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George M.R.,University of California at Davis | Larsen R.E.,UC Cooperative Extension | McDougald N.M.,UC Cooperative Extension | Vaughn C.E.,Hopland Research and Extension Center | And 5 more authors.
Rangelands | Year: 2010

Various changes have been proposed to the Noninsured Crop Disaster Assistance Program (NAP), administered by USDA Farm Services Agency (FSA) that would make it more compatible with USDA conservation programs. Meteorological drought is usually defined on the basis of the degree of dryness compared to some normal or average amount and the duration of the dry period. Range forage production is strongly influenced by the amount and timing of precipitation. The USDA FSA NAP provides payments for crop or grazing feed losses that are not covered by a federal crop insurance program. The FSA should consider amending the NAP program in California so that it requires maintenance of minimum RDM levels and starts payments when forage losses exceed 50% of the available forage (total produced minus RDM target). It is crucial to the credibility of the NAP program that it be based on locally accurate information collected using standard methods. Source


Leffler A.J.,U.S. Department of Agriculture | Leffler A.J.,University of Alaska Anchorage | James J.J.,U.S. Department of Agriculture | James J.J.,Sierra Foothill Research and Extension Center | And 2 more authors.
Ecology | Year: 2014

Functional differences between native and exotic species potentially constitute one factor responsible for plant invasion. Differences in trait values between native and exotic invasive species, however, should not be considered fixed and may depend on the context of the comparison. Furthermore, the magnitude of difference between native and exotic species necessary to trigger invasion is unknown. We propose a criterion that differences in trait values between a native and exotic invasive species must be greater than differences between co-occurring natives for this difference to be ecologically meaningful and a contributing factor to plant invasion. We used a meta-analysis to quantify the difference between native and exotic invasive species for various traits examined in previous studies and compared this value to differences among native species reported in the same studies. The effect size between native and exotic invasive species was similar to the effect size between co-occurring natives except for studies conducted in the field; in most instances, our criterion was not met although overall differences between native and exotic invasive species were slightly larger than differences between natives. Consequently, trait differences may be important in certain contexts, but other mechanisms of invasion are likely more important in most cases. We suggest that using trait values as predictors of invasion will be challenging. © 2014 by the Ecological Society of America. Source


Richmond O.M.W.,University of California at Berkeley | Richmond O.M.W.,U.S. Fish and Wildlife Service | Tecklin J.,Sierra Foothill Research and Extension Center | Beissinger S.R.,University of California at Berkeley
Ecological Applications | Year: 2012

Impacts of livestock grazing in arid and semiarid environments are often concentrated in and around wetlands where animals congregate for water, cooler temperatures, and green forage. We assessed the impacts of winter-spring (November-May) cattle grazing on marsh vegetation cover and occupancy of a highly secretive marsh bird that relies on dense vegetation cover, the California Black Rail (Laterallus jamaicensis coturniculus), in the northern Sierra Nevada foothills of California, USA. Using detection- nondetection data collected during repeated call playback surveys at grazed vs. ungrazed marshes and a "random changes in occupancy" parameterization of a multi-season occupancy model, we examined relationships between occupancy and habitat covariates, while accounting for imperfect detection. Marsh vegetation cover was significantly lower at grazed marshes than at ungrazed marshes during the grazing season in 2007 but not in 2008. Winter- spring grazing had little effect on Black Rail occupancy at irrigated marshes. However, at nonirrigated marshes fed by natural springs and streams, grazed sites had lower occupancy than ungrazed sites. Black Rail occupancy was positively associated with marsh area, irrigation as a water source, and summer vegetation cover, and negatively associated with marsh isolation. Residual dry matter (RDM), a commonly used metric of grazing intensity, was significantly associated with summer marsh vegetation cover at grazed sites but not spring cover. Direct monitoring of marsh vegetation cover, particularly at natural spring- or streamfed marshes, is recommended to prevent negative impacts to rails from overgrazing. © 2012 by the Ecological Society of America. Source


Vasquez E.A.,Humboldt State University | Sheley R.L.,Ecologist | James J.J.,Research Leader | Svejcar T.J.,U.S. Department of Agriculture | Pellant M.L.,Sierra Foothill Research and Extension Center
Rangelands | Year: 2012

Designing restoration strategies based on successional management requires an initial assessment of the functional status of ecological attributes across a management unit. Seriously damaged rangelands may not have the capacity for self-repair and often experience continued degradation. Rangeland health assessment uses the ecological site concept in combination with professional knowledge of soils and vegetation properties to evaluate the biological and physical components of a site relative to a reference state. Once the soils and ecological site(s) occurring in the evaluation area have been identified, reference sheets provided in ecological site descriptions are then used to identify the natural range of variability of indicators in the reference state. Obtaining or developing an ecological site reference sheet facilitates consistent application of the process throughout the ecological site or management unit by integrating all available sources of data and knowledge to generate a description of the natural range of expected variation for each indicator of rangeland health. Source


McCreary D.D.,Sierra Foothill Research and Extension Center | Tietje W.,UCCE | Davy J.,UCCE | Larsen R.,UCCE | And 3 more authors.
California Agriculture | Year: 2011

Blue oak is regenerating poorly in portions of its range. Techniques to artificially regenerate trees by collecting acorns, growing seedlings in a nursery and then planting them are effective but costly. Improving the growth and survival rate of existing volunteer seedlings in woodlands could be more cost efficient and therefore more widely used. We tested tree shelters and weed control treatments over 3 years at six woodland sites to evaluate whether they helped blue oak seedlings grow into saplings. The tree shelters enhanced height growth, and weed control improved survival. Together, these two techniques can improve the chances for managing blue oak sustainably and conserving this native California oak for future generations. Source

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