This document summarizes information about plant competition in temperate regions. It discusses how abiotic factors like precipitation determine plant growth forms in different biomes like deserts and grasslands. Competition between plant species can limit population sizes and influence community structure and diversity. The competitive exclusion principle and niche differentiation theory suggest that closely similar species cannot coexist. Tilman's R* model of competition for limiting resources was tested in Minnesota grasslands, finding support that the species with the lowest resource threshold (R*) for nitrogen wins interspecific competition. Species' R* values correlated with root biomass, indicating their different resource allocation strategies influence competitive abilities.