Leaf and stem economics spectra drive diversity of functional plant traits in a dynamic global vegetation model

Abstract

Functional diversity is critical for ecosystem dynamics, stability and productivity. However, dynamic global vegetation models (DGVMs) which are increasingly used to simulate ecosystem functions under global change, condense functional diversity to plant functional types (PFTs) with constant parameters. Here, we develop an individual- and trait-based version of the DGVM LPJmL (Lund-Potsdam-Jena managed Land) called LPJmL- flexible individual traits (LPJmL-FIT) with flexible individual traits) which we apply to generate plant trait maps for the Amazon basin. LPJmL-FIT incorporates empirical ranges of five traits of tropical trees extracted from the TRY global plant trait database, namely specific leaf area (SLA), leaf longevity (LL), leaf nitrogen content (N ), the maximum carboxylation rate of Rubisco per leaf area (vcmaxarea), and wood density (WD). To scale the individual growth performance of trees, the leaf traits are linked by trade-offs based on the leaf economics spectrum, whereas wood density is linked to tree mortality. No preselection of growth strategies is taking place, because individuals with unique trait combinations are uniformly distributed at tree establishment. We validate the modeled trait distributions by empirical trait data and the modeled biomass by a remote sensing product along a climatic gradient. Including trait variability and trade-offs successfully predicts natural trait distributions and achieves a more realistic representation of functional diversity at the local to regional scale. As sites of high climatic variability, the fringes of the Amazon promote trait divergence and the coexistence of multiple tree growth strategies, while lower plant trait diversity is found in the species-rich center of the region with relatively low climatic variability. LPJmL-FIT enables to test hypotheses on the effects of functional biodiversity on ecosystem functioning and to apply the DGVM to current challenges in ecosystem management from local to global scales, that is, deforestation and climate change effects.

Predicting species dominance shifts across elevation gradients in mountain forests in Greece under a warmer and drier climate

“…In addition to the above, the role of inter-and intra-specific functional trait variation has been recently highlighted as an important component that needs to be incorporated into vegetation dynamics model (Scheiter et al 2013;Fyllas et al 2014;van Bodegom et al 2014;Sakschewski et al 2015). Traditionally, parameterisation of species and/or plant functional types (PFTs) is based on the use of some ''average'' or ''appropriate'' mean trait value, for characteristics that have a direct effect on the regeneration, the growth and the mortality of the simulated species.…”

Large-scale climatic and geophysical controls on the leaf economics spectrum

“…At the other end of the spectrum, a plant strategy of lower foliar nutrient concentrations and slower plant growth in relatively low-fertility ecosystems invests proportionally more into leaf construction, expressed as higher leaf mass per unit area (LMA) (4), supporting longer-lived foliage and slower decomposition rates (5). Central to the LES theory, plants are thought to fall along simple axes indicating this trade-off, with important implications for global dynamic vegetation and climate models (6).…”

“…The ability to map and assess N:P ratio and similar metrics provides a biogeophysically explicit basis upon which to assess previous or plan future field studies to test the role of nutrient limitation in mediating ecological processes. Similarly, these maps can serve as new input to the next generation of ecosystem, dynamic vegetation, and climate models, which are beginning to rely on LES traits and their interrelationships to simulate vegetation responses to environmental change (6,60,61). Future airborne, and perhaps space-based, studies of LES traits will open new doors to understanding and modeling the functional assembly of the biosphere and its responses to climate change.…”

Reply to Verbeeck and Kearsley: Addressing the challenges of including lianas in global vegetation models

“…Finally, global vegetation models themselves will benefit from further development and refinement. The inclusion of a greater diversity of plant functional traits in global models (6), for example, may be critical to improving these models and for predicting how lianas affect future carbon dynamics and storage in tropical forests.…”