Significance and problems of uneven species distribution for species coexistence
The formation of micro-landscape heterogeneity is related to patchy and spatial self-organization in the process of alpine meadow degradation and succession (Rietkerk et al. 2021). Patchiness is an early warning sign of ecosystem degradation (Scheffer et al. 2009; Bury et al. 2021) or the degradation threshold point features of alpine meadow (Song et al. 2020). After patch development, plant communities begin the process of spatial self-organization (Rietkerk et al. 2021), which completely changes the relatively uniform plant landscape to form a unique, stable and degraded alpine meadow landscape (Van de Koppel et al. 2001). Therefore, early patchiness is a critical period for grassland restoration. If patch gaps are occupied by natural reseeding, the critical degradation threshold points can be avoided to reverse the degradation of alpine meadows; if this period is missed and community self-organization is completed in the degraded alpine meadow, the community structure is difficult to restore.
The community may be jointly influenced by ecological processes at multiple scales (Levin 1992). The unification of patterns or processes of ecological communities at local, regional, and global scales is a focus of recent ecological research (Buckley & Puy 2021; Neves et al. 2021). However, relatively little is known about the effects of the microscale (i.e., smaller than the local scale). First, it is not possible to define a ”correct” scale for characterizing broad ecological phenomena because processes that determine community structure and dynamics operate at different scales (Levin 1992). Further, although the local microzone conditions, such as temperature (Klinges et al. 2021), snow cover, and microtopography (Dobbert et al. 2021), can be quantified by meteorological data monitoring, and similarly, microscale landscape patches can be interpreted and quantified by aerial drone photography (Li et al. 2021), the quantification of community characteristics is limited by sampling methods. Specifically, the characteristics of grassland plant communities are traditionally investigated by the quadrat sampling method, which assumes that the plant species are evenly distributed within the quadrat; accordingly, the size of the sample quadrat will affect the discovery of heterogeneity in this microlandscape, which will be ignored when the quadrat scale is set too large. Therefore, the study of the size of the quadrat is critical for determining whether landscape factors play a role, and how to determine an appropriate quadrat sizes according to plant community types and ecological processes is a new challenge in community ecology research.
In conclusion, in the degraded alpine meadow the N preferences shifted, and plant spatial distributions promote N use niche differentiation, both of which may jointly maintain community stability in degraded alpine meadows. We emphasize the importance of considering fine-scale perspectives in studies of niche theory. Our results have an important implication for restoration of degraded alpine meadows.