Concepts, theories and models of succession in the boreal forest of central Canada.

摘要

Predicting plant community compositional responses to changing environmental conditions and disturbances is a key element of forecasting and managing for the effects of global climate change. With advances in ecological modeling, many forms of succession models are available. Empirical-based succession models have been criticized as inflexible and limited by the quality and coverage of data for formulation however, mechanistic models are tied to the underlying theory (quality and comprehensiveness) from which they are developed and make key limiting assumptions that the modeled processes they represent are adequately understood, thus underscoring the continual necessity for empirical testing of successional processes.Overall, we observed a compositional shift over time, in which post-fire stands dominated by fast growing shade-intolerant species are eventually replaced by late seral, shade-tolerant species. This phenomenon, however, is not a simple unidirectional sequence of stages, but rather compositionally similar stands may exhibit multiple successional pathways dependent on differential species responses to physical site conditions, initial stand composition and intermediate disturbances. Individual species responses appeared largely controlled by shade-tolerance and regeneration strategy. We suspect these are the most important life history traits in explaining boreal forest succession.Keywords: strategic planning, qualitative models, quantitative models, empirical models, mechanistic models, stand dynamics, competition, disturbance, fire cycle, regression, diversity spruce budworm, toleranceCurrently, a great deal of our knowledge of succession in boreal forest is expert opinion-based or has been inferred from chronosequence studies. As a result, many commonly held assumptions on the nature and existence of succession in boreal forests are still debated. We, therefore, constructed a dataset of long-term repeated stand measurements, collected over a wide geographical area in central Canada, to test fundamental concepts and theories about boreal forest succession at the landscape and tree population levels, including the existence of theorized multiple successional pathways and species population dynamics in the prolonged absence of stand replacing fire.