Forest age strongly influences the functional trajectories of reintroduced vascular epiphytes over time

Abstract

Active restoration has helped vascular epiphytes colonize forests where they are absent or insufficiently abundant. This study was the first attempt to assess how reintroduced epiphytes adjust and acclimate over time through changes in leaf traits in restored forests. Four epiphyte species were monitored over a year in one forest aged six years and one forest aged over 20 years in the Atlantic Forest, Brazil. The younger forest has a more heterogeneous canopy structure. Eight leaf traits were analyzed individually or in a multivariate manner. The effects of within- and between-forest heterogeneity and time on trait variation were assessed by PCA, GLMM, and variance partitioning analyses. Our findings supported half of the four hypotheses. First, the hypothesis that individuals would show more variation in trait values and trait spaces in the younger forest was supported, as in this forest, trait hypervolumes became larger and showed greater overlaps with the initial hypervolumes. Second, the hypothesis that trait variation would be more pronounced in the rainy season was not supported; however, time significantly influenced the trajectory of trait variation. Third, the hypothesis that within-forest heterogeneity would drive most of the trait variance was supported, as this factor contributed 71 %, on average, to the variance across traits and species. Fourth, the hypothesis that the timing and magnitude of changes would depend on the species’ ecological strategy was not confirmed, as all species showed similar patterns. Our findings suggest that deciding where epiphytes should be reintroduced will strongly influence their functional trajectories over time.