Abstract
The maintenance of seedling diversity of animal-dispersed tree species is fundamental for the structure and function of forest patches in fragmented tropical rainforests. Nonetheless, the effects of landscape structure at different spatial scales on α- and β-diversity of tree seedling communities are recently explored. Using a multi-scale approach, we assessed the relative effect of landscape composition and configuration on α- and β-diversity of animal-dispersed seedlings within 16 forest patches in the Lacandona rainforest, Mexico. We assessed these effects at 13 spatial scales (from 300 to 1500 m radius, at 100 m intervals) for three metrics of effective number of species considering α- and β-diversity. We found that α-diversity was largely affected by landscape composition and β-diversity by landscape configuration. On the one hand, the amount of secondary forest influenced α-diversity. Additionally, species richness increased in landscapes with highly aggregated forest patches. On the other hand, β-diversity was affected positively by forest fragmentation and negatively by the edge contrast of forest patches with the surrounding matrix. Our findings indicate that landscape configuration is a strong driver of seedling diversity in highly deforested rainforests. Promoting forest patches and secondary forests through payment for ecosystem services' programs, favoring matrix quality within land-sharing schemes of smallholder agriculture and secondary forest management, and identifying restoration opportunities for assisted or unassisted natural regeneration are urgently needed for conservation of seedling diversity in human-modified tropical landscapes.
Highlights
We focused on the following question: Which components of landscape structure are influencing seedling α- and β-diversity and at which spatial scales?
We found that α- and β-diversity metrics were significantly higher than the other metrics when species abundances were not considered (Fig E in S1 Text)
We found a decrease of α-diversity in forest patches surrounded by secondary forests, which are documented to exert a significant influence in the composition of tree communities within forest patches [32,33,96]
Summary
Forest patches of HMTLs are generally small (mean size = 13–17 ha), and their number are expected to rise in the following years [4].Yet, these patches can preserve a large number of plants and animals species [5,6], and contribute to improve forest regeneration, landscape connectivity, metapopulation persistence, and resource availability for native species [7,8] These contributions are strongly influenced by patches’ tree community, which provides of food and habitat for an important proportion of the old-growth fauna, and drive biomass production and carbon storage [9,10]. We tested the following predictions: (1) α-diversity will increase in landscapes with high forest cover and β-diversity will increase in fragmented landscapes with low edge contrast; and (2) there should be larger scales of effect for richness-based metrics than for abundance-based metrics of seedling α- and β-diversity (i.e. dominant < typical < all species)
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