ABSTRACT
Species richness–soil pH curves within biomes often show a decrease in species richness at extreme pH values, especially with acidity, although globally some of the most species-rich habitats occur on acidic tropical soils. Many domesticated crop plants grow best at around neutral soil pH, especially the cereals that produce the majority of calories consumed by humans. Humans have altered the soil pH on a local scale for millennia. For example, drainage of previously saturated soils frequently decreases their pH. All plants probably have to use some, perhaps all, of these mechanisms to counteract minor changes in soil pH, but they have also been adapted to enable plants to inhabit soils with pH values that are somewhat different to that of the plant cell cytoplasm. Plant root cells have pH-stats that can buffer cytosolic pH against variation in soil pH.
