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The relative importance of the species pool, productivity and disturbance in regulating grassland plant species richness: a field experiment

The relative importance of the species pool, productivity and disturbance in regulating grassland plant species richness: a field experiment,Timothy L

The relative importance of the species pool, productivity and disturbance in regulating grassland plant species richness: a field experiment   (Citations: 9)
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Summary 1. Ecologists have generally focused on how species interactions and available niches control species richness. However, the number of species in the regional species pool may also control richness. Moreover, the relative influence of the species pool and species interactions on plant richness may change along productivity and disturbance gradients. 2. We test the hypothesis that many species from the propagule pool will colonize into habitats of moderate productivity and moderate disturbance, and the number of species in the pool will, therefore, primarily control plant species richness in such habitats. The hypothesis also states that few species from the propagule pool will colonize into habitats of high productivity and minimal disturbance because competitive species interactions primarily control plant richness in such habitats. 3. To test this hypothesis, we experimentally varied resource availability via fertilization and irrigation, the size of the available propagule pool via sowing the seeds of 49 species and disturbance via vegetation clipping. 4. A larger propagule pool increased species richness 80% in the absence of fertilization and the presence of clipping but had no significant effect on richness in the presence of fertilization and the absence of clipping (significant fertilization × clipping × seed addition interaction). Irrigation increased species richness primarily in the absence of fertilization and the presence or clipping (significant fertilization × clipping × irrigation interaction). 5. Synthesis . These results support the assertion that the control of plant species richness shifts from the number of species in the propagule pool to the intensity of species interactions as productivity due to soil fertility increases and disturbance decreases. However, increases in productivity due to irrigation caused an increase in species richness, probably because of reduced seedling desiccation. Other studies have found similar outcomes along natural productivity gradients where productivity is confounded with other variables, but this study is the first to find such an outcome along an experimental productivity gradient. These results suggest habitats with moderate soil fertility and disturbance may be more open to colonization from the propagule pool than other habitats, a finding that has implications for plant restoration and invasive species management.
Published in 2008.
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    • ...For example, the following factors have all been implicated in controlling grassland species diversity: (1) local species pool, historic, and present management (e.g., Wells et al. 1976; Gustavsson et al. 2007; Klimek et al. 2007; Field et al. 2009), (2) water regime and soil physico-chemical properties (e.g., Marini et al. 2007, 2008a, b; Auestad et al. 2008; Dickson and Foster 2008), (3) atmospheric nitrogen deposition (Stevens et al. ...

    Dana Michalcováet al. The combined effect of waterlogging, extractable P and soil pH on α-di...

    • ...However, many studies suggest that seed limitation is ubiquitous and that species diversity at a site is more strongly controlled by seed availability than by other factors (Foster and Tilman 2003; Ehrlen et al. 2006; Clark et al. 2007; but see Dickson and Foster 2008)...
    • ...Despite the potential for such synergisms between safe-site and seed limitation, few studies have simultaneously manipulated both safe-site availability and seed supply across environmental gradients to examine their relative impact on patterns of seedling recruitment and richness (Hubbell et al. 1999; Xiong et al. 2003; Houseman and Gross 2006; Poulsen et al. 2007; Dickson and Foster 2008)...

    Gwenllian D. Iaconaet al. Effects of resource availability on seedling recruitment in a fire-mai...

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