Numerous studies have observed significant relationships between the spatial heterogeneity of soil elements and plant cover, or plant diversity. However, little effort has been made to differentiate the impacts on spatial heterogeneity of soil elements caused by the colonization of single and multiple plant species. In this study, we examined the spatial heterogeneity of soil elements in relation to the percent cover of two colonizing grasses (Megathyrsus maximus and Dichanthium annulatum) in a pastureland converted from a subtropical moist forest in Guayama, Puerto Rico; and compared the spatial heterogeneity of soil elements between colonizing plots of one and two grass species.
Soil total C and N, and water-extractable soil nutrients showed high spatial heterogeneity in the Guayama pastureland. The spatial heterogeneity of water-extractable soil nutrients was significantly correlated with the spatial distribution of two colonizing grass species. Soil pH values were significantly higher under M. maximus than under D. annulatum. There were strong spatial correlations between soil pH and percent cover of the two colonizing grasses, and between soil pH and water-extractable soil nutrients. Compared to single-species colonization, the colonization by two grass species promoted spatial heterogeneity of water-extractable soil P, S, Na, K, Ca, Mg, Mn and soil pH. Our study suggests that increase in grass-species richness can enhance the spatial heterogeneity of soil elements in man-made subtropical pasturelands.