California Rangelands Research Articles

Terrain attributes and forage productivity predict catchment-scale soil organic carbon stocks

Accurate assessments of soil organic carbon (SOC) stocks are needed at multiple scales given their importance to both local soil health and global C cycles. Rangelands cover 54% of California, representing a large stock of SOC, but existing SOC estimates are uncertain. To improve understanding of fine-resolution SOC stocks in complex terrain and provide guidance to rangeland SOC inventories, we grid-sampled 105 locations (21-m grid cells) at two depths (0–10 and 10–30 cm) in a 10-ha annual grassland catchment in California’s Central Coast Range. Soils were analyzed for bulk density, coarse fragments, SOC and texture. Monthly aerial imagery was acquired by an unmanned aerial vehicle to compare surface reflectance during two contrasting years (wet vs. dry) to SOC stocks. We found that the 0–30 cm soil thickness held 3.64 ± 0.71 kg SOC m−2 (mean ± SD) with a range of 1.97–5.49 kg SOC m−2. The 0–10 cm soil thickness stored 47% of the 0–30 cm SOC stock with SOC concentrations twice as high in the 0–10 cm layer (1.40 ± 0.38%) as in the 10–30 cm layer (0.71 ± 0.15% SOC). Multiple linear regression (MLR) models explained 50–57% of SOC variability at 0–30 and 10–30 cm, but only 25% of variability at 0–10 cm. Based on cross-validation tests, MLR outperformed spatial interpolation methods and Random Forest models, best explaining SOC stocks with five environmental covariates: wet-year greenness, mean curvature, elevation, insolation, and slope. Lower hillslope positions, concave landforms, and enhanced wet-year greenness were associated with more SOC, and explained 11%, 24%, and 31% of variability in 0–30 cm SOC stocks, respectively. This study demonstrates that the accuracy of regional-scale SOC mapping of California rangelands benefits from considering microclimatic and topographic controls at the catchment-scale, in addition to broader scale mineralogical and macroclimatic controls identified in previous SOC studies.

Bridging the Research-Implementation Gap in Weed Management on California Rangelands

Substantial gaps exist between weed management researchers and practitioners with respect to prompt exchange of knowledge between the two groups, hindering the implementation of effective management to solve weed problems. We conducted a survey between 2016 and 2018 among weed management practitioners (n = 259) across diverse ecoregions on California rangelands and collected essential information from practitioners for bridging the research-implementation gap. The information included management costs, high-priority weeds, and spatial scales and temporal changes in weed management. The management cost had a mean of $5.12 ha−1yr−1 with a large variance implying the uncertainty of this information. The percentage of annual budget dedicated to weed management explained about 30% of the variation in this cost. Moreover, this annual per-unit area cost decreased with increasing management area. The average size of rangeland managed by survey respondents was 1 256 ha. The top three high-priority weeds statewide were yellow starthistle (Centaurea solstitialis), medusahead (Taeniatherum caput-medusae), and all thistles combined. Medusahead and some thistle species remained on the top list in each ecoregion. Respondents overwhelmingly (80.9%) noted changes in weed problems in the past 5−10 yr, specifically citing greater weed pressure and changes in weed species. A significantly higher proportion of respondents from agencies and private businesses reported changes in weed problems than those from universities and nongovernmental organizations (NGOs), further underscoring the gap between practitioners and researchers. A majority of the respondents (75.3%) indicated the record-setting California drought had a negative effect on weed management, reducing treatment efficacy and favoring weeds over desirable species. Overall, our findings illustrate increasing challenges in weed management on California rangeland. These challenges call for adaptive management-research programs to increase cost-effectiveness of weed management and to swiftly and effectively respond to dynamic weed problems on large spatial and long temporal scales.

Practitioner Insights into Weed Management on California's Rangelands and Natural Areas.

