Co‐development of alluvial fan surfaces and arid botanical communities, Stonewall Flat, Nevada, USA

Abstract

Arid alluvial fan and fluvial dry wash surfaces in Stonewall Flat, Nevada, USA, are characterized using surface geomorphic surveys, soil pits, botanical line surveys, and varnish microlamination dating techniques. Active and abandoned washes, and active fan surfaces are dominated by primary geomorphic processes of high‐energy sedimentation from flash floods. These surfaces are characterized by bar and swale topography, a lack of stone pavements, soil horizons, and rock varnish. Younger terraces and slightly older intermediate fan surfaces are in transition from primary sedimentation processes to lower energy secondary surface‐modifying processes of sheet wash and eolian transport and deposition. These surfaces are characterized by faint to no bar and swale topography, incipient to moderately well‐developed pavements and soil horizons, and abundant coppices. Old and stable fan surfaces are dominated by lower energy secondary processes and manifest well‐developed pavements, soils, and sparse coppices around widely distributed shrubs. Varnish microlamination dating yields ages of 13·15 ka for intermediate fan surfaces and 25·55 to 86·75 ka for stable fan surfaces. Plant communities co‐developing with these surfaces affect and are affected by both primary and secondary geomorphic fan processes. Relatively active surfaces contain few woody species. Co‐dominance of shrubs and annuals with abundant annuals between the shrubs is characteristic of surfaces transitional from primary processes to secondary processes. Stable surfaces dominated by secondary processes are characterized by woody perennials, with long‐lived woody species inhabiting the oldest surfaces. Feedback mechanisms between early botanical communities and eolian deposition affect coppice and pavement development. In turn, these surface features control both the composition and distribution of botanical communities on older, more stable surfaces. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.

Architectural analysis of a Triassic fluvial system: The Sherwood Sandstone of the East Midlands Shelf, UK

“…It is also conceivable (based on modern dryland systems) that overbank regions were subject to microbial crust development rather than plant colonisation (cf. Dickerson et al 2013). However, despite conditions possibly being favourable to the growth of microbial communities no such evidence is also observed, perhaps suggesting that the outcrop did indeed occupy a position within the braid system.…”

Emergent geomorphic–vegetation interactions on a subalpine alluvial fan

“…It follows that the two transects should have very different plant communities including biodiversity. In the literature, there are few observations of this effect, but on an arid environment alluvial fan surface, Dickerson et al (2013) found that sites in the more frequently disturbed channel zones had similar plant communities that were, in turn, different to those found on older and more stable surfaces. Figure 1 considers only time since perturbation as the variable that influences the development of plant communities.…”

“…In the literature, there are few observations of this effect, but on an arid environment alluvial fan surface, Dickerson et al . () found that sites in the more frequently disturbed channel zones had similar plant communities that were, in turn, different to those found on older and more stable surfaces.…”

“…The time since the last effective perturbation, which may be a geomorphic perturbation, is a critical parameter in plant succession (e.g. Jones, 1980;Burga et al, 2010;Dickerson et al, 2013). However, whilst perturbation can lead to substantial ecosystem losses if of too high a magnitude, it may also provide crucial ecosystem resources.…”

“…Lacoste and Salanon, 1969;Garcia-Aguirre et al, 2007) and plant growth (e.g. Howard and Mitchell, 1985;Dickerson et al, 2013), provided the deposition rate is not too great (e.g. Viles et al, 2008).…”