Abstract
Plant recruitment in tropical forests reflects the chance that seeds arrive at a site resulting in seedling establishment. To inform tropical forest restoration, we ask how seed and seedling densities differentially affect dispersal and establishment limitation in successional habitats in a tropical agricultural landscape. Methods: In Los Tuxtlas Biosphere Reserve, we calculated indices of dispersal and establishment limitation using data on seed rain and seedling establishment in old-growth forest, secondary forest, and fenced pasture. We present an index that considers variations in dispersal- and establishment-limitation including density-weighted calculations. Results: There were greater dispersal and establishment limitations in pasture than in forests. Substantial differences in both dispersal and establishment limitation occurred among the 33 species for which seed and seedling data were available. Only 5% of all species had mid to low limitation in both dispersal and establishment. In contrast, 60% of all species showed high dispersal and establishment limitation. Plant recruitment in pastures is impeded by low seed arrival, given that 77% of the recorded species showed extremely high dispersal limitation (>90%). Conclusions: The low capacity of most species to arrive, seeds to germinate and seedlings to establish in pastures slow down succession back to forest.
Highlights
Implications of dispersal and recruitment limitation have a long history in plant ecology
Dispersal limitation was higher in pastures than in primary and secondary forests using both the presence index (Figure 2A) and the density-weighted index (Figure 2B)
The difference between the two dispersal limitation indices was larger in primary forest than secondary forest (p < 0.01) and pasture (p < 0.001) but was similar between secondary forest and pasture (Figure 3)
Summary
Implications of dispersal and recruitment limitation have a long history in plant ecology. Advantages occur when seeds are dispersed far away from conspecific adults because density-dependent seed or seedling mortality from pathogens, insects, other enemies or competition are greater near fruiting trees [5,6,7,8,9]. There is a general negative effect of density on seed survival and seedling emergence independent of samples close to fruiting trees [10]. It has become clear that mortality may be density-dependent or density-independent at different stages of plant development, from seeds to adults [11]. Density is a key component when evaluating dispersal and establishment limitations because intra- or interspecific competition in these forming communities matters
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