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Managers of forested water supply catchments require efficient and accurate methods to quantify changes in forest water use due to changes in forest structure and density after disturbance. Using Light Detection and Ranging (LiDAR) data with as few as 0.9 pulses m⁻², we applied a local maximum filtering (LMF) method and normalised cut (NCut) algorithm to predict stocking density (S_Den) of a 69-year-old Eucalyptus regnans forest comprising 251 plots with resolution of the order of 0.04 ha. Using the NCut method we predicted basal area (BA_Ha) per hectare and sapwood area (SA_Ha) per hectare, a well-established proxy for transpiration. Sapwood area was also indirectly estimated with allometric relationships dependent on LiDAR derived S_Den and BA_Ha using a computationally efficient procedure. The individual tree detection (ITD) rates for the LMF and NCut methods respectively had 72% and 68% of stems correctly identified, 25% and 20% of stems missed, and 2% and 12% of stems over-segmented. The significantly higher computational requirement of the NCut algorithm makes the LMF method more suitable for predicting S_Den across large forested areas. Using NCut derived ITD segments, observed versus predicted stand BA_Ha had R² ranging from 0.70 to 0.98 across six catchments, whereas a generalised parsimonious model applied to all sites used the portion of hits greater than 37 m in height (PH₃₇) to explain 68% of BA_Ha. For extrapolating one ha resolution SA_Ha estimates across large forested catchments, we found that directly relating SA_Ha to NCut derived LiDAR indices (R² = 0.56) was slightly more accurate but computationally more demanding than indirect estimates of SA_Ha using allometric relationships consisting of BA_Ha (R² = 0.50) or a sapwood perimeter index, defined as (BA_HaS_Den)^½ (R² = 0.48).

Item Type:	Refereed Article
Research Division:	Engineering
Research Group:	Geomatic engineering
Research Field:	Photogrammetry and remote sensing
Objective Division:	Environmental Management
Objective Group:	Fresh, ground and surface water systems and management
Objective Field:	Assessment and management of freshwater ecosystems
UTAS Author:	Wallace, L (Dr Luke Wallace)
ID Code:	105726
Year Published:	2015
Web of Science® Times Cited:	14
Deposited By:	Geography and Environmental Studies
Deposited On:	2016-01-13
Last Modified:	2017-10-25
Downloads:	264 View Download Statistics