DOI: 10.5061/dryad.4t46jj6
title: Data from: Soil nutrients and dispersal limitation shape compositional variation in secondary tropical forests across multiple scales

description: 1. Soil resource partitioning and dispersal limitation have been shown to
 shape the tree community structure of mature tropical forests, but are
 poorly studied in the context of forest succession. We examined the
 relative contributions of both ecological processes to the variation in
 the species composition of young tropical secondary forests at different
 spatial scales, and if the relative importance of these two ecological
 processes changed during succession. At the species level, we examined if
 the association between species abundances and soil fertility differed
 between early and late successional species and/or changed over the course
 of succession. 2. We used vegetation and soil data from 47 secondary
 forest sites with two plots each in a tropical agricultural landscape. A
 distance-based redundancy analysis and variation partition were employed
 to examine the relative importance of spatial distance (proxy for
 dispersal limitation) and heterogeneity in soil nutrients (proxy for soil
 nutrient partitioning) at the landscape scale, and a linear regression to
 test their effects at the local scale. We examined interspecific variation
 in species’ responses to successional age and soil nutrients with a joint
 species distribution model. 3. Dispersal limitation and soil niche
 partitioning drove considerable variation in the composition of plant
 communities at local and landscape scales. The relative contribution of
 these two ecological processes changed with scale (local versus
 landscape), topography (lower slope versus upper slope plots). At the
 species level, significant abundance-soil fertility associations were
 mostly positive. Most species became less responsive to soil nutrients
 over the first few decades of tropical forest succession, probably because
 light became the main limiting resource in older forests. 4. Synthesis.
 Our key finding is that spatial heterogeneity in soil resources and
 spatial distance jointly drive compositional variation within and across
 early successional forests. Our results highlight that a network of forest
 fragments enhances the resilience of ecological processes and the
 potential of secondary forests to restore and preserve biodiversity in
 human-modified landscapes. To advance our understanding of ecological
 succession, we need to move beyond single-factor and local-scale studies
 and examine the effects of multiple variables on succession at multiple
 spatial scales.
description: site
 dataSites are defined as a
 single slope within an abandoned field or pasture. Information on land-use
 history and time since abandonment was obtained from interviews with
 former landowners and local residents. All study sites were former
 pastures, although small areas within pastures may have been used
 temporarily for crop cultivation. No records exist of within-site land-use
 dynamics but extensive discussions with former land owners and neighbors
 indicate that such areas were generally small and cultivated for one to
 two years before being converted back to pasture. In each site, two 20×50
 m plots were established, one on the upper portion of the slope and
 another on the lower portion of the slope. In each plot, all stems of
 trees, shrubs, and palms with a diameter ≥ 5 cm and all stems of woody
 climbing plants with a diameter of ≥ 1 cm were tagged, identified and
 measured. In one-half of each plot, stems with 1 ≤ DBH &lt; 5 cm of woody,
 non-climbing plants were treated similarly. This data file contains
 site-level data: "site+ = site id; "age" = forest age since
 abandonment, in years; "BA" = average of the basal areas of the
 two plots, in m2/ha; "dist" = distance between the two plots, in
 meters; "nutr" = dissimilarity in soil nutrients between the
 upper and lower plots, calculated using Al, P, Ca, Mg, and Cu, and
 Euclidean distances; "abdis" = species dissimilarity, calculated
 using the abundance-weighted Jaccard index.site.data.csvdistance_between_plotsPairwise distances (in meters) between all 94 plots. "trans1" and "trans2" give the plot numbers, and "dist" the distance between the two plots in meters.plot_dataThis data file contains plot-level data: "site" = site id; "transect" = plot id; "TP" = topographic position, either upper slope (UP) or lower slope (LS); "BA" = basal areas of the plot, in m2/ha; “P” = P concentration, in ppm; “Mg” = Mg concentration, in ppm; “Ca” = Ca concentration, in ppm; “Cu” = Cu concentration, in ppm; “Al” = Al concentration, in ppm. Soils were sampled at the end of the wet season (late November–early December) at nine points along the mid line of each plot at 5 m intervals. Soil cores were taken from the upper 15 cm of the mineral soil, bulked, thoroughly mixed, and then sub-sampled for nutrient analysis. Concentrations of base cations and plant available phosphorus were extracted using the Mehlich III method.Species abundances per plotSpecies abundances per plot. Sampling was nested, with plants with 1-5 cm dbh sampled in 500 m2 per plot, and plants with dbh &gt; 5 cm sampled in 1000 m2 per plot. To account for difference in sample effort, we counted each plant with a diameter less than 5 cm double in the calculation of abundance. "transect" = plot number; "specid" = species identification codes used by the Center for Tropical Forest Studies; "nr" = estimated number of plants per species.species_abundances.csv