Landscape forest cover, not edge contrast, modulates edge effects on palm diversity

Edge effects are among the most important consequences of habitat
fragmentation, altering abiotic conditions and biological communities in
remnant forests. However, the magnitude of edge effects is highly
variable, and the factors that modulate them, particularly the interplay
between local edge type and the landscape context, remain poorly
understood. Given ongoing increases in the proportion of the world's
remaining forest found near edges, understanding these effects is critical
for conservation. We investigated how edge effects are mediated by type of
edge (cacao plantation vs. cattle pasture) and landscape forest cover (%),
shaping palm density and diversity across forest fragments in the
Ecuadorian Chocó. We established plots (100 m2) at four distances to the
edge (0-10 m, 30-40 m, 60-70 m, and 90-100 m) in 30 sites, 15 for each
type of edge across a gradient of landscape forest cover. In each plot, we
recorded all adult palms, juveniles and seedlings. The response of palms
to distance to the edge and level of landscape forest cover varied across
life stages: seedling communities were primarily associated with distance
from the edge, showing an increase in density and richness, but a decrease
in evenness, towards the forest interior. For juveniles, landscape forest
cover was as important an additive predictor as distance to the edge, both
increased density and richness, whereas evenness declined with higher
surrounding forest cover. Adult density also increased with distance to
edge and higher levels of landscape forest cover. Negative edge effects on
adult richness and evenness were buffered with an increase in landscape
forest cover. Unexpectedly, the type of edge contrast had no significant
effect on palm density or diversity at any life stage. Synthesis and
applications: Our findings demonstrate that landscape forest cover plays a
critical role in modulating edge effects in plant communities in our study
system, but not all woody crops systems provide buffering benefits, as
cacao plantations in our study failed to soften edge effects.
Consequently, conservation strategies should prioritize maintaining high
landscape forest cover to ensure the integrity of remaining forest
fragments.