Treesearch

Parasitic plants are among the most problematic pests of agricultural crops worldwide. Effective means of control are generally lacking, in part because of the close physiological connection between the established parasite and host plant hindering efficient control using traditional methods. Seed germination and host location are critical early-growth stages that occur prior to host attachment, and provide promising targets for ecologically sound management of parasitic weeds. Knowledge of parasite-host interactions, particularly chemical cues that induce parasite seed germination and...

Subgenus Tridentatae (Artemisia, Asteraceae) can be considered a polyploid complex. Both polyploidy and hybridization have been documented in the Tridentatae. Fluorescent in situ hybridization (FISH) and fluorochrome banding were used to detect and analyze ribosomal DNA changes linked to polyploidization in this group by studying four diploidpolyploid species pairs. In addition, genome sizes and heterochromatin patterns were compared between these populations. The linked 5S and 35S rRNA genes are confirmed as characteristic for Artemisia, and a pattern at the diploid level of three rDNA...

Although long-lived tree species experience considerable environmental variation over their life spans, their geographical distributions reflect sensitivity mainly to mean monthly climatic conditions.We introduce an approach that incorporates a physiologically based growth model to illustrate how a half-dozen tree species differ in their responses to monthly variation in four climatic-related variables: water availability, deviations from an optimum temperature, atmospheric humidity deficits, and the frequency of frost. Rather than use climatic data directly to correlate with a species'...

Lichens are very responsive to environmental stressors in forests, including changes in forest structure, air quality, and climate. Each lichen species on a plot is an indicator of how lichen communities respond to ecological conditions. Individual lichen species occur erratically and even common species are often absent from plots with suitable habitat. The combined response of all species is a better indicator of ecological conditions than responses of any one or a few lichen species.

Aerial detection surveys indicate that widespread conifer mortality has been steadily increasing in Colorado, particularly since 2002. The Forest Inventory and Analysis (FIA) annual inventory system began in Colorado in 2002, which coincided with the onset of elevated conifer mortality rates. The current mortality event coupled with collection of 6 years of annual inventory data provided an opportunity to test the usefulness of the FIA annual inventory system for quantifying rapid change in the conifer resource over a large geographic area. The estimate of conifer mortality during the...

The magnitude and distribution of incoming shortwave solar radiation (SW) has significant influence on the productive capacity of forest vegetation. Models that estimate forest productivity require accurate and spatially explicit radiation surfaces that resolve both long- and short-term temporal climatic patterns and that account for topographic variability of the land surface. This paper presents a validation of monthly average total (SWt) and diffuse (SWdf) incoming solar radiation surfaces taken from North American Regional Reanalysis (NARR) data and Moderate Resolution Imaging Spectrora...

El cambio climatico, conocido comunmente como calentamiento global, es el incremento de la temperatura a nivel mundial y los cambios que de ello derivan, causados por el "efecto invernadero" del bioxido de carbono (CO2) y otros gases emitidos a la atmosfera. El uso de combustibles fosiles (carbon y derivados del petroleo, como gasolina, diesel, combustoleo y otros) en vehiculos de transporte, para generar electricidad y para muchos procesos industriales, han incrementado los niveles de bioxido de carbono en la atmosfera a una concentracion arriba de lo normal. El bioxido de carbono tiene...

Twelve watersheds in the oak savannas on the eastern side of the Peloncillo Mountains in the Southwestern Borderlands Region of New Mexico are being monitored to document the ecological and hydrologic characteristics, and to determine the effects of burning treatments on this ecosystem. Ecological components monitored include tree overstories, loadings of fuel fractions, and numbers and diversity of mammals and birds. Hydrologic components monitored are streamflow regimes, soil erosion and deposition, and sedimentation. Watershed descriptors for each watershed include its designation,...

Water repellent (hydrophobic) soils impact the infiltration process of a water budget by restricting the movement of water into and through a soil body. The infiltration of water into a water repellent soil can be inhibited or completely impeded in which case much of the incoming precipitation reaching the soil surface becomes overland flow. One mechanism causing the formation of water repellent soils is the distillation of organic compounds in the litter and duff layers during combustion in a fire (DeBano 1981, 1999, 2003, Doerr et al. 2000). This mechanism resulted in the formation of...

Oak woodlands and savannas comprise more than 31,000 square miles (80,290 square kilometers) in the southwestern United States and northern Mexico and provide various resources including forage for livestock, wildlife habitat, fuelwood, and recreational areas. Increased woody-plant encroachment into the more open savanna ecosystems has presented a problem to managers and ranchers concerned with maintaining these ecosystems with less overstory density. Prescribed fire has been proposed as a managerial tool to help control woody-plant encroachment and improve the production of forage....