Dynamic steady state of patch-mosaic tree size structure of a mixed dipterocarp forest regulated by local crowding

Authored by T Kohyama, E Suzuki, T Partomihardjo, T Yamada

Date Published: 2001

DOI: 10.1046/j.1440-1703.2001.00374.x

Sponsors: Japanese Society for the Promotion of Science (JSPS)

Platforms: No platforms listed

Model Documentation: Other Narrative Flow charts Mathematical description

Model Code URLs: Model code not found

Abstract

A patch age- and tree size-structured simulator was applied to demonstrate the landscape dynamics of a lowland mixed dipterocarp forest, using census data over a 3 year interval from two 1 ha plots in northern West Kalimantan, Indonesia (Western Borneo). Tree growth rate and recruitment rate were estimated as functions of tree size and local crowding. The effect of local crowding was assumed to be one-sided through light competition, where the basal area for all trees larger than a target tree inside the circle of 10 m radius around the target was employed as the index of crowding. Estimated parameters were similar between the two plots. Tree mortality was expressed by descending function of tree size with asymptotic mortality for large trees corresponding to the gap formation rate. One parameter specifying the survival of trees at gap formation, which was required for the landscape-level simulation of a shifting-gap mosaic, was left undetermined from plot census data. Through simulation, this parameter was estimated so as to best fit the observed among-patch variation in terms of local basal area. The overall time course of simulation and tree size structure were not sensitive to this parameter, suggesting that one-sided competition along the vertical forest profile is a stronger determinant of average forest structure than among-patch horizontal heterogeneity in this forest. Simulated dynamic steady state successfully reproduced the observed forest architecture in the gap-dynamic landscape. It took about 400 years for a vacant landscape to be replaced by a steady-state architecture of forest. Sensitivity analysis suggests that steady-state basal area and biomass are most sensitive to changing gap formation rate and intrinsic size growth rate.

Tags

Individual-based model Simulation Coexistence growth Stands Rain-forests Borneo Dwarf bamboo Conifers