Báo cáo lâm nghiệp: Modelling the coppice stand structure: an ecophysiological approach

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Báo cáo lâm nghiệp: "Modelling the coppice stand structure: an ecophysiological approach"Modelling the coppice stand structure:an ecophysiological approachG.E. Scarascia-Mugnozza, R. Valentini E. Giordanoand A. Del Lungo A. Del Lungo Oi i00 Viterbo, University of Tuscia, ItalyInstitute of Forest Biology, and the climate is mediterranean with a meanIntroduction annual temperature of 17°C, a mean annual precipitation of 900 mm and a marked summer drought. The stand is managed as a coppiceLimitations of water availability have seri- with standards, with 2400 sprouts on about impact on biomass production inous 1200 stumps/ha and with 96 standards/ha. Themediterranean forest ecosystems. There latter are trees, managed on a longer rotationis also growing evidence about the than the coppice, to produce seeds for theinfluence of water deficits on the develop- regeneration of the stand. The rotation interval is 18 yr for the coppice and a multiple of it forment of insect or pathogen problems that the standards. The mean annual abovegroundeventually result in a general decline of biomass increment is 7 tons!ha-!!yr-!.these forests. Therefore, the analysis of description of the canopy structure A detailedthe interactions between the water rela- accomplished by analyzing the crowns of wastions of a forest and its carbon cycle is of 12 representative trees divided into 3 differentfundamental importance, in order to identi- diameter classes for the coppice (4, 10, 17 cm) and one for the standards (25 cm); these obser-fy the most suitable silvicultural tech- vations were made in September 1987, whenniques to optimize productivity relative to the leaf area display was at its seasonal peak consumption (Jarvis, 1985).water and the stand was at the end of the rotation. For each model tree, leaf area measured on A promising approach consists of representative branches was significantly andthe implementation of ecophysiological highly correlated (R 0.70) to branch length. 2 2models that include the description of the Using this regression and knowing the length,structure of a forest stand together with location and orientation of each first orderthe relationships between physiological branch, the vertical distribution of leaf area of each model tree was derived. The orientationprocesses and environmental parameters. (azimuth, midrib and lamina angles) of an appropriate sample of leaves was also mea- sured, after stratification among trees and canopy layers (isebrands and Michael, 1986).Materials and Methods Ecophysiological (stomatal conductance and plant water potentia!), climatic and soil moisture data were collected throughout 4 growing sea-An established in experimental plot was a sons in the same experimental plot, by meansQuercus cerris L. forest stand ...