Ginger B. Paige

Long‐term meteorological and soil hydrology database, Walnut Gulch Experimental Watershed, Arizona, United States

A 17 year (1990-2006) meteorological and soil hydrology database has been developed for the Walnut Gulch Experimental Watershed in southeastern Arizona. Data have been acquired at three automated weather stations, 5 soil profile trench sites, and 19 locations dispersed across the watershed colocated with recording rain gauges. Meteorological elements measured at the weather stations include air temperature, relative humidity, wind speed, wind direction, barometric pressure, solar radiation, photosynthetically active radiation, and net radiation. Soil hydrology properties measured at the weather stations, trench sites, and rain gauges include soil moisture, soil temperature, soil heat flux, and soil surface temperature. Data are available at http://www.tucson.ars.ag.gov/dap.

DEM Development from Ground-Based LiDAR Data: A Method to Remove Non-Surface Objects

Topography and land cover characteristics can have significant effects on infiltration, runoff, and erosion processes on watersheds. The ability to model the timing and routing of surface water and erosion is affected by the resolution of the digital elevation model (DEM). High resolution ground-based Light Detecting and Ranging (LiDAR) technology can be used to collect detailed topographic and land cover characteristic data. In this study, a method was developed to remove vegetation from ground-based LiDAR data to create high resolution DEMs. Research was conducted on intensively studied rainfall-runoff plots on the USDA-ARS Walnut Gulch Experimental Watershed in Southeast Arizona. LiDAR data were used to generate 1 cm resolution digital surface models (DSM) for 5 plots. DSMs created directly from LiDAR data contain non-surface objects such as vegetation cover. A vegetation removal method was developed which used a slope threshold and a focal mean filter method to remove vegetation and create bare earth DEMs. The method was validated on a synthetic plot, where rocks and vegetation were added incrementally. Results of the validation showed a vertical error of ±7.5 mm in the final DEM.

AGWA: The Automated Geospatial Watershed Assessment Tool to Inform Rangeland Management

AGWA: The Automated Geospatial Watershed Assessment Tool to Inform Rangeland Management DOI:10.2458/azu_rangelands_v33i4_goodrich

Ecological Site-Scale Hydrologic Response in a Semiarid Rangeland Watershed ☆

ABSTRACT Rangelands, due to their large expanse, are responsible for processing a significant portion of freshwater in the western United States. Rangeland managers are in need of methods to quantify hydrologic processes and scientifically based decision tools to effectively manage water resources under growing populations and a changing climate. The ecological site (ES) concept provides a useful framework to study complex rangeland hydrological processes in order to parameterize these tools. Traditionally, rangeland hydrology has been studied at the plot and watershed scale. ESs are intermediate-scale land units considered to have homogeneous site characteristics, which allow for mapping the spatial variability of hydrologic processes at a higher resolution compared with a lumped watershed approach. We conducted 20 variable-intensity rainfall simulation experimental runs using the Walnut Gulch Rainfall Simulator to characterize the hydrologic response of four different ESs in the Upper Crow Creek Watershed in southeastern Wyoming. An analysis of variance test with post hoc comparisons showed that sites were significantly different in runoff-infiltration dynamics. Sites ranged from exhibiting a large runoff ratio of 0.44 to infiltrating the entire applied rainfall volume. Multiple linear regressions showed that, on average, 83% of the variability of key hydrologic variables across sites could be explained by significant relationships (P ≤ 0.05) consisting of two or three ground cover variables. Beta weights for the regression variables indicated that percent cover of lesser spikemoss (Selaginella densa Rydb.) and bare soil were typically the most influential variables. Additional site-specific characteristics explain the remaining variability. The results fromthis study directly support the concept of using ESs to assess hydrologic response of rangelands. Incorporating quantitative hydrologic datasets into ecological site descriptions and decision tools should increase their utility for the management of rangeland ecosystems.

