Journal
AGRICULTURAL AND FOREST METEOROLOGY
Volume 296, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.agrformet.2020.108212
Keywords
Ecosystem CO2 fluxes; Eddy covariance; Underlying surface change; Wetland reclamation; Yangtze estuary
Categories
Funding
- National Key Research and Development Program of China [2017YFC0505706]
- National Natural Science Foundation of China [31800411]
- Natural Science Foundation of Shanghai [17ZR1427400]
- Shanghai Committee of Science and Technology Fund [19DZ1203301]
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The study investigates the response of CO2 budget in coastal wetlands to agroforestry reclamations. The results show that agroforestry conversions substantially decrease the CO2 fixation service by changing the ecosystem's structure and function, with wetland vegetation productivity decrease being the main reason. The interannual variability of NEE is primarily attributed to functional changes rather than meteorological variations, suggesting the importance of wise land-use policy and management measures in reclaimed coastal areas for global warming mitigation.
How does the CO2 budget in coastal wetlands respond to dynamic and composite agroforestry reclamations is unclear. For six consecutive years, CO2 flux data were measured using the eddy covariance (EC) technique to determine the CO2 budget changes and the key factors controlling the variations of net CO2 ecosystem exchange (NEE) over a reclaimed coastal wetland in the Yangtze estuary, China. After agroforestry conversions in spring 2013, the annual NEE decreased substantially from -655.7 (day 109-365 in 2011) and -558.4 (2012) to 258.1 (2013) and -198.1(2014) and persisted on decreasing to -160.8 (2015) and -141.2 (2016) g C m(-2 )yr(-1). vertical bar ER/GPP vertical bar ratio persistently increased from 0.40 in 2011 to 0.89 in 2016, suggesting a decoupling between ER and GPP in the coastal reclaimed site. The decrease of GPP was possibly attributed more to the decreased wetland vegetation productivity. The increased ER was due to the emergence of young forest (YF) and aquaculture pond (AP) with high net CO2 emissions in the flux footprint. A homogeneity-of-slopes (HOS) analysis showed that the interannual variability (IAV) of NEE was attributed more to the functional changes (19.0 %), rather than the interannual meteorological variations (9.2 %). The functional changes were also verified by the significant decreased A(max) and the slightly increased partial derivative, both of which might be caused by the changed dominant wetland plant species and their growth pattern. The fluctuated Q(10) and R-10 during the agroforestry reclamations reflected the seasonal changes in the compositions and respiration characteristics of different land-use types within the CO2 flux footprint. Findings imply that agroforestry reclamations in temperate coastal wetlands substantially decrease the CO2 fixation service by changing the ecosystem's structure and function. Our results call for more wise land-use policy and management measures in reclaimed coastal areas around the world to pursue global warming mitigation.
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