Water‐Repellent Soils, Fire, and Annual Plant Cover in a Desert Scrub Community of Southeastern California

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology.Abstract. Surveys relating soil wettability and the establishment of annual plants were conducted on soil hummocks under burned and unburned shrubs and trees in a desert scrub community 4 years following a fire. Hummocks under burned and unburned individuals of Larrea divaricata, Prosopis juliflora, and Cercidium floridum were nearly devoid of established annual vegetation, whereas the surrounding soil was densely populated with several species of annual plants, predominately Sphaeralcea emoryi. Hydrophobic (water-repellent) layers of soil were found at various depths in the barren hummocks. In general, the layers were further below the soil surface under burned shrubs or trees, and the degree of water repellency was greater. The soil surrounding the hummocks did not contain hydrophobic layers. The mosaic of annuals in the desert scrub vegetation is probably the result of a reduction of available soil moisture due to the formation of water-repellent soils under the shrubs. The effect was more pronounced following fire. LITERATURE CITED Bond, R. D. 1964. The influence of the microflora on the physical properties of soils. II. Field studies on water repellent sands. Australian J. Soil Res. 2: 123-131. Bond, R. D., and J. R. Harris. 1964. The influence of the microflora on physical properties of soils. I. Effects associated with filamentous algae and fungi.

Impacts of invasive alien plants on water quality, with particular emphasis on South Africa

“…High intensity fires can lead to the development of water repellency, or 'hydrophobicity' in soil (Adams et al, 1970;DeBano and Conrad, 1976;DeBano, 1981;Keeley, 2009). The waterrepellent layer is formed as hydrophobic materials (such as resins) are volatized during fire near the soil surface and then distil downward according to the temperature gradient within the soil profile.…”

On using the effective contact angle and the water drop penetration time for classification of water repellency in dune soils

“…It is the time required for complete infiltration of a water drop placed on the surface of soil material. An example of classification of water repellency with the use of the WDPT is given by Adams et al (1969), who suggest the following index: when the WDPT exceeds 60 seconds, the soil is labelled strongly repellent; when the WDPT is less than 60 s but longer than 10 s, the soil is termed slightly repellent; and when the WDPT is less than 10 seconds, the soil is called non-repellent. This index is, of course, an arbitrary subdivision; any chosen number of seconds can be used to characterize water repellency.…”

Fire-mediated effects of shrubs, lichens and herbs on the demography of Hypericum cumulicola in patchy Florida scrub

“…In many communities, the spatial structure and population dynamics of herbaceous species are aected by asymmetric interactions with shrubs (Knoop and Walker 1985;TielboÈ rger and Kadmon 1995;Menges and Kimmich 1996). For example, shrub shade and interference limit the access of herbs to light, soil moisture, and nutrients (Adams et al 1970;Belsky 1994;Roux et al 1995). Allelopathic agents released from some shrubs may inhibit seed germination and decrease growth (Tanrisever et al 1988;Williamson 1990; but see Keeley and Keeley 1989).…”