Abstract:

Aims Population density changes with spatial scales in plant communities. Surprisingly, few previous studies explored this theme, despite the possibility that variation in density with spatial scales should be significant for detecting ecological phenomena and answering ecological problems. In this study, we call variation in density with spatial scales (the local neighborhood density at different spatial scales) as scale density.
Methods O-Ring function can measure the local neighborhood density at different spatial scales. We used it to measure scale densities of Leymus chinensis, Agropyron michnoi and A. michnoi relative to L. chinensis in different restorative successional stages in steppe community in Inner Mongolia.
Important findings Local densities of two populations (L. chinensis and A. michnoi) were both higher in a degraded community than the other two restoration communities, which demonstrated the “stress gradient hypothesis” and further illustrated that the ecological phenomena were induced by facilitation. By comparing the scale densities of L. chinensis and A. michnoi relative to L. chinensis, we found that L. chinensis and A. michnoi were negatively associated as induced by facilitation in a degraded community, and positively associated as induced by competition in the other two restoration communities. Findings illustrate that analyzing the variation in the population density with spatial scales in plant communities is valuable in ecology.

Key words: density, O-Ring function, scale