HR: 16:00h
AN: B12G-01    [PDF]
TI: Looking at Boreal Ecosystem Dynamics With a Disturbance Perspective
AU: * Apps, M
EM: mapps@nrcan.gc.ca
AF: Natural Resources Canada, Pacific Forestry Centre 506 W. Burnside Rd., Victoria, BC V8Z 1M5 Canada
AB: Disturbances such as fire, insect outbreaks and storm damage play pivotal roles in dynamics of terrestrial ecosystems, especially in the boreal zone. Not only do such disturbances facilitate the adaptation of these biomes to the changing environmental conditions associated with global change pressures (Overpeck et al 1990), they can also trigger changes at the landscape scale that can result in ecosystems switching from sources to sinks of atmospheric CO2 (Kurz and Apps 1999) or from sinks to sources (Kurz et al 1998). The intrinsic connection of the influence of age-class structures on ecosystem productivity and carbon cycle processes, and the focus this brings to the importance of understanding and documenting past disturbance regimes has clear implications for mitigation issues, influenced by both natural and human-induced processes. Gaining improved data for, and predictive understanding of the role of disturbances in the state and dynamics of terrestrial ecosystems, especially in the boreal zone where very large carbon stocks are affected, is clearly an important goal for terrestrial ecosystem research. Equilibrium and steady-state approaches are inadequate: disturbances are intrinsically non-linear processes associated with complex systems whose subsystem parts are driven away from equilibrium by changes within these subsystems and the interactions between them. This gives rise to a rich pattern of variation and change over both time and over space in which the complex web of interacting subsystems and non-linearities forces us to adopt new systems approaches. Emergent properties and new system states are characteristic features of such approaches. As pointed out by Per Bak (1996), self-organized criticality is the new way of viewing nature - perpetually out-of-balance, but organized in a poised state. In this new view, disturbances play a strong role in the coupling of the subsystems and act as triggers that alter the distribution of these systems (structure and pattern) in both time and space. These structural changes in turn alter the behavior (function) of these subsystems and become imbedded in the dynamics of the larger system. Disturbances, and the long-term response of the affected subsystems, thus play an integral role in linking across scales of time and space.
DE: 8015 Local crustal structure
SC: Biogeosciences [B]
MN: 2003 Fall Meeting