Abstract
Abstract. The dynamics of terrestrial ecosystems are shaped by the coupled cycles of carbon, nitrogen, and phosphorus, and these cycles are strongly dependent on the availability of water and energy. These interactions shape future terrestrial biosphere responses to global change. Here, we present a new terrestrial ecosystem model, QUINCY (QUantifying Interactions between terrestrial Nutrient CYcles and the climate system), which has been designed from scratch to allow for a seamless integration of the fully coupled carbon, nitrogen, and phosphorus cycles with each other and also with processes affecting the energy and water balances in terrestrial ecosystems. This new model includes (i) a representation of plant growth which separates source (e.g. photosynthesis) and sink (growth rate of individual tissues, constrained by temperature and the availability of water and nutrients) processes; (ii) the acclimation of many ecophysiological processes to meteorological conditions and/or nutrient availability; (iii) an explicit representation of vertical soil processes to separate litter and soil organic matter dynamics; (iv) a range of new diagnostics (leaf chlorophyll content; 13C, 14C, and 15N isotope tracers) to allow for a more in-depth model evaluation. In this paper, we present the model structure and provide an assessment of its performance against a range of observations from global-scale ecosystem monitoring networks. We demonstrate that QUINCY v1.0 is capable of simulating ecosystem dynamics across a wide climate gradient, as well as across different plant functional types. We further provide an assessment of the sensitivity of key model predictions to the model's parameterisation. This work lays the ground for future studies to test individual process hypotheses using the QUINCY v1.0 framework in the light of ecosystem manipulation observations, as well as global applications to investigate the large-scale consequences of nutrient-cycle interactions for projections of terrestrial biosphere dynamics.
Highlights
Past, present, and future changes in climatic conditions and atmospheric CO2 concentrations affect terrestrial vegetation and soils (Hou et al, 2018; De Kauwe et al, 2013; Swann et al, 2016), which in turn induce biogeophysical and biogeochemical feedbacks to the atmosphere (Bonan, 2008; Friedlingstein et al, 2014; Zaehle et al, 2010)
The effect of diurnal and seasonal variability in soil nutrient availability is buffered through the labile and reserve storage pools in the vegetation, such that it affects vegetation gross carbon uptake only via slow processes such as foliar nutrient and allocation changes but has no effect on variability at the daily to weekly timescale. This is demonstrated in the LAI values that are influenced by the long-term dynamics
At FR-Hes and AU-Tum the LAI is lower at the nitrogen- and phosphorus-dynamicsenabled version than with the C-only version (6.0 compared to 6.2 m2 m−2 at FR-Hes, 3.7 compared to 5.9 m2 m−2 at AU-Tum), whereas it does not have a notable effect for the needle-leaved evergreen site of FI-Hyy
Summary
Present, and future changes in climatic conditions and atmospheric CO2 concentrations affect terrestrial vegetation and soils (Hou et al, 2018; De Kauwe et al, 2013; Swann et al, 2016), which in turn induce biogeophysical and biogeochemical feedbacks to the atmosphere (Bonan, 2008; Friedlingstein et al, 2014; Zaehle et al, 2010). To predict the likely trajectories of terrestrial ecosystems under climate change and their climate feedbacks, it is important to develop and test advanced modelling tools for the terrestrial biosphere (Sitch et al, 2015). Global terrestrial biosphere models (TBMs) have evolved during the last decades alongside our understanding of soil and vegetation functioning (Bonan and Doney, 2018).
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