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Title: Age-dependent leaf physiology and consequences for crown-scale carbon uptake during the dry season in an Amazon evergreen forest

Satellite and tower-based metrics of forest-scale photosynthesis generally increase with dry season progression across central Amazônia, but the underlying mechanisms lack consensus. We conducted demographic surveys of leaf age composition, and measured age-dependence of leaf physiology in broadleaf canopy trees of abundant species at a central eastern Amazon site. Using a novel leaf-to-branch scaling approach, we used this data to independently test the much-debated hypothesis—arising from satellite and tower-based observations—that leaf phenology could explain the forest-scale pattern of dry season photosynthesis. Stomatal conductance and biochemical parameters of photosynthesis were higher for recently mature leaves than for old leaves. Most branches had multiple leaf age categories simultaneously present, and the number of recently mature leaves increased as the dry season progressed because old leaves were exchanged for new leaves. These findings provide the first direct field evidence that branch-scale photosynthetic capacity increases during the dry season, with a magnitude consistent with increases in ecosystem-scale photosynthetic capacity derived from flux towers. In conclusion, interaction between leaf age-dependent physiology and shifting leaf age-demographic composition are sufficient to explain the dry season photosynthetic capacity pattern at this site, and should be considered in vegetation models of tropical evergreen forests.
Authors:
ORCiD logo [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ; ORCiD logo [8] ;  [9] ;  [10] ;  [11] ;  [12] ;  [13] ;  [14] ;  [9] ;  [15] ;  [3]
  1. Univ. of Arizona, Tucson, AZ (United States). Dept. of Ecology and Evolutionary Biology; Brown Univ., Providence, RI (United States). Inst. at Brown for Environment and Society
  2. Univ. of Arizona, Tucson, AZ (United States). Dept. of Ecology and Evolutionary Biology; Brookhaven National Lab. (BNL), Upton, NY (United States). Environmental and Climate Sciences Dept.
  3. Univ. of Arizona, Tucson, AZ (United States). Dept. of Ecology and Evolutionary Biology
  4. Univ. of Sao Paulo (Brazil). Center for Nuclear Energy in Agriculture (CENA)
  5. Univ. of California, Irvine, CA (United States). Ecology and Evolutionary Biology and Center for Environmental Biology
  6. Federal Univ. of Western Para, Santarem (Brazil). Inst. for Biodiversity and Forest (UFOPA)
  7. Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Civil and Environmental Engineering
  8. Univ. of Campinas (UNICAMP), Sao Paulo (Brazil). Dept. of Plant Biology
  9. National Inst. of Amazonian Research (INPA), Manaus (Brazil). Tropical Forest Sciences
  10. Univ. of Arizona, Tucson, AZ (United States). Dept. of Ecology and Evolutionary Biology; Michigan State Univ., East Lansing, MI (United States). Dept. of Forestry
  11. Brazilian Agricultural Research Corp. (EMBRAPA), Herbarium of Embrapa Amazônia Oriental (IAN), Santarem (Brazil)
  12. Univ. of Technology, Sydney (Australia). Plant Functional Biology and Climate Change Cluster
  13. Federal Univ. of Western Para, Santarem (Brazil). Inst. for Biodiversity and Forest (UFOPA). Atmospheric Sciences Dept. and Inst. of Engineering and Geosciences
  14. Michigan State Univ., East Lansing, MI (United States). Dept. of Forestry
  15. Federal Univ. of Western Para, Santarem (Brazil). Inst. for Biodiversity and Forest (UFOPA). Society, Nature and Development Dept.
Publication Date:
Report Number(s):
BNL-203201-2018-JAAM
Journal ID: ISSN 0028-646X
Grant/Contract Number:
SC0012704; OISE-0730305; SC0008383
Type:
Accepted Manuscript
Journal Name:
New Phytologist
Additional Journal Information:
Journal Volume: 218; Journal Issue: 1; Journal ID: ISSN 0028-646X
Publisher:
Wiley
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23); National Science Foundation (NSF); Univ. of Arizona, Tucson, AZ (United States); Brazilian Agricultural Research Corp. (EMBRAPA); Large Scale Biosphere-Atmosphere Program in the Amazon (LBA); Herbarium of Embrapa Amazônia Oriental (IAN)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES
OSTI Identifier:
1424982
Alternate Identifier(s):
OSTI ID: 1423698