Response of vegetation to coffee pulp addition

Applying nutrient-rich agricultural by-products, such as fruit peels and
pulp, to degraded land has been proposed as a strategy to overcome a
number of barriers to tropical forest recovery. While such linkages
between agroindustry and restoration represent win-win scenarios,
practical applications remain largely unexplored. In this case study, we
tested coffee pulp as an amendment to catalyze forest succession on
post-agricultural land in southern Costa Rica. A 0.5-m-deep layer of
coffee pulp was deposited across a 35 × 40-m area and an adjacent
similar-sized control plot (no coffee pulp addition) was delineated. Over
two years, we measured changes in soil nutrients, ground cover, understory
vegetation, tree establishment, and canopy cover across both coffee pulp
and control treatments. Our results show that soil carbon, nitrogen,
phosphorous were significantly elevated in the coffee pulp compared to
control treatment after two years. Coffee pulp addition significantly
altered the ground cover characteristics, eliminating pasture grasses,
facilitating establishment of herbaceous plants, and increasing the
percent area covered by leaf litter. Early-successional trees and shrubs
established quickly in coffee pulp treatment, reaching 30-fold greater
mean basal area and 20-fold greater woody stem density (>1-cm-dbh)
compared to the control treatment. Structural metrics showed 4-fold
greater mean canopy height in the coffee pulp compared to control
treatment and >80% canopy cover overall. Canopy height >5 m
was ~40% in the coffee pulp but was negligible in the control treatment.
Our study highlights the significant potential for using agricultural
waste, like coffee pulp, to jump start forest succession on degraded
tropical lands and encourages further research to optimize linkages
between agroindustry and restoration.