B14B-08
Millennial-scale drivers of carbon storage and flux in terrestrial ecosystem models

Monday, 14 December 2015: 17:45
2004 (Moscone West)
Christine Rollinson1, Yao Liu2, Michael Dietze1, David J Moore2, Ann Raiho3, Jason S McLachlan3, Neil Pederson4, Ben Poulter5, Kevin M Schaefer6, Joerg Steinkamp7 and Tristan L Quaife8, (1)Boston University, Boston, MA, United States, (2)University of Arizona, Tucson, AZ, United States, (3)University of Notre Dame, Notre Dame, IN, United States, (4)Harvard University, Harvard Forest, Cambridge, MA, United States, (5)University of Montana, Missoula, MT, United States, (6)University of Colorado, National Snow and Ice Data Center, Boulder, CO, United States, (7)Senckenberg, Frankfurt, Germany, (8)University of Reading, Reading, RG6, United Kingdom
Abstract:
Terrestrial ecosystem models have largely been built to reflect environmental controls such as changing climate on ecosystem carbon cycling at time scales that range from minutes to days. However, the natural complexity of ecosystems can cause environmental drivers of long-term and large-scale carbon to be drastically different from the underlying constraints of temperature and precipitation on physiology. Comparison of climate sensitivities among multiple models and empirical data sources can reveal systemic weaknesses in ecosystem representation of the carbon cycle.

Coordinated collection of multiple types empirical data is essential to determine whether inconsistencies between model and data sensitivity to climate is an artifact of model parameterization or systemic weaknesses in model structures. The PalEON Project has gathered 10 terrestrial ecosystem models to simulate monthly carbon pools and fluxes from 850 to 2010 A.D. at six data-rich sites in the northeastern and upper midwestern United States. These sites were chosen for their potential to construct multiple long-term empirical data records from tree-rings, flux towers, and pollen that could then be compared to model simulations.

The primary drivers of temporal variation in carbon storage and flux vary by ecosystem model and often change with the spatial and temporal scale of analysis. However, agreement between model and empirical data sensitivity to climate is poor. In some cases, models and tree rings even differ in the directionality of climate effect. Several explanations exist for poor model-data agreement. One leading hypothesis is that poor representation of interactions among ecosystem components may cause the drivers of one process such as NPP to differ from a downstream carbon cycle component such as change in aboveground biomass. Within individual ecosystem models, correlations among carbon cycle components were very low (mean R2 = 0.10 SD 0.10 across all models) and generally decreased with coarser temporal resolution. Further comparisons with empirical data will reveal whether similar components of the carbon cycle in natural systems are similarly disjointed.

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