Pattern in Desert Perennials

Influence of leaf-cutting ants (Atta mexicana) on performance and dispersion patterns of perennial desert shrubs in an inter-tropical region of Central Mexico

“…The apparently random dispersion showed by Acacia constricta and Cercidium praecox, could correspond to the pattern suggested by Anderson (1971) and Barbour (1973) for populations of 'medium-aged' shrubs. However, it could be due to several causes such as a homogeneous ('fine-grained') perception of the environment by the plants, or even to artifacts of the method caused by the relatively small number of individuals of these species recorded (12 of A. constricta and six of C. praecox) in the stand.…”

“…Woodell et al, 1969;Anderson, 1971;King & Woodell;1973;Skarpe, 1991; but see Zhang & Skarpe, 1995 for counterevidence). According to this idea, seed dispersion and the availability of suitable habitats for the seedlings, would initially produce an aggregated distribution, but density dependent mortality would modify this pattern, turning it into a random distribution of shrubs of intermediate size.…”

High-resolution images reveal rate and pattern of shrub encroachment over six decades in New Mexico, U.S.A.

“…A single image would show only one of these patterns, possibly leading to erroneous conclusions about the causes of spatial pattern. This temporal dynamic has been assumed to reflect the increasing importance of competition as shrubs mature (Anderson, 1971;Phillips & McMahon, 1981). An analysis using estimates of individual shrub centers instead of patch centroids produced very similar results, so the observed change in spatial pattern was probably not due to overlapping adjacent shrubs, as has been suggested by Cox (1987).…”

“…Differences in type of pattern with plant age have also been observed. Stands composed of young shrubs tend to have an aggregated pattern, medium-aged a random pattern, and old shrubs a regular pattern, suggesting the increasing importance of competition as shrubs mature (Anderson, 1971;Phillips & MacMahon, 1981;Fowler, 1986). Remote sensing imagery can be used to examine the dynamics of spatial pattern over long time periods (Rango et al, 2002).…”

Clump spacing in a desert dwarf shrub community

“…Phillips & MacMahon, 1981) a continuation of this competitive process should ultimately generate a regular pattern. However, Anderson (1971) was sceptical of claims for regularity, and also doubted the prime role of competition in causing a random distribution pattern in mature vegetation. We investigated pattern in an environmentally homogeneous patch of desert vegetation (Fig.…”