There has and continues to be concern about the effects of elevated nitrogen (N) deposition on natural ecosystems. In this paper, research on natural ecosystems, including wetlands, heathlands, grasslands, steppe, naturally regenerated forests and deserts, is evaluated to determine what is known about nitrogen cycling in these ecosystems, the effects of elevated nitrogen on them and to identify...

interest in arid ecosystems as a source of food supply for rapidly increasing population of the world, on the one hand, and the problems pertaining to the climatic characteristics, water shortages and soil sensitivity for the inhabitants in such areas, on the other have prompted efforts at both national and international levels to develop a better understanding of these problems as well as to f...

The purpose of this study is to determine the woody species diversity in Sweet chestnut tree, Hazel-tree and Italian cypress ecosystems in the Guilan forests. A lozeng 0.5 ha sample plot was selectively established on each site. In the Sweet chestnut ecosystems , 4 sites were classified, whereas 10 sites of Hazel tree and Italian cypress ecosystems were classified based on species composition. ...