Spatial and Temporal Variation of Seed Distributions in Sonoran Desert Soils

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.. Wiley is collaborating with JSTOR to digitize, preserve and extend access to Journal of Biogeography.ABSTRACT. Samples taken in seventeen different microhabitats in the Sonoran Desert, NW of Tucson, Arizona (U.S.A.), revealed large variation in spatial (78-fold) and temporal (28-fold) patterns of seed distribution. Seed densities were lowest in normally dry washes and open areas between shrubs, were intermediate between shrubs, and were highest in artificial and naturally occurring depressions in the soil surface. There were microsites with high seed densities within microhabitats of low overall seed density. Differences between microhabitats were greatest during periods of high seed production and tended to disappear in seasons when rainfall was low.Seed densities were not correlated with shrub canopy volume, but were correlated with the dimensions of microtopographic depressions. Seeds which were small, or round, tended to form higher density patches than large or long seeds.

The fate of seeds in the soil: a review of the influence of overland flow on seed removal and its consequences for the vegetation of arid and semiarid patchy ecosystems

“…A strong relationship was found between the magnitude of seed transport by runoff and rainfall and slope characteristics. Similar to what happens to soil particles (Govers, 1989;Parsons et al, 1993;de Vente and Poesen, 2005;Boix-Fayos et al, 2006), seed losses increased as slope angle (García-Fayos et al, 1995;Jiao et al, 2011;Han et al, 2011;but Cerdà and García-Fayos, 1997) and rain duration and intensity increased (García-Fayos et al, 1995;Jiao et al, 2011;Han et al, 2011), but it decreased with soil surface roughness (Reichman, 1984;Chambers, 2000;Aerts et al, 2006;Isselin-Nondedeu et al, 2006;Isselin-Nondedeu and Bédécarrats, 2007) and with total slope length (García-Fayos et al, 1995). Soil texture also influenced seed losses, since larger soil particles increased the amount of seeds trapped in the soil (Chambers et al, 1991;Traba et al, 2006).…”

“…Under these conditions, seeds in the seed bank or resting on the soil surface after primary dispersal are exposed to overland flow, especially in bare patches where high rates of runoff and sediment transport have been reported (Cerdà, 1997;Calvo-Cases et al, 2003;Boix-Fayos et al, 2005;Bochet et al, 2006). The first evidence that runoff may act as a vector of seed transport was indirect and based on observations of seed dispersal strategies in runoff-prone areas (Friedman and Orshan, 1975;Friedman and Stein, 1980), comparisons of plant distribution with different dispersal mechanisms between slopes and wadis (Reichman, 1984), or descriptions of seed distribution patterns in different microhabitats (Ellner and Schmida, 1981) in desert ecosystems worldwide. In the 1990s, it was argued that seed removal by runoff led to seed loss and might explain the lack or scarcity of vegetation on semiarid and arid hillslopes (Debusche and Lepart, 1992;Francis, 1991;Chambers and Mac Mahon, 1994).…”

“…Our focus will be placed on drylands, because secondary dispersal has been recognized as a significant part of dispersal in environments with sparse vegetation (Nelson and Chew, 1977;Reichman, 1984;Chambers et al, 1991).…”

Emergence dynamics and bet hedging in a desert bee, Perdita portalis

“…Desert annual plants have been model organisms for testing the predictions of bet-hedging models and the empirical results support many of the theoretical expectations. For example, many desert annuals have seed banks (Nelson & Chew 1977;Freas & Kemp 1983;Reichman 1984;Price & Reichman 1987), seed germination is induced by rainfall (Freas & Kemp 1983;Philippi 1993), not all viable seeds germinate in any one year (e.g. bet hedging; Freas & Kemp 1983), seeds that do not germinate under good conditions in the ¢rst year germinate under the same conditions in subsequent years (Philippi 1993), germination is age dependent (Philippi 1993), seed germination patterns may be heterogeneous, such that conditions that trigger emergence in one species may not be the same as those that trigger emergence in another species (Venable et al 1993;Pake & Venable 1996) and germination may be`predictive', such that higher germination occurs in years that are favourable for reproduction (Venable & Lawlor 1980;Pake & Venable 1996).…”

Seed predation in a Mediterranean pasture: can ants modify the floristic composition of soil seed banks?

“…As spatial heterogeneity changes the spatial pattern of seed accumulation, ant predation would probably be spatially modified through ant foraging behaviour, becoming a subordinate process. This could lead to the masking-up of its effects, as other authors have reported (Reichman 1984, Henderson et. al.…”