tailieunhanh - Báo cáo lâm nghiệp: "Physiological responses to air pollutants"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: Physiological responses to air pollutants. | 536s Ann. Sci. For. 1989 46 suppl. 536s-542s Forest Tree Physiology E. Dreyer et al. eds. Elsevier INRA Physiological responses to air pollutants G. Halbwachs Zentrum fur Umwelt- und Naturschutz Universitat fur Bodenkultur Wien õsterreich When investigating the phenomenon of large scale forest decline particularly its appearance in so-called clean air regions plant physiology has gained considerable importance. Especially tree physiology which deals with the life processes of trees has again become interesting not only for scientists but also for the ecologically conscious public Eschrich 1987 . Trees are long-lived organisms which over many decades pass through various stages of development seedling sapling young growth and old growth each with its own distinctive physiological characteristics. In addition to these variations sensitivity varies during the daily and annual rhythm. Since trees tower over all other forms of vegetation they have a definite advantage in the struggle for light. Furthermore they have evolved a system of compartmentalization which allows them the loss of larger plant parts without substantially affecting their chances for survival. Because of these attributes they possess a dominant position in a forest. Nevertheless the term forest not only includes all closely interacting trees located in a defined area but it also includes the complex structure of interactions be tween trees bushes herbs animals the soil including the organisms that live in and on it and the special climatic conditions. In the forest ecosystem with its diversity in vegetation and animal life a near equilibrium is reached between decomposition and synthesizing processes. Even though this equilibrium is rather labile because of permanent natural changes it still works very efficiently to maintain nutrients in the system. An additional attribute is the ability of trees whose tops are strongly coupled with the atmosphere to filter out dust and trace elements which are then