An object-based image analysis of pinyon and juniper woodlands treated to reduce fuels.

Mechanical and prescribed fire treatments are commonly used to reduce fuel loads and maintain or restore sagebrush steppe rangelands across the Great Basin where pinyon (Pinus) and juniper (Juniperus) trees are encroaching and infilling. Geospatial technologies, particularly remote sensing, could potentially be used in these ecosystems to (1) evaluate the longevity of fuel reduction treatments, (2) provide data for planning and designing future fuel-reduction treatments, and (3) assess the spatial distribution of horizontal fuel structure following fuel-reduction treatments. High-spatial resolution color-infrared imagery (0.06-m pixels) was acquired for pinyon and juniper woodland plots where fuels were reduced by either prescribed fire, tree cutting, or mastication at five sites in Oregon, California, Nevada, and Utah. Imagery was taken with a Vexcel UltraCam X digital camera in June 2009. Within each treatment plot, ground cover was measured as part of the Sagebrush Steppe Treatment Evaluation Project. Trimble eCognition Developer was used to classify land cover classes using object-based image analysis (OBIA) techniques. Differences between cover estimates using OBIA and ground-measurements were not consistently higher or lower for any land cover class and when evaluated for individual sites, were within ±5 % of each other. The overall accuracy and the K hat statistic for classified thematic maps for each treatment were: prescribed burn 85 % and 0.81; cut and fell 82 % and 0.77, and mastication 84 % and 0.80. Although cover assessments from OBIA differed somewhat from ground measurements, they are sufficiently accurate to evaluate treatment success and for supporting a broad range of management concerns.

Ecological-niche modeling reveals current opportunities for Agave dryland farming in Sonora, Mexico and Arizona, USA.

For centuries, humans occupying arid regions of North America have maintained an intricate relationship with Agave (Agavoideae, Asparagaceae). Today Agave cultivation, primarily for beverage production, provides an economic engine for rural communities throughout Mexico. Among known dryland-farming methods, the use of rock piles and cattle-grazed areas stand out as promising approaches for Agave cultivation. Identifying new cultivation areas to apply these approaches in Arizona, USA and Sonora, Mexico warrants a geographic assessment of areas outside the known ranges of rock piles and grasslands. The objective of this study was to predict areas for dryland-farming of Agave and develop models to identify potential areas for Agave cultivation. We used maximum entropy (MaxEnt) ecological-niche-modeling algorithms to predict suitable areas for Agave dryland farming. The model was parameterized using occurrence records of Hohokam rock piles in Arizona and grassland fields cultivated with Agave in Sonora. Ten environmental-predictor variables were used in the model, downloaded from the WorldClim 2 climate database. The model identified potential locations for using rock piles as dryland-farming methods from south-central Arizona to northwestern Sonora. The Agave-grassland model indicated that regions from central to southern Sonora have the highest potential for cultivation of Agave, particularly for the species Agave angustifolia. Results suggest that there are many suitable areas where rock piles can be used to cultivate Agave in the Sonoran Desert, particularly in the border of southeastern Arizona and northwest Sonora. Likewise, cattle-grazing grasslands provide a viable environment for cultivating Agave in southern Sonora, where the expanding bacanora-beverage industry continues to grow and where different Agave products (e.g., syrups, fructans, saponins, and medicinal compounds) can potentially strengthen local economies.

Extraction chromatographic methods in the sample preparation sequence for thermal ionization mass spectrometric analysis of plutonium isotopes.

A sample preparation sequence for actinide isotopic analysis by thermal ionization mass spectrometry (TIMS) is described that includes column-based extraction chromatography as the first separation step, followed by anion-exchange column separations. The sequence is designed to include a wet ashing step after the extraction chromatography to prevent any leached extractant or oxalic acid eluent reagents from interfering with subsequent separations, source preparation, or TIMS ionization. TEVA resin and DGA resin materials, containing extractants that consist only of C, N, O, and H atoms, were investigated for isolation of plutonium. Radiotracer level studies confirmed expected high yields from column-based separation procedures. Femtogram-level studies were carried out with TIMS detection, using multiple monoisotopic spikes applied sequentially throughout the separation sequence. Pu recoveries were 87% and 86% for TEVA and DGA resin separations, respectively. The Pu recoveries from 400 µL anion-exchange column separation sequences were 89% and 93% for trial sequences incorporating TEVA and DGA resin. Thus, a prior extraction chromatography step in the sequence did not interfere with the subsequent anion-exchange separation when a simple wet ash step was carried out in between these column separations. The average measurement efficiency for Pu, encompassing the chemical separation recoveries and the TIMS ionization efficiency, was 2.73% ± 0.77% (2σ) for the DGA resin trials and 2.67% ± 0.54% for the TEVA resin trials, compared to 3.41% and 2.37% (average 2.89%) for two control trials. These compare with an average measurement efficiency of 2.78% ± 1.70%, n = 33 from process benchmark analyses using Pu spikes processed through a sequence of oxalate precipitation, wet ash, iron hydroxide precipitation, and anion-exchange column separations. We conclude that extraction chromatography can be a viable separation procedure as part of a multistep sequence for TIMS sample preparation.

Feature extraction techniques for measuring piñon and juniper tree cover and density, and comparison with field-based management surveys.

