Longer growing seasons lead to less carbon sequestration by a subalpine forest

摘要: As global temperatures increase, the potential for longer growing seasons to enhance terrestrial carbon sink has been proposed as a mechanism reduce rate of further warming. At Niwot Ridge AmeriFlux site, subalpine forest in Colorado Rocky Mountains, we used 9-year record (1999-2007) continuous eddy flux observations show that season length (GSL) actually resulted less annual CO 2 uptake. Years with GSL were correlated shallower snow pack, measured using water equivalent (SWE). Furthermore, years lower SWE an earlier start spring. For three years, 2005, 2006, and 2007, stable hydrogen isotopes (δD) vs. rain, extracted xylem from dominant tree species, lodgepole pine, Engelmann spruce, fir, trees relied heavily on melt even late into season. By mid-August, 57% 68% reflected isotopic signature melt. coupling measurements ecosystem model, SIPNET, found uptake was highly dependent water, which decreases abundance during seasons. Once again, 3 gross primary productivity, derived optimized parameter SIPNET model estimated be 67% 77%, 71% respectively. Past studies have shown mean winter pack mountain ecosystems Western US declining decades is positive temperature anomalies. Since climate change models predict continuation warming reduced mountains US, strength likely decline further.