DOI: 10.5061/dryad.nk98sf85n
title: Does increasing canopy liana density decrease the tropical forest carbon sink?

description: The ongoing decline in the American tropical forest carbon sink has
 serious ramifications for atmospheric carbon levels and global climate
 change. Increasing liana abundance may explain the decaying carbon sink
 because lianas reduce canopy tree growth and survival, which limits forest
 carbon storage. However, canopy lianas, not solely understory lianas,
 would have to be increasing for this hypothesis to be credible because
 canopy lianas compete especially intensely with canopy trees. Data in this
 archive were used to examine the change in canopy lianas over 10 years on
 Barro Colorado Island (BCI), Panama to test three hypotheses. 1) Canopy
 lianas are increasing on BCI. 2) Increasing canopy lianas decrease
 aboveground canopy tree and forest carbon storage. 3) Lianas are the
 numerically dominant and most diverse woody plant growth form in the
 canopy. Our findings indicated that lianas are the numerically
 dominant and diverse woody plant group in the BCI canopy, and this
 dominance is increasing, reducing forest-level carbon storage and possibly
 explaining the decaying American tropical forest carbon sink.
description: We conducted this study in the BCI 50-ha forest dynamics plot in
 central Panama. The BCI 50-ha plot is one km in length and one-half km in
 width and is divided into 1250 20 x 20 m quadrats. A single hectare in the
 north-eastern part of the plot may have been disturbed ~125 years ago
 during the construction of the Panama Canal; however, the rest of the plot
 appears to be intact old-growth forest with no previous agriculture or
 burning. We tested the effect of canopy liana change on
 canopy tree carbon change (H2) using Bayesian linear regression (Eq. 1 in
 the associated article) to model the mean change in aboveground canopy
 tree carbon (∆AGC) in each quadrat () as a Gaussian response to the change
 in liana density, basal area, and mean stem diameter. We confirmed that
 the relationship was linear by comparing linear and non-linear regression
 techniques (Appendix S1: Fig. S2). We controlled for spatial
 autocorrelation among adjacent quadrats using a quadrat-specific spatial
 random effect. We tested the numerical dominance and diversity of canopy
 lianas (H3) using Kruskal-Wallis <em>H</em> tests to determine
 whether median per-quadrat canopy liana density and species richness were
 greater than canopy tree density and species richness.
description: # Does increasing canopy liana density decrease the tropical forest carbon
 sink? File: 2025-07-14_datafile_for_dryad.csv Description of variables: *
 aboveground_canopy_tree_carbon_change_mg - the change in canopy tree
 carbon from 2005 - 2015 in Megagrams * quadrat - the numeric identifier
 for each of the 1250 20x20 meter quadrats * canopy_liana_density_change -
 the change in canopy liana rooted stem density from 2007 - 2017,
 individuals per quadrat * canopy_liana_mean_stem_size_change - the change
 in mean canopy liana rooted stem size from 2007 - 2017, in millimeters *
 canopy_liana_ba_change - the change in canopy liana basal area from 2007 -
 2017, in square meters * final_ba_height - 2015 diameter-based canopy
 height estimate for each quadrat, in meters *
 understory_liana_density_change - the change in understory liana
 individual density from 2007 - 2017, individuals per quadrat *
 understory_liana_mean_stem_size_change - the change in mean understory
 liana individual stem size from 2007 - 2017, in millimeters *
 understory_liana_ba_change - the change in understory liana individual
 basal area from 2007 - 2017 in square meters * canopy_liana_richness -
 canopy liana species richness 2017 * canopy_liana_density - canopy liana
 density 2017, number of species per quadrat * canopy_tree_richness -
 canopy tree species richness 2015, number of species per quadrat *
 canopy_tree_density - canopy tree density 2015, number of individuals per
 quadrat