Working rangelands and natural areas span diverse ecosystems and face both ecological and economic threats from weed invasion. Restoration practitioners and land managers hold a voluminous cache of place-based weed management experience and knowledge that has largely been untapped by the research community. We surveyed 260 California rangeland managers and restoration practitioners to investigate invasive and weedy species of concern, land management goals, perceived effectiveness of existing practices (i.e., prescribed fire, grazing, herbicide use, and seeding), and barriers to practice implementation. Respondents identified 196 problematic plants, with yellow starthistle (Centaurea solstitialis L.) and medusahead (Elymus caput-medusae L.) most commonly listed. Reported adoption and effectiveness of weed management practices varied regionally, but the most highly rated practice in general was herbicide use; however, respondents identified considerable challenges including nontarget effects, cost, and public perception. Livestock forage production was the most commonly reported management goals (64% of respondents), and 25% of respondents were interested in additional information on using grazing to manage invasive and weedy species; however, 19% of respondents who had used grazing for weed management did not perceive it to be an effective tool. Across management practices, we also found common barriers to implementation, including operational barriers (e.g., permitting, water availability), potential adverse impacts, actual effectiveness, and public perception. Land manager and practitioner identified commonalities of primary weeds, management goals, perceived practice effectiveness, and implementation barriers across diverse bioregions highlight major needs that could be immediately addressed through management-science partnerships across the state's expansive rangelands and natural areas.

Microclimate–forage growth linkages across two strongly contrasting precipitation years in a Mediterranean catchment

AbstractGiven the complex topography of California rangelands, contrasting microclimates affect forage growth at catchment scales. However, documentation of microclimate–forage growth associations is limited, especially in Mediterranean regions experiencing pronounced climate change impacts. To better understand microclimate–forage growth linkages, we monitored forage productivity and root‐zone soil temperature and moisture (0–15 and 15–30 cm) in 16 topographic positions in a 10‐ha annual grassland catchment in California's Central Coast Range. Data were collected through two strongly contrasting growing seasons, a wet year (2016–17) with 287‐mm precipitation and a dry year (2017–18) with 123‐mm precipitation. Plant‐available soil water storage (0–30 cm) was more than half full for most of the wet year; mean peak standing forage was 2790 kg ha−1 (range: 1597–4570 kg ha−1). The dry year had restricted plant‐available water and mean peak standing forage was reduced to 970 kg ha−1 (range: 462–1496 kg ha−1). In the wet year, forage growth appeared energy limited (light and temperature): warmer sites produced more forage across a 3–4°C soil temperature gradient but late season growth was associated with moister sites spanning this energy gradient. In the dry year, the warmest topographic positions produced limited forage across a 10°C soil temperature gradient until late season rainfall in March. Linear models accounting for interactions between soil moisture and temperature explained about half of rapid, springtime forage growth variance. These findings reveal dynamic but clear microclimate–forage growth linkages in complex terrain, and thus, have implications for rangeland drought monitoring and dryland ecosystems modeling under climate change.

Statewide Cross-Sectional Survey of Cryptosporidium and Giardia in California Cow-Calf Herds

Cryptosporidium spp. and Giardia duodenalis are common protozoal parasites in livestock including beef cattle on rangeland and irrigated pasture. A statewide cross-sectional study was conducted to determine the prevalence, species or genotype, and risk factors for fecal shedding of Cryptosporidium and Giardia by cattle from California cow-calf operations. Species and genotypes of Cryptosporidium and Giardia were determined by molecular fingerprinting. Prevalence of Cryptosporidium (19.8%) and Giardia (41.7%) in fecal samples from calves were approximately twice as high as fecal samples from cows (9.2% and 23.1%, respectively). In addition to age, multivariable logistic regression showed that higher stocking density and a higher number of replacement heifers were positively associated with fecal shedding of Cryptosporidium while longer calving interval, a winter/spring calving season, and higher numbers of replacement heifers were positively associated with shedding of Giardia. The dominant species and genotypes of Cryptosporidium and Giardia in feces from these cow-calf herds were Cryptosporidium ryanae (75%) and assemblage E for Giardia duodenalis (90%), which have low impact on public health compared with other zoonotic species/genotypes of these two parasites. We identified host and potential management practices that can be used to protect cattle health and reduce the risk of surface water contamination with protozoal parasites from cow-calf operations. In addition, this work updated the scientific data regarding the predominance of low zoonotic genotypes of Cryptosporidium and Giardia shed in the feces of commercial cow-calf herds on California rangeland and irrigated pasture.

Are Landowners, Managers, and Range Management Academics on the Same Page About Conservation?

On the Ground • Conservation of California rangelands hinges on partnerships among ranchers, agency and nongovernmental organization managers, and academics. • A “sustainable use” perspective on conservation was predominate among ranchers, whereas a more preservation-oriented perspective was common among managers; the perspective of academics was in between the two. • Conservation priorities among ranchers and managers largely overlapped, except that ranchers prioritized livestock production and ranch succession, and managers prioritized habitat protection. • Land use change was a shared concern among the three groups. • Opportunities for rangeland conservation included improving communication among diverse stakeholders and applying recent scientific developments to on-the-ground range management.

