Net effects of early phenology, increased cloud cover, and altered timing of plant animal-interactions dampen climate change impacts on net ecosystem exchange of C in a coastal Alaska wetland
Abstract
Northern ecosystems are changing dramatically. Rapid warming over the past four decades has: (1) advanced plant phenology with spring beginning one or more weeks earlier now than the past, (2) increased precipitation and cloud cover over much of the Arctic, and (3) altered the timing of plant-animal interactions. Advanced phenology potentially leads to longer growing seasons and greater CO2 uptake; greater precipitation may alleviate water deficits leading to more biomass but also increased cloud cover suppressing photosynthesis; and delaying grazing with respect to plant phenology impacts nutrient cycling and may increase plant biomass. Furthermore, these changes are not mutually exclusive, and their interaction could potentially lead to unexpected consequences for the New Arctic. For three years we examined the relative importance of advanced phenology, cloud cover, and timing of grazing on CO2 exchange in the Yukon-Kuskokwim Delta of western Alaska. Our study included experimental plots where the growing season was advanced using passive open-top chambers or left under ambient condition, crossed with three different periods of grazing by migratory geese (early, typical, and late) and one grazing removal treatment. We used an automated chamber-based CO2 flux system to monitor hourly net ecosystem exchange (NEE). Data were used to construct daily light curves for each experimental plot, and locally monitored sunlight and a clear-sky model were used to produce daily and seasonal NEE over a range of light conditions. Of the three consequences of warming on daily NEE, cloudy days had the largest effect size followed by delaying peak grazing intensity; advancing the growing season had the smallest effect size. Moreover, the gains in CO2 uptake due to greater biomass associated with delaying grazing were offset by cloudy days. For the entire season, the net effects of the expected conditions of the New Arctic (advanced phenology, delayed grazing, and cloudier skies) largely offset one another; but the two strongest and opposing effects (delayed grazing and cloudier skies) each have the potential to alter future growing season NEE depending on the magnitude of response.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.B31F2518L
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCESDE: 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCESDE: 0475 Permafrost;
- cryosphere;
- and high-latitude processes;
- BIOGEOSCIENCESDE: 1640 Remote sensing;
- GLOBAL CHANGE