DOI: 10.5061/dryad.pvmcvdnjb
title: Leaf economics in a three‐dimensional environment: Testing leaf trait responses in vascular epiphytes to land use, climate, and tree zone

description: 1. The study of functional traits offers predictive power for community
 ecology. Particularly in cases where individual species are difficult to
 study, known properties of trait spectra, such as the leaf economics
 spectrum (LES), and trait-environment relationships can provide crucial
 generalizable information that can contribute to forecasts of
 distributional shifts in response to the abiotic effects of climate and
 land use changes. 2. Vascular epiphytes have been proposed as indicators
 of environmental change, but we know little about the ecology of most
 species. Key functional trait assumptions are based on terrestrial plants;
 testing these in epiphytes verifies their universality and will inform
 applying functional traits in predicting epiphyte responses to climate and
 land use change. 3. In this study, we use functional traits from 37
 vascular epiphyte species from forests and shade coffee farms at two sites
 in northern Nicaragua. We compare correlations among traits and
 intraspecific trait variances with those of terrestrial plants and among
 epiphyte taxonomic groups. We also test trait responses to environmental
 differences between sites and land use types, and within zones of the
 tree. 4. We find that epiphyte leaf traits fall toward the slower end of
 the LES, but with about one-third lower leaf nitrogen per change in
 specific leaf area (SLA) relative to terrestrial herbaceous plants.
 Bromeliads show less relationship between these traits than other epiphyte
 groups and also deviate in other trait interrelationships, suggesting
 unique leaf construction. 5. Trait-environment relationships varied most
 strongly along vertical gradients within trees, but some traits, including
 SLA and carbon isotope ratio, also responded to land use and site
 differences. 6. We present evidence that trait relationships established
 for terrestrial plants appear to translate to epiphytes, but identify some
 possible caveats. Strong trait response to vertical gradients within trees
 suggests that within-canopy shifts could provide resilience to climate and
 land use changes for some epiphyte species.
description: We measured leaf thickness (mm) using a thickness gauge
 micrometer at the midpoint along the lamina between the midvein and margin
 avoiding major veins. We used photographs of fresh leaves to calculate
 leaf area (cm<sup>2</sup>) with ImageJ (version 1.52h,
 National Institutes of Health). Leaves were packed in silica and
 transported to our laboratory in Wisconsin, USA, where they were oven
 dried at 50°C for 72 hours and weighed on a Mettler Toledo balance to
 derive specific leaf area (SLA, cm<sup>2</sup>
 mg<sup>-1</sup>). Elemental analysis of leaf N content, leaf C
 content, δ<sup>13</sup>C and δ<sup>15</sup>N was
 performed on one leaf per plant from several haphazardly selected
 individuals per species, and nitrogen per area
 (N<sub>area</sub>, mg cm<sup>-2</sup>) and C:N
 ratio were also derived. Dried leaves were ground in a Wiley Mill and
 packed in tins. When a single leaf did not provide enough material for
 analysis, two leaves from the same plant were combined or combined leaves
 across multiple plants of the same species (Table 2). Analyses were
 performed at Idaho State University Stable Isotope Lab using a 2010
 ThermoFisher Delta V Plus continuous flow isotope ratio mass spectrometer
 coupled with ConFlo IV/EA, TC/EA, and GasBench II at &lt;0.1 ‰
 precision.
description: See readme files for data descriptions.