Treesearch

The Santa Rita Experimental Range (SRER) soils are mostly transported alluvial sediments that occur on the piedmont slope flanking the Santa Rita Mountains in Arizona. The major geomorphic land forms are alluvial fans or fan terraces, but there are also areas of residual soils formed on granite and limestone bedrock, basin floor, stream terraces, and flood plains. The soils range in age from recent depositions to soil material one to two million years of age. We sampled A and B horizons of soil series from different geomorphic surfaces, and measured the dry spectral reflectance (0.4 to 2.5...

The purpose of the grazing trials described in this paper was to provide information to aid in the development of grazing management strategies where Lehmann lovegrass has become a dominant species. Seven pastures were utilized from 1984 to 1987 for a comparison of four yearlong stocking rates to seasonal grazing rotated through three pastures. A second trial, 1988 to 1993, rotated cows and calves through all pastures at a very low stocking rate. Spot grazing created patchy grazing patterns that persisted throughout the study period on all treatment pastures, except the yearlong very heavy...

We established a large-scale manipulative experiment in a semidesert grassland on the Santa Rita Experimental Range to determine how the recruitment and physiology of woody plants (Prosopis velutina Woot.) are affected by invasive grasses, seasonal precipitation regimes, and underlying soil characteristics. We established 72 2.8-m2 plots beneath six large rainout shelters divided evenly between a clay-rich and a sandy loam soil less than 1 km apart. Monospecific stands of the the invasive African grass Eragrostis lehmanniana and the native grass Heteropogon contortus were established into...

The Santa Rita Experimental Range (SRER) digital database was developed to automate and preserve ecological data and increase their accessibility. The digital data holdings include a spatial database that is used to integrate ecological data in a known reference system and to support spatial analyses. Recently, the Advanced Resource Technology (ART) facility has added three new Federal geographic data products to this spatial database. U.S. Geological Survey (USGS) digital raster graphics (DRG) are scanned images of USGS topographic maps. Digital orthophoto quarter quads (DOQQ) are...

In 1934, Eragrostis lehmanniana was introduced into southeastern Arizona to control erosion and provide forage for cattle. The earliest of these introductions took place on the Santa Rita Experimental Range (SRER) in 1937 and continued there until the early 1960s. Numerous researchers have observed a convincing association between an increased proportion of E. lehmanniana and decreasing species richness in these grasslands. This grass is both invasive and persistent: just 50 years after its introduction, the area occupied by E. lehmanniana had doubled. Published evidence indicates that...

The Moderate Resolution Imaging Spectroradiometer (MODIS) provides temporal enhanced vegetation index (EVI) data at 250, 500, and 1,000 m spatial resolutions that can be compared to daily, weekly, monthly, and annual weather parameters. A study was conducted at the grassland site (less than 10 percent velvet mesquite [Prosopis juliflora, var. velutina]) and the mesquite site (approximately 30 to 40 percent mesquite cover) of the Santa Rita Experimental Range (SRER) to relate MODIS monthly EVI to temperature and rainfall patterns. Preliminary results show that these two climate attributes...

In the arid Southwest United States, monsoon precipitation plays a key role in ecosystem water balance and productivity. The sensitivity of deeply rooted plants to pulses of summer precipitation is, in part, controlled by the interaction between soil texture, precipitation intensity, and plant rooting depth and activity. In this study we evaluated the water relations of a leguminous tree species Prosopis velutina Woot. (velvet mesquite) occurring across three different aged soils varying in soil texture during two consecutive summers that substantially differed in the amount of monsoonal...

Determining the effects of mesquite (Prosopis velutina) overstory removal, posttreatment control of sprouting, and mulching treatments on herbage production (standing biomass) and selected soil chemical properties on the Santa Rita Experimental Range were the objectives of this study. Mesquite control consisted of complete overstory removals with and without the control of the resulting regrowth of stump sprouts. The mulching treatments were applications of mesquite wood chips, commercial compost, and lopped-and-scattered mesquite branchwood. Herbage production was estimated in the spring...

Diets of Gambel (Lophortyx gambelii Gambel) and scaled quail (Callipepla squamata Vigors) from 1982 to 1984 were examined on the Santa Rita Experimental Range in southern Arizona. Quail selected some foods yearlong and others on a seasonal basis, but exhibited a preference for the seeds and leaves of forbs and insects. Seeds of bristlegrasses were selected primarily during winter. Gonadal development was strongly associated with the availability of spring forbs. Forbs were most common in areas frequented by cattle in native range pastures, and nearly absent from Lehmann lovegrass (Eragrosti...

The historical flora of the Santa Rita Experimental Range was composed from historical lists of plants collected by various investigators since 1903. Plant accessions were verified from lists of plant specimens housed at the Rocky Mountain Research Station herbarium in Flagstaff, AZ, and the Rocky Mountain National Herbarium in Laramie, WY. Recent additions (1980 to 1996) to the flora were from plant collections associated with wildlife and plant studies. This list represents the most comprehensive and current inventory of plants found on the Range.