PARENT SESSION
Wednesday, August 9, 8:00-11:30 am
COS 46 - Climate and global change I: carbon cycling
Chickasaw, Mezzanine Level, Cook Convention Center
Presiders: A Dikou and K Treseder
A model of the light response of net CO2 flux in heterogeneous tundra ecosystems in Alaska and Sweden.
Shaver, Gaius*,1, Street, Lorna1, Rastetter, Edward1, vanWijk, Mark2, Williams, Matthew3, 1 The Ecosystems Center, Woods Hole, MA, USA2 Plant Production Systems, 6709 RZ Wageningen, Netherlands3 School of GeoSciences, Edinburgh, EH9 3JN, UK
ABSTRACT- Arctic landscapes are characterized by extreme patchiness in the distribution of vegetation types, often with sharply-defined borders between very different kinds of vegetation. This patchiness makes difficult the problem of predicting landscape-level C balance and its change in response to short- and long-term environmental change. In this paper we develop a model of net CO2 flux by arctic landscapes that is independent of vegetation composition, using instead a measure of leaf area derived from plot-scale measurements of NDVI (Normalized-Difference Vegetation Index). Using measurements of the light response of whole-system CO2 flux (Net Ecosystem Production, NEP) collected from a wide range of vegetation types in northern Alaska and northern Sweden, we calibrate and then exercise the model using various data subsets for parameter estimation and for tests of model predictions. Overall, the model consistently explains >75% of the variance in measured NEP knowing only the NDVI-derived estimate of Leaf Area Index (LAI), the incident photosynthetically active photon flux density (PPFD), and the air temperature above the vegetation canopy. Each of these input variables can be measured remotely at any spatial scale, thus facilitating the model's application over both large and small areas. Further improvements in model accuracy at predicting NEP may come from incorporating an estimate of moss photosynthetic area in addition to the vascular-only LAI, and from using vegetation-type-specific estimates of LAI. Nonetheless, the remarkable success of this model at predicting NEP independent of any information on species or functional type composition of the vegetation indicates a high level of convergence in canopy structure and function in the heterogeneous arctic landscape.
Key words: Net Ecosystem Production, Climate Change, Arctic Tundra