Western North America is experiencing a dramatic expansion of piñon (Pinus spp.) and juniper (Juniperus spp.) (P-J) trees into shrub-steppe communities. Feature extracted data acquired from remotely sensed imagery can help managers rapidly and accurately assess this land cover change in order to manage rangeland ecosystems at a landscape-scale. The objectives of this study were to: (1) develop an effective and efficient method for accurately quantifying P-J tree canopy cover and density directly from high resolution photographs and (2) compare feature-extracted data to typical in-situ datasets used by land managers. Tree cover was extracted from aerial-photography using Feature Analyst®. Tree density was calculated as the sum of the total number of individual polygons (trees) within the tree cover output file after isolation using a negative buffer post-processing technique. Feature-extracted data were compared to ground reference measurements from Utah's Division of Wildlife Resources Range Trend Project (DWR-RTP). We found that the proposed feature-extraction techniques used for measuring cover and density were highly correlated to ground reference and DWR-RTP datasets. Feature-extracted measurements of cover generally showed a near 1:1 relationship to these data, while tree density was underestimated; however, after calibration for juvenile trees, a near 1:1 relationship was realized. Feature-extraction techniques used in this study provide an efficient method for assessing important rangeland indicators, including: density, cover, and extent of P-J tree encroachment. Correlations found between field and feature-extracted data provide evidence to support extrapolation between the two approaches when assessing woodland encroachment.

Influence of an abscisic acid (ABA) seed coating on seed germination rate and timing of Bluebunch Wheatgrass.

Semi-arid rangeland degradation is a reoccurring issue throughout the world. In the Great Basin of North America, seeds sown in the fall to restore degraded sagebrush (Artemisia spp.) steppe plant communities may experience high mortality in winter due to exposure of seedlings to freezing temperatures and other stressors. Delaying germination until early spring when conditions are more suitable for growth may increase survival. We evaluated the use of BioNik™ (Valent BioSciences LLC) abscisic acid (ABA) to delay germination of bluebunch wheatgrass (Pseudoroegneria spicata). Seed was either left untreated or coated at five separate rates of ABA ranging from 0.25 to 6.0 g 100 g-1 of seed. Seeds were incubated at five separate constant temperatures from 5 to 25°C. From the resultant germination data, we developed quadratic thermal accumulation models for each treatment and applied them to 4 years of historic soil moisture and temperature data across six sagebrush steppe sites to predict germination timing. Total germination percentage remained similar across all temperatures except at 25°C, where high ABA rates had slightly lower values. All ABA doses delayed germination, with the greatest delays at 5-10°C. For example, the time required for 50% of the seeds to germinate at 5°C was increased by 16-46 d, depending on the amount of ABA applied. Seed germination models predicted that the majority of untreated seed would germinate 5-11 weeks after a 15 October simulated planting date. In contrast, seeds treated with ABA were predicted to delay germination to late winter or early spring. These results indicate that ABA coatings may delay germination of fall planted seed until conditions are more suitable for plant survival and growth.

Accelerated analyte uptake on single beads in microliter-scale batch separations using acoustic streaming: plutonium uptake by anion exchange for analysis by mass spectrometry.

The use of acoustic streaming as a noncontact mixing platform to accelerate mass-transport-limited diffusion processes in small-volume heterogeneous reactions has been investigated. Single-bead anion exchange of plutonium at nanomolar and subpicomolar concentrations in 20 microL liquid volumes was used to demonstrate the effect of acoustic mixing. Pu uptake rates on individual approximately 760 microm diameter AG 1 x 4 anion-exchange resin beads were determined using acoustic mixing and compared with Pu uptake rates achieved by static diffusion alone. An 82 MHz surface acoustic wave (SAW) device was placed in contact with the underside of a 384-well microplate containing flat-bottomed semiconical wells. Acoustic energy was coupled into the solution in the well, inducing acoustic streaming. Pu uptake rates were determined by the plutonium remaining in solution after specific elapsed time intervals using liquid scintillation counting (LSC) for nanomolar concentrations and thermal ionization mass spectrometry (TIMS) analysis for the subpicomolar concentration experiments. It was found that this small batch uptake reaction could be accelerated by a factor of about 5-fold or more, depending on the acoustic power applied.

Postfire soil water repellency in piñon-juniper woodlands: Extent, severity, and thickness relative to ecological site characteristics and climate.

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 m2 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 R2adj 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, reductions in relative humidity brought about by a changing climate have the potential to link additively with infilling processes to increase the frequency and intensity of wildfires and produce stronger water repellency over a greater spatial extent. In working through these challenges, land managers can apply the predictive models developed in this study to prioritize fuel control and postfire restoration treatments.

Testing VHF/GPS collar design and safety in the study of free-roaming horses.

Effective and safe monitoring techniques are needed by U.S. land managers to understand free-roaming horse behavior and habitat use and to aid in making informed management decisions. Global positioning system (GPS) and very high frequency (VHF) radio collars can be used to provide high spatial and temporal resolution information for detecting free-roaming horse movement. GPS and VHF collars are a common tool used in wildlife management, but have rarely been used for free-roaming horse research and monitoring in the United States. The purpose of this study was to evaluate the design, safety, and detachment device on GPS/VHF collars used to collect free-roaming horse location and movement data. Between 2009 and 2010, 28 domestic and feral horses were marked with commercial and custom designed VHF/GPS collars. Individual horses were evaluated for damage caused by the collar placement, and following initial observations, collar design was modified to reduce the potential for injury. After collar modifications, which included the addition of collar length adjustments to both sides of the collar allowing for better alignment of collar and neck shapes, adding foam padding to the custom collars to replicate the commercial collar foam padding, and repositioning the detachment device to reduce wear along the jowl, we observed little to no evidence of collar wear on horses. Neither custom-built nor commercial collars caused injury to study horses, however, most of the custom-built collars failed to collect data. During the evaluation of collar detachment devices, we had an 89% success rate of collar devices detaching correctly. This study showed that free-roaming horses can be safely marked with GPS and/or VHF collars with minimal risk of injury, and that these collars can be a useful tool for monitoring horses without creating a risk to horse health and wellness.