DOI: 10.5061/dryad.djh9w0vxj
title: Data from: The weight of the crust: biomass of crustose lichens in tropical dry forest represents more than half of foliar biomass

description: In recent years, our ecological knowledge of tropical dry forests has
 increased dramatically. However, the functional contributions of whole
 ecosystem components, such as lichens, remain mostly unknown. In these
 forests, the abundance of epiphyte crustose lichens is responsible for the
 characteristic white bark on most woody plants, conspicuous during the dry
 season, but the amount of resources that the lichen component represents
 remains unexplored. We estimated lichen biomass in a Mexican tropical dry
 forest using the bark area of trees, the dry mass of lichens per unit area
 and the percentage of bark covered by lichens, together with previously
 known tree densities. The lowest 2.5 m of the forests main trunks
 contained 188 kg/ha of lichen biomass, with lichens covering 85% of the
 available bark for trees &lt;12 cm DBH and 38% for trees &gt;12
 cm. Total epiphytic lichen biomass was 1.34–1.99 Mg/ha. Lichen biomass
 represented 61% of the foliar biomass in the forest. To our knowledge,
 this is the first time that a lichen biomass estimate is provided for an
 ecosystem in which crustose lichens are the dominant lichen growth form.
 Crustose lichens are typically considered to contribute little to the
 total lichen biomass and to be difficult to include in ecological
 analyses. The high lichen biomass in this ecosystem implies a significant
 ecological role which so far is unexplored. We suggest the crustose lichen
 component should not be underestimated a priori in ecological studies,
 especially in ecosystems with abundant lichen cover.
description: For Table S1: Lichen tissue on top of a 2
 cm<sup>2</sup> area of bark was carefully scraped from each of
 20 previously collected pieces of bark, representing 20 common lichen
 species in the forest. Collection technique for these bark pieces
 consisted of using a knife to remove, from a living tree, a small and thin
 piece of the outer bark with the lichen of interest on it. Each cut was
 made carefully to avoid reaching into the cambium layer of the tree. Loss
 of material was avoided by continuously dampening each bark sample and
 scraping it with a single razor blade under the stereoscope. Special care
 was taken to avoid removing the bark layer which has a different texture
 and color than the wet lichens. The collected tissue was heated for 24 h
 at 60°C and weighed immediately to the nearest 0.1 mg with an Ohaus
 Analytical Plus balance. All measurements were transformed to
 g/m<sup>2</sup>. For Table S2:
 We measured the bark surface area of 62 randomly selected trees
 that did not branch below 2.5 m. Trees were haphazardly selected a few
 meters to the side of a sinuous transect of 2.5 km that followed three
 trails inside the Reserve. The selected trees were a typical
 representation of the species present in the Reserve and included
 different DBH sizes and percentages of lichen cover. For each tree, we
 measured the bark surface area on the lowest 2.5 m of the main trunk using
 the formula for the lateral surface area of a truncated cone with diameter
 measurements at 0.3 m and 2.5 m high. The lichen cover of the measured
 area was visually estimated as a percentage by dividing the area in at
 least 8 smaller zones that included the lower and upper parts of the
 lowest 2.5 m of the main trunk at each cardinal point. The lichen biomass
 in the lowest 2.5 m of each tree was calculated as the product of the bark
 surface area in m<sup>2</sup>, the lichen cover percentage per
 tree, and the mean lichen dry mass in
 g/m<sup>2</sup>.