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Title: Photodegradation accelerates ecosystem N cycling in a simulated California grassland

Abstract

Photodegradation accelerates litter decay in arid grasslands where plant growth and litter decay are strongly controlled by precipitation and evapotranspiration. However, the effects of photodegradation on ecosystem C and N dynamics are not well understood. We examined the effects using an ecosystem biogeochemical model DayCent-UV with photodegradation explicitly represented and validated. The model was parameterized for a California grassland where photodegradation was documented to release CO 2 from litter. The model was parameterized with an inverse modeling approach using an extensive data set of six years of daily observed carbon and water gas exchange (gross primary production, ecosystem respiration, and evapotranspiration), soil temperature, and soil moisture. DayCent-UV correctly simulated the seasonal patterns of the observed gas exchange and closely simulated the inter-annual variation in the gas exchange and biomass production rates. The simulations suggested that the inter-annual variation is driven more by actual evapotranspiration than by precipitation because a large portion of precipitation is lost as runoff during wet years. Photodegradation in DayCent-UV accelerated C and N cycling, decreasing system C and N by 9.2% and 9.5% and C and N residence times by 9.4% and 18.2%. Accelerated N cycling made a greater fraction of system N available for plants,more » increasing net N mineralization and plant production for a given amount of system N. Increased net N mineralization was due to decreased immobilization by microbes in the aboveground organic matter. Photodegradation did not alter the control on plant production by evapotranspiration. These results suggest that at the ecosystem level, the central effect of photodegradation is to suppress microbial activity. Here, we conclude that photodegradation accelerates N cycling at the expense of microbes in this grassland, making it more efficient in supporting plant growth for a given amount of N in the system.« less

Authors:
ORCiD logo [1];  [1];  [1];  [1]
  1. Colorado State Univ., Fort Collins, CO (United States)
Publication Date:
Research Org.:
Univ. of Illinois, Champaign, IL (United States). Center for Advanced Bioenergy and Bioproducts Innovation
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Contributing Org.:
U.S. Department of Agriculture (USDA) UV-B Monitoring and Research Program, Colorado State University, under USDA National Institute of Food and Agriculture Grant 2016-34263-25763. S. Asao was also supported by Australian Research Council Grant CE140100008. AmeriFlux data used were supported in part by the Office of Science (BER), U.S. Department of Energy, Grant No. DE-FG02-03ER63638. W.J. Parton was also supported by USDA cooperative agreements (58-5402-4-001, 59-1902-4-00), the USDA National Institute of Food and Agriculture (NIFA) project (2015-67003-23456),
OSTI Identifier:
1464424
Alternate Identifier(s):
OSTI ID: 1465377; OSTI ID: 1467752
Grant/Contract Number:  
SC0018420; FG02-03ER63638; 090634-16921
Resource Type:
Published Article
Journal Name:
Ecosphere
Additional Journal Information:
Journal Volume: 9; Journal Issue: 8; Journal ID: ISSN 2150-8925
Publisher:
Ecological Society of America
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; biogeochemistry; C and N cycling; DayCent; ecosystem modeling; grassland; litter decomposition; photodecay; photodegradation; solar radiation; ultraviolet radiation

Citation Formats

Asao, Shinichi, Parton, William J., Chen, Maosi, and Gao, Wei. Photodegradation accelerates ecosystem N cycling in a simulated California grassland. United States: N. p., 2018. Web. doi:10.1002/ecs2.2370.
Asao, Shinichi, Parton, William J., Chen, Maosi, & Gao, Wei. Photodegradation accelerates ecosystem N cycling in a simulated California grassland. United States. doi:10.1002/ecs2.2370.
Asao, Shinichi, Parton, William J., Chen, Maosi, and Gao, Wei. Mon . "Photodegradation accelerates ecosystem N cycling in a simulated California grassland". United States. doi:10.1002/ecs2.2370.
@article{osti_1464424,
title = {Photodegradation accelerates ecosystem N cycling in a simulated California grassland},
author = {Asao, Shinichi and Parton, William J. and Chen, Maosi and Gao, Wei},
abstractNote = {Photodegradation accelerates litter decay in arid grasslands where plant growth and litter decay are strongly controlled by precipitation and evapotranspiration. However, the effects of photodegradation on ecosystem C and N dynamics are not well understood. We examined the effects using an ecosystem biogeochemical model DayCent-UV with photodegradation explicitly represented and validated. The model was parameterized for a California grassland where photodegradation was documented to release CO2 from litter. The model was parameterized with an inverse modeling approach using an extensive data set of six years of daily observed carbon and water gas exchange (gross primary production, ecosystem respiration, and evapotranspiration), soil temperature, and soil moisture. DayCent-UV correctly simulated the seasonal patterns of the observed gas exchange and closely simulated the inter-annual variation in the gas exchange and biomass production rates. The simulations suggested that the inter-annual variation is driven more by actual evapotranspiration than by precipitation because a large portion of precipitation is lost as runoff during wet years. Photodegradation in DayCent-UV accelerated C and N cycling, decreasing system C and N by 9.2% and 9.5% and C and N residence times by 9.4% and 18.2%. Accelerated N cycling made a greater fraction of system N available for plants, increasing net N mineralization and plant production for a given amount of system N. Increased net N mineralization was due to decreased immobilization by microbes in the aboveground organic matter. Photodegradation did not alter the control on plant production by evapotranspiration. These results suggest that at the ecosystem level, the central effect of photodegradation is to suppress microbial activity. Here, we conclude that photodegradation accelerates N cycling at the expense of microbes in this grassland, making it more efficient in supporting plant growth for a given amount of N in the system.},
doi = {10.1002/ecs2.2370},
journal = {Ecosphere},
number = 8,
volume = 9,
place = {United States},
year = {2018},
month = {8}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: 10.1002/ecs2.2370

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Works referenced in this record:

Correction of flux measurements for density effects due to heat and water vapour transfer
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