Reviews and syntheses: Field data to benchmark the carbon cycle models for tropical forests

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 CO 2 levels. Projections of the future C balance of the tropics vary widely among global models. A current effort of the modeling community, the IL-AMB (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 CO 2 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.

Tropical forest temperature thresholds for gross primary productivity

“…Satellite-derived NPP has revealed decreasing trends across the tropical forest biome between~2000 and 2010 (e.g., Running 2010, Cleveland et al 2015), while process models predict a long-term increase in NPP (Cleveland et al 2015). Accurate projections of carbon cycling for the tropical forest biome will require direct field measurements from representative sites to capture landscape-level variability, over a sufficiently long time (Clark et al 2017). To complement such large-scale analyses, continuous, high-resolution measurements of in situ canopy temperatures, such as described here, will be critical to understanding diverse canopy responses to rapid climate warming expected in coming years.…”

Ecohydrological changes after tropical forest conversion to oil palm

“…Hence, T&C has been also parameterized for two tropical forest ecosystems in Indonesia and Malaysia (see supplementary material). An accurate representation of carbon/water fluxes in the tropics is particularly challenging given the lack of reliable short-and long-term observations (Clark et al 2017) and the fact that most of existing terrestrial biosphere models systematically fail to reproduce forest seasonal dynamics (Restrepo-Coupe et al 2017). However, based on recent findings on the role of leaf age in regulating photosynthetic seasonality (Wu et al 2016), T&C has been modified to account for a mechanistic light-controlled phenology and provides an improved representation of the observed temporal dynamics of tropical forests (Manoli et al 2018).…”

Testing for changes in biomass dynamics in large‐scale forest datasets

“…The large uncertainty surrounding estimated fluxes and their long-term trends observed here, even with such a large-scale long-term study, highlights the difficulty of accurately capturing changes in forest dynamics from field data (Clark, Asao, et al, 2017). Wagner, Rutishauser, Blanc, and Herault (2010) trends to the precise methods of data quality assessment and quality control (QAQC; Figure S18).…”