Vegetation Effects on Soil Resource Heterogeneity in Prairie And Forest

Abstract

A current, widespread example of vegetation change is the invasion of grassland by woody plants. This is associated with an increase in soil heterogeneity, and it has been argued that woody plants both cause and benefit from high heterogeneity. We know of no experimental demonstrations of differences between grasses and woody plants in their effects on heterogeneity. Here we compare heterogeneity between mixed-grass prairie and aspen forest, and we report the results of a soil transplant experiment that tested for differences between these vegetation types in their effects on soil resource heterogeneity. We measured the heterogeneity of resources and plant mass along 10 transects in both prairie and aspen forest in spring and summer. Light and available nitrogen (N; sum of ammonium and nitrate) were significantly more variable in forest than prairie, as were root and understory shoot mass. The variability of soil moisture and topography did not differ between prairie and forest. In our experiment, N and water in cores of prairie soil moved to forest attained the relatively high variability of forest soils. Further, forest soils moved to prairie attained the relatively low variability of prairie soils. In summary, both the biomass heterogeneity measurements and the soil transplant experiment suggested that plant uptake contributed to greater heterogeneity in forests.

The Fluctuation Niche in Plants

“…In that way, they compared grasslands and desert shrublands and settled that shrubs increase the scale of heterogeneity by their coarse root systems and by creating "fertility islands." Kleb and Wilson [13] have analysed heterogeneity for light and soil resources availability and biomass, comparing a prairie and a forest. They used autocorrelation techniques and coefficients of variation to conclude that the forest increased heterogeneity (coarser root systems, stem flow, interception and evaporation patterns, etc.…”

“…Organisms can produce heterogeneity by themselves [12,13], and in some cases they can produce self-organized patterns that are likely to be scale-dependent [17]. So, we can conclude that different scales and variables, and a more specific conceptual approach, are needed to gain understanding of Wilson's "heterogeneity partition.…”

Vascular plant species richness on wetland remnants is determined by both area and habitat heterogeneity

“…Therefore, soil resource heterogeneity was considered as a strong driver of plant species coexistence and community diversity (Tilman 1988). Currently, studies on the effect of soil resource heterogeneity on plant species have reported conflicting results: some studies showed a positive effect (e.g., Davies et al 2005;Marchand and Houle 2006;Zhou et al 2008), and others found no significant effect (e.g., Stevens and Carson 2002;Wijesinghe et al 2005;Reynolds et al 2007) or even negative effect (Kleb and Wilson 1997). These inconsistent patterns could be the result of different processes operating at different spatial scales (Davies et al 2005).…”

Spatio-temporal patterns of soil available nutrients following experimental disturbance in a pine forest

“…The recognition of the importance of the soil resource heterogeneity has resulted in research designed to characterize soil heterogeneity in terrestrial ecosystems. This research has clearly shown that soil resource heterogeneity is substantial, highly structured at different spatial scales (Bell et al 1993;Caldwell 1993a, 1993b;Halvorson et al 1994;Ehrenfeld et al 1997;Kleb and Wilson 1997), and changing over time (Ryel et al 1996;Cain et al 1999;Farley and Fitter 1999;Guo et al 2002). However, ecological agents and processes governing spatio-temporal patterns of soil heterogeneity are not well understood (Pickett et al 2000).…”