Anthropogenic effects on forest ecosystems at various spatio-temporal scales.

Michael Bredemeier

doi:10.1100/tsw.2002.129

Abstract

The focus in this review of long-term effects on forest ecosystems is on human impact. As a classification of this differentiated and complex matter, three domains of long-term effects with different scales in space and time are distinguished: 1- Exploitation and conversion history of forests in areas of extended human settlement 2- Long-range air pollution and acid deposition in industrialized regions 3- Current global loss of forests and soil degradation.There is an evident link between the first and the third point in the list. Cultivation of primary forestland — with its tremendous effects on land cover — took place in Europe many centuries ago and continued for centuries. Deforestation today is a phenomenon predominantly observed in the developing countries, yet it threatens biotic and soil resources on a global scale. Acidification of forest soils caused by long-range air pollution from anthropogenic emission sources is a regional to continental problem in industrialized parts of the world. As a result of emission reduction legislation, atmospheric acid deposition is currently on the retreat in the richer industrialized regions (e.g., Europe, U.S., Japan); however, because many other regions of the world are at present rapidly developing their polluting industries (e.g., China and India), “acid rain” will most probably remain a serious ecological problem on regional scales. It is believed to have caused considerable destabilization of forest ecosystems, adding to the strong structural and biogeochemical impacts resulting from exploitation history.Deforestation and soil degradation cause the most pressing ecological problems for the time being, at least on the global scale. In many of those regions where loss of forests and soils is now high, it may be extremely difficult or impossible to restore forest ecosystems and soil productivity. Moreover, the driving forces, which are predominantly of a demographic and socioeconomic nature, do not yet seem to be lessening in strength. It can only be hoped that a wise policy of international cooperation and shared aims can cope with this problem in the future.

Highlights

Forest ecosystems are characterized by the unique longevity of their most prominent organisms, the dominating trees
The general environmental setting of any natural forest ecosystem uninfluenced by man would be defined by climate and soil substrate
In spite of the uncertainty and complexity involved, all assessments arrive at hazardous figures and ratings of actual global soil degradation, which is strongly and intimately linked with a global retreat and conversion of forest ecosystems

Summary

INTRODUCTION

Forest ecosystems are characterized by the unique longevity of their most prominent organisms, the dominating trees. With the end of excessive utilization practices, a prospect of recovery was given for forest soils, at least to some extent It would seem there were two opposing developments operating at the same time: (1) on the one hand, recovery of forest structure and of soil organic matter, offering some potential for a slow recovery of soil structure and of nutrient stores; and (2) on the other hand, acid deposition that played an important role in deteriorating site quality, as was directly evidenced in some comparisons of chemical parameters in forest soils over long time spans[30,31]. In spite of the uncertainty and complexity involved, all assessments arrive at hazardous figures and ratings of actual global soil degradation, which is strongly and intimately linked with a global retreat and conversion of forest ecosystems

Findings

DISCUSSION

CONCLUSION