Abstract
Background and aimsCurrent knowledge of soil heterogeneity-diversity relationships (HDR) is largely based on studies manipulating single factor, but the advancements in HDR may require a comprehensive experiment incorporating multiple factors.MethodsWe conducted a three-year field experiment in which a seed mixture of 16 common grassland species was sown in plots with heterogeneous soils consisting of small (10 cm × 10 cm) or large patches (30 cm × 30 cm) of low and high nutrients or low and high pH, and homogeneous soils with an even mixture of low and high nutrient/pH soils. Soil nutrients and pH were manipulated in separate treatments. We determined plant species richness and diversity at two focal scales (40 cm × 40 cm plot-scale and 10 cm × 10 cm patch-scale).ResultsPlot-scale richness and diversity were not influenced by soil heterogeneity, but patch-scale richness was lower in plots with heterogeneous nutrients than in plots where nutrients were distributed homogeneously. There was no difference between the two heterogeneous nutrient soils with different grain sizes. Patch-scale diversity was higher in heterogeneous pH soils of large patch size than in heterogeneous pH soils of small patch size or the homogeneous pH soil at the final harvest. Species richness and diversity quantified at both plot and patch scales declined in all soils over time.ConclusionsThe influence of soil heterogeneity on plant species diversity depends on whether the soil varies in nutrients or pH, and on the temporal-spatial scale at which species diversity and soil heterogeneity are measured. These results indicate that soil heterogeneity has the potential to promote plant coexistence and future HDR studies should consider multiple soil factors at various temporal-spatial scales.
Highlights
Soil heterogeneity is widely thought to promote plant species coexistence and plant species diversity by increasing niche availability (Levine and HilleRisLambers 2009) and by creating shelters and refuges from harsh environmental conditions
Hutchings et al (2003) predicted that when the scale of soil heterogeneity is larger than the size of the plant rooting system, different soil patches will support distinct sub-communities, and the overall diversity will be higher than in equivalent homogeneous soils
We only focused on plants in the central 40 × 40 cm of each plot to reduce edge effects, and performed analysis at two focal scales: 0.16 m2 (40 cm × 40 cm plot-scale) and 0.01 m2 (10 cm × 10 cm patch-scale)
Summary
Soil heterogeneity is widely thought to promote plant species coexistence and plant species diversity by increasing niche availability (Levine and HilleRisLambers 2009) and by creating shelters and refuges (e.g. competition-free patches) from harsh environmental conditions (e.g. competition-dominant patches; Chesson 2000; Hutchings et al 2003) This phenomenon, howerver, depends on the spatial scale at which herterogeneity varies (Eilts et al 2011; Hutchings et al 2003; Tamme et al 2010). Current knowledge of soil heterogeneity-diversity relationships (HDR) is largely based on studies manipulating single factor, but the advancements in HDR may require a comprehensive experiment incorporating multiple factors
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