Forest decline

Abstract

Forest decline is a major environmental issue today. However, there are numerous examples of past declines in the condition of individual species within forests or of the entire forests themselves. Many of these declines are natural, being brought about by a variety of factors, including stand dynamics, pests and diseases. The emphasis that has been placed on air pollution in recent declines does not appear to be justified, although air pollution has undoubtedly brought about the decline of forests at some locations. Much of the literature exaggerates the extent of the decline in forest health in Europe. The overestimation of its extent has occurred because of the assessment techniques that are used: these are unable to distinguish trees that have recently declined from those that have always been in poor condition. In addition, the techniques that are most frequently used are nonspecific and no cause can be readily attributed to the defoliation that has been observed.

Advanced Land Observing Satellite Phased Array Type L-Band SAR (ALOS PALSAR) to Inform the Conservation of Mangroves: Sundarbans as a Case Study

“…For example, some coastal areas at least 25 km from the cyclone's path were classified as 'highly affected', whilst large areas of mangroves, some on the coastline, classified as 'slightly to not affected' were within 10 km of the same part of the cyclone's path. Without a point of reference pre-event, damages are likely to be both over and under-estimated, since forest degradation cannot be inferred without knowledge of prior condition [48]. Moreover, these attempts aimed at simply outlining the potential area where damages might have occurred, without providing a clear assessment of the impact of Sidr.…”

Monitoring the effects of air pollution on forest condition in Europe: is crown defoliation an adequate indicator?

“…Crown defoliation and discolo ration are not specific to any direct or indi rect influence of air pollutants. Instead, they integrate the effects of natural factors such as site conditions (e.g., soil), intrinsic factors (e.g., age, phenology), biotic stress (pests, fungi), and meteorological conditions, as well as air pollutants (Innes 1992. In addition, several relevant stress factors, which may affect defoliation are currently not included in the current monitoring program, these include forest management practices (e.g., thinning), me chanical hazards due to meteorological events (e.g., storm damage) as well as biotic stress (e.g., diseases and competition - Klap et al 2000).…”

The extreme drought in the 1920s and its effect on tree growth deduced from tree ring analysis: a case study in North China

“…However, tree mortality may result from multiple factors, including human activity, fire suppression, competition, insect infestation, or a combination of these disturbances [22,45]. Prior to 1950, the Xilin River Basin was still a virgin territory, implying that no direct relationship existed between human activity and forest dieback in the 1920s.…”