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Portland, OR, United States

Hemstrom M.A.,Forestry science Laboratory | Hemstrom M.A.,Oregon State University
USDA Forest Service - General Technical Report PNW-GTR

The Integrated Landscape Assessment Project (ILAP) uses spatial vegetation data and state and transition models (STM) to forecast future vegetation conditions and the interacting effects of natural disturbances and management activities. Results from ILAP will help land managers, planners, and policymakers evaluate management strategies that reduce fire risk, improve wildlife habitat, and benefit rural communities. This case study illustrates the methodology for modeling timber volume, biomass estimates, and the forest carbon over time with the output of STM simulations. It presents how the Forest Inventory and Analysis data were applied to assist the interpretation of STM simulation results and derives useful information to the public. The method was applied in the central Washington study area to project the timber production, biomass supply potential, and aboveground carbon stock for two alternative management scenarios. Source

Tipton J.,Colorado State University | Opsomer J.,Colorado State University | Moisen G.,Forestry science Laboratory
Remote Sensing of Environment

Post-stratification is commonly used to improve the precision of survey estimates. In traditional post-stratification methods, the stratification variable must be known at the population level. When suitable covariates are available at the population level, an alternative approach consists of fitting a model on the covariates, making predictions for the population and then stratifying on these predicted values. This method is called Endogenous Post-Stratification Estimation (EPSE) and it is well suited for applications using remote sensing data. In this article, we investigate the performance of EPSE in a realistic setting using data from the United States Forest Service Forest Inventory Analysis and Landsat Enhanced Thematic Mapper Plus. This article has three specific objectives: first, to evaluate the statistical properties of EPSE when using linear regression, spline regression, and the machine learning tool Random Forest to predict tree canopy cover using remote sensing and Geographic Information System data; second, to investigate the effect on the EPSE variance estimator using estimated stratum boundaries instead of fixed stratum boundaries; and third, to investigate the effect on the EPSE variance estimator when optimizing the stratum boundaries to minimize the variance estimate. The main findings of this article are that the EPSE variance estimator performs well using Random Forests, but can underestimate the true variance if an optimization is performed on the stratum boundaries in an attempt to minimize the variance estimate. This result supports the use of the EPSE estimator using remote sensing data in cases where there is no optimization on the variance estimator. 2013 Elsevier Inc. Source

Harrington T.B.,Forestry science Laboratory
USDA Forest Service - Research Paper PNW-RP

Greenhouse pot studies were conducted to quantify the competitive abilities of three native perennial grass species to inhibit development of Scotch broom (Cytisus scoparius (L.) Link) seedlings: spike bentgrass (Agrostis exarata Trin.), blue wildrye (Elymus glaucus Buckley), and western fescue (Festuca occidentalis Hook.). In single-species stands (1) soil water content decreased with increasing grass density, (2) soil water depletion per plant differed among species as ratios of 2.4:1.3:1 for bentgrass, fescue, and wildrye, respectively, and (3) average percentage of ground cover per plant was ranked by species as bentgrass (14 percent), wildrye (8 percent), broom (8 percent), and fescue (5 percent). Regression models predicted 90, 85, and 72 percent reductions in average biomass per plant of broom when grown with approximately 250 plants/m 2 of bentgrass, wildrye, and fescue, respectively. Bentgrass and wildrye were more competitive than fescue because of their early-season depletion of soil water and rapid development of cover. Source

Root H.T.,Oregon State University | McCune B.,Oregon State University | Jovan S.,Forestry science Laboratory

Because of their unique physiology, lichen communities are highly sensitive to climatic conditions, making them ideal bioindicators for climate change. Southeast and south-central Alaska host diverse and abundant lichen communities and are faced with a more rapidly changing climate than many more southerly latitudes. We develop sensitive lichen-based indicators for tracking the effects of climate change in south-central and southeast Alaska. Using 196 plots, we model community composition and 12 individual species abundances in relation to synthetic climate variables. Both types of lichen indicator are closely related to the climate variable describing a transition from warm, wet oceanic climates to cooler, drier suboceanic climates. Lichen communities and individual species exhibited thresholds associated with average December minimum temperatures between -10.2 and -7.8°C and annual precipitation between 106 and 172 cm, suggesting rapid turnover with relatively small changes within these ranges. These climate conditions occur close to the coast in northern portions of the region and further inland in southeast Alaska. Because lichen communities in the threshold region may be most sensitive to a changing future climate, they should be targeted for monitoring efforts. © The American Bryological and Lichenological Society, Inc. Source

Harrington T.B.,Forestry science Laboratory | Anderson H.W.,Forestry science Laboratory
USDA Forest Service - Research Paper PNW-RP

Amendment of soil nutrients through fertilization is used to increase wood production of forest stands. Subsequent allocation of growth to individual trees and the resulting increase in stand volume and value, however, depend on stand density at the time of treatment. Our primary research question was: To what extent can volume growth per acre in precommercially thinned or nonthinned portions of a poor-site, 30-year-old coast Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco var. menziesii) plantation be increased by a single application of 200 or 400 lb nitrogen (N)/acre as urea? Each fertilizer treatment was replicated on three 0.2-acre plots in thinned and nonthinned stands located in Rocky Brook drainage on the Olympic Peninsula in Washington. All trees in the interior 0.1-acre plots with a diameter at breast height (d.b.h.) of 1.6 inches and larger were measured for stem diameter, and a subset of trees was measured for total height and height to live crown. We anticipated that poor site quality, prolonged overstocking, and a subsequent severe thinning would influence the responses we observed. In the 20 years after fertilization, net growth in total stem volume on fertilized plots averaged 50 percent greater than on nonfertilized plots in the previously thinned stand and 31 percent greater in the nonthinned stand. In both stands, mortality losses were relatively small, averaging 1 to 15 percent of gross annual growth. Diameter growth of the 100 largest trees per acre was improved by both thinning and fertilization. Present net value (PNV) (in 2014 dollars) at the hypothetical final harvest of the thinned stand was increased by delaying the harvest from 10 years (age 40) until 20 years after fertilization (age 50), and by fertilization, although differences between the 200 and 400 lb N/acre treatments were not significant. Present net value of the nonthinned stand also was increased by delaying final harvest until 20 years after fertilization; however, PNV did not differ significantly among the 0, 200, and 400 lb N/acre treatments, indicating no financial benefit from fertilizing this nonthinned stand. The 90-percent confidence interval for PNV of nonfertilized plots in the thinned stand ($919 ± $278 per acre) did not overlap with that of nonfertilized plots in the nonthinned stand ($2,639 ± $498 per acre), suggesting that the thinning prescription reduced the economic value of this overstocked stand at Rocky Brook. Clearly, the severe thinning at age 30 reduced stocking to the point at which the stand was slow to reoccupy this poor quality site. © 2016, USDA Forest Service. All rights reserved. Source

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