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Changes in boreal and arctic ecosystems productivity : deriving metrics of photosynthetic activity and limitation from MAIAC data.
Gabriel
Hmimina, University of Lincoln Nebraska, hmimina@unl.edu
(Presenter)
Rong
Yu, University of Nebraska, rong.j.yu@gmail.com
Karl
Fred
Huemmrich, NASA GSFC/UMBC, karl.f.huemmrich@nasa.gov
Dave
Billesbach, University of Nebraska, dbillesbach1@unl.edu
John
A
Gamon, University of Nebraska, jgamon@gmail.com
Large-scale greening and browning trends have been reported in northern terrestrial ecosystems over the last two decades. The greening has been interpreted as an increased productivity in response to increases in temperature. Boreal and arctic ecosystem productivity is expected to increase as the length of growing seasons increases, resulting in a bigger northern carbon sink.
While evidences of such greening based on the use of remotely-sensed vegetation indices is compelling, analysis over the network of flux tower sites available in northern latitudes paints a more complex story, and raise some issues as to whether vegetation indices based on NIR reflectance at large spatial scales are suited to the analysis of complex northern landscapes that exhibit strong patterns in snow and standing water cover. In a broader sense, whether “greenness” is a sufficiently good proxy of ecosystem productivity in northern latitudes is unclear.
The current work focused on deriving continuous estimates of ecosystem potential productivity and photosynthetic limitation over a network of flux towers, and on using MAIAC reflectance data to extrapolate those metrics over time and space. A novel partitioning method was used to derive ecophysiological parameters from sparse carbon fluxes measurements, and those parameters were then used to train a random forest approach in order to predict them from remote-sensing data.The resulting metrics can be used to estimate potential yearly productivity and loss of productivity due to photosynthesis limitation over a wide range of ecosystems.
Trends in productivity were derived from both flux-tower and remote-sensing derived data and were deconvolved into changes in potential productivity and changes in limitation, showing contrasting spatial patterns of productivity increase in arctic ecosystems, decrease, and of imbalance between potential productivity and photosynthesis limitation in boreal ecosystems.
Associated Project(s):
Poster Location ID: 79
Session Assigned: Carbon Dynamics
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