Evaluating a State-and-Transition Model Using a Long-Term Dataset

Abstract State-and-transition models (STMs) are used in natural resource management to describe ecological site scale response to natural and anthropogenic disturbances. STMs are primarily based for expert opinion and literature reviews, lacking analytical testing to support vegetation community dynamics, thresholds, and state changes. We developed a unique approach, combining ordination and permutation MANOVA (perMANOVA) with raw data interpretation, to examine vegetation data structure and identify thresholds for a STM. We used a long-term monitoring dataset for an ecological site on the Santa Rita Experimental Range, Arizona. Basal cover of perennial grasses and canopy cover of shrubs and cacti were measured on permanent transects beginning in 1957. Data were grouped by drivers identified by the STM including species invasion, grazing, drought, and mesquite treatment. Ordination by nonmetric multidimensional scaling described the structure of the data. PerMANOVA was used to test for differences between groups of sample units. Analyses of combined key species (Lehmanns lovegrass and mesquite [Prosopis velutina Woot.]) and nonkey species patterns demonstrated an irreversible transition and occurrence of a structural threshold due to Lehmanns lovegrass invasion, as well as a short-term reversible transition (restoration pathway) following mesquite treatment. Sensitivity analysis, in which key species were removed from the dataset, showed that the relative composition of nonkey species did not differ between states previously defined by the key species. This apparent disconnect between dynamics of key and nonkey species may be related to changes in the functional attributes that were not monitored during this time series. Our analyses suggest that, for this ecological site, transition to a Lehmanns lovegrass state occurs when basal cover of this species exceeds 1–2%, which often occurs within 6 yr of its arrival. Evaluation of the restoration pathway showed a recrossing of the threshold within 6 yr of treatment and when mesquite canopy cover exceeded 10%.

Integrated reclamation: Approaching ecological function?

Attempts to reclaim arid and semiarid lands have traditionally targeted plant species composition. Much research attention has been directed to seeding rates, species mixes and timing of seeding. However, in order to attain functioning systems, attention to structure and process must compliment existing efforts. We ask how to use a systems approach to enhance reclamation success. Using a case study example, we discuss ways to target key drivers that return the functional and dynamic nature of western wildlands. Integration of a multitude of abiotic (soil stability, hydrology and nutrient cycling) and biotic processes (plant functional traits, species turnover and regeneration, and wildlife interactions) into reclamation planning will be crucial to uniting research with management experience. Long-term monitoring coupled with tools to unify diverse datasets will be key to future management decisions. Reclamation is constrained by our inability to unify varied experiences with documented evidence. Research should assist managers with integrating spatial and temporal variability of ecosystem processes into long-term management planning. Using an integrated approach, we can more fully comprehend reclamation within the context of ecosystem function. An integrated knowledge base should serve as a communication tool and facilitate more sustainable landscape solutions.

A fuzzy logic approach to analyse the suitability of nesting habitat for greater sage-grouse in western Wyoming

Abstract Habitat suitability analysis is complex and requires integration of multiple attributes at a range of spatial scales. We use fine- and broad-scale variables within a spatial modelling framework to determine the suitability of greater sage-grouse nesting habitat using fuzzy logic. Fuzzy theory allows for a landscape component to have full, partial, or no membership in a particular management target. We used seven biophysical and anthropogenic variables correlated with nest site locations to build the fuzzy model. Using field and remotely sensed data and expert opinion, we developed fuzzy functions to define numerical membership values describing relationships between landscape characteristics and nesting habitat suitability. We used a fuzzy gamma overlay function to define five suitability classes in the resulting habitat map. Using a fuzzy logic model, we were able to spatially distinguish the suitability of nesting habitat using fine- and broad-scale attributes and characterise the uncertainty of the habitat model.

