Ecosystem development on reclaimed china clay wastes. II. Nutrient compartmentation and nitrogen mineralization.
The accumulation of biomass and nutrients in 3 compartments (plant shoots, roots and surface soil) in developing grass/clover ecosystems in 2 types of reclaimed china clay waste, sand tips and mica dam walls was measured. Biomass and N accumulated mainly in the root compartment whereas all other elements measured, with the exception of K in mica dam wall soils, accumulated in the soil fraction. The accumulation of nutrients in the shoot and root pools was not due to redistribution of nutrients from the soil pool, as accumulation was demonstrated in all 3 pools. Soil N mineralization tests showed an increase in mineralizable N in the reclaimed waste compared with the raw waste. A significant correlation with age since treatment was demonstrated for sand tip soils. The importance of nutrient cycling and of N cycling in particular in recently established ecosystems such as reclaimed china clay wastes is emphasized. The relative contributions to N cycling from mineralization and grazing sources are discussed.