DOI: 10.5061/dryad.v9r72q7
title: Data from: Drivers of tropical rainforest composition and alpha diversity patterns over a 2,520 m altitudinal gradient

description: We determined the relationship of forest composition and alpha diversity
 (species diversity of a local assemblage) to altitude, soil and spatial
 factors over a 440 - 2950 ma.s.l gradient. Altitudinal gradient on the
 Atlantic slope of the Talamanca Cordillera, Costa Rica. We measured and
 identified all stems &gt; 10 cm dbh in 32 0.25-ha undisturbed rain
 forest plots over the gradient. We determined compositional patterns using
 Non-Metric Multidimensional Scaling (NMS) ordination, and used linear
 regressions to explore the relationship between four alpha diversity
 metrics and altitude. With variation partitioning (VARPART) we determined
 the compositional variation explained by altitude, soil and spatial
 variables quantified using Principle Components of Neighbour matrices. We
 identified 425 species. NMS axis 1 separated a lowland zone (440-1120 m
 asl) from a transitional one dominated by holarctic Oreomunnea mexicana
 (1400-1600 m asl) and Quercus-dominated forests at altitudes &gt;2100
 m asl. The lowland zone was separated into two clusters of plots on NMS
 axis 2, the first in the 430-620 m asl range and the second at 1000-1120
 masl. . Regressions showed that alpha diversity metrics were strongly
 negatively related to altitude (R2&gt;0.78). Overall adjusted R2 from
 VARPART was 0.43, with 0.30, 0.21 and 0.17 for altitude, soil and space
 respectively. The respective adjusted R2 of individual matrices, on
 controlling for the other two, were 0.06, 0.05 and 0.09 (p&lt;0.001).
 There are two well-defined forest compositional zones on this gradient –
 lowlands and montane forests – with a transitional zone at 1400-1600 m asl
 where lowland tropical and montane holarctic species are found together.
 Montane forests are very distinct in their composition and low alpha
 diversity. Vegetation and soil respond to altitude, and therefore
 temperature, as an integrated system, a model that goes beyond niche
 assembly as shown by the significant effect of space in the VARPART.
description: Supporting data for the
 Ms ECE-2018-10-01225.R1The table contains 469
 variables (columns) recorded and calculated in 32 plots (rows). Column 1:
 contains the life zone of each plot, according to Holdridge´s system :
 Tropical Wet Forest (TWF), Premontane Rain Forest (PRF), Lower Montane
 Rain Forest (LMFR) and Montane Rain forest (MRF). Column 2: contains the
 plot codes Columns 3 to 453: contain each of the species identified with
 its code: this code corresponds to the first two letters of the genus and
 the first four letters of the species. The complete list of species is
 provided in the appendix 4 related to the paper. Columns 453 and 454:
 contain the altitude of each plot is located and its standardized
 versions. Columns 455 to 457: contain the PCNMs selected by forward
 selection, which explain spatial variability of species composition.
 Columns 458 to 462: contain the soil variables selected and standardized.
 Column 463 and 464: contain the auto vectors of the NMS analysis. Column
 465 to 468: contain the calculated four alpha-diversity
 metrics.