DOI: 10.5061/dryad.7521p2p
title: Data from: Dispersal and nutrient limitations of decomposition above the forest floor: evidence from experimental manipulations of epiphytes and macronutrients

description: 1. Decomposition is a major component of global carbon cycling. However,
 approximately 50% of wood necromass and a small proportion of leaf litter
 do not contact the forest floor, and the factors that regulate the
 decomposition above the forest floor are largely untested. We hypothesized
 that separation from soil resources causes slower decomposition rates
 above the forest floor. Specifically, we tested whether slower
 decomposition results from decreased nutrient availability (the nutrient
 limitation hypothesis) and/or microbial dispersal limitation (the
 dispersal limitation hypothesis) in the absence of soil resources. 2. We
 tested these hypotheses by combining experimental manipulations of
 epiphytes and macronutrient fertilization with elemental analyses and
 community metabarcoding (fungi and prokaryotes). Specifically, we compared
 wood stick and cellulose decomposition among three treatments: an
 unaltered trunk section, an epiphyte mat, and a “removal treatment” where
 an epiphyte mat was removed to test the effect of soil resources. We also
 performed a factorial fertilization experiment to test the effects of
 nitrogen (N) and phosphorus (P) on the decomposition of suspended
 cellulose. 3. Decomposition rates were fastest on the epiphyte mats,
 intermediate in the removal treatment, and slowest in the controls.
 Phosphorus addition increased decomposition rates in the fertilization
 experiment, and greater P concentrations, along with some micronutrients,
 were associated with increased rates of decomposition on the epiphyte mats
 and in the removal treatments. Locally dispersed fungi dominated the wood
 stick communities, indicating that fungal dispersal is limited in the
 canopy, and fungal saprotrophs were associated with increased rates of
 decomposition on the epiphytes. 4. These experiments show that slowed
 decomposition above the forest floor is caused, in part, by separation
 from soil resources. Moreover, our findings provide support for both the
 nutrient limitation and dispersal limitation hypotheses and indicate that
 mechanisms regulating canopy-level decomposition differ from those
 documented on the forest floor. This demonstrates the need for a holistic
 approach to decomposition that considers the vertical position of
 necromass as it decomposes. Further experimentation is necessary to
 quantify interactions between community assembly processes, nutrient
 availability, substrate traits, and microclimate.
description: Rarefied fungal OTUs for
 wood sticks in an epiphyte manipulation experimentfungi_rarefied3934.csvRarefied bacterial OTUs in wood sticks from epiphyte manipulation experimentbacteria_rarefied3548.csvMapping file information and covariates for fungal community datafungi_covariates.csvMapping file information and covariates for bacterial community databacteria_covariates.csvElemental compositionThe elemental composition of wood sticks after decomposing for 1 year in the canopy in one of three different treatmentselemental_composition.csvEpiphyte decompositionPatterns of mass loss for wood sticks and epiphytes in one of three treatments in the canopyepiphyte_decomposition.csvnutrient_manipulationMass loss from cellulose disks attached to tree trunks above the forest floor and treated with nitrogen or phosphorus in a factorial design