Treesearch

Erosion following wildfire can be as much as 1000 times the erosion from an undisturbed forest. In August, 2005, the largest fire in the lower 48 states occurred in the Umatilla National Forest in Southeast Washington. Researchers from the Rocky Mountain Research Station assisted the forest in estimating soil erosion using three different applications of the WEPP model. GeoWEPP was used to determine the onsite distribution of soil erosion. WEPP Windows Watershed Version was used to estimate peak runoff rates of each of the ten small watersheds analyzed. The ERMiT interface to WEPP was used...

Conspecific brood parasitism occurs in many songbird species but has not been reported in Song Sparrows (Melospiza melodia). In three separate study areas where breeding Song Sparrows experience heavy nest predation pressure and Brown-headed Cowbird (Molothrus ater) parasitism, we observed six instances in which newly laid eggs were attributable to female Song Sparrows other than the nest owners. We also recorded the ejection of a sparrow egg from each of two videotaped nests. In a fourth study area without cowbird parasitism, genetic analysis of parentage revealed no conspecific brood...

From early to present-day outbreaks, white pine blister rust caused by the fungus Cronartium ribicola, in combination with mountain pine beetle outbreaks and fire exclusion has caused ecosystem-wide effects for all five-needled pines (McDonald and Hoff 2001). To be successful, efforts to restore whitebark pine will require sound management decisions that incorporate an understanding of many interacting factors, including the biology and life cycle of the fungus, whether it may adapt and change its behavior when exposed to different environments and hosts, and mechanisms and predicted...

Phylogenetic and genetic relationships among 10 North American Armillaria species were analysed using sequence data from ribosomal DNA (rDNA), including intergenic spacer (IGS-1), internal transcribed spacers with associated 5.8S (ITS + 5.8S), and nuclear large subunit rDNA (nLSU), and amplified fragment length polymorphism (AFLP) markers. Based on rDNA sequence data, the nLSU region is less variable among Armillaria species than the ITS + 5.8S and IGS-1 regions (nLSU < ITS + 5.8S < IGS-1). Phylogenetic analyses of the rDNA sequences suggested Armillaria mellea, A. tabescens and A....

The following definitions have been formulated with reference, in particular, to Musselman et al. (2006; see below).

We explore some of the underlying assumptions used to derive the density or WPL terms (Webb et al. (1980) Quart J RoyMeteorol Soc 106:85-100) required for estimating the surface exchange fluxes by eddy covariance. As part of this effort we recast the origin of the density terms as an assumption regarding the density fluctuations rather than as a (dry air) flux assumption. This new approach, which is similar to the expansion/compression approach of Liu (Boundary-Layer Meteorol 115:151-168, 2005), eliminates the dry-air mean advective vertical velocity from the development of theWPL terms...

Thinning of forest stands is frequently used to reduce the risk of catastrophic fire. But thinning requires that the refuse (or slash) be removed from the site, which can be done either by burning it or by mastication and dispersal. Either method has long term consequences to the soil and to soil moisture and soil CO2 levels. For example, after the initial drying of the soil by a fire, soil moisture in burned areas tends to exceed that of unburned areas because the loss of vegetation reduces or eliminates transpiration (Neary and Ffolliott, 2005). This situation may persist until the...

We present an approach for assessing the impact of systematic biases in measured energy fluxes on CO2 flux estimates obtained from open-path eddy-covariance systems. In our analysis, we present equations to analyse the propagation of errors through the Webb, Pearman, and Leuning (WPL) algorithm [Quart. J. Roy. Meteorol. Soc. 106, 85­100, 1980] that is widely used to account for density fluctuations on CO2 flux measurements. Our results suggest that incomplete energy balance closure does not necessarily lead to an underestimation of CO2 fluxes despite the existence of surface energy...

Currently, stomatal O3 flux and flux-response models only exist for wheat and potato (LRTAP Convention, 2004), as such there is a need to extend these models to include additional crop types. The possibility of establishing robust stomatal flux models for five agricultural crops (tomato, grapevine, sugar beet, maize and sunflower) was investigated. These crops were selected on consideration of their distribution across Europe, sensitivity to ozone and economic value.

The ozone deposition model (D03SE) that has been developed and applied within the EMEP photooxidant model (Emberson et al., 2000, Simpson et al. 2003) currently estimates stomatal ozone flux using a stomatal conductance (gs) model based on the multiplicative algorithm initially developed by Jarvis (1976). This model links gs to environmental and phenological parameters with a set of response functions. However, there exist a number of alternative and well established methods to calculate gs, with the photosynthesis-based algorithm becoming increasingly more popular in situations where...