A Comparison of Regional and Site Specific Biomass Equations for Three North Idaho Conifers PDF Download

Author: Ann M. Abbott
Publisher:
ISBN: 9780355235616
Category : Conifers
Languages : en
Pages : 140

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Book Description
Predictive equations were developed for both individual branch and total tree branch biomass, branch wood biomass, leaf biomass, and specific leaf area for grand fir (Abies grandis Douglas ex D. Don Lindl.), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. glauca), and western hemlock (Tsuga heterophylla (Raf.) Sarg.) in northern Idaho, USA based on observations representing a range of variability in mixed species stands. Based on two randomly selected branches from each of four crown quarters, both full and reduced models were generated to predict branch quantities, however the reduced models were able to account for nearly as much variability in the response variables as the full models. The individual branch equations were scaled to generate whole-tree biomass and leaf area estimates from which both full and reduced models were developed. All models explained a significant amount of variability in crown biomass components, resulting in an improved ability to explain crown biomass in these three species. A nonlinear mixed effects model was developed to predict branch basal diameter (mm) from the distance from the branch to the top of the tree for grand, Douglas-fir, and western hemlock in northern Idaho, USA. An asymptotic model was used to describe the nonlinear relationship with an autocorrelation term to account for the lack of independence in the residuals. As indicated by both the significance of the parameter estimates and plots of predicted values overlaid onto observed values, these models are sufficiently accurate to predict branch basal diameter in grand fir, Douglas-fir, and western hemlock. These models provide improved estimates of tree biomass for carbon accounting and improved crown biomass estimations for use in empirical modeling efforts. Douglas-fir crown biomass data from two separate studies were validated and pooled for use in examining whether a regional allometric equation for estimating crown biomass is sufficient or whether site-specific equations are required. Soil parent material was the basis for stratifying the sites in terms of soil nutrition. To account for potential confounding of site effects by climate regime, a suite of climate variables were selected using hierarchical cluster analysis and were included in the modeling as predictor variables. While diameter at breast height (DBH) accounted for most of the variability in crown biomass (R2 = 0.76), both soil parent material and climate variables added modest yet significant improvements to the model. The results suggest that interactions may be present between soil parent material and climate variables, however the sites from which the trees sampled for the two studies included in this research did not have enough variability in the climate variables to allow for full exploration of the interactions.