Characterizing the boundary between California annual grassland and coastal sage scrub with differential profiles

Hobbs, Elizabeth

doi:10.1007/bf00044882

Cited by 39 publications

(25 citation statements)

References 28 publications

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“…The post-fire phase is well-studied (Christensen and Muller 1975, Malanson and O'Leary 1982, Keeley 1987, Moreno and Oechel 1994; however, much less is known about population dynamics between recurring fires. Shrub species recruit seedlings not only in mature coastal sage scrub stands (Malanson and Westman 1985) but also colonize grasslands (Oberbauer 1978, Hobbs 1986 , Callaway and Davis 1993, Zedler 1995. Shrub species recruit seedlings not only in mature coastal sage scrub stands (Malanson and Westman 1985) but also colonize grasslands (Oberbauer 1978, Hobbs 1986 , Callaway and Davis 1993, Zedler 1995.…”

Section: Introductionmentioning

confidence: 99%

Shrub Seedling Recruitment in Unburned Californian Coastal Sage Scrub and Adjacent Grassland

DeSimone¹,

Zedler²

1999

Ecology

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Shrub species of southern Californian coastal sage scrub recruit seedlings immediately after fire but also recruit in unburned coastal sage scrub stands and annual grasslands. We examined the influence of natural disturbances other than fire on shrub seedling establishment, especially the role of small-scale disturbance. Our goals were to determine: (1) whether seedling recruitment is associated with gaps in grassland, scrub, and grassland-scrub ecotones; (2) the identity of gap-creating agents; (3) the influences of biotic (vertebrates and ants) and abiotic (late spring moisture) disturbances on seedling establishment; and (4) whether disturbance effects vary spatially, both among and within (gap vs. nongap microsites) the three zones. We censused natural seedlings and vegetation gaps monthly in belt transects for two growing seasons and also measured seed banks at three 16-yr-old sites of adjacent grassland and coastal sage scrub. We initiated factorial experiments at one site to determine effects of animals, gaps, and late spring moisture on seed and seedling numbers. Gap-creating agents varied among the three zones, but seedlings were associated with gaps in each. Animals, especially small mammals, were important in creation and maintenance of gaps. Animal effects varied among but not within zones. Small mammals positively affected seedling recruitment in the grassland (germination on pocket gopher mounds) and negatively affected seed numbers of species with larger and multipleseeded propagules in the ecotone and scrub; they created and/or maintained gaps in all three zones. Late spring moisture did not play an important role in shrub seedling recruitment in any zone. Because coastal sage shrub seedlings lose transpiring surfaces during drought, they may be less vulnerable than evergreen mediterranean shrubland species to the variability in both annual and seasonal extent of rainfall that is typical of mediterranean climates.

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Section: Introductionmentioning

confidence: 99%

Shrub Seedling Recruitment in Unburned Californian Coastal Sage Scrub and Adjacent Grassland

DeSimone¹,

Zedler²

1999

Ecology

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“…Zonneveld 1974;Kent et al 1997). The ʻsoftnessʼ of a boundary may be an expression of relevant processes like disturbance, invasion, or disintegration; transitional zones are frequently associated with problems of environmental management, and a proper map representation can be advantageous (Weaver & Albertson 1956;van der Maarel 1976;Hobbs 1986;Fortin et al 2000). Transitional zones are highly affected by environmental change, since species are often at the limit of their tolerance.…”

Section: Introductionmentioning

confidence: 99%

Mapping the floristic continuum: Ordination space position estimated from imaging spectroscopy

et al. 2007

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Objective: To present a non-classificatory technique of map representation of compositional patterns of vegetation as no two plant species assemblages are completely alike and gradations often occur. Variation is depicted as continuous fields instead of classes. Location: Murnauer Moos, Bavaria. Methods: The study combined vegetation ecology and remote sensing methods. The gradual representation of compositional patterns was based on techniques of ordination and regression, instead of mapping class fractions. The floristic field data were collected in relevés and subjected to three-dimensional non-metric multidimensional scaling (NMS). The reflectance information corresponding to plots was gathered from remotely sensed imagery with a high spectral resolution. Reflectance values in numerous wavelengths were related to NMS axes scores by partial least squares regression analysis. The regression equations were applied to the imagery and yielded three grey-scale images, one for each ordination axis. These three images were transformed into a red, green, and blue colour map with a specific colour for each position in the ordination space. Similar colours corresponded to similar species compositions. Results: Compositional variation was mapped accurately (R 2 = 0.79), using continuous fields. The results took account of various types of stand transitions and of heterogeneities within stands. The map representation featured relatively homogeneous stands and abrupt transitions between stands as well as within-stand heterogeneity and gradual transitions. Conclusions: The use of NMS in combination with imaging spectroscopy proved to be an expedient approach for nonclassificatory map representations of compositional patterns. Ordination is efficiently extended into the geographic domain. The approach in abandoning pre-defined plant communities is able to reconcile mapping practice and complex reality.

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“…1969). After t h e introduction of sheep t o t h e island in t h e 1850s (Dunkle 1950), most of t h e chaparral and coastal sage vegetation was converted t o grassland by grazing (Hobbs 1986). The island has been protected from fire for at least t h e last 100 years.…”

Section: Study Areamentioning

confidence: 99%

Mass Movement Effects on Grassland Vegetation and Soils on Santa Cruz Island, California

Beatty

1988

Annals of the Association of American Geographers

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Grasslands are characteristically heterogeneous, with disturbances ranging from largescale fire and grazing t o the smaller patches of gopher and ant mounds (Baxter and Hole 1967; Zedler and Loucks 1969; Platt 1975; King 1977; Foster and Stubbendieck 1980). Little has been done on grassland responses to heterogeneity caused by mass movement.The purpose of this study is twofold: (1) t o identify the changes in surface soil properties due to mass movement disturbances, and (2) to investigate the patterns in grassland vegetation

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Characterizing the boundary between California annual grassland and coastal sage scrub with differential profiles

Cited by 39 publications

References 28 publications

Shrub Seedling Recruitment in Unburned Californian Coastal Sage Scrub and Adjacent Grassland

Shrub Seedling Recruitment in Unburned Californian Coastal Sage Scrub and Adjacent Grassland

Mapping the floristic continuum: Ordination space position estimated from imaging spectroscopy

Mass Movement Effects on Grassland Vegetation and Soils on Santa Cruz Island, California

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