This animation shows daily gross photosynthesis estimates for 1989 over an area approximately corresponding to the boundaries of the Columbia River basin inside the U.S. These results are from the Biome-BGC model. These simulations used about 900 meteorological observation stations and a current vegetation distribution map as input. Output was generated on a grid with 2km resolution. Regional topography is shown by the grey-shaded background.
Mid-winter photosynthesis (PSN) is very low and restricted to the evergreen vegetation types. By mid-spring, with warming temperatures, PSN is increasing in both evergreen and deciduous vegetation types. Snowmelt results in moist soils through the late spring and early summer, when PSN rates are at their highest. By mid-summer, the onset of drought can be detected, as PSN rates decline, especially at the lower elevations that receive less precipitation and have smaller snowpacks. By late summer most of the region is under some degree of drought stress, with periodic and short-lived relief from summer rainstorms. By early- to mid-fall temperatures have moderated, precipitation has increased, and there is a secondary increase in PSN rates, before cold temperatures and leaf-drop once again reduce PSN to its low winter rates.