The particular species determining spatial heterogeneity in shady and terrace on the Qinghai-Tibetan Plateau, China

Spatial patterns of plant species and patchy community are important properties in grasslands. However, research regarding spatial patterns of formed patches with various species has not fully advanced until now. Our purpose is to clarify differences in spatial pattern formed by species and community constructed under shady and terrace habitats. The three common Kobresia-Carex patches (Size 1, 0.6–0.9 m²; Size 2, 3.0–3.8 m² and Size 3, 6.5–8.8 m²) were selected in shady and terrace on the Qinghai-Tibetan Plateau, and corresponding quadrats of 1m×1m, 2m×2m and 3m×3m were placed for S1, S2 and S3 patches, respectively. The surveyed quadrats were divided into 20cm×20cm large cells (L-cells), and further divided into four 10cm×10cm small cells (S-cells). We used the binary occurrence system (presence/absence data) to record occurrences of all species in S-cells. The analysis shows that the power law model was well able to determine the spatial distribution pattern of species or patchy community in shady and terrace. All species and patches show aggregated distribution in shady and terrace habitats. In the shady habitat, the relative spatial heterogeneity (ε) of individual plant species was lowest at presence frequency (P) of 0.1–0.3, whereas in the terrace habitat ε was lowest at P <0.1, and ε increased monotonically with increasing P. For most dominant species, P and ε values were higher in terrace than those in shady. We concluded that the dominant species largely determine spatial heterogeneity of the Kobresia-Carex patches, while companion and rare species have weak influence on the community-level heterogeneity in shady and terrace habitats.