title: Forest fragmentation and selective logging have inconsistent effects on multiple animal-mediated ecosystem processes in a tropical forest.
abstract: Forest fragmentation and selective logging are two main drivers of global environmental change and modify biodiversity and environmental conditions in many tropical forests. The consequences of these changes for the functioning of tropical forest ecosystems have rarely been explored in a comprehensive approach. In a Kenyan rainforest, we studied six animal-mediated ecosystem processes and recorded species richness and community composition of all animal taxa involved in these processes. We used linear models and a formal meta-analysis to test whether forest fragmentation and selective logging affected ecosystem processes and biodiversity and used structural equation models to disentangle direct from biodiversity-related indirect effects of human disturbance on multiple ecosystem processes. Fragmentation increased decomposition and reduced antbird predation, while selective logging consistently increased pollination, seed dispersal and army-ant raiding. Fragmentation modified species richness or community composition of five taxa, whereas selective logging did not affect any component of biodiversity. Changes in the abundance of functionally important species were related to lower predation by antbirds and higher decomposition rates in small forest fragments. The positive effects of selective logging on bee pollination, bird seed dispersal and army-ant raiding were direct, i.e. not related to changes in biodiversity, and were probably due to behavioural changes of these highly mobile animal taxa. We conclude that animal-mediated ecosystem processes respond in distinct ways to different types of human disturbance in Kakamega Forest. Our findings suggest that forest fragmentation affects ecosystem processes indirectly by changes in biodiversity, whereas selective logging influences processes directly by modifying local environmental conditions and resource distributions. The positive to neutral effects of selective logging on ecosystem processes show that the functionality of tropical forests can be maintained in moderately disturbed forest fragments. Conservation concepts for tropical forests should thus include not only remaining pristine forests but also functionally viable forest remnants.
authors: Department of Ecology, Institute of Zoology, University of Mainz, Mainz, Germany. matthias.schleuning@senckenberg.de
authors: Matthias
authors: M
authors: Schleuning
authors: Nina
authors: N
authors: Farwig
authors: Marcell K
authors: MK
authors: Peters
authors: Thomas
authors: T
authors: Bergsdorf
authors: Bärbel
authors: B
authors: Bleher
authors: Roland
authors: R
authors: Brandl
authors: Helmut
authors: H
authors: Dalitz
authors: Georg
authors: G
authors: Fischer
authors: Wolfram
authors: W
authors: Freund
authors: Mary W
authors: MW
authors: Gikungu
authors: Melanie
authors: M
authors: Hagen
authors: Francisco Hita
authors: FH
authors: Garcia
authors: Godfrey H
authors: GH
authors: Kagezi
authors: Manfred
authors: M
authors: Kaib
authors: Manfred
authors: M
authors: Kraemer
authors: Tobias
authors: T
authors: Lung
authors: Clas M
authors: CM
authors: Naumann
authors: Gertrud
authors: G
authors: Schaab
authors: Mathias
authors: M
authors: Templin
authors: Dana
authors: D
authors: Uster
authors: J Wolfgang
authors: JW
authors: Wägele
authors: Katrin
authors: K
authors: Böhning-Gaese
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D044822:Biodiversity; D017753:Ecosystem; D006802:Human Activities; D006801:Humans; D008962:Models, Theoretical; D014197:Trees; D014329:Tropical Climate