Treesearch

Nigeria has abundant natural resources, and the nation, working with its partners over the years, has made large strides toward conservation of this natural wealth, but the future of Nigeria's natural resources remains uncertain.

Theoretical models and empirical evidence suggest that the invasion of nonnative species in freshwaters is facilitated through the interaction of three factors: habitat quality, biotic resistance, and connectivity. We measured variables that represented each factor to determine which were associated with the occurrence of nonnative brook trout Salvelinus fontinalis in Panther Creek, a tributary to the Salmon River, Idaho. Habitat variables included measures of summer and winter temperature, instream cover, and channel size. The abundance of native rainbow trout Oncorhynchus mykiss within...

Bed load transport is a fundamental physical process in alluvial rivers, building and maintaining a channel geometry that reflects both the quantity and timing of water and the volume and caliber of sediment delivered from the watershed. A variety of formulae have been developed to predict bed load transport in gravel-bed rivers, but testing of the equations in natural channels has been fairly limited. Here, I assess the performance of 4 common bed load transport equations (the Meyer-Peter and Muller [1948], Ackers and White [1973], Bagnold [1980], and Parker [1990] equations) using data...

In the paper "A general power equation for predicting bed load transport rates in gravel bed rivers" by Jeffrey J. Barry et al. (Water Resources Research, 40, W10401, doi:10.1029/2004WR003190, 2004), the y axis for Figures 5 and 10 was incorrectly labeled and should have read "log10 (predicted transport) - log10 (observed transport)." In addition, flow depth (D) is incorrectly shown in the denominator of equation (A9) of Barry et al. [2004] and should be replaced by di, the mean particle diameter for the ith size class as shown. [2] Similarly, equation (A24) of Barry et al. [2004] incorrect...

Human influence on the Middle Rio Grande has resulted in major changes throughout the Middle Rio Grande region in central New Mexico, including problems with erosion and sedimentation. Hydraulic modeling analyses have been performed on the Middle Rio Grande to determine changes in channel morphology and other important parameters. Important changes occurring in the Escondida reach between 1918 and 2005 were analyzed for this study.

This chapter presents a synthesis of current computer modeling tools that are, or could be, adopted for use in evaluating the cumulative watershed effects of fuel management. The chapter focuses on runoff, soil erosion and slope stability predictive tools. Readers should refer to chapters on soil erosion and stability for more detailed information on the physical processes involved.

Shallow landslides on steep slopes often mobilize as debris flows. The size of the landslide controls the initial size of the debris flows, defines the sediment discharge to the channel network, affects rates and scales of landform development, and influences the relative hazard potential. Currently the common practice in digital terrain-based models is to set the landslide size equal to an arbitrarily chosen grid cell dimension. Here we apply a multidimensional landslide model that assumes that a soil block fails as a rigid mass when downslope forces overcome cohesive and frictional...

Herbivores can directly impact ecosystem function by altering litter quality of an ecosystem or indirectly by shifting the composition of microbial communities that mediate nutrient processes. We examined the effects of tree susceptibility and resistance to herbivory on litter microarthropod and soil microbial communities to test the general hypothesis that herbivore driven changes in litter inputs and soil microclimate will feedback to the microbial community. Our study population consisted of individual pinyon pine trees that were either susceptible or resistant to the stem-boring moth...

In the western United States and throughout the world, three general classes of coniferous forests can be identified with each having similar vegetative complexes, native disturbances, and climate (Daubenmire and Daubenmire 1968, Hann et al. 1997). Dry forests, often dominated by pines (Pinus), cold forests often dominated by spruces (Picea), and moist forests dominated by hemlocks (Tsuga) represent the majority of the world's forests. The soils within each of these forest classifications are a product of their inherent climate and vegetation dynamics. Because soils are the foundation of...

In virtually all ecological communities around the world, most species are represented by few individuals, and most individuals come from only a few of the most common species. Why this distribution of species abundances is so regularly observed among different taxonomic sets in geographically diverse systems is a question that has received considerable theoretical and empirical investigation (Preston 1948, 1962; Harte et aL 1999; Hubbell. 2001). Understanding the mechanisms leading to the pattern of few common and many rare species extends beyond basic interest in how natural communities...