OOS 2-5
Litter decomposition and diversity of decomposers along altitudinal gradients in tropical and temperate streams

Monday, August 10, 2015: 2:50 PM
314, Baltimore Convention Center
Andrea C. Encalada, Laboratorio de Ecología Acuática-Colegio de Ciencias Biológicas y Ambientales, Universidad San Francisco de Quito, Quito, Ecuador
Alexander S. Flecker, Ecology and Evolutionary Biology, Cornell University, Ithaca, NY
LeRoy Poff, Biology, Colorado State University, Fort Collins, CO
Manuel A. S. Graca, Universidade de Coimbra
Cristina Salgado, Departamento de Ciências da Vida, Universidade de Coimbra, Coimbra, Portugal

One of the most recognizable ecological patterns on the earth is the variation in species composition and diversity among latitudinal and altitudinal gradients. Changes in water temperature along these gradients can alter the structure of benthic communities, thus resulting in changes in ecosystem processes. To understand the role of microbial and invertebrate stream decomposers on decomposition rates, and the influence of latitude and altitude, we analyzed diversity of decomposers and litter decomposition in five headwater streams ranging from 1800 and 3800 m elevation in tropical Ecuador and temperate Colorado (USA). Coarse and fine-mesh litterbags were filled with either aliso (Alnus acuminata) in Ecuador or alder (Alnus incana) in Colorado. Samples were incubated in the streams and recovered after 7, 14, 28, 56 and 94 days to allow estimation of litter decay rates. We analyzed invertebrate shredders associated with coarse mesh bags and microbial decomposers (bacteria and fungi) associated with fine mesh bags.


Diversity of microbial and invertebrate decomposers decrease with increasing altitude in both tropical and temperate streams. In both, tropical and temperate streams, litter processing was faster at lower altitudes, and decomposition rates were positively correlated with invertebrate shredder abundance, but not with shredder diversity.  Litter decomposition in fine mesh bags were positively correlated with fungal decomposers but only in tropical sites and not in temperate sites.  Decomposition was slower in tropical vs temperate streams in both coarse and fine mesh bags, despite the relatively higher water temperatures recorded in tropical streams. This pattern might be explained by lower diversity and biomass of fungi recorded in the tropical sites. Here, we explore the role of temperature and other stream factors on the structure of benthic communities and the ecosystem processes that they control.