The Global Ecosystems Monitoring network: Monitoring ecosystem productivity and carbon cycling across the tropics

A rich understanding of the productivity, carbon and nutrient cycling of terrestrial ecosystems is essential in the context of understanding, modelling and managing the future response of the biosphere to global change. This need is particularly acute in tropical ecosystems, home to over 60% of global terrestrial productivity, over half of planetary biodiversity, and hotspots of anthropogenic pressure. In recent years there has been a surge of activity in collecting data on the carbon cycle, productivity, and plant functional traits of tropical ecosystems, most intensively through the Global Ecosystems Monitoring network (GEM). The GEM approach provides valuable insights by linking field-based ecosystem ecology with the needs of Earth system science. In this paper, we review and synthesize the context, history and recent scientific output from the GEM network. Key insights have emerged on the spatial and temporal variability of ecosystem productivity and on the role of temperature and drought stress on ecosystem function and resilience. New work across the network is now linking carbon cycling to nutrient cycling and plant functional traits, and subsequently to airborne remote sensing. We discuss some of the novel emerging patterns and practical and methodological challenges of this approach, and examine current and possible future directions, both within this network and as lessons for a more general terrestrial ecosystem observation scheme.The core establishment of the GEM network has been supported by the Gordon and Betty Moore Foundation, and European Research Council Advanced Investigator Grant GEM-TRAIT (321131). Site development in individual locations have been supported by multiple grants from the UK Natural Environment Research Council, in particular NE/D014174/1, NE/J023418/1, NE/I014705/1, NE/K016369/1, NE/K016385/1, NE/F005776/1, NE/N012453/1, NE/P001092/1 and NE/S01084X/1. Activities in Africa have been additionally supported by Royal Society-Leverhulme and Royal Society-DFID Africa Capacity Building Awards. Work in Malaysia has been greatly supported by the Sime Darby Foundation. YM is supported by the Jackson Foundation