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.

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Plant area index (PAI) measured with a LI-COR LAI-2000 plant canopy analyser (PCA) was calibrated with leaf area index (LAI) in a young stand of Eucalyptus grandis in the KwaZulu-Natal Midlands, South Africa. Destructive sampling and allometric equations were used to estimate LAI at 2 and 3 years after planting. Significant correlations (P<0.001) were found between LAI and PAI for each age with different equations being generated for the two ages (LAI=1.0594(PAI)−0.892 at 2 years of age, and LAI=1.0393(PAI) at 3 years of age). The equations differed from those reported in other eucalypt studies, as the PCA in this study over-predicted LAI at 2 years, and slightly underpredicted at 3 years, of age. It is argued that the stage of growth influenced this calibration, as the canopy and foliar structure may have been different in the young stands, affecting the basic assumptions for the PCA. A broad conversion from PCA derived PAI to LAI may not necessarily be valid for young, short rotation eucalypt plantations.

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