Management of forests under nutrient and water stress

Abstract

Management of forest nutrition through fertilization and other forestry practices has, undoubtedly, helped to increase the productivity of forests. Relatively little attention has been given to the potential for manipulating available water, although water relations of trees have been studied extensively. It is being increasingly recognized that, for fast-growing tree species, availability of water and its interaction with nutrients have overriding influences on growth, with major implications for the development of cost effective management practices to increase yield. For example, it has been argued that leaf area development is primarily controlled by available water and that in turn, determines the response to nutrient management. Crucial questions which need to be examined inlude: At the process level, how does the interplay between water and nutrients influence nutrient dynamics in forests? How do trees and associated vegetation interact with respect to the use of water and nutrients? How does water and nutrient availability influence leaf area development, assimilation and in particular assimilate partitioning? Does improved nutrition influence water use efficiency? An urgent need for the study of nutrition of trees under water stress also arises from the many problems encountered in reforesting arid and degraded land. This paper is an overview of these issues, emphasizing the mechanisms and processes that underly the response of trees and stands to manipulations of water and nutrient availability.