Different rainforest ecosystems in central Sumatra have undergone rapid conversions within the last few decades. Our studies showed that before transformations took place, these ecosystems persisted already under natural and human disturbance. The palaeoecological approach extends our knowledge of long-term ecological functioning and resilience of rainforests under changing natural and anthropogenic disturbance at different time periods. In the third phase, we will complete our palaeoecological and palaeoenvironmental investigation for a synthesis of the long-term vegetation, fire and climate dynamics as well as past human impact in work package (WP) 1. As a new innovative approach we will study at least two cores from key sites applying metabarcoding on subfossil pollen, as well as pollen rain samples, in collaboration with B14 Gailing for identification to a lower taxonomic rank (e.g. genus or species level). The synthesis and upscaling of this unique palaeoecological approach, studying a heterogeneity gradient on landscape level from the coast, riparian depressions, lowland and submontane will extend our knowledge of ecological functioning of the rainforest ecosystems and provide important information on past vegetation response to natural and human disturbance as background information for A, B and C groups of EFForTS. This synthesis includes also long-term changes of nitrogen deposition and hydrology in different landscapes in collaboration with A05 Veldkamp/Corre and B08 Scheu, respectively.
Modern pollen rain studies are essential to investigate plant phenological responses to climate and environmental variability (e.g. occurrences of El Niño and La Niña vs. normal year). We will continue the pollen rain studies in WP 2 for another two years for a synthesis of data sets of 9 years in the rainforest and in the different land-use systems (rubber jungle, rubber and oil palm plantation) in collaboration with B06 Kreft and Z02 Scheu/Knohl/Erasmi. This will be the first long-term modern pollen rain study in tropical rainforest and transformation systems. We will also continue our pollen rain study (started in 2017) in order to capture intra-annual variability effects (4 times per year) on pollen production and reproductive success rate of plants in the B11 Oil Palm Biodiversity Enrichment Experiment – EFForTS BEE (B11 Hölscher/Kreft/Wollni). We will also contribute to the Landscape Assessment for the characterisation of naturalness, disturbance and grade of transformation of the vegetation, including the loss of plant diversity.
The differences in plant diversity, ecosystem dynamics, and reproductive phenology between tropical rainforest and rainforest transformation systems should result in differences in plant – pollinator interactions and pollinator populations. In WP 3 as a new innovative approach we will study pollen collected by stingless bees from different land-use systems (forest, shrub-land, rubber, oil palm) and with changes in landscape heterogeneity (forest amount at the landscape scale) in collaboration with B09 Westphal/Grass and B14 Gailing. The combination of pollen analysis and metabarcoding will allow a precise quantitative and qualitative identification for a better understanding of plant-pollinator interactions and of the drivers of pollinator populations in human-modified tropical landscapes.