understanding of the operation mode of grassland ecosystems but also provides scientific references for grassland restoration, degradation control, and sustainable utilization. 2 Basic Characteristics of Grassland Ecosystems 2.1 Climatic conditions and vegetation types Grasslands are widely distributed, ranging from temperate grasslands, tropical savannas to alpine meadows. There are significant differences in climatic conditions, but the general characteristics are: the annual precipitation is at a medium level and the seasonal distribution is obvious. The evapotranspiration is often similar to or slightly higher than that of precipitation, resulting in water becoming an important limiting factor determining productivity (Zheng et al., 2023). The seasonal combination of temperature and precipitation determines the length of the growing season and the production intensity of the grassland. In temperate grasslands, summer is the main growing season, while in plateau and high-latitude grasslands, the growing period is short and the growth intensity is limited by low temperatures. The vegetation types are mainly grasses of the Poaceae family, mostly perennial herbs, accompanied by legumes, compositae, and a small number of shrubs or semi-shrubs. There are differences in species composition, root distribution and biomass allocation among different types of grasslands: the aboveground biomass of moist grasslands is higher, while the root system is shallower. The underground root system in arid grasslands takes up a larger proportion, with deep and resilient roots to enhance water acquisition capacity. The functional differences of forage communities (such as nitrogen-fixing plants, drought-tolerant species, and fast-decomposing species) directly affect the litter quality and nutrient cycling patterns (Zheng et al., 2023). 2.2 Soil characteristics and moisture conditions Grassland soil is usually formed on sedimentary or aeolian materials, featuring good mineral content and high air permeability. However, the distribution and stability of soil organic matter are significantly influenced by climate, vegetation and management intensity. Typical grassland soil is rich in humus and root residues in the surface layer, and there is a relatively high aggregate structure beneath the surface layer, which plays an important role in water retention and organic carbon protection. Moisture status is the core constraint of grassland ecological function: the seasonal variation of soil moisture controls microbial activity, enzymatic reactions and root metabolism. Arid grasslands often exhibit a distinct alternation of dry and wet conditions: after a rainfall event, the soil responds rapidly, and the activities of microorganisms and root systems briefly increase, followed by a re-entry into a state of drought suppression. Soil texture (such as sandy soil or loam) and topography (aspect, slope) can affect infiltration, runoff and evapotranspiration, thereby determining local water availability and nutrient cycling efficiency (Zheng et al., 2023). 2.3 Main functional groups Herbaceous plants: As primary producers, they not only fix carbon through photosynthesis but also input carbon and nutrients into the soil through root secretions, root turnover, and fallen ground debris. Different functional groups (grasses, legumes, etc.) have different nutrient configurations and litter masses, thereby affecting the subsequent decomposition rate and nutrient release.
RkJQdWJsaXNoZXIy MjQ4ODYzNA==