Deriving Novel Allometric Equations for Northern Sierra Nevada Trees Using Terrestrial Laser Scanning
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Authors
Wade, Laura E
Issue Date
2022
Type
Thesis
Language
Keywords
Allometric Equations , Northern Sierra Nevada , Terrestrial Laser Scanning , trees
Alternative Title
Abstract
The biomass of trees is estimated by using allometric equations, which use simple tree metrics, such as diameter and height, to predict the size of the tree. Biomass is extremely important for determining carbon sequestration rates and carbon mapping in forests, as an individual tree’s biomass is approximately fifty percent carbon. However, estimating the biomass of the trees is traditionally accomplished via the use of allometric equations calibrated by destructively harvesting trees in the field. Requiring destructive sampling to calibrate these models often leads to small sample sizes and a lack of a complete range of tree sizes and species sampled. An alternative solution to destructive harvesting uses terrestrial laser scanning (TLS) to estimate the volume, diameter, and height of trees in the field, and combine these with estimates of wood specific gravity. These data can then be used to generate allometric equations without many of the limitations of destructive sampling approaches. In our analysis, we scanned 108 plots located in the northern Sierra Nevada. We used TreeQSM to estimate volume for sampled trees and determined the mean species wood specific gravity to estimate biomass. We compared our QSM tree metrics against metrics measured in the field and ran a non-linear mixed effects model to determine the effect of climate on our allometric equations. Our results suggest that our two topoclimatic variables, climatic water deficit, and actual evapotranspiration, did not affect our biomass equations. We then used three allometric equation forms to estimate biomass using two different tree parameters, height, and diameter. We found that TLS can be used as a rapid method for estimating volume, height, and diameter, and we created species-specific allometric equations for trees across the Sierra Nevada that may have important applications for large-scale AGB estimation.