Statistical characteristics of forest succession

Background/Question/Methods

The challenge of forest ecology is to understand and predict dynamics of forests under various disturbance regimes and climatic change scenarios. Forest stands are complex adaptive systems that can be characterized by different attributes. Widely used forest stand characteristics describe stand age and size structures, tree abundance, biodiversity and biomass. These parameters do not directly measure forest successional status. Our goal is to find an axis which includes a successional component which can be applied to the modeling landscape-level forest dynamics within the recently proposed Matreshka modeling framework (Strigul et al, 2012). 

Results/Conclusions

In this presentation, we introduce a macroscopic parameter called the shade-tolerance index. This index is defined as a weighted average of proportion of shade tolerant trees in the stand. We employ this parameter to describe the patch-mosaic patterns of the forests in the different parts of the USA. The shade-tolerance index does not correlate with other macroscopic characteristics of forest stands such as stand age, biomass, basal area of canopy trees, and biodiversity measures such as numbers of tree species, Shannon and Simpson's indexes. This parameter is also robust with respect to the forest inventory procedure, and, therefore, gives compatible estimates when different national and regional forest inventories are used, for example similar results were obtained for old (before 1999) and new (since 1999) sampling methods in USDA FIA data. Therefore, we anticipate the shade-tolerance index and its statistical derivatives are useful for the modeling of forest stand dynamics.