Highlighting Complex Long-Term Succession Pathways in Mixed Forests of the Pacific Northwest: A Markov Chain Modelling Approach

Abstract

Forest succession is an ecological phenomenon that can span centuries. Although the concept of succession was originally formulated as a deterministic sequence of different plant communities by F. Clements more than a century ago, nowadays it is recognized that stochastic events and disturbances play a pivotal role in forest succession. In spite of that, forest maps and management plans around the world are developed and focused on a unique “climax” community, likely due to the difficulty of quantifying alternative succession pathways. In this research, we explored the possibility of developing a Markov Chain model to study multiple pathway succession scenarios in mixed forests of western red cedar, hemlock and Pacific silver fir on northern Vancouver Island (western Canada). We created a transition matrix using the probabilities of change between alternative ecological stages as well as red cedar regeneration. Each ecological state was defined by the dominant tree species and ages. Our results indicate that, compared to the traditional Clementsian, deterministic one-pathway succession model, which is unable to replicate current stand distribution of these forests in the region, a three-pathway stochastic succession model, calibrated by a panel of experts, can mimic the observed landscape distribution among different stand types before commercial logging started in the region. We conclude that, while knowing the difficulty of parameterizing this type of models, their use is needed to recognize that for a given site, there may be multiple “climax” communities and hence forest management should account for them.

Incorporating small‐scale disturbances in models of forest structure and aboveground biomass of tropical mountains

“…Beyond the methodological challenges, disregarding the role of land use also stems from an epistemological issue. Analyses of forest structure, composition, and dynamics are, in many cases, still approached from a “stability/fragility” paradigm where tropical forests are regarded as pristine and untouched instead of as dynamic landscapes in constant flux (Blanco et al, 2021; Chazdon, 2003). Hence, most of the field observations used to scale up AGB estimates come from field plots established in undisturbed forests, likely biasing the process of modeling and validation over the approximately 53% of forests that are not considered primary (Asner et al, 2010; Chazdon et al, 2016; Rozendaal et al, 2022).…”

Simulation and prediction of changes in tree species composition in subtropical forests of China using a nonlinear difference equation system model

“…Some of these researchers in this area have paid more attention to the basal area and compositional changes during tropical forest succession, and demographic forest models have been developed to analyze the growth-survival and stature-recruitment trade-offs (Ouyang et al, 2016;Hu et al, 2018;Ruger et al, 2020). Other researchers have focused on the dynamic disturbances involved, such as the survival rate of tree species in the process of forest succession (Peng et al, 2010), the regeneration rate after disturbance (Blanco et al, 2021), and the occurrence of natural disasters (Yin et al, 2009). The Markov chain model is used to describe the state of the forest ecosystem in forest growth scenarios, in which dynamic disturbances are treated as special events of forest growth scenarios that are constantly transferred according to a certain probability (Risch et al, 2009).…”