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Title: Field evidences for the positive effects of aerosols on tree growth

Theoretical and eddy-covariance studies demonstrate that aerosol-loading stimulates canopy photosynthesis, but field evidence for the aerosol effect on tree growth is limited. For this study, we measured in-situ daily stem growth rates of aspen trees under a wide range of aerosol-loading in China. The results showed that daily stem growth rates were positively correlated with aerosol-loading, even at exceptionally high aerosol levels. Using structural equation modelling analysis, we showed that variations in stem growth rates can be largely attributed to two environmental variables co-varying with aerosol loading: diffuse fraction of radiation and vapor pressure deficit (VPD). Furthermore, we found that these two factors influence stem growth by influencing photosynthesis from different parts of canopy. By using field observations and a mechanistic photosynthesis model, we demonstrate that photosynthetic rates of both sun and shade leaves increased under high aerosol-loading conditions but for different reasons. For sun leaves, the photosynthetic increase was primarily attributed to the concurrent lower VPD; for shade leaves, the positive aerosol effect was tightly connected with increased diffuse light. Overall, our study provides the first field-evidence of increased tree growth under high aerosol loading. We highlight the importance of understanding biophysical mechanisms of aerosol-meteorology interactions, and incorporating themore » different pathways of aerosol effects into earth system models to improve the prediction of large-scale aerosol impacts, and the associated vegetation-mediated climate feedbacks.« less
Authors:
 [1] ; ORCiD logo [2] ;  [3] ;  [4] ;  [1] ;  [1] ;  [1] ;  [5] ;  [6] ;  [7] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1]
  1. Chinese Academy of Sciences (CAS), Beijing (China). State Key Lab. of Vegetation and Environmental Change and Inst. of Botany; Univ. of Chinese Academy of Sciences, Beijing (China)
  2. Brookhaven National Lab. (BNL), Upton, NY (United States). Environmental and Climate Sciences Dept.
  3. Carnegie Inst. of Science, Stanford, CA (United States). Dept. of Global Ecology; Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Joint Global Change Research Inst.
  4. Harvard Univ., Cambridge, MA (United States). Dept. of Organismic and Evolutionary Biology
  5. Peking Univ., Beijing (China). Dept. of Ecology and College of Urban and Environmental Science
  6. Minzu Univ. of China, Beijing (China). College of Life and Environmental Sciences
  7. Univ. of Illinois, Urbana-Champaign, IL (United States). Dept. of Natural Resources and Environmental Sciences
Publication Date:
Report Number(s):
BNL-205741-2018-JAAM
Journal ID: ISSN 1354-1013
Grant/Contract Number:
SC0012704; 2014CB954003; 2017YFC0503900
Type:
Accepted Manuscript
Journal Name:
Global Change Biology
Additional Journal Information:
Journal Name: Global Change Biology; Journal ID: ISSN 1354-1013
Publisher:
Wiley
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States); Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23); National Basic Research Program of China; National Natural Science Foundation of China (NNSFC)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; aerosol loading; tree stem growth; vapor pressure deficit; diffuse radiation; sun/shade leaf; canopy photosynthesis; mechanistic photosynthesis model; aerosol‐meteorology interactions
OSTI Identifier:
1440889