Abstract
Abstract. For more accurate projections of both the global carbon (C) cycle and the changing climate, a critical current need is to improve the representation of tropical forests in Earth system models. Tropical forests exchange more C, energy, and water with the atmosphere than any other class of land ecosystems. Further, tropical-forest C cycling is likely responding to the rapid global warming, intensifying water stress, and increasing atmospheric CO2 levels. Projections of the future C balance of the tropics vary widely among global models. A current effort of the modeling community, the ILAMB (International Land Model Benchmarking) project, is to compile robust observations that can be used to improve the accuracy and realism of the land models for all major biomes. Our goal with this paper is to identify field observations of tropical-forest ecosystem C stocks and fluxes, and of their long-term trends and climatic and CO2 sensitivities, that can serve this effort. We propose criteria for reference-level field data from this biome and present a set of documented examples from old-growth lowland tropical forests. We offer these as a starting point towards the goal of a regularly updated consensus set of benchmark field observations of C cycling in tropical forests.
Highlights
The near-future research effort should be on development of a set of widely acceptable benchmarks that can be used to objectively, effectively, and reliably evaluate fundamental properties of land models to improve their prediction performance skills. (Luo et al, 2012).Improved modeling of tropical-forest carbon (C) cycling is urgently needed for projecting future climate and for guiding global policy concerning greenhouse gases
Projecting the future integrated effects of climatic and atmospheric change on tropical forest C cycling can only be approached through process-based modeling
Do the modeled leaf area index (LAI), aboveground live biomass, and aboveground wood production fall within the 95 % confidence limits of the observations from tropical forests? Do relationships among stocks and fluxes match the relationships found among the field observations? Such questions can be posed at the biome level or for specific tropical regions, depending on a model’s spatial resolution and the available data
Summary
The near-future research effort should be on development of a set of widely acceptable benchmarks that can be used to objectively, effectively, and reliably evaluate fundamental properties of land models to improve their prediction performance skills. (Luo et al, 2012). Improved modeling of tropical-forest carbon (C) cycling is urgently needed for projecting future climate and for guiding global policy concerning greenhouse gases. Projecting the future integrated effects of climatic and atmospheric change on tropical forest C cycling can only be approached through process-based modeling. A further indication of unresolved issues for modeling this biome is that 9 of 10 C cycle models failed to simulate the climatic responses of the global land C sink through 1980–2009 as inferred from the atmospheric data (most models overestimated the land sink’s sensitivity to rainfall and/or underestimated its sensitivity to temperature; Fig. 6.17 in Ciais et al, 2013). We review the current availability of such data and present a set of documented examples We offer these ideas and examples as a starting point towards the goal of a constantly updated consensus set of benchmark field observations for the tropical-forest biome
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