Southern California Mountains and Foothills Assessment: Habitat and Species Conservation Issues

Stephenson, John; Calcarone, Gena M.

doi:10.2737/psw-gtr-172

Cited by 54 publications

(59 citation statements)

References 76 publications

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“…First, the degree of redistribution was independent of initial elevation (Table 1) (15). The fire frequency in the upper transect has not diverged markedly from the historic regime, and forested sections of the transect are not thought to have experienced large demographic changes from fire suppression (21). Third, we are unaware of previous studies that have attributed a net altitudinal redistribution of vegetation (Fig.…”

Section: Discussionmentioning

confidence: 91%

Rapid shifts in plant distribution with recent climate change

Kelly

Goulden²

2008

Proc. Natl. Acad. Sci. U.S.A.

1,041

793

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A change in climate would be expected to shift plant distribution as species expand in newly favorable areas and decline in increasingly hostile locations. We compared surveys of plant cover that were made in 1977 and 2006 -2007 along a 2,314-m elevation gradient in Southern California's Santa Rosa Mountains. Southern California's climate warmed at the surface, the precipitation variability increased, and the amount of snow decreased during the 30-year period preceding the second survey. We found that the average elevation of the dominant plant species rose by Ϸ65 m between the surveys. This shift cannot be attributed to changes in air pollution or fire frequency and appears to be a consequence of changes in regional climate.plant migration ͉ range shift C limate controls the distribution of many plants (1, 2). Future changes in climate are projected to cause changes in vegetation distribution (3). The global mean land surface has warmed 0.27°C per decade since 1979 (4), but it is unclear whether this change has caused widespread shifts in plant distribution (5). Parmesan and Yohe (6) compiled studies on many species, including alpine herbs, birds, and butterflies, and found an average poleward shift of 6.1 km per decade. Several studies have attributed widespread changes in plant growth or mortality to climate change (7), but these efforts have focused on general trends within biomes rather than identifying spatially coherent redistribution patterns. Studies of plant phenology have attributed longer growing seasons, earlier onset of flowering, and earlier harvest to climate warming (5, 6). The few studies that have shown evidence of plant shifts have focused on the edges of plant ranges (8-10). The lack of evidence of widespread plant range shifts may reflect the limited dispersal of plants (11,12), or it may simply reflect the paucity of long-term records of plant distribution.The Deep Canyon Transect in Southern California's Santa Rosa Mountains spans several plant communities and climates (13) and provides an excellent opportunity to investigate the climatic controls on plant distribution (2, 14). The transect rises from 244 m to 2,560 m over 16 km, climbing through desert scrub, pinyon-juniper woodland, chaparral shrubland, and conifer forest. The overall climate is arid and semiarid, with predominantly cool-season precipitation. The annual precipitation, proportion of precipitation falling as snow, and probability of frost increase with increasing elevation, and the annual mean temperature and interannual precipitation variability decrease with increasing elevation [supporting information (SI) ResultsA total of 141 species were recorded along the transect in 2006-2007. Many of these species were found at only one or two elevations. Ten of the species were dominant at three or more elevations, and we focused our analysis on these plants (Fig. 1).The distributions of some of these species were similar; for example, Ceanothus greggii and Quercus cornelius-mulleri had broadly similar distributions throughout ...

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Section: Discussionmentioning

confidence: 91%

Rapid shifts in plant distribution with recent climate change

Kelly

Goulden²

2008

Proc. Natl. Acad. Sci. U.S.A.

1,041

793

View full text Add to dashboard Cite

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“…Wildfires generally are recognized as enhancing quality of habitat for mountain sheep (Bleich and Holl 1982;Wakelyn 1987;Smith et al 1999;Holl et al 2004;DeCesare and Pletscher 2006;Bleich et al 2008). Under natural conditions, wildfires likely occurred every 20-60 years in chaparral regions of southern California and resulted in a mosaic of vegetation of differing successional stages (Stephenson and Calcarone 1999). Such fires probably were beneficial to mountain sheep because they reduced density and height of vegetation with a resultant increase in visibility and promoted growth of nutritious forage species (Holl et al 2004).…”

Section: Discussionmentioning

confidence: 98%

Mining activity and habitat use by mountain sheep (Ovis canadensis)

et al. 2008

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We studied mountain sheep in the vicinity of three high-wall limestone mines in San Bernardino County, CA, USA to evaluate factors that influenced habitat use and, specifically, to investigate the influence of mining activity on distribution of those specialized ungulates. We used aerial telemetry data to estimate a resource selection function by fitting a logistic regression model and then comparing environmental characteristics at observed sheep locations to those at random locations. Distribution of mountain sheep was most influenced by a fire in 1999 that resulted in an area they avoided. Mountain sheep used steeper slopes, areas of lower terrain roughness, higher elevations, and areas closer to escape terrain than were random points. In contrast, sheep avoided areas near roads (federal and state highways, local roads, and off-road vehicle trails) but used areas near hiking trails and a railway. Water sources had the smallest effect of the factors considered, with sheep being associated with areas further from water points than were random locations. The disturbed area associated with the mines had a moderate influence on distribution, with sheep being associated with areas closer to the mine than were random points. Mining activities can alter terrain features and vegetation structure or composition in a way that promotes occupancy by sheep if they create steep slopes and rugged terrain (escape terrain) or reduce vegetation density or height (i.e., improve visibility). Whether increased occupancy reflects a benefit depends on the demographic responses of those sheep to the resources and conditions available on mine sites; information about those responses remains lacking.

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“…The increased density of small trees (ladder fuels) may have enhanced the potential for stand-replacing crown fires that result in mortality of even large trees . This shift in forest structure from shadeintolerant pines (Pinus jeffreyi, P. coulteri, P. ponderosa) to shade-tolerant species, and increased stem density, has been documented in Cuyamaca Rancho State Park (CRSP), in the Peninsular Ranges within San Diego County, California, USA (Krofta, 1995;Stephenson and Calcarone, 1999). For example, four previously mapped fires affected the ''West Mesa'' area of the Park in the 20th century (prior to 2003) including the Conejos Fire of 1950, Peak Fire of 1986, and a prescribed fire conducted in 1988; areas outside of these fires have not burned since records have been kept, e.g., prior to 1911.…”

Section: Introductionmentioning

confidence: 96%

“…Based on the literature, it was expected that species, fire severity, previous stand age, and tree density would be the most important factors determining tree mortality (Parsons and DeBenedetti, 1979;Swezy and Agee, 1990;Savage, 1997;Stephenson and Calcarone, 1999;Barbour and Minnich, 2000;Minnich et al, 2000;Taylor, 2000). Very recently burned areas are expected to have lower tree densities, and therefore experience lower fire severity, while stands of young trees can be dense and their small trees could be susceptible to higher fire-caused mortality than older stands of larger trees.…”

Section: Introductionmentioning

confidence: 99%