Review of nitrogen distribution and cycling in forest ecosystems

Sustained productivity of forests depends on the maintenance of soil fertility. In order to assess the long term impacts of forest management practices on soil fertility, it is not sufficient merely to examine the balances between the nutrient gains from various natural and fertilizer inputs and the losses resulting from soil leaching or tree crop removal. It is also important to understand the functioning and the rates of biological cycling within the forest ecosystem, as the processes governing the cycling may affect the condition of the nutrient capital within the soil and hence soil fertility. The productivity of forests in many countries throughout the world is primarily limited by nitrogen deficiency, despite the fact that the soils may contain substantial quantities of nitrogen. In north-eastern China, nitrogen deficiency is thought to be the main nutrient deficiency limiting the growth of plantation forests, and it may also govern the pattern of forest succession in natural forest ecosystems, such as those at Changbai mountain. As a contribution to studies of nutrient cycling in forests in north-eastern China, this review of literature on nitrogen cycling has been compiled