David L. Azuma

Cool Water Formation and Trout Habitat Use in a Deep Pool in the Sierra Nevada, California

Abstract We documented temperature stratification in a deep bedrock pool in the North Fork of the American River, described the diel movement of rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta, and determined whether these trout used cooler portions of the pool. From July 30 to October 10, 1992, the main study pool and an adjacent pool were stratified (temperature differences between surface and bottom were as great as 4.5°C) on all but two days. Six rainbow and one brown trout equipped with temperature-sensitive radio transmitters used water with temperatures ranging from 12 to 19.3°C. During the late afternoon, when the widest range of water temperature was available, trout were found in temperatures up to 19.3°C even though cooler (14.5°C) water was available. Radio tracking indicated that fish were significantly more active and had significantly larger home ranges at night; fish were least active during the day. Because we found no evidence of subsurface seepage into the pool and water ...

Carbon stocks on forestland of the United States, with emphasis on USDA Forest Service ownership

The U.S. Department of Agriculture Forest Service (USFS) manages one-fifth of the area of forestland in the United States. The Forest Service Roadmap for responding to climate change identified assessing and managing carbon stocks and change as a major element of its plan. This study presents methods and results of estimating current forest carbon stocks and change in the United States for public and private owners, consistent with the official 2010 U.S. greenhouse gas inventory, but with improved data sources for three states. Results are presented by National Forest System region, a major organizational management unit within the Forest Service, and by individual national forest. USFS forestland in the United States is estimated to contain an average of 192 Mg C/ha (mega grams carbon per hectare) on 60.4 million ha, for a total of 1 1,604 Tg C (teragrams C) in the year 2005. Privately-owned forestland averages 150 Mg C/ha on 173.8 million ha, with forestland of other public owners averaging 169 Mg C/ha on 43.1 million ha. In terms of change, private and USFS ownerships each sequester about a net 150 Tg C O2/yr, but an additional 92 Tg C O2/yr is stored in products from private harvests compared to about 3 Tg C O2/yr from harvest on USFS land. Emissions from other disturbances such as fires, as well as corresponding area estimates of disturbance are also important, but the needed datasets are not yet available. Recommendations are given for improving the estimates.

Modeling the spatially dynamic distribution of humans in the Oregon (USA) Coast Range

A common approach to land use change analyses in multidisciplinary landscape-level studies is to delineate discrete forest and non-forest or urban and non-urban land use categories to serve as inputs into sets of integrated sub-models describing socioeconomic and ecological processes. Such discrete land use categories, however, may be inappropriate when the socioeconomic and ecological processes under study are sensitive to a range of human habitation. In this paper, we characterize the spatial dynamic distribution of humans throughout the forest landscape of western Oregon (USA). We develop an empirical model describing the spatial distribution and rate of change in historic building densities as a function of a gravity index of development pressure, existing building densities, slope, elevation, and existing land use zoning. We use the empirical model to project changes in building densities that are applied to a 1995 base map of building density to describe future spatial distributions of buildings over time. The projected building density maps serve as inputs into a multidisciplinary landscape-level analysis of socioeconomic and ecological processes in Oregons Coast Range Mountains.

Bare soil and rill formation following wildfires, fuel reduction treatments, and pine plantations in the southern Sierra Nevada, California, USA.

Accelerated erosion commonly occurs after wildfires on forested lands. As burned areas recover, erosion returns towards prefire rates depending on many site-specific characteristics, including fire severity, vegetation type, soil type and climate. In some areas, erosion recovery can be rapid, particularly where revegetation is quick. Erosion recovery is less well understood for many fuel load reduction treatments. The rate of post-disturbance erosion recovery affects management options for forested lands, particularly when considering the combined ramifications of multiple disturbances on resource recovery rates (i.e. cumulative watershed effects). Measurements of percentage bare soil and rilling on over 600 plots in the southern Sierra Nevada with slopes less than 75% and within 1 km of roads were made between 2004 and 2006. Results suggest that after high-, moderate- or low-severity wildfire, rilling was seldom evident more than 4 years after fire. Percentage bare soil generally did not differ significantly between reference plots and wildfire plots greater than 6 years old. Little rilling was evident after treatment with a variety of fuel reduction techniques, including burning of machine- and hand-piled fuel, thinning, mastication, and crushing. Percentage bare soil at the fuel load reduction treatment plots also did not differ significantly from reference conditions. Percentage bare soil at pine plantation plots was noticeably higher than at reference sites.

Changes in land use and housing on resource lands in Washington state, 1976–2006

Changes in human land use patterns have wide-ranging social, economic and ecological implications. How urban and residential areas develop to accommodate population increase can have varying effects on forest and agricultural production from resource lands. Estimates of the amount and type of land use change differ substantially with definitions and analytical methods used. The purpose of this study was to apply a robust manual image classification method to assess changes in land use and housing density across Washington state for a 30-year period. Digital imagery from 1976, 1994, and 2006 was classified to land use, classifications were assigned to a systematic-random grid of 44,554 photointerpretation points on nonfederal lands, and houses were identified within 80-ac circles around each nonurban point. Population in the state increased by 2.5 million people (66 percent) over the 30-year period, during which time 1.16 million acres were converted from forest and agriculture land use classes to residential and urban land uses. The greatest changes were in western Washington, where forest lands declined at a rate of 0.2 percent per year and intensive agricultural lands declined at a rate of 0.7 percent per year. Twenty percent of nonfederal land in western Washington was in developed land uses in 2006. The density of housing structures on lands that remained in forest and agricultural land uses also increased over the period of interest, particularly in areas close to developed land uses. The rate of housing increase on resource lands was greater from 1994 to 2006 than from 1976 to 1994 in eastern Washington, but declined in western Washington. This method of assessing land use change compared favorably with other approaches, and had the advantage that it could be applied consistently to a longer period of time and allowed detailed assessment of patterns at local scales.

Evaluating forest land development effects on private forestry in eastern Oregon.

Research suggests that forest land development can reduce the productivity of remaining forest land because private forest owners reduce their investments in forest management. We developed empirical models describing forest stocking, thinning, harvest, and postharvest tree planting in eastern Oregon, as functions of stand and site characteristics, ownership, and building densities. The models are based on USDA Forest Service Forest Inventory and Analysis data gathered in eastern Oregon in 1987 and 1998, and data describing building densities gathered by the Oregon Department of Forestry from aerial photographs taken over the same period. We used the models to examine the potential effects of population growth and development, as described by increasing building densities, on the likelihood that private forest owners maintain forest stocking, precommercially thin, harvest, and plant trees following harvest. Empirical results suggest that population growth and development have had no measurable effect on these activities in eastern Oregon during the period examined. Any development effects on private forest management and investment so far are likely to be fairly localized.