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

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 diameter.Methods: 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 Washington.Results: Variable exponent taper equations were generally better than the simple polynomial taper equations.The 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 respectively.Conclusions: 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 users of FIA-PNW volume equations.

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

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Unprecedented Heatwave in Western North America during Late June of 2021: Roles of Atmospheric Circulation and Global Warming

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Advances in Atmospheric Sciences 2023年第1期40卷 14-28页

作者： Chunzai WANG Jiayu ZHENG Wei LIN Yuqing WANG Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou) Guangzhou 511458China State Key Laboratory of Tropical Oceanography South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou 510301China Innovation Academy of South China Sea Ecology and Environmental Engineering Chinese Academy of SciencesGuangzhou 510301China University of Chinese Academy of Sciences Beijing 100049China State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China

An extraordinary and unprecedented heatwave swept across western North America(i.e.,the pacific northwest)in late June of 2021,resulting in hundreds of deaths,a massive die-off of sea creatures off the coast,and horrific wildfires.Here,we use observational data to find the atmospheric circulation variabilities of the North pacific and Arctic-pacific-Canada patterns that co-occurred with the development and mature phases of the heatwave,as well as the North America pattern,which coincided with the decaying and eastward movement of the heatwave.Climate models from the Coupled Model Intercomparison Project(Phase 6)are not designed to simulate a particular heatwave event like this one.Still,models show that greenhouse gases are the main reason for the long-term increase of average daily maximum temperature in western North America in the past and future.

关键词： heatwave climate change atmospheric circulation pattern pacific northwest

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FREEZE/THAW EFFECTS ON RILL AND GULLY EROSION IN THE northwestERN WHEAT AND RANGE REGION

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International Journal of Sediment Research 2005年第3期20卷 48-56页

作者： D. K. MCCOOL,J. D. WILLIAMS Pendleton OR. Supervisory Agricultural Engineer Land Management and Water Conservation Research USDA-ARS Pullman WA USA Hydrologist Columbia Plateau Conservation Research Center USDA-ARS

Hydrology of the northwestern Wheat and Range Region (NWRR) of the pacific northwest USA is dominated by winter events. Fifty-five to sixty-five percent of the precipitation occurs from November through March, and formation of impermeable frost, intensified by excessive tillage and tillage pans, has long been a major factor in rill and gully formation in the region. Saturated zones can form above tillage pans, freeze solid, and significantly reduce infiltration. Frost heaved surface soils thaw and weaken with warming temperatures or rain. Under these conditions, runoff from rain or snowmelt or a combination of the two is inevitable, concentrating in rills and channels, and carrying with it the loosened soil. Slopes are frequently quite steep and there may be little deposition above the toe slope. Classical over-fall head-cut gullies are uncommon. Concentrated flow channels form because of collection of water from impervious areas such as conventionally tilled fall seeded small grains and bare grass seed fields. In some soils, gullies are created by seepage from saturated layers above permanent restrictive layers in the soil. Gullies can also result from terrace failures due to rodent burrows and low compaction at the time of construction. In naturally unconsolidated soil, rodent activity can lead to piping failures that remove large quantities of subsurface soil and can become gullies. Rill measurements on conventionally tilled fields in Oregon, Washington, and Idaho were used to determine coefficients for relationships between slope length and steepness and size of rills. This paper describes these studies and the results as well as analysis of long-term erosion and weather records from southeastern Washington.

关键词： Erosion Slope length Slope steepness Topography pacific northwest Frozen soil Thawing soil

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