BORON DEFICIENCY AND EXCESS IN FOREST TREES - A REVIEW

Boron deficiency of forest trees occurs in many countries, notably in exotic plantations of eucalyptus and pines, but also in plantations and natural stands of native species on soils altered by macronutrient fertilization, fire or erosion. The symptoms are usually characteristic, although diagnosis may be comfounded by variable foliar concentrations, erratic occurrence, and posible climatic damages. Chronic deficiency causes stunting, poor survival and stand irregularities. Even single episodes of deficiency cause severe stem defects and loss of wood quality. Incidence of deficiency is associated with soil characteristics. Species and genotyes within species differ in vulnerability to damage. Preventive application of slowly soluble B fertilizer is becoming routine in intensively managed plantations on susceptible soils. Boron toxicity in forest trees is uncommonly but arises from a variety of causes, including irregular distribution of B fertilizers intended to prevent deficiency. Other localized causes are application or atmospheric deposition of B-containing wastes and waste waters. Natural sources are also known but rare in forested regions. Foliar symptoms and concentrations are diagnostic. The literature of the past two decades concerning these topics and normal B concentrations is reviewed. © 1990.