Seeding plants for long-term multiple ecosystem service goals

The historical management of agroecological systems, such as California's rangelands, have received criticism for a singular focus on agricultural production goals, while society has shifting expectations to the supply of multiple ecosystem services from these working landscapes. The sustainability and the multiple benefits derived from these complex social-ecological systems is increasingly threatened by weed invasion, extreme disturbance, urban development, and the impacts of a rapidly changing and increasingly variable climate. California's grasslands, oak savannas, and oak woodlands are among the most invaded ecosystems in the world. Weed eradication efforts are rarely combined with seeding on these landscapes despite support for the inclusion of the practice in a weed management program. Depending on seed mix choice, cost and long-term uncertainty, especially for native seed, is an impediment to adoption by land managers. We investigated four seeding mixes (forage annual, native perennial, exotic perennial, and exotic-native perennial) to evaluate how these treatments resist reinvasion and support the delivery of simultaneous multiple ecosystem services (invasion resistance, native richness, nitrogen fixing plants, pollinator food sources, plant community diversity, forage quality, and productivity). We found the increase of exotic and native perennial cover will drive resistance to an invading weedy summer flowering forb Centaurea solstitialis but provides a mixed response to resisting invasive annual grasses. The resistance to invasion is coupled with little tradeoff in forage productivity and quality and gains in plant diversity and native cover.

Estimation of the Requirement for Water and Ecosystem Benefits of Cow-Calf Production on California Rangeland

On the Ground • Beef production is perceived as using large amounts of water, and some studies recommend decreasing or ceasing meat consumption to decrease water use. • Water footprints include different types of water, including green water (i.e., precipitation used for plant growth), blue water (i.e., drinking water and irrigation water used to grow alfalfa and irrigated pasture), and grey water (i.e., freshwater required for integrating water pollutants to a level accepted by water quality standards). • A static model depicting blue and green water use for cow-calf production on California rangeland was developed. • In this study, green water, which is sourced from rainfall and not available for another use, contributed the largest component to the total water footprint of cow-calf production at each location. • It is important to consider the water use associated with beef production in the context of ecosystem services cattle provide to rangelands, such as preventing grassland conversion to shrub lands or woodlands, and the role that grazing cattle play in management of rangeland.

Field evaluation of a simple infiltration test and its relationship with bulk density and soil organic carbon in California rangelands

Water infiltration is commonly recommended as an indicator of soil dynamic properties and water cycling on rangelands. We investigated the utility of a two-trial single-ring infiltration test by evaluating the relationship between the first and second trial, the spatial variation in infiltration rates within and between sampling locations, and the relationship between water infiltration and bulk density and soil organic carbon (SOC) in the context of texture and water content. We measured water infiltration rates at 156 sites in 14 counties in California. We found a strong correlation between first and second infiltration trials. In pairwise correlations, both first and second trials were significantly correlated with SOC and bulk density. However, we did not find a significant relationship between water infiltration and either initial water content or soil texture. Model comparison revealed that in the context of soil texture, infiltration can serve as an indicator of bulk density and SOC; shorter water infiltration time (i.e., faster rate) is associated with decreased bulk density and increased SOC. Our results suggest that a single-ring infiltration test can be a useful, but imprecise, indicator of soil dynamic properties such as SOC and bulk density.

Raptor Use of Artificial Perches in California Rangelands in Fall

Author(s): Kross, Sara; Chapman, Renata; Craig, Andrea; Kelsey, T. Rodd | Abstract: Most raptor species rely on perches for hunting, resting, preening and roosting and in many agricultural areas the availability of adequate perches can limit raptor abundance and diversity. This has negative implications for both raptor conservation and the natural pest control services they can provide for farmers. Installing artificial perches on agricultural lands can therefore benefit both raptors and farmers. However, installing perches under current guidelines is difficult on California’s 38 million acres of rangelands, where rocky soil can be restrictive to anchoring poles belowground. We developed a novel method for modifying existing fenceposts to support raptor perches. These raptor perches are relatively light, easy to construct, can be transported in multiple pieces and assembled in the field. We installed 16 artificial raptor perches in four representative habitats on a California ranch to 1) determine if raptors will use artificial perches in each habitat; 2) test raptor preferences for different perch configurations; and 3) observe which raptor species utilize perches. Here, we share our perch design as well as our results from monitoring perches between August and November 2017. We found that American kestrels, great horned owls, barn owls, and red-tailed hawks utilized perches, as did a number of non-raptor species. Perch use by raptors was highest in an irrigated pasture and at a mid-elevation grassland site located on a hill. Perches at a low-elevation, unirrigated pasture with no slope and perches located in higher elevation oak woodland sites were used significantly less. In all habitats raptors preferred to utilize 15-foot perches over 20-foot perches. Raptors rarely utilized a lower perch when two were available on a single pole, suggesting that this added feature is not necessary to attract the species we observed.

