A distance-independent individual-tree growth model to simulate management regimes in native Araucaria forests

Unfettered exploitation of Brazilian forests over the past century, through conversion to cropping and pasture lands and commercial tree plantations, has reduced native Araucaria forests to fragments, restricted largely to small landholdings and protected areas. To encourage sustainable forestry activity in smallholdings and stimulate the expansion of Araucaria natural forests, we developed a distance-independent individual-tree growth model designed to simulate management regimes in native Araucaria forests. The model was constructed with data collected from 25 contiguous 1-ha permanent plots established in the Irati National Forest in southern Brazil. Because native Araucaria forests are comprised of hundreds of species, we parameterized diameter increment, survival, and recruitment models for six ecological species groups: understory, subcanopy, upper canopy shade-tolerant, upper canopy light-demanding, pioneer, and emergent. The observed and estimated stand volumes were very similar (R2 = 0.97) using independent data. Simulations using a plot with an average density were performed to present the model outputs, including harvest simulations. The constructed model may be suitable for exploring management regimes in smallholdings and predicting aboveground biomass.