Straube, Jonathan R., authorOjima, Dennis S., advisorParton, William J., committee memberBurns, Patrick J., committee member2007-01-032007-01-032011http://hdl.handle.net/10217/70831We integrated a photosynthetic sub-model into the daily Century model, DayCent, to improve the estimations of carbon fluxes at the Niwot Ridge LTER site; the new version is called DayCent-Photosyn. The photosynthetic sub-model, adapted from the SIPNET/PnET family of models, includes solar radiation and vapor pressure deficit controls on production, as well as temperature and water stress terms. A key feature we added to the base photosynthetic equations is the addition of a variable maximum net photosynthetic rate (Amax). We optimized the parameters controlling photosynthesis using a variation of the Metropolis-Hastings algorithm along with data-assimilation techniques. The model was optimized and validated against level 4 data available from the Ameriflux website using observed net ecosystem exchange (NEE) and estimated gross primary production (GPP) and ecosystem respiration (Re) values. The inclusion of a variable Amax rate greatly improved model performance (NEE RMSE = 0.63 gC m-2, AIC= 2099) versus a version with a single Amax parameter (NEE RMSE = 0.74 gC m-2, AIC= 3724). DayCent-Photosyn is able to capture the inter-annual and seasonal flux patterns, including the critical early season assimilation, but tends to overestimate yearly NEE uptake. The simulated influence of a variable Amax rate suggest a need for further studies on the process controls affecting the seasonal photosynthetic rates.born digitalmasters thesesengCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.DayCentphotosynthesisNiwot RidgeAmaxText