Estimation of carrying capacity in loblolly pine (Pinus taeda L.)

For plant populations, carrying capacity is the maximum number or biomass of a species that can be sustained under finite site resources on a long-term basis. This study was aimed at estimating the carrying capacity in planted stands of loblolly pine. Maximum stand basal area (BA) that can be sustained over a long period of time can be regarded as a measure of carrying capacity. To quantify and project stand BA carrying capacity, one approach is to use the estimate from a fitted cumulative BA-age equation; another approach is to obtain BA estimates implied by maximum size-density relationships (MSDRs), denoted implied maximum stand BA. The efficacy of three diameter-based MSDR measures: Reineke's self thinning rule, competition-density rule and Nilson's sparsity index, were evaluated. Estimates from these three MSDR measures were compared with estimates from the Chapman-Richards (C-R) equation fitted to the maximum stand BA observed on plots from spacing trials. The spacing trials, established in two physiographic regions (Piedmont and Coastal Plain) in the southeastern United States, and at two different scales (operational and miniature) were examined to provide an empirical basis for potential carrying capacity of loblolly pine. Results showed that the value of implied maximum stand BA converted from three diameter-based MSDR measures was similar to the maximum stand BA curve obtained from the C-R equation. All three MSDR measures provided similar estimates of stand BA carrying capacity, with Nilson's sparsity index yielding the most stable and reliable estimate. The potential stand BA carrying capacity between the two physiographic regions was significantly different. The maximum stand BA associated with planting density developed similarly at the operational and miniature scales. (C) 2016 Elsevier B.V. All rights reserved.