Effect of site management on leaf area, early biomass development, and stand growth efficiency of a Eucalyptus grandis plantation in South Africa

The effects of intensive site management operations on leaf area index (LAI), aboveground woody biomass (WB) development, and stand growth efficiency were studied in a South African Eucalyptus grandis (Hill ex Maiden) stand from establishment to 3.5 years of age. Site management treatments included slash removal, slash retention, fertilization, slash burning, and slash disturbance through mechanized harvesting operations. Stand LAI development responded strongly and significantly to the site management treatments imposed at establishment. Responses were driven by nutrient supply but were apparently limited by a severe drought after establishment. At 1.3 years, LAI in the slash removal treatment reached 2.1, compared to 4.5 following fertilization or slash burning. Treatments also significantly affected the development of aboveground WB, which ranged from 53.6 (slash removal) to 64.9 (fertilization) and 65.8 Mg.ha^-1 (slash burning) at 3.5 years. Biomass allocation to roots and stand growth efficiency (i.e., WB increment per unit of LAI) did not differ significantly between treatments. We conclude that the fast-growing treatments produced more WB because of more rapid development of maximum LAI. The possible implications of this response mechanism for management operations that aim to improve growth through improved nutrient supply are discussed, with reference to unthinned, short-rotation crops.