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Evaluation of sampling strategies to estimate crown biomass

Forest Ecosystems 2015年第1期2卷 20-30页

作者： Krishna P Poudel hailemariam temesgen Andrew N Gray Department of Forest Engineering Resources and Management College of Forestry Oregon State University USDA Forest Service PNW Research Station3200 SW Jefferson WayCorvallis OR 97331 USA

Background：Depending on tree and site characteristics crown biomass accounts for a significant portion of the total aboveground biomass in the *** biomass estimation is useful for different purposes including evaluating the economic feasibility of crown utilization for energy production or forest products,fuel load assessments and fire management strategies,and wildfire ***,crown biomass is difficult to predict because of the variability within and among species and *** the allometric equations used for predicting crown biomass should be based on data collected with precise and unbiased sampling *** this study,we evaluate the performance different sampling strategies to estimate crown biomass and to evaluate the effect of sample size in estimating crown ***：Using data collected from 20 destructively sampled trees,we evaluated 11 different sampling strategies using six evaluation statistics：bias,relative bias,root mean square error（RMSE）,relative RMSE,amount of biomass sampled,and relative biomass *** also evaluated the performance of the selected sampling strategies when different numbers of branches（3,6,9,and 12）are selected from each *** specific log linear model with branch diameter and branch length as covariates was used to obtain individual branch ***：Compared to all other methods stratified sampling with probability proportional to size estimation technique produced better results when three or six branches per tree were ***,the systematic sampling with ratio estimation technique was the best when at least nine branches per tree were *** the stratified sampling strategy,selecting unequal number of branches per stratum produced approximately similar results to simple random sampling,but it further decreased RMSE when information on branch diameter is used in the design and estimation ***：Use of auxiliary information in design or estimation phase reduc

关键词： Aboveground biomass Crown Sampling strategies Pacific Northwest

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Estimating upper stem diameters and volume of Douglas-fir and Western hemlock trees in the Pacific northwest

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Forest Ecosystems 2018年第3期5卷 199-210页

作者： Krishna P.Poudel hailemariam temesgen Andrew N.Gray Department of Forest Engineering Resources and Management College of Forestry Oregon State University USDA Forest Service PNW Research Station

Background: Volume and taper equations are essential for obtaining estimates of total and merchantable stem volume. Taper functions provide advantages to merchantable volume equations because they estimate diameter inside or outside bark at specific heights on the stem, enabling the estimation of total and merchantable stem volume, volume of individual logs, and a height at a given ***: Using data collected from 1218 trees(1093 Douglas-fir(Pseudotsuga menziesii(Mirbel) Franco) and 125 western hemlock(Tsuga heterophylla)), we evaluated the performance of one simple polynomial function and four variable-exponent taper functions in predicting upper stem diameter. Sample trees were collected from different parts of the states of Oregon, Washington, and California. We compared inside-bark volume estimates obtained from the selected taper equation with estimates obtained from a simple logarithmic volume equation for the data obtained in this study and the equations used by the Forest Inventory and Analysis program in the Pacific Northwest(FIA-PNW) in the state of California and western half of the states of Oregon and ***: Variable exponent taper equations were generally better than the simple polynomial taper *** FIA-PNW volume equations performed fairly well but volume equations with fewer parameters fitted in this study provided comparable results. The RMSE obtained from taper-based volume estimates were also comparable with the RMSE of the FIA-PNW volume equations for Douglas-fir and western hemlock trees ***: The taper equations fitted in this study provide added benefit to the users over the FIA-PNW volume equations by enabling the users to predict diameter at any height, height to a given diameter, and merchantable volume in addition to cubic volume including top and stump(CVTS) of Douglas-fir and western hemlock trees in the Pacific Northwest. The findings of this study also give more confidence to the use

关键词： Pacific northwest Biomass equations Utilization standards Diameter inside bark

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Forest observational studies-an essential infrastructure for sustainable use of natural resources

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Forestry Studies in China 2014年第2期16卷 61-70页

作者： XiuHai Zhao Javier Corral-Rivas ChunYu Zhang hailemariam temesgen Klaus v Gadow Beijing Forestry University Universidad Autonóma de Nuevo León DurangoMéxico Oregon State University CorvallisUSA Burckhardt Institute Georg-August UniversityGttingenGermany Institute of Forestry and Wood Science University of StellenboschStellenboschSouth Africa

This contribution complements Forest Ecosystems＇ Thematic Series on ＂Forest Observational Studies＂. We provide essential clarification regarding the definition and purpose of long-term field studies, review some of the extensive literature and discuss different approaches to collecting field data. We also describe two newly established forest observational networks that serve to illustrate the scope and diversity of forest field studies. The first is a large-scale network of forest observational studies in prominent natural forest ecosystems in China. The second example demonstrates observational studies in mixed and uneven-aged pine-oak forests which are selectively managed by local communities in Mexico. We summarize the potential for analysing and modeling forest ecosystems within interdisciplinary projects and provide argumentation in favour of long-term institutional commitment to maintaining forest observational field studies.

