Medium plant cover maximizes fine-scale spatial heterogeneity in humid grasslands of Southwest China.

Fine-scale spatial vegetation patterns are widespread and can significantly affect large-scale ecological processes. Quantifying these patterns may provide valuable insight into larger scale ecological processes, facilitating the development of effective management strategies. In this paper, to quantify fine-scale spatial vegetation patterns, we analyzed seventy plots from seven humid grasslands in southwest China, using images with pixel sizes of 0.04, 0.25, 1, and 4 cm and plant cover levels ranging from 30.8 to 99.3%. The results showed that with increasing pixel size, plant patch density and total edge density decreased, while patch size increased, and the shape of plant patches became more regular. When plant cover was below 50%, increasing cover caused the small stems, branches, and leaves of grasses to fragment non-plant patches into smaller units, leading to higher patch density and larger patches, thus enhancing spatial heterogeneity. However, when plant cover exceeded 50%, further increases in cover resulted in rapid patch expansion and reduced patch density, creating a more homogeneous landscape dominated by plant patches. These findings suggest that medium plant cover levels are associated with the highest fine-scale spatial heterogeneity, which may facilitate biodiversity, stability, and functioning, with implications for ecosystem management and conservation, and warranting further investigation.