A global perspective on forest decline

Abstract

Abstract-Carbon dioxide, the major plant food, is on the rise, but forests on both sides of the Atlantic are known to be declining, and industrial pollution is widely suspected to be the principal cause. However, significant contemporary forest declines also are occurring in several Pacific forests, in areas completely unaffected by industrial pollution. This paper focuses on researched forest declines in the Pacific area (New Zealand, Japan, and the Hawaiian and Galapagos islands), where canopy dieback was found to be a natural aspect of forest dynamics. It then summarizes characteristics of forest decline in central Europe (Czechoslovakia and Germany), where decline relates mostly to anthropogenic causes. Commonalities among the natural causes in the Pacific and anthropogenic causes in the European forests are emphasized through recognition of a third factor complex, the demographic component, which so far has been largely neglected in the European forest decline research. The natural cause complexes identified as demographic, disturbance, and biotic components are placed into a causal hierarchy theory based on cohort senescence. It is suggested that this may serve as a framework for comparative ecosystem research of forest declines at the global level, which includes a consideration of ongoing biotic impoverishment and climate change.

Long‐term rain forest succession and landscape change in Hawai'i: The ‘Maui Forest Trouble’ revisited

“…'Bog-formation dieback', the second focus of this paper, refers to tree dieback in boggy terrain. Dieback and decline has been interpreted in the cohort senescence theory (Mueller-Dombois 1987, 1992b) as related to stand demography and its history of increasing stress with growth, development and age in a generation of trees (a cohort), which finally collapses due to a subtle (largely unknown) trigger. In the Hawaiian succession model, bog-formation dieback is shown as an end stage of primary succession.…”

A typology of stand structure and dynamics of Quaking aspen in northwestern Colorado

“…The idea of cohort senescence, first formulated by Mueller-Dombois (1992), suggests that forests with low species diversity, predominantly even-aged stands of genetically similar trees, and distinct life spans tend to undergo periods of widespread dieback. Dieback of a forest can result in the self-replacement of the dieback species underneath its own canopy, called ''replacement dieback''.…”