Sub-Compartment Variation in Tree Height, Stem Diameter and Stocking in a Pinus radiata D. Don Plantation Examined Using Airborne LiDAR Data

Hanieh Saremi,Christine Stone,Russell Turner,Lalit Kumar,Gavin Melville

doi:10.3390/rs6087592

Abstract

Better information regarding the spatial variability of height, Diameter at Breast Height (DBH) and stocking could improve inventory estimates at the operational Planning Unit since these parameters are used extensively in allometric equations, including stem volume, biomass and carbon calculations. In this study, the influence of stand stocking on height and DBH of two even aged radiata pine (Pinus radiata D. Don) stands were investigated using airborne Light Detection and Ranging (LiDAR) data at a study site in New South Wales, Australia. Both stands were characterized by irregular stocking due to patchy establishment and self-thinning in the absence of any silvicultural thinning events. For the purpose of this study, a total of 34 plots from a 34 year old site and 43 plots from a nine year old site were established, from which a total of 447 trees were sampled. Within these plots, DBH and height measurements were measured and their relationships with stocking were evaluated. LiDAR was used for height estimation as well as stem counts in fixed plots (stocking). The results showed a significant relationship between stem DBH and stocking. At both locations, trees with larger diameters were found on lower stocking sites. Height values were also significantly correlated with stocking, with taller trees associated with high stocking. These results were further verified of additional tree samples, with independent field surveys for DBH and LiDAR-derived metrics for height analysis. This study confirmed the relationship between P. radiata tree heights and stem diameter with stocking and demonstrated the capacity of LiDAR to capture sub-compartment variation in these tree-level attributes.

Highlights

Tree Diameter at Breast Height (DBH), height and stocking are the most common variables used in forest inventory
The DBH and height of the 193 trees in the older stand were fitted to stocking using the multivariate mixed linear model (Equation (2))
In this research the interrelationship between stem diameter, height and stocking were investigated with the use of Light Detection and Ranging (LiDAR) for the case of two large even-aged radiata pine stands in Australia

Summary

Introduction

Tree Diameter at Breast Height (DBH), height and stocking (number of tree stems per ha) are the most common variables used in forest inventory Spatial variability of these inventory attributes directly influences the precision of growth and yield estimates. Various environmental factors such as water and nutrient availability, climatic variables and soil nutrition, texture and depth have been reported to affect the growth and canopy structure of radiata pine [1,2,3]. Silvicultural practices, in particular the manipulation of stocking, are commonly used by plantation growers to optimize stand growth and structure Stand density influences both internal and external characteristics of trees between and within a stand by altering competition between trees for water, nutrients and solar radiation [4,5]. Klitscher [11] reported a reduction in mortality percentage of this species within lower stand densities

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