- I focus on plant ecology associated with vegetation management on semiarid rangelands.edit
Research Interests:
Research Interests:
... glandulosa, Larrea tridentata, Gutierrezia sarothrae Larrea tridentata Prosopis juliflora var. ... 110 Page 118. 48 SEEDED 1969A68»--Ltl * v B. 3 L19 \\ u-*--L28 ■-«-UB \\^^-O--A84 V^^ -ERAT J'^-^■ or ■%\\^-eras-»■-SEMA... more
... glandulosa, Larrea tridentata, Gutierrezia sarothrae Larrea tridentata Prosopis juliflora var. ... 110 Page 118. 48 SEEDED 1969A68»--Ltl * v B. 3 L19 \\ u-*--L28 ■-«-UB \\^^-O--A84 V^^ -ERAT J'^-^■ or ■%\\^-eras-»■-SEMA BsA'-^ s. ■ PAAN vk. ...
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Wildfires can create or intensify water repellency in soil, limiting the soil's capacity to wet and retain water. The objective of this research was to quantify soil water repellency characteristics within burned piñon-juniper... more
Wildfires can create or intensify water repellency in soil, limiting the soil's capacity to wet and retain water. The objective of this research was to quantify soil water repellency characteristics within burned piñon-juniper woodlands and relate this information to ecological site characteristics. We sampled soil water repellency across forty-one 1,000 m(2) study plots within three major wildfires that burned in piñon-juniper woodlands. Water repellency was found to be extensive-present at 37% of the total points sampled-and strongly related to piñon-juniper canopy cover. Models developed for predicting SWR extent and severity had R(2)adj values of 0.67 and 0.61, respectively; both models included piñon-juniper canopy cover and relative humidity the month before the fire as coefficient terms. These results are important as they suggest that postfire water repellency will increase in the coming years as infilling processes enhance piñon-juniper canopy cover. Furthermore, reduct...
Research Interests:
ABSTRACT Soil nutrient availability influences plant invasions. Resin capsules were used to examine soil nutrient bioavailability along 2 sagebrush-grassland elevation transects in the east Tintic Range (Utah) and Shoshone Range (Nevada).... more
ABSTRACT Soil nutrient availability influences plant invasions. Resin capsules were used to examine soil nutrient bioavailability along 2 sagebrush-grassland elevation transects in the east Tintic Range (Utah) and Shoshone Range (Nevada). In the fall of 2001, treatments were applied to 3 replicate plots at each site, which included prescribed burning, herbaceous vegetation removal, and controls. Cheatgrass (Bromus tectorum L.) was overseeded in small subplots within each treatment. Following treatments in each plot, resin capsules were installed at 15-cm depth in a shrub interspace and a B. tectorum-overseeded area. Nutrient availability was integrated during late fall to spring and spring to late fall for 2 years. Herbaceous vegetation removal increased availability of nitrate (Nevada and Utah) and Ca and Mg (Nevada only) but only during the second sampling period (growing season). Availability of K and ortho-P (Nevada and Utah) and nitrate (Nevada only) was greater on prescribed burned plots. For Utah, availability of ortho-P, K, Ca, Mg, and Fe generally increased with increasing elevation. Availability of Ca, Mg, K, and Fe was greatest during late fall to spring integration periods for Nevada. Overseeding with B. tectorum interacted with the burn treatment to influence availability of Ca, Mg, and Fe (Nevada sites only). Patterns of nutrient availability can be explained by a combination of decreased root uptake in relation to mineralization, differences in soil water content with season and elevation, and nutrient release from vegetation and soil as a consequence of prescribed burning. Herbaceous vegetation removal and burning can raise nitrate availability and increase risk of invasion by nitrophilic species such as B. tectorum. Nutrient availability can be out of phase with plant growth; plants capable of taking up nutrients during cold periods may have a competitive advantage. Resin capsules have utility in quantifying the effects of treatments on the availability of many soil nutrients.
Research Interests:
Research Interests:
Research Interests:
Research Interests: Circular()
()
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests: Notes()
()
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests: Circular()
()
Hydrothermal time models are often used to predict seed germination rates. In this study, soil water potential data from three resistance-type sensors (Colman cells, Watermark brand sensors, and Delmhorst gypsum blocks) and from a... more
Hydrothermal time models are often used to predict seed germination rates. In this study, soil water potential data from three resistance-type sensors (Colman cells, Watermark brand sensors, and Delmhorst gypsum blocks) and from a time-domain reflectometry (TDR) probe (Campbell Scientific 615) were input into a hydrothermal time model to predict seedling emergence in a growth chamber experiment for six desert
Research Interests:
Research Interests:
Background/Question/Methods To stem catastrophic wildfires and create firebreaks, whole Juniperus osteosperma trees are being mechanically shredded into coarse woody debris (CWD) and deposited on soils. CWD often alters belowground... more
Background/Question/Methods To stem catastrophic wildfires and create firebreaks, whole Juniperus osteosperma trees are being mechanically shredded into coarse woody debris (CWD) and deposited on soils. CWD often alters belowground processes, ultimately increasing or decreasing the availability of limiting nutrients for establishing plant species. However, semi-arid woodlands are exposed to tree-induced changes creating “tree-islands of fertility.” These drastic differences in belowground characteristics between barren plant interspace and tree-island soils may alter the impact of CWD on nutrient cycling. We evaluated C cycling, N transformation rates, and P availability in three Juniperus tree-island microsites (i.e., interspace soils, soils beneath the canopy, and at the edge of the canopy) exposed to field CWD manipulation in over forty cold desert sites. For each microsite, we linked our measured belowground processes to the frequency of one exotic grass (Bromus tectorum) and th...
Following wildfires, plant materials are direct-seeded to limit erosion and annual weed invasion. Seedlings often fail to establish because selected plant materials are not always well adapted to local soil moisture and temperature... more
Following wildfires, plant materials are direct-seeded to limit erosion and annual weed invasion. Seedlings often fail to establish because selected plant materials are not always well adapted to local soil moisture and temperature conditions. In an effort to help improve plant materials selection and to evaluate sites potential revegetation, we have worked toward developing methodology to predict germination and root growth based on site specific soil moisture and temperature conditions. First, we characterized the seedbed environment of 24 sagebrush (Artemisia spp.) steppe sites throughout the Intermountain West to determine the wet-thermal time of five temperature ranges relevant to germination response and thermal-time model accuracy (Chapter 1). Second, we predicted potential germination for 31 plant materials at those same sites (Chapter 2). Third, in preparation to predict root growth at multiple sites, we characterized the drying patterns and the associated plant-available w...
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Eragrostis lehmmniana (Lehrnann lovegrass) is a warm-season bunchgrass native to South Africa which dominates many desert grassland sites in southern Arizona. To determine why fire results in high seedling recruitment of this species, we... more
Eragrostis lehmmniana (Lehrnann lovegrass) is a warm-season bunchgrass native to South Africa which dominates many desert grassland sites in southern Arizona. To determine why fire results in high seedling recruitment of this species, we measured germination of seeds in the seedbank and field seedling emergence following 1) no treatment, 2) burning, 3) clipping and herbicide and 4) herbicide d y . Treatments were designed to compare the effects of initial fire heat treatment with those of canopy removal, as affecting seedbed temperatwe, light and water availability, on seedling emergence. Treatments were replicated over 2 years on a stand of Lehrnann lovegrass at the Santa Rita Experimental Range. Canopy removal, by either clipping or burning, increased seedling emergence in seedbank samples taken prior to summer rains and greatly increased field seeding emergence. High seedling emer- gence after canopy removal was not the result of greater seedbed water availability but probably th...