关键词： Mexico China India Longitudinal Cross-sectional Interval study Experiment Social media surveillance

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Generating Tree-Lists by Fusing Individual Tree Detection and Nearest Neighbor Imputation Using Airborne LiDAR Data

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Open Journal of Forestry 2018年第4期8卷 500-531页

作者： Joonghoon Shin hailemariam temesgen Department of Forest Engineering Resources and Management Oregon State University Peavy Hall Corvallis OR USA

Individual tree detection (ITD) and the area-based approach (ABA) are combined to generate tree-lists using airborne LiDAR data. ITD based on the Canopy Height Model (CHM) was applied for overstory trees, while ABA based on nearest neighbor (NN) imputation was applied for understory trees. Our approach is intended to compensate for the weakness of LiDAR data and ITD in estimating understory trees, keeping the strength of ITD in estimating overstory trees in tree-level. We investigated the effects of three parameters on the performance of our proposed approach: smoothing of CHM, resolution of CHM, and height cutoff (a specific height that classifies trees into overstory and understory). There was no single combination of those parameters that produced the best performance for estimating stems per ha, mean tree height, basal area, diameter distribution and height distribution. The trees in the lowest LiDAR height class yielded the largest relative bias and relative root mean squared error. Although ITD and ABA showed limited explanatory powers to estimate stems per hectare and basal area, there could be improvements from methods such as using LiDAR data with higher density, applying better algorithms for ITD and decreasing distortion of the structure of LiDAR data. Automating the procedure of finding optimal combinations of those parameters is essential to expedite forest management decisions across forest landscapes using remote sensing data.

关键词： Tree-List Generation Individual Tree Detection Nearest Neighbor Imputation Parameter Sensitivity Airborne LiDAR

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A Comparison of Selected Parametric and Non-Parametric Imputation Methods for Estimating Forest Biomass and Basal Area

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Open Journal of Forestry 2014年第1期4卷 42-48页

作者： Donald Gagliasso Susan Hummel hailemariam temesgen Department of Forest Engineering Resources and Management Oregon State University Corvallis USA USDA Forest Service Goods Services and Values Program Portland Forest Sciences Laboratory US Forest Service Pacific Northwest Research Station Portland USA

Various methods have been used to estimate the amount of above ground forest biomass across landscapes and to create biomass maps for specific stands or pixels across ownership or project areas. Without an accurate estimation method, land managers might end up with incorrect biomass estimate maps, which could lead them to make poorer decisions in their future management plans. The goal of this study was to compare various imputation methods to predict forest biomass and basal area, at a project planning scale (a combination of ground inventory plots, light detection and ranging (LiDAR) data, satellite imagery, and climate data was analyzed, and their root mean square error (RMSE) and bias were calculated. Results indicate that for biomass prediction, the k-nn (k = 5) had the lowest RMSE and least amount of bias. The second most accurate method consisted of the k-nn (k = 3), followed by the GWR model, and the random forest imputation. For basal area prediction, the GWR model had the lowest RMSE and least amount of bias. The second most accurate method was k-nn (k = 5), followed by k-nn (k = 3), and the random forest method. For both metrics, the GNN method was the least accurate based on the ranking of RMSE and bias.

关键词： Gradient Nearest Neighbor Most Similar Neighbor K-Nearest Neighbor Random Forest Geographic Weighted Regression Biomass LiDAR

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Mixed-Species Allometric Equations to Quantify Stem Volume and Tree Biomass in Dry Afromontane Forest of Ethiopia

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Open Journal of Forestry 2022年第3期12卷 263-296页

作者： Mindaye Teshome Carlos Moreira Miquelino Eleto Torres Gudeta Weldesemayat Sileshi Patricia Povoa de Mattos Evaldo Muñoz Braz hailemariam temesgen Samuel José Silva Soares da Rocha Mehari Alebachew Departamento de Engenharia Florestal Universidade Federal de Vi&#231 osa (UFV) Vi&#231 osa MG Brazil Central Ethiopia Environment and Forest Research Centre Addis Ababa Ethiopia University of Kwazulu-Natal Pietermaritzburg South Africa Embrapa Florestas Colombo PR Brazil Department of Forest Engineering Resources and Management College of Forestry Oregon State University Corvallis USA Departamento de Ciências Florestais Universidade Federal de Lavras (UFLA) Lavras MG Brazil

Volume and biomass equations are essential tools to determine forest productivity and enable forest managers to make informed decisions. However, volume and biomass estimation equations are scarce for Afromontane forests in Africa in general and Ethiopia in particular. This limits our knowledge of the standing volume of wood, biomass, and carbon stock of the forests therein. In this study, we developed a new mixed-species volume and biomass equations for Afromontane forests and compared them with generic pantropical and local models. A total of 193 sampled trees from seven dominant tree species were used to develop the equations. Various volume and biomass equations were fitted using robust linear and nonlinear regression. Model comparison indicated that the best model to estimate stem volume was ln(v)=-9.909+ 0.954*ln(d2h), whereas the best model to estimate biomass was ln(b)=-2.983+ 0.949*ln(ρd2h) . These equations explained over 85% of the variations in the stem volume and biomass measurements. The mean density and basal area of trees in the forest with d ≥ 2 cm was 631.5 stems·ha-1 and 24.4 m2·ha-1. Based on the newly developed equations, the forest has on average 303.0 m3·ha-1 standing volume of wood and 283.8 Mg·ha-1 biomass stock. The newly developed allometric equations derived from this study can be used to accurately determine the stem volume, biomass, and carbon storage in the Afromontane forests in Ethiopia and elsewhere with similar stand characteristics and ecological conditions. By contrast, the generic pan-tropical and other local models appear to provide biased estimates and are not suitable for dry Afromontane forests in Ethiopia. The estimated stem biomass and carbon stock in the Chilimo forest are comparable with the estimates from various tropical forests and woodlands elsewhere in Africa, indicating the importance of dry Afromontane fores

关键词： Carbon Stock Site-Specific Model Robust Regression Natural Forest

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