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

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: Modelling the coppice stand structure: an ecophysiological approach. | 519s Ann. Sci. For. 1989 46 suppl. 519s-522s Forest Tree Physiology E. Dreyer et al. eds. Elsevier INRA Modelling the coppice stand structure an ecophysiological approach . Scarascia-Mugnozza R. Valentini E. Giordano and A. Del Lungo Institute of Forest Biology University of Tuscia 01100 Viterbo Italy Introduction Limitations of water availability have serious impact on biomass production in mediterranean forest ecosystems. There is also growing evidence about the influence of water deficits on the development of insect or pathogen problems that eventually result in a general decline of these forests. Therefore the analysis of the interactions between the water relations of a forest and its carbon cycle is of fundamental importance in order to identify the most suitable silvicultural techniques to optimize productivity relative to water consumption Jarvis 1985 . A promising approach consists of the implementation of ecophysiological models that include the description of the structure of a forest stand together with the relationships between physiological processes and environmental parameters. Materials and Methods An experimental plot was established in a Quercus cerris L. forest stand in central Italy 42 23 N 11 55 E . Its elevation is 150 m . and the climate is mediterranean with a mean annual temperature of 17 c a mean annual precipitation of 900 mm and a marked summer drought. The stand is managed as a coppice with standards with 2400 sprouts on about 1200 stumps ha and with 96 standards ha. The latter are trees managed on a longer rotation than the coppice to produce seeds for the regeneration of the stand. The rotation interval is 18 yr for the coppice and a multiple of it for the standards. The mean annual aboveground biomass increment is 7 tons ha- -yr . A detailed description of the canopy structure was accomplished by analyzing the crowns of 12 representative trees divided into 3 different diameter classes for the coppice 4 10 17 cm and one for