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© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 14 Feb 2019

Research article | 14 Feb 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).

Global variability of carbon use efficiency in terrestrial ecosystems

Xiaolu Tang1,2,3, Nuno Carvalhais1,4, Catarina Moura1,4, Bernhard Ahrens1, Sujan Koirala1, Shaohui Fan5, Fengying Guan5, Wenjie Zhang6,7, Sicong Gao7, Vincenzo Magliulo8, Pauline Buysse9, Shibin Liu2, Guo Chen2, Wunian Yang2, Zhen Yu10, Jingjing Liang11, Leilei Shi12, Shenyan Pu3,13, and Markus Reichstein1,14,15 Xiaolu Tang et al.
  • 1Department Biogeochemical Integration, Max Planck Institute for Biogeochemistry, Jena, Germany
  • 2College of Earth Science, Chengdu University of Technology, Chengdu, Sichuan, China
  • 3State Environmental Protection Key Laboratory of Synergetic Control and Joint Remediation for Soil & Water Pollution, Chengdu University of Technology, Chengdu, China
  • 4Departamento de Ciências e Engenharia do Ambiente, DCEA, Faculdade de Ciênciase Tecnologia, FCT, Universidade Nova de Lisboa, Caparica, Portugal
  • 5Key laboratory of Bamboo and Rattan, International Centre for Bamboo and Rattan, Beijing, P.R. China
  • 6State Key Laboratory of Resources and Environmental Information System, Institute of Geographic Sciences and Natural Resources Research, Beijing, China
  • 7School of Life Science, University of Technology Sydney, NSW, Australia
  • 8CNR – Institute for Mediterranean Agricultural and Forest Systems, Via Patacca 85, Ercolano (Napoli), Italy
  • 9UMR ECOSYS, INRA-AgroParisTech, Université Paris Saclay, Thiverval-Grignon, France
  • 10Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA, USA
  • 11Department of Forestry and Natural Resources, Purdue University, 715 W. State St, West Lafayette, IN, USA
  • 12Laboratory of Geospatial Technology for the Middle and Lower Yellow River Regions, College of Environment and Planning, Henan University, Jinming Avenue, Kaifeng, China
  • 13State Key Laboratory of Geohazard Prevention and Geoenvironment Protection (Chengdu University of Technology), Chengdu, Sichuan, China
  • 14German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, 04103 Leipzig, Germany
  • 15Michael Stifel Center Jena (MSCJ) for Data-Driven & Simulation Science, 07743 Jena, Germany

Abstract. Vegetation carbon use efficiency (CUE) is a key measure of carbon (C) transfer from the atmosphere to terrestrial biomass, and indirectly reflects how much C is released through autotrophic respiration from the vegetation to the atmosphere. Diagnosing the variability of CUE with climate and other environmental factors is fundamental to understand its driving factors, and to further fill the current gaps in knowledge about the environmental controls on CUE. Thus, to study CUE variability and its driving factors, this study established a global database of site-year CUE based on observations from 188 field measurement sites for five ecosystem types – forest, grass, wetland, crop and tundra. The spatial pattern of CUE was predicted from global climate and soil variables using Random Forest, and compared with estimates from Dynamic Global Vegetation Models (DGVMs) from the TRENDY model ensemble. Globally, we found two prominent CUE gradients in ecosystem types and latitude, that is, CUE varied with ecosystem types, being the highest in wetlands and lowest in grassland, and CUE decreased with latitude with the lowest CUE in tropics, and the highest CUE in higher latitude regions. CUE varied greatly between data-derived CUE and TRENDY-CUE, but also among TRENDY models. Both data-derived and TRENDY-CUE challenged the constant value of 0.5 for CUE, independent of environmental controls. However, given the role of CUE in controlling the spatial and temporal variability of the terrestrial biosphere C cycle, these results emphasize the need to better understand the biotic and abiotic controls on CUE to reduce the uncertainties in prognostic land-process model simulations. Finally, this study proposed a new estimate of net primary production based on CUE and gross primary production, offering another benchmark for net primary production comparison for global carbon modelling.

Xiaolu Tang et al.
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Xiaolu Tang et al.
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Short summary
Vegetation CUE is a key measure of carbon transfer from the atmosphere to terrestrial biomass. This study modelled global CUE with published observations using random forest. CUE varied with ecosystem types and spatially decreased with latitude, challenging the previous conclusion that CUE was independent of environmental controls. Our results emphasize a better understanding of environmental controls on CUE to reduce uncertainties in prognostic land-process model simulations.
Vegetation CUE is a key measure of carbon transfer from the atmosphere to terrestrial biomass....