Treesearch

This work is undertaken as a portion of long-term large-scale studies developed to determine how climate and disturbance (primarily fire and grazing) interact to structure desert grasslands. The results presented here are the initial grazing portions of the study. The analysis presented here indicates that following the reintroduction of cattle to the research area in 2000 (following a decade of rest) that the abundance and diversity of vegetation and small mammals increased significantly on the treatment plots (P < 0.05), while remaining unchanged on the control plots.

The USDA Forest Service’s Southwestern Borderlands Ecosystem Management Project mission is to contribute to the scientific basis for developing and implementing a comprehensive ecosystem management plan to restore natural processes, improve the productivity and biological diversity of grasslands and woodlands, and sustain an open landscape with a viable rural economy and social structure in the borderlands of southeastern Arizona and southwestern New Mexico. The Project works closely with its numerous research and management partners from Federal and State agencies, universities, conservati...

Ecoregional Systems Heritage and Encroachment Monitoring (ESHEM) examines issues of land management at an ecosystem level using remote sensing. Engineer Research and Development Center (ERDC), in partnership with Western Illinois University, has developed an ecoregional database and monitoring capability covering the Sonoran region. The monitoring time horizon will extend from the 1970s to at least 2020. The driving issues behind the design of ESHEM are military installation sustainability and encroachment. This paper describes the data in ESHEM as well as “beyond the fence-line” issues...

Eight species of bumble bees (Hymenoptera: Apidae: Bombus) are present within five major Sky Island mountains of southern Arizona. Another four species exist in the nearby large mountainous region stretching from the Arizona White Mountains to Flagstaff. The distribution and number of bumble bee species within the individual Sky Island mountains varies from six in the Catalina and Chiricahua Mountains to only one in the Santa Rita Mountains. The overall distribution of species within the Sky Island region is consistent with the theory of island biogeography advanced by MacArthur and Wilson...

We report the first voucher of the cliff chipmunk (Neotamias dorsalis) and observations of Brazilian free-tailed bats (Tadarida brasiliensis) from the Huachuca Mountains, Arizona, where these species had not been documented. While presence of T. brasiliensis was expected on Fort Huachuca, N. dorsalis was a surprise after a century of unexpected absence. The chipmunk carcass from a cave on the Fort in 2003 suggests recent dispersal from other mountain islands.

We evaluated nutrient uptake efficiency and subsequent leaching fractions for western white pine (Pinus monticola Dougl. ex D. Don) seedlings grown with exponentially increasing or conventional (constant) fertilization in a greenhouse. Conventional fertilization was associated with higher leachate electrical conductivity and greater nutrient losses, which were more pronounced for the more mobile NO3-N than for NH4-N. Exponential fertilization increased seedling nitrogen (N) uptake efficiency (75%), which helped reduce leaching losses compared to conventional fertilization (50%). Although...

[First paragraph] On November 1, 1917, the first Mexican gray wolf (Canis lupus baileyi) of many to follow was killed by the Federal government in Arizona. The female animal was one of a pair of the diminutive subspecies of the much more widely distributed gray wolf (Canis lupus). Typical of their kind, and of the arid and less biologically productive habitat in which they evolved, the two peripatetic animals covered a territory much larger than those of northern, heavier wolves. They ranged from Sonora, Mexico, into the Canelo Hills of southern Arizona, traveling in a regular circuit of...

We thank Michel [2005] for the opportunity to improve our bed load transport equation [Barry et al., 2004, equation (6)] and to resolve the dimensional complexity that he identified. However, we do not believe that the alternative bed load transport equation proposed by Michel [2005] provides either the mechanistic insight or predictive power of our transport equation.

The symbolic values of wilderness have been largely overlooked, compared with the ecological and experiential values of wilderness. The prominence of the word untrammeled as a descriptor of the wilderness ideal suggests that the primary general symbolic value of wilderness is as a symbol of a human–environment relationship characterized by restraint and humility. This value is compromised when wilderness is manipulated for human purposes. This article notes several ways in which the symbolic values of wilderness are mischaracterized and trivialized as being a matter of philosophy (as...

Pinyon-juniper woodlands and Wyoming big sagebrush ecosystems have undergone major changes in vegetation structure and composition since settlement by European Americans. These changes are resulting in dramatic shifts in fire frequency, size and severity. Effective management of these systems has been hindered by lack of information on: (1) presettlement fire regimes and the spatial and temporal changes that have occurred in Intermountain Region woodlands and sagebrush ecosystems since settlement; (2) changes in fuel loads and the consequences for the ecosystem types and conditions that...