Table 8. Mean residence time for organic matter and nutrients in the surface litter layer of contrasting forest types (*). Values are calculated by dividing the forest floor mass by the mean annual litterfall. Organic matter and nutrient turnover rates show a large increase with decreasing altitude, reflecting the temperature increase with decreasing latitude. Deciduous species have greater turnover rates than conifers due to better litter quality.
Forest TypenOrganic MatterNKCaMgP
Mean residence time (yr)
Boreal coniferous335323094149455324
Boreal deciduous12627.110.013.814.215.2
Temperate coniferous131717.92.25.912.915.3
Temperate deciduous144.05.51.33.03.45.8
mediterranean deciduous23.43.90.84.42.52.3
Tropical rain forest40.42.00.71.51.11.6
(*) Data for boreal and temperate forests and one Mediterranean forest are from Cole and Rapp (1981); one from Mediterranean forest from gray and Schlesinger (1981); and tropical forests from Edwards and Grubb (1982).