Rainfall, evapotranspiration, and soil moisture as herbage production predictors for Wyoming rangelands

ABSTRACT Rangelands are an important ecosystem in the western US, and herbage and livestock production are important issues throughout the western states. Making stocking rate decisions early in the growing season is difficult because of high variation in annual herbage production. In this study, regression analysis was used to relate herbage biomass to monthly and growing season predicator variables (rainfall, actual evapotranspiration, and soil moisture) using data collected from fifteen Wyoming rangeland sites. Both predictor and response variables were scaled before regression to correct for different physical and environmental conditions between sites. Growing season precipitation was the strongest predictor of herbage biomass production (r2 = 0.79), followed by growing season actual evapotranspiration (r2 = 0.69), and growing season profile-average soil water content (r2 = 0.59). April profile-average (0–90 cm) and April surface (0–30 cm) soil moisture also predicted herbage biomass (r2 = 0.53–0.54), indicating that early growing season soil moisture can be used to inform stocking rate and grazing management decisions as it provides information at the onset of the growing season.

Songbird Relationships to Shrub-Steppe Ecological Site Characteristics

Abstract Rangeland managers are often faced with the complex challenge of managing sites for multiple uses and for the diverse interests of stakeholders. Standardized monitoring methods that can be used and understood by different agencies and stakeholders would aid management for long‐term sustainability of rangelands. In the United States, federal land management agencies have recently based their assessments of rangeland health and integrity on state‐and‐transition models to consider management trajectories. Ecological sites provide a foundation for these efforts but have not been used to address wildlife habitat. Habitat preferences are documented for North American shrub‐steppe songbirds but have yet to be related to ecological sites and site characteristics. We characterized ecological sites at Browns Park National Wildlife Refuge, Colorado, using established rangeland monitoring methods to test whether 1) songbird species density and diversity differ among adjacent shrub‐steppe ecological sites and 2) quantifiable ecological site characteristics could be identified that account for significant variation in songbird density and diversity. Vegetation structure (represented as basal and canopy gaps, cover, height, and shrub density) differentiated the four ecological sites and was related to songbird density and diversity. Sage sparrows (Amphispiza belli) and vesper sparrows (Pooecetes gramineu) selected habitat based on horizontal characteristics of vegetation structure, such as basal and canopy gap and plant species cover. Brewers sparrow (Spizella breweri), lark sparrow (Chondestes grammacus), and songbird diversity were more strongly related to vegetation structure of the plant communities than to plant composition. Our results support use of ecological sites as management units to characterize songbird habitat given that songbird density and diversity were related to site vegetation characteristics. By incorporating basal and canopy gap, height, plant cover, and shrub density monitoring methods into ecological site descriptions, managers would be provided with additional tools to assist in differentiating songbird habitat.

Hydrologic Response of Four Ecological Sites to Natural Rainfall Events Within a Semiarid Watershed

ABSTRACT Understanding the capture and redistribution of water within ecological sites should improve our understanding of the function of rangeland watersheds. We compare ecological site physical properties, runoff events, and precipitation event characteristics to assess the variability in hydrologic response of four ecological sites to natural rainfall events in a semiarid watershed in southeast Wyoming, United States. Ecological sites were selected on the basis of their extent of areal coverage in the watershed and their perceived importance in watershed scale hydrologic response. At each study site, four 12-m2 runoff plots were installed with collection troughs to capture and quantify the rate and amount of runoff. A tension infiltrometer was used to measure effective saturated hydraulic conductivity at the point scale, and a data-logging rain gauge was installed at each site to measure rainfall. One-way analysis of variance (α = 0.05) was used to compare the hydrologic characteristics of ecological sties. Amounts and intensities of rainfall required to generate runoff, timing of overland flow, and peak runoff rates differed (P < 0.05) among sites in their current state. We found differences in effective hydraulic conductivity, 20.30 mm hr-1 on shallow loamy site up to 50.40 mm hr-1 on the coarse upland, and plot water storage potential, which varied from 101.8 mm on the shallow loamy site to 472.0 mm on the loamy upland site, due to differences in soil depth and porosity among sites. After normalizing runoff according to rainfall depth, we found no statistical difference (P > 0.05) in the volumes of runoff produced by different sites. The amount of runoff generated on all sites was very small, indicating high infiltration and limited ponding and overland flow. Ecological sites were shown to have different hydrologic response characteristics (i.e., timing of runoff), suggesting that they can be used to better quantify and understand the variability in hydrology in rangeland watersheds.