Abstract
Ongoing habitat loss and fragmentation alter the functional diversity of forests. Generalising the magnitude of change in functional diversity of fragmented landscapes and its drivers is challenging because of the multiple scales at which landscape fragmentation takes place. Here we propose a multi-scale approach to determine whether fragmentation processes at the local and landscape scales are reducing functional diversity of trees in the East Usambara Mountains, Tanzania. We employ a structural equation modelling approach using five key plant traits (seed length, dispersal mode, shade tolerance, maximum tree height, and wood density) to better understand the functional responses of trees to fragmentation at multiple scales. Our results suggest both direct and indirect effects of forest fragmentation on tree functional richness, evenness and divergence. A reduction in fragment area appears to exacerbate the negative effects resulting from an increased amount of edge habitat and loss of shape complexity, further reducing richness and evenness of traits related to resource acquisition and favouring tree species with fast growth. As anthropogenic disturbances affect forests around the world, we advocate to include the direct and indirect effects of forest fragmentation processes to gain a better understanding of shifts in functional diversity that can inform future management efforts.
Highlights
Shape complexity was positively associated with fragment area, with larger fragments characterized by more complex shapes than small fragments
We found that direct and indirect effects between fragment-level fragmentation attributes appeared to be important drivers of local functional diversity within plots, while landscapelevel attributes seemed to be less important in most cases
At the fragment-level, we find an indirect effect of fragment area on functional richness and functional divergence via its effects on shape complexity and edge effects, respectively
Summary
Study areaThe forest of the East Usambara Mountains stretches continuously from about 250 m to 1100 m asl in the southern part of this mountain range to form what is protected as Amani Nature Reserve (8380 ha; -5 ̊04’58.80" S 38 ̊40’1.20" E). To the north of this reserve is Nilo Nature Reserve, and eastwards is the Derema corridor and several large fragments of lowland forest. The forest on the submontane plateau, in and around the primary study area of Amani Nature Reserve, is dominated by a suite of wet rainforest species. These include two emergent species Newtonia buchananii (Fabaceae) and Maranthes goetzeniana (Chrysobalanaceae), and several canopy and midstory/understorey species such as Allanblackia stuhlmannii (Clusiaceae), Cephalosphaera usambarensis (Myristicaceae), Sorindeia madagascariensis (Anacardiaceae), Parinari excelsa (Chrysobalanaceae), Isoberlinia schefflerii (Fabaceae), Greenwayodendron suaveolens (Annonaceae), Anisophyllea obtusifolia (Anisophylleaceae), Leptonychia usambarensis (Sterculiaceae), Myrianthus holstii (Urticaceae), Macaranga capensis (Euphorbiaceae), Trilepisium madagascariense (Moraceae) and Strombosia scheffleri (Olacaceae). The forest contains Maesopsis eminii (Rhamnaceae), an exotic, invasive gap- and edge-specialist tree species [29,30]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
