Oak Woodlands and Forests

Allen-Díaz, Barbara; Standiford, Richard B.; Jackson, Randall D.

doi:10.1525/california/9780520249554.003.0012

Cited by 37 publications

(27 citation statements)

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“…Identifying changes in demography and spatial structuring of recruitment around microenvironments through modeling and field investigation is a promising technique to reduce uncertainty around species response to warming. Our study joins a body of growing evidence on the importance of riparian zones and groundwater for woodland systems (Allen-Diaz et al 2007, Howard and Merrifield 2010, Miller et al 2010, and highlights the potential roles of high groundwater levels and topographic diversity in regulating a system's response to a warming climate. At the landscape planning scale, managers may consider prioritizing protection and restoration of areas with the presence of climate microrefugia, including high groundwater and topographic diversity, to increase a systems' resilience to warming.…”

Section: Discussionsupporting

confidence: 63%

“…Blue oak is an endemic California species covering ;1,480,000 hectares (Davis et al 1998) and supports an exceptionally rich biotic community (Zack 2002, Allen-Diaz et al 2007). Diverse stand structure (i.e., presence of multiple age and size classes) in blue oak woodlands is important to conserving the full complement of ecological niche spaces and species assemblage (Tietje andVreeland 1997, Allen-Diaz et al 2007).…”

Section: Introductionmentioning

confidence: 99%

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Demography linked to climate change projections in an ecoregional case study: integrating forecasts and field data

McLaughlin

Morozumi

MacKenzie³

et al. 2014

Ecosphere

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Abstract. Anticipating species movement under climate change is a fundamental concern in 21st century conservation. For blue oak (Quercus douglasii ), an endemic, flagship species in California, we modeled potential responses to future climate, then tested the fit of those projections to empirical field data from natural populations. Specifically, we tested how well species forecasts captured observed recruitment and adult tree mortality, and whether recruitment was structured spatially as a function of fine-scale microtopographic and hydrologic environments. In this ecoregional case study, observed demographic patterns were broadly consistent with theoretical expectations. Adult survivorship was three times lower in areas forecasted to be least suitable as a result of climate change than in areas projected to become suitable. This novel field validation exercise documents patterns of adult tree mortality consistent with model predictions of an emergent shift in distribution. Seedlings and saplings showed evidence of spatial structuring into local refugia in areas projected to contract, suggesting that climate change may reshape how blue oak associates with California landscapes and highlighting the potential importance of micro-environmental diversity in enhancing species resilience to warming.

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Section: Discussionsupporting

confidence: 63%

Section: Introductionmentioning

confidence: 99%

Demography linked to climate change projections in an ecoregional case study: integrating forecasts and field data

McLaughlin

Morozumi

MacKenzie³

et al. 2014

Ecosphere

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“…Vegetation structure is a mostly annual grass ground layer interspersed with sparse oak trees (Allen-Diaz et al 2007). The climate is Mediterranean, with cool, wet winters and hot, dry summers.…”

Section: Site Descriptionmentioning

confidence: 99%

“…The oak savanna covers 4 million hectares, approximately 10% of the land area in California (Allen-Diaz et al 2007). It is valuable grazing land and filters two thirds of the state's drinking water (FRRAP 1988).…”

Section: Introductionmentioning

confidence: 99%

Nitrogen deposition across scales: hotspots and gradients in a California savanna landscape

Tulloss

Cadenasso

2015

Ecosphere

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Abstract. Nitrogen (N) deposition is a key component of global change. In order to predict the consequences of those changes, the spatial and temporal patterns of N deposition need to be quantified. We investigated patterns of inorganic-N deposition across two spatial scales-regional and local-in six oak savanna sites across north-central California during the 2008-2009 wet season. We found a regional-scale deposition gradient in which sites closer to urban and agricultural sources received higher rates of deposition than more remote sites. Additionally, sites closer to urban sources received a greater proportion of N as NO 3 À -N. At the local, within-site scale, canopy understories received greater N inputs compared to the adjacent open grassland. Temporal heterogeneity in N deposition was also found. Deposition exhibited a strong seasonal pattern, corresponding to the distinct wet-dry cycles characteristic of this Mediterranean ecosystem. While these spatial and temporal results were expected, it was surprising that the magnitude of the hotspot effect under oaks changed across the regional gradient. At the high deposition end of the regional gradient proportionally more N was received beneath canopies than at the low end of the gradient. This nonlinearity between local and regional scales demonstrates the importance of landscape context for understanding within-site dynamics and the need for multi-scalar research approaches. Incorporating regional-scale landscape context and local-scale vegetation structure, as well as temporal variability, into our understanding of deposition patterns is crucial for monitoring efforts as well as addressing potential ecological effects of increased N deposition.

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“…A cross California, annual rangelands cover approximately 16 million acres and are among the most species-rich ecosystems in the state, supporting thousands of plant and animal species (Allen-Diaz et al 2007;Barrett 1980;Garrison and Standiford 1996). California's modern-day rangelands are largely dominated by nonnative annuals, which some believe replaced previously diverse native forb and grass communities (Bartolome 1987;Schiffman 2007).…”

Section: Introducing Cattle Grazing To a Noxious Weed-dominated Rangementioning

confidence: 99%

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

Davy¹,

Roche²,

Robertson³

et al. 2015

Cal Ag

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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. The spread of invasive weeds changes plant community composition and can lead to shifts in soil moisture and nutrient availability as well as the suppression of both native plants and other desirable and more palatable nonnatives, thereby reducing herbaceous diversity, wildlife habitat, forage quality and agricultural productivity (DiTomaso 2000;Eviner et al. 2010;George 1992). Across California's annual rangelands, noxious weeds have been estimated to reduce livestock carrying capacity by as much as 50% to 80% (DiTomaso 2000;George 1992;Hironaka 1961;Major et al. 1960). Research Article

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Oak Woodlands and Forests

Cited by 37 publications

References 0 publications

Demography linked to climate change projections in an ecoregional case study: integrating forecasts and field data

Demography linked to climate change projections in an ecoregional case study: integrating forecasts and field data

Nitrogen deposition across scales: hotspots and gradients in a California savanna landscape

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

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