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Yit Arn Teh (Newcastle University) – Disentangling the effects of functional diversity, land-use change and environmental conditions on biogeochemical cycling in human-modified tropical forest in northern Borneo
6th December 2019 @ 3:00 pm - 4:00 pm
Abstract: Land-use change in the lowland tropics is irrevocably altering biodiversity, and transforming ecosystem structure and function in the tropics. Here we report the results of a large-scale research programme investigating the interactive effects of functional diversity and land-use change on ecosystem structure and function in Borneo. Major cover types included old-growth forest, moderately logged forest (logged once or twice), heavily logged forest (logged twice or more) and oil palm. Carbon dynamics were quantified at multiple spatial and temporal scales using RAINFOR-GEM carbon plots, soil flux and isotope measurements, remote sensing, process-based modelling and data assimilation. The functional diversity of plant, microbial and invertebrate communities across different land-uses was determined using taxonomic surveys, substrate utilisation experiments, molecular and lipid biomarker analysis, and quantification of eco-physiological traits. Targeted plot-level manipulations were also implemented to test the role of key functional groups in modulating biogeochemical cycles. Key ecosystem processes, such as net primary productivity, were comparable among different land-uses. Other processes (e.g. decomposition, respiration) or system properties (e.g. canopy structure, foliar nitrogen and phosphorus) varied depending on the effects of land-use history, biotic functional traits, or underlying site conditions (e.g. topography, soil nutrient status, microclimate). Use of the CARDAMOM data assimilation scheme was effective in simulating temporal trends in carbon dynamics, with limits imposed by litterfall and leaf area index data. Evidence for both top-down and bottom-up regulation of ecosystem processes was observed. For example, the functional composition of the plant community appeared to regulate the structure and function of soil microbial communities; removal of ectomycorrhizal Dipterocarpaceae due to selective logging led to significant reductions in mycorrhizae and a concomitant rise in saprotrophic fungi. In contrast, invertebrates appeared to exert a bottom-up control on ecosystem structure and function. For example, termites mitigated the effects of drought on soil moisture, decomposition and seedling survival.