Abiotic factors, including temperature and precipitation, and litter chemistry are the most important factors in determining decomposition rates, but biota can play an important, often overlooked, role. Many potential pathways can link biota across trophic levels to decomposition processes.
In shaded coffee agro-ecosystems, the other plants, insects and other animals and even the coffee plants themselves can be biotic drivers of decomposition dynamics.
Read on to learn more about projects on home-field advantage in leaf litter decomposition, the impact of a keystone arboreal ant species, interactive effects of shade tree litter and flower petals, and trophic structure in meta-communities.
Home-field advantage in decomposition
Home-field advantage, when applied to decomposition, predicts that litter will decompose more quickly where conspecifics are growing, compared to other ("away") environments. I tested this theory for two species of coffee, C. arabica and C. robusta, using a reciprocal transfer experiment. I also evaluated the rate of decomposition in a neutral "away" environment where neither species of coffee is grown. I found evidence of home-field advantage in the short term, but not over longer periods of time.
You can find the full paper published in Applied Soil Ecology.
Cascading effects of a keystone arboreal ant species
Keystone species are categorized by their widespread impact. Azteca sericeasur is a keystone ant species in coffee agro-ecosystems, with demonstrated effects on the insect community across trophic levels. We wanted to see if the outsized impact of this arboreal ant influences decomposition dynamics.
To answer this question we sampled the invertebrate community around sites with and without A. sericeasur nests using tuna baits (for ants) and pitfall traps. We used litterbags to measure the decomposition rates of Inga micheliana leaf litter, a common shade tree on coffee farms in the region.
Contrary to previous studies, we found no decrease in ant species richness around shade trees with A. sericeasur nests. Ultimately, there was no difference in the decomposer community or leaf litter decay in the presence of A. sericeasur . However, the ant community composition did change around A. sericeasur nests, so we suspect that a community of ants that is not in direct competition with A. sericeasur is able to persist in the leaf litter around the shade trees with the A. sericeasur nests.
You can find the full paper published in Biotropica.
Collaborators: Bolivar Aponte-Rolon, Research assistant: Megan Shibley
Interactive effects of shade tree leaf litter
Non-additive effects can occur when multiple species of leaf litter are decomposing in combination. In coffee agro-ecosystems, where coffee plants are grown in the understory of larger shade trees, I asked: how will coffee decomposition change in the presence of two common shade trees, Inga micheliana and Alchornea latifolia?
Pulse of flower petals
Coffee (Coffea arabica) flowers synchronously, with thousands of flowers blooming in the span of a few weeks. I asked: how does this pulse of flower petals affected the decomposer community and decomposition dynamics?
You can read the full paper published in Ecosphere.
Trophic structure in meta-communites
Meta-community theory predicts the spatial organization of species interactions. We tested the meta-communities theory empirically, using leaf litter macro-arthropods.
We found that when migration was manipulated, leaf litter macro-arthropods responded in trophic-specific ways.
You can read the full paper published in Oikos.
Collaborators: Zachary Haijan-Forooshani, Nicholas Medina and John Vandermeer