ABSTRACT
This chapter explains the importance of climate and soils, outlines general characteristics of grasslands and heathlands, and examines the range of grassland and heathland communities that exists today. The characteristics of grassland and heathland soils can influence soil microbial activity. Soil biological activity is usually greater in neutral or slightly alkaline soils. Diversity of vesicular-arbuscular (VA) mycorrhizal fungi appears to be a major factor contributing to plant biodiversity in calcareous grassland, since plant species composition and relative abundance change when the VA mycorrhizal fungi taxa that are present are varied experimentally. Symbioses between plants and nitrogen-fixing bacteria are of great agricultural importance and are of ecological significance because nitrogen is in limited supply in semi-natural grasslands and heathlands. Before prehistoric forest clearance, grasslands and heathlands would have been confined to areas where climatic or maritime conditions prevented tree growth, or to thin infertile soils, or to clearings maintained by wild herbivores.
