Estimating canopy gross primary production by combining phloem stable isotopes with canopy and mesophyll conductances

• Published in: Plant, Cell & Environment
• Main Authors: Vernay, Antoine, Tian, Xianglin, Chi, Jinshu, Linder, Sune, Mäkelä, Annikki, Oren, Ram, Peichl, Matthias, Stangl, Zsofia R., Tor‐Ngern, Pantana, Marshall, John D.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2020
• Subjects: Northern Sweden
• Online Access: https://repository.hkust.edu.hk/ir/Record/1783.1-119363; https://doi.org/10.1111/pce.13835; http://lbdiscover.ust.hk/uresolver?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:journal&rfr_id=info:sid/HKUST:SPI&rft.genre=article&rft.issn=0140-7791&rft.volume=43&rft.issue=9&rft.date=2020&rft.spage=2124&rft.aulast=Vernay&rft.aufirst=Antoine&rft.atitle=Estimating+canopy+gross+primary+production+by+combining+phloem+stable+isotopes+with+canopy+and+mesophyll+conductances&rft.title=Plant,+Cell+%26amp%3B+Environment; http://www.scopus.com/record/display.url?eid=2-s2.0-85088384113&origin=inward; http://gateway.isiknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=LinksAMR&SrcApp=PARTNER_APP&DestLinkType=FullRecord&DestApp=WOS&KeyUT=000551855300001

Gross primary production (GPP) is a key component of the forest carbon cycle. However, our knowledge of GPP at the stand scale remains uncertain, because estimates derived from eddy covariance (EC) rely on semi-empirical modelling and the assumptions of the EC technique are sometimes not fully met. We propose using the sap flux/isotope method as an alternative way to estimate canopy GPP, termed GPP iso/SF , at the stand scale and at daily resolution. It is based on canopy conductance inferred from sap flux and intrinsic water-use efficiency estimated from the stable carbon isotope composition of phloem contents. The GPP iso/SF estimate was further corrected for seasonal variations in photosynthetic capacity and mesophyll conductance. We compared our estimate of GPP iso/SF to the GPP derived from PRELES, a model parameterized with EC data. The comparisons were performed in a highly instrumented, boreal Scots pine forest in northern Sweden, including a nitrogen fertilized and a reference plot. The resulting annual and daily GPP iso/SF estimates agreed well with PRELES, in the fertilized plot and the reference plot. We discuss the GPP iso/SF method as an alternative which can be widely applied without terrain restrictions, where the assumptions of EC are not met.