Presence frequency of plant species can predict spatial patterns of the species in small patches on the Qinghai-Tibetan Plateau

Abstract

Patchiness is an important feature in grassland ecosystems, but the distribution pattern of plant species in small patches on the Qinghai-Tibetan Plateau (QTP) is largely unknown. We questioned: (1) whether the power law can be applied to determine the spatial pattern of plant species in small patches; and (2) how species frequency (dominant, companion and rare) affects the spatial heterogeneity of small patches on the QTP? The power law was used to examine the spatial pattern of plant species and examine the relationship between the plant species presence frequency and spatial pattern in three types of small patches (Cyperaceae, Polygonaceae and Compositae), each with three spatial extents according to the size of the area (scale 1: 0.6–0.9 m2, scale 2: 3.0–3.8 m2 and scale 3: 6.5–8.8 m2) on the QTP. Plant species in patches showed an aggregated distribution and the spatial heterogeneity index differed among species. The spatial heterogeneities of Cyperaceae and Polygonaceae patches were influenced strongly by dominant and companion plant species, while the Compositae patch was influenced by dominant and rare species. The Compositae patches exhibited a lower species diversity and higher spatial heterogeneity index than the other patches, and the extensive distribution of Compositae community can be linked to degradation processes in the alpine meadow. We concluded that the spatial pattern of plant species and the heterogeneity index for small patches could be determined by the species presence frequency on the QTP.