Coping With Historic Drought in California Rangelands: Developing a More Effective Institutional Response

On the Ground Drought response is widely varied depending on both the characteristics of the drought and the ability of individual ranchers to respond. Assistance from institutions during drought has not typically considered preemptive, during, and post-drought response as a strategic approach, which recognizes biophysical, sociological, and economic complexities of drought. A USDA Southwest Climate Hub-sponsored workshop brought together a range of representatives from public and private institutions with drought response responsibilities to examine how those institutions could better support drought decision-making. Institutions can greatly improve their support for individual land managers by doing more systematic collecting and organizing of drought-related information as a basis for programs, and by collaborating to enhance both institutional and individual learning.

Coping With Drought on California Rangelands

On the Ground Rangeland livestock producers were among the first agricultural communities affected by California's multiyear drought. Rancher surveys and in-person interviews have identified key strategies for coping with and adapting to drought. Increasing flexibility, resource valuation, and information sharing are important components of building adaptive capacity. Web-based communication systems have provided new tools for peer-to-peer learning, public education, and extending knowledge to larger audiences. Insights from managers experiences are important for adaptation planning to enhance resilience of rangeland social-ecological systems to climate stresses.

Cattle as Dispersal Vectors of Invasive and Introduced Plants in a California Annual Grassland

Plant invasions are a threat to rangelands in California. Understanding how seeds of invasive plants are dispersed is critical to developing sound management plans. Domestic livestock can transport seeds long distances by ingesting and passing seeds in dung (endozoochory) or by the attachment of seeds to skin and fur (epizoochory). Our objective was to characterize the role of cattle as seed dispersers of both invasive and noninvasive species via endozoochory and epizoochory in a Sierra foothills rangeland. To quantify endozoochory, we sampled dung from two dry-season grazing periods and evaluated seed content by growing dung for 3 months in a greenhouse. To quantify epizoochory, we collected seeds directly from the fur of 40 cattle. We categorized the invasion status and functional groups of all species found and quantified landscape-scale vegetation composition in order to determine whether dispersal mode was associated with functional group, invasion status, or vegetation composition. Finally, we evaluated the potential for the noxious weed medusahead (Taeniatherum caput-medusae [L.] Nevski) to travel long distances on cattle fur using a detachment experiment with a model cow. We found that forbs were more likely to be dispersed by endozoochory, and invasive species were more likely to be dispersed by epizoochory. Medusahead was dispersed exclusively by epizoochory and was able to travel up to 160 m on a model cow. Our results suggest that cattle may be an important dispersal vector for both invasive and noninvasive plants.

Introducing cattle grazing to a noxious weed-dominated rangeland shifts plant communities

Invasive weed species in California's rangelands can reduce herbaceous diversity, forage quality and wildlife habitat. Small-scale studies (5 acres or fewer) have shown reductions of medusahead and yellow starthistle using prescribed grazing on rangelands, but little is published on the effects of pasture-scale (greater than 80 acres) prescribed grazing on weed control and plant community responses. We report the results of a 6-year collaborative study of manager-applied prescribed grazing implemented on rangeland that had not been grazed for 4 years. Grazing reduced medusahead but did not alter yellow starthistle cover. Medusahead reductions were only seen in years that did not have significant late spring rainfall, suggesting that it is able to recover from heavy grazing if soil moisture is present. Later season grazing appears to have the potential to suppress medusahead in all years. In practice, however, such grazing is constrained by livestock drinking water availability and forage quality, which were limited even in years with late spring rainfall. Thus, we expect that grazing treatments under real-world constraints would reduce medusahead only in years with little late spring rainfall. After 10 years of grazing exclusion, the ungrazed plant communities began to shift, replacing medusahead with species that have little value, such as ripgut and red brome.

