B06 - Taxonomic, functional, phylogenetic, and biogeographical diversity of vascular plants in rainforest transformation systems on Sumatra (Indonesia)
Understanding changes of plant diversity at different spatial and temporal scales is essential for an overall assessment of economic-ecological trade-offs and for developing science-based solutions for sustainable land use and biodiversity conservation. Subproject B06 investigates changes in different dimensions of plant diversity from local to biogeographical scales. In the first phase, we studied the impact of forest conversion on vascular plant diversity across the four land-use systems lowland rainforest, jungle rubber, rubber plantations and oil palm plantations in Sumatra. We conducted plot-based species inventories on all 32 core plots from February 2013 till August 2014. Forest had a clearly distinct floristic composition while the floristic composition of the other systems - and especially the two plantations - converged. Forest was almost entirely composed by native species, but the number and relative abundance of alien species increased from forest towards the plantations and was highest in oil palm plantations (see e.g. Wahyuni et al. 2016). Driving factors for altered plant communities in the plantations are management (weeding, fertilization, and herbicide application) and stand characteristics such as canopy openness and microclimate which creates unfavourable conditions for most forest species. Forest has a denser canopy and a cooler and more humid microclimate while the canopy in jungle rubber and especially in the plantations is more open, corresponding with a hotter and dryer climate (Drescher et al. 2016).
Community phylogenies were constructed of understorey plant communities to investigate phylogenetic signatures in the responses of plant communities to land-use change and biological invasions that are particularly important in plantations. Our results showed that forest conversion into agriculture areas negatively affects understorey plant diversity both at taxonomic and phylogenetic level.
These data help to understand changes in plant diversity at different spatial scales which is essential to assess possible ecological consequences and to identify science-based options for sustainable land-use management and conservation. Further, about 80,000 standardized high-quality digital photographs of all collected specimen were taken for our Sumatra plant database that is currently under development (http://184.108.40.206/sumatra/home).
Additionally, 120 epiphyte plots were established with 30 plots in each of the four land-use systems (Böhnert et al. 2016). We recorded a total of 3,955 individuals of vascular epiphytes belonging to 81 species and 20 families. At plot level, forest, jungle rubber, and oil palm were statistically indistinguishable in terms of species richness, diversity, and evenness but had significantly higher values than rubber plantations. Oil palm plantations had the highest epiphyte abundance, but lowest total species numbers of all systems. Furthermore, oil palm had distinct, fern-dominated epiphyte communities, while jungle rubber and rubber plots were more similar to forest. In conclusion, epiphyte diversity in monocultural plantations is severely reduced.
In the second phase, we will expand our studies to include functional, phylogenetic and biogeographical aspects of plant diversity. Following our sampling protocols from the first phase, we will inventory the 12 new core plots in riparian habitats to compare them to the 32 core plots with well-drained soils. We will investigate how changes in micro-topography and edaphic conditions affect alpha- and beta-diversity, evenness, and species composition. Further, we will extend our investigations of ecologically relevant plant traits within the core plots to quantify changes in functional diversity and composition. Combining species diversity with the functional and phylogenetic dimensions of plant diversity will allow us to disentangle effects of land management and ecological filters on plant diversity and composition along gradients of land-use intensity and topography and to quantify losses in ecological functions in direct comparison with species loss.
The overarching goal of B06 is to quantify the effects of rainforest conversion on plant diversity and ecosystem functioning and to elucidate the underlying mechanisms by (1) integrating different dimensions of plant diversity (species diversity, functional and phylogenetic diversity, native vs. alien naturalized species); (2) investigating how plant diversity is affected by conversion of rainforest and land-use changes from local to landscape scales.