Volume 199, 1 January 2015, Pages 43–51
Highlights
- •
- Most tree species on the farms were native and originated from natural regeneration.
- •
- Most individuals, however, were planted exotics.
- •
- Increasing forest cover around farms increased on-farm species richness.
- •
- Increasing forest cover around farms increased similarity between farms and forest.
- •
- Organic agroforestry may enhance reproduction and survival of native trees.
Abstract
Understanding
the processes that influence tree species composition in agricultural
landscapes is essential for conservation of tropical biodiversity
outside of protected areas. We analyzed the effects of landscape
composition (amount of surrounding forest cover) and farm management
(conventional vs. organic) on the diversity and structure of woody plant
species assemblages in Costa Rican coffee agroforestry systems. We
utilized information from a GIS land-use database, surveys of 1-ha plots
located in 14 coffee farms and 4 forest fragments, and farmer
interviews on management practices. The coffee farms harbored over 100
tree species, including 19% of the native tree species found in the
surrounding forests. The majority of tree species on the farms were
native (82%) to the study area and originated from natural regeneration
(73%). Among the tree species that regenerated naturally, 71% were
dispersed by animals. On the other hand more than half of the
individuals were non-natives (55%) and originated from planting, which
resulted in low species similarity between farms and forests and a low
density for most native species on the farms. Forest cover within a
1000 m radius around the farms varied between 4 and 38%. Increasing
forest cover around the farms had a significant, positive effect on
species richness; especially on tree species dispersed by animals, and
on species similarity between farms and forests. This suggests that the
connection to natural forests increases seed dispersal into adjacent
farms. The number of regenerated species was higher on the organic
farms, but tree species richness was not affected by management type.
Although species assemblages on the coffee farms are strongly determined
by natural regeneration, the number of individuals contributed by these
processes is low. Tree species conservation in agricultural landscapes
would greatly benefit from protecting remnant forests, from facilitating
natural regeneration processes and promoting native trees on farms,
with particular attention to rare species.
Keywords
- Agroforestry;
- Biodiversity conservation;
- Ecosystem services;
- Forest fragmentation;
- Organic agriculture;
- Seed dispersal
- Corresponding author. Tel.:
+506 2446 5558.
Copyright © 2014 Elsevier B.V. All rights reserved.
