Treesearch

The Sky Island Archipelagos of the Sierra Madre Oriental and Occidental contain a unique array of endemic flora and fauna. Plant species composition in these elevationally restricted forests is thought to vary in relation to environmental gradients. This study quantifies plant population abundance and spatial distribution patterns in pine-oak woodlands of Big Bend National Park using cluster analysis and non-metric multidimensional scaling. Results from this study indicate that vegetation abundance and spatial distribution patterns are correlated with environmental gradients of potential...

Managers are increasingly moving toward an ecosystem-based, multiple-use approach in managing Emory oak woodlands in the Southwestern United States. Often of particular interest is managing the coppice that evolves from earlier fuelwood harvesting activities. Emory oak (Quercus emoryi) is a prolific sprouting species and, as a consequence, post-harvesting stands can support copious coppice on the cut rootstocks. Thinning the coppice to obtain a desired density of multiple benefits is one management option. A decision matrix based on resource proxies derived from earlier studies has been...

Biological inventories are important for natural resource management and interpretation, and can form a foundation for long-term monitoring programs. We inventoried vascular plants and vertebrates in nine National Parks in southern Arizona and western New Mexico from 2000 to 2004 using repeatable designs, commonly accepted methods, and standardized protocols. At Tumacácori National Historical Park alone, we recorded 378 species of plants and 213 species of vertebrates, including a total of 273 species that were previously undocumented in the park. Data collected in all nine parks will be...

Few studies investigating effects of fire on ant communities have been conducted worldwide, and none in the biologically diverse and fire prone region of the Sky Islands. Ant genera richness and total abundance are significantly higher in burned areas. Ant community structure changes between unburned and burned sites, implying that disturbance may influence the role of ant communities in Sky Island ecosystems.

Pima pineapple cactus (PPC) (Coryphantha sheeri var. robustispina), a federally listed endangered species, occurs throughout southeastern Arizona and has relatively low population densities. To determine whether pollination limits reproduction of PPC we used florescent dye to quantify pollen flow between individuals in a PPC population. Preliminary results suggest Diadasia bees are capable of transferring pollen analogs nearly 1 km, but most transfers occur over a few hundred meters. PPC may not be pollen limited, at least when few competing cactus species are in bloom. Ongoing work will...

Fire suppression over the past century has contributed to the conversion of grasslands to shrublands in Sky Island communities. Two prescribed fires were ignited in the Peloncillo Mountains: Baker Canyon in 1995 and Maverick Spring in 1997. Remote sensing data were used to examine prescribed fire effectiveness in reducing shrub cover and to monitor post-fire regeneration. Landcover maps identified an initial decrease in shrubcover due to foliage loss and top-killing, with shrubcover increasing in following years where low burn severity did not kill shrubs completely. Results indicate the...

Field studies are being conducted to quantify runoff and erosion rates following wildfires in semiarid rangelands. Rainfall simulator experiments were conducted on two grassland sites and one oak woodland site in Southern Arizona immediately following wildfires in 2002 and 2003. The experiments applied a range of rainfall intensities between 50 and 180 mm/h. Infiltration, runoff, and erosion rates were measured for each application rate. The post wildfire runoff and erosion responses are much higher on the oak woodland site and show much more variability than the responses from the two...

Prairie dog is a keystone species throughout the habitat where it occurs, but its populations have declined about 98% in the last century. This species has been considered of international importance for the United States of America, Canada, and Mexico. Only two populations are recorded for Mexico, and the westernmost (isolated by Sierra Madre Occidental from the other) remains basically unknown, in the Upper San Pedro River Watershed in Mexico. This species has been eradicated from Arizona. The closest population is hundreds of kilometers away, in New Mexico. Since July 2003, we have been...

Throughout the southwestern United States, vegetation in what historically was grassland has changed to a mixture of trees and shrubs; exotic grass species and undesirable shrubs have also invaded the grasslands at the expense of native grasses. The availability and amount of soil nutrients influence the relative success of plants, but few studies have examined fire effects on soil characteristics in a temporal, spatial, and species group-specific fashion. Our research investigates the effects of fire events on selected soil characteristics (pH, NO3-, PO4-3, TOC) on native grass-, exotic...

The Greater Huachuca Mountains Fire Management Group is developing a fire management plan for 500,000 acres in southeast Arizona. Partner land managers include Arizona State Parks, Arizona State Lands, Audubon Research Ranch, Coronado National Forest, Coronado National Memorial, Fort Huachuca, The Nature Conservancy, San Pedro Riparian National Conservation Area, and private ranches. The plan will guide cross-jurisdiction collaborations on wildland fire use, prescribed burns, suppression, and non-fire fuels reduction around developed and other sensitive areas. Group members have outlined...