Medium Plant Cover has the Highest Heterogeneity of Fine-Scale Spatial Vegetation Patterns in Humid grasslands

Abstract Context Fine-scale spatial vegetation patterns are ubiquitous and can have profound impacts on large scale ecological processes including surface runoff, soil erosion, and livestock forage efficiency. However, we have limited knowledge of the fine-scale spatial vegetation patterns in humid grasslands.Objectives The objectives were to characterize the spatial vegetation patterns at centimeter scale in humid grasslands, quantify the vegetation patterns variation under different image pixel sizes and plant covers, and explore the potential ecological implications of the spatial vegetation patterns.Methods Seventy plots with plant covers ranging from 30.8–99.3% were selected from seven humid grasslands in southwest China and their spatial vegetation patterns quantified at image pixel sizes of 0.04, 0.25, 1, and 4 cm.Results With increasing pixel size, plant patch density and total edge density decreased, plant patch size increased, and the plant patch shape became more regular. At a plant cover level below 50%, increasing plant cover will result in increasing patch density and patch size, leading to greater spatial heterogeneity. At plant cover levels above 50%, increasing plant cover will cause the rapid expansion of patch size, along with a lower patch density, forming a more homogeneous landscape dominated by plant patches. The small stems, branches, and leaves of grasses fragmented non-plant patches into smaller patches with increasing plant cover; this fragmentation resembles road-induced landscape fragmentation processes.Conclusions Medium plant cover has the highest heterogeneity of spatial vegetation pattern at the fine scale, which may have significant implications on ecological processes and related management practices.