A triple tree-ring constraint for tree growth and physiology in a global land surface model

Abstract

Abstract. Annually resolved tree-ring records extending back to pre-industrial conditions have the potential to constrain the responses of global land surface models at interannual to centennial timescales. Here, we demonstrate a framework to simultaneously constrain the representation of tree growth and physiology in the ORCHIDEE global land surface model using the simulated variability of tree-ring width and carbon (Δ13C) and oxygen (δ18O) stable isotopes in six sites in boreal and temperate Europe. We exploit the resulting tree-ring triplet to derive integrative constraints for leaf physiology and growth from well-known mechanistic relationships among the variables. ORCHIDEE simulates Δ13C (r=0.31–0.80) and δ18O (r=0.36–0.74) better than tree-ring width (r<0.55), with an overall skill similar to that of a tree-ring model (MAIDENiso) and another isotope-enabled global vegetation model (LPX-Bern). The comparison with tree-ring data showed that growth variability is not well represented in ORCHIDEE and that the parameterization of leaf-level physiological responses (stomatal control) to drought stress in the temperate region can be constrained using the interannual variability of tree-ring stable isotopes. The representation of carbon storage and remobilization dynamics emerged as a critical process to improve the realism of simulated growth variability, temporal carryover, and recovery of forest ecosystems after climate extremes. Simulated forest gross primary productivity (GPP) correlates with simulated tree-ring Δ13C and δ18O variability, but the origin of the correlations with tree-ring δ18O is not entirely physiological. The integration of tree-ring data and land surface models as demonstrated here should guide model improvements and contribute towards reducing current uncertainties in forest carbon and water cycling.

Using the International Tree-Ring Data Bank (ITRDB) records as century-long benchmarks for global land-surface models

“…The novel benchmarks proposed here may also provide new targets for evaluating LSMs' performance, as the metrics could be used in the objective function of any data assimilation technique (Peylin et al, 2016) to rigorously account for the information contained in TRW datasets. The value of tree-ring records for LSM verification might be further enhanced by (i) developing new, unbiased networks, such as the European biomass network, to both complement and identify biases in the ITRDB; (ii) adding their stable isotope ratios to verification benchmarks that may be simulated by isotope-enabled LSMs (Levesque et al, 2019;Barichivich et al, 2021); and (iii) combining their use with high-frequency but short-term eddy covariance measurements (Pappas et al, 2020;Teets et al, 2018), experimental data from plant growth under pre-industrial CO 2 concentrations (Temme et al, 2015), and proxies of atmospheric composition (Campbell et al, 2017).…”

Detecting long‐term changes in stomatal conductance: challenges and opportunities of tree‐ring δ18O proxy

“…a negative relationship), in line with our interpretation. Studies integrating tree ring δ 18 O data into land surface models (Keel et al ., 2016 ; Barichivich et al ., 2021 ) or using it as a proxy in paleoclimatological estimates in tropical regions (Evans, 2007 ), generally assume a fixed L‐value; however, this did not prevent the interannual variability of tree ring δ 18 O chronologies from being reproduced. Using a fixed L‐value, as applied in early demonstrations of the Péclet effect (see e.g.…”

Strongly Active Responses of Pinus tabuliformis Carr. and Sophora viciifolia Hance to CO2 Enrichment and Drought Revealed by Tree-Ring Isotopes on the Central China Loess Plateau

“…If the rise of C a alone were responsible for changing iWUE, the ensuing measured long-term stomatal regulation of leaf gas exchange would fall within the natural ranges expected for active (constant C i ) or passive (constant C i /C a and C a -C i ) responses [41]. These scenarios differ only in the degree to which the increase in C i follows the increase in C a (either not at all, in a proportional way, or at the same rate, respectively) [42]. Mean C i concentration over the first 3 years of each species was used as the starting point for the scenarios in our study.…”