Simulation of soil carbon and nutrient development under Pinus sylvestris and Pinus contorta

Pinus contorta and Pinus sylvestris differ in their allocation of growth as well as in their chemical composition of tissues. These factors modify the production and decomposition of litter, and thereby in the long run change the soil storage of carbon and nutrients. We have used conventional forest yield models to calculate litter production in combination with a model of soil carbon and nutrients to predict expected changes both in steady state and transitory soil properties. P. sylvestris has a higher litter producti on rate and a faster litter decomposition than P. contorta. Together, these two factors balance each other such that the specific site conditions, tim e horizon, and management determine which of the two species gives rise to the largest soil storages of carbon and nutrients. P. sylvestris is also le ss sensitive to variations in site conditions and management than P. contor ta. From a practical point of view, it is difficult to foresee if a replace ment of P. sylvestris with P. contorta would change soil storages of carbon and nutrients; the specific management of a stand is likely to dominate ov er species differences. The increased growth of P. contorta increases the d emand on base cations in the soil, but the difference between the two pine species is less than the difference between methods of accounting for acidi fication. (C) 2001 Elsevier Science B.V. All rights reserved.