An evaluation of spatial dependency in juvenile loblolly pine stands using stem diameter

Abstract

A simultaneous autoregressive model (SAR) was used to evaluate the amount of spatial influence juvenile loblolly pine (Pinus taeda L.) stems in a plantation have on one another. The presence of spatial autocorrelation between stems in a stand indicates that the characteristics of one stem are related to the characteristics of neighboring stems. The stands evaluated in this study had planting densities that varied from 747 to 6,727 trees per hectare. The SAR model contains a spatial dependency parameter that captures the inter-tree influences. Analysis on detrended diameter data showed that across ages 2 to 5 for groundline diameter measurements and ages 5 to 11 for breast height diameter measurements, the simultaneous autoregressive model indicated significant spatial dependency parameters in 23.2% of the plots (alpha-level = 0.10). A generally increasing trend in the occurrence of significant spatial influence from 18.2% to 28.4% was noted with an increase in planting density from 747 to 3,364 trees per hectare, beyond which the trend decreased. Estimation of the spatial dependency parameter will aid in describing juvenile competition processes and developing a more precise representation of juvenile forest stands. Copyright © 2005 by the Society of American Foresters.