Estimating canopy gross primary production by combining phloem stable isotopes with canopy and mesophyll conductances.
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 GPPiso/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 GPPiso/SF
estimate was further corrected for seasonal variations in photosynthetic capacity and mesophyll conductance. We compared our estimate of GPPiso/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 GPPiso/SF
estimates agreed well with PRELES, in the fertilized plot and the reference plot. We discuss the GPPiso/SF
method as an alternative which can be widely applied without terrain restrictions, where the assumptions of EC are not met.
Vernay, A; Tian, X; Chi, J; Linder, S; Mäkelä, A; Oren, R; Peichl, M; Stangl, ZR; Tor-Ngern, P; Marshall, JD
Volume / Issue
Start / End Page
Electronic International Standard Serial Number (EISSN)
International Standard Serial Number (ISSN)
Digital Object Identifier (DOI)