Nutrient Cycling in Mixed-Forest Plantations

Abstract

A continuous supply of nutrients is necessary to maintain the tree growth in forest ecosystems. This continuous supply is maintained by nutrient cycling. In managed forests a large amount of nutrients is removed with the harvest. This fact opens the nutrient cycle, being necessary, in many cases, fertilizer application to ensure adequate nutrient supply for the trees. Our goal with this chapter is to compare the nutrient cycling of mixed forest (mainly Acacia with Eucalyptus) with monospecific plantation and natural vegetation (Atlantic Forest and Savannah). The introduction of nitrogen-fixing trees (NFTs) in monospecific eucalypt plantation can improve the capacity of the trees in obtain nutrients, mainly due to the atmospheric N2 fixation and by the wider soil exploration. Beyond that, the introduction of NFTs also accelerates the nutrient cycling, especially to P. These two facts reduce the dependence of mixed plantation on fertilizer application. However, the concentration of some nutrients in the acacia biomass is higher than in eucalypt biomass. Thus, if mixed plantations reach the same productivity of monospecific eucalypt plantation, an increase in the nutrient harvest output can occur.