Plasticity and Extrapolation in Modeling Mixed-Species Stands

Authored by Min Jun Lee, Oscar Garcia

Date Published: 2016

DOI: 10.5849/forsci.15-027

Sponsors: No sponsors listed

Platforms: R

Model Documentation: Other Narrative Mathematical description

Model Code URLs: Model code not found

Abstract

We studied tree interactions by estimating competition under different modeling frameworks and relating it to observed stem volume growth. Three types of models were tested: type 1, spatially explicit simulation based on the measured tree coordinates; type 2, distance-independent perfect plasticity approximations, relating volume growth to tree height; and type 3, purely empirical size-driven models, regressing growth on size. We used three stem-mapped mixed-wood plots from central British Columbia, Canada, approximately 37 years old. The stand was planted with spruce seedlings and subsequently received hardwood natural regeneration, mostly birch, alder, aspen, and willows. The plots represented an untreated control and two different brushing treatments. Models of type 1 showed less prediction ability than the simpler type 2 models, suggesting that plasticity is important and diminishes the effects of spatial structure. Type 3 models, using current volume as a predictor of volume increment, resulted in much higher R-2 values. Tree size reflects accumulated past growth, so that these models are largely simple empirical extrapolations. Size-driven models can be highly effective for yield forecasting in relatively undisturbed stands but may not be reliable after natural disturbances, management interventions, or environmental changes.

Tags

Efficiency growth Size Forest dynamics