Restoration of Native Plants Is Reduced by Rodent-Caused Soil Disturbance and Seed Removal

Granivory and soil disturbance are two modes by which burrowing rodents may limit the success of native plant restoration in rangelands. This guild of animals has prolific effects on plant community composition and structure, yet surprisingly little research has quantified the impact of rodents on plant restoration efforts. In this study, we examined the effects of seed removal and soil disturbance by the giant kangaroo rat (Dipodomys ingens) on native plant restoration in a California rangeland. Using experimental exclosures and stratifying restoration plots on and off rodent-disturbed soil, we assessed the individual and combined effects of seed removal and soil disturbance on seedling establishment of four native plant species. Across all species, biotic soil disturbance by kangaroo rats reduced seedling establishment by 19.5% (range = 1–43%), whereas seed removal reduced seedling establishment by only 6.7% (range = 4–12%). Rates of seed removal across species weakly paralleled kangaroo rat dietary preferences. These results indicate the indirect effects of burrowing rodents such as kangaroo rats on native seedling establishment via changes in soil properties may rival or exceed the direct effects of seed removal.

Erratum to: Integrated climate and land use change scenarios for California rangeland ecosystem services: wildlife habitat, soil carbon, and water supply

Erratum to: Integrated climate and land use change scenarios for California rangeland ecosystem services: wildlife habitat, soil carbon, and water supply

Integrated climate and land use change scenarios for California rangeland ecosystem services: wildlife habitat, soil carbon, and water supply

Context In addition to biodiversity conservation, California rangelands generate multiple ecosystem services including livestock production, drinking and irrigation water, and carbon sequestration. California rangeland ecosystems have experienced substantial conversion to residential land use and more intensive agriculture. Objectives To understand the potential impacts to rangeland ecosystem services, we developed six spatially explicit (250 m) climate/land use change scenarios for the Central Valley of California and surrounding foothills consistent with three Intergovernmental Panel on Climate Change emission scenario narratives. Methods We quantified baseline and projected change in wildlife habitat, soil organic carbon (SOC), and water supply (recharge and runoff). For six case study watersheds we quantified the interactions of future development and changing climate on recharge, runoff and streamflow, and precipitation thresholds where dominant watershed hydrological processes shift through analysis of covariance. Results The scenarios show that across the region, habitat loss is expected to occur predominantly in grasslands, primarily due to future development (up to a 37 % decline by 2100), however habitat loss in priority conservation errors will likely be due to cropland and hay/pasture expansion (up to 40 % by 2100). Grasslands in the region contain approximately 100 teragrams SOC in the top 20 cm, and up to 39 % of this SOC is subject to conversion by 2100. In dryer periods recharge processes typically dominate runoff. Future development lowers the precipitation value at

Update of the 2014 Drought on California Rangelands

On the Ground Droughts are common on California rangelands. The current drought in California is listed as severe or exceptional for most of the state. The drought has affected rangeland, and the livestock industry, more than other commodities. The actual costs associated with this drought are just beginning to be realized.

History of University of California Rangeland Extension, Research, and Teaching

On the Ground The Agricultural Extension Service at the University of California (UC) was established in Humboldt County in 1913 preceding the nationwide establishment of the extension service in 1914. Improving rangelands by controlling weeds and brush, seeding, fertilization, and grazing management has been a continuing theme of research by UC since the late 1800s. Restoration of annual-dominated grasslands with native perennials has been a recurring research theme that continues to challenge grassland researchers. The complexity of research questions and education programs increased when environmental issues including grazing effects on riparian areas, oak regeneration, wildlife habitat, and water quality began to influence range research and extension programs in the 1980s. A more diversified range extension audience evolved with the increase in small farms and ranches and diversification of agency staff in response to affirmative action.

History of Rangeland Management in California

On the Ground Spanish colonists brought cattle to California when they landed in San Diego in 1769, with two hundred head of cattle arriving by overland routes. Mexico, achieving independence, established rules to petition for land grants in California, paving the way for additional settlers by making land grants easier to obtain. The Gold Rush resulted in cattle numbers quadrupling and sheep numbers increasing more than 60-fold between 1850 and 1860. Multiple uses, such as agriculture crop production, impacted California rangelands. Public policies now influence management of approximately 38 million acres of privately and publicly owned rangelands.