Mechanisms and feedback consequences of shrub expansion following long-term increases in winter snow depth in northern Alaska: a legacy for IPY (NSF-OPP 0612534)
The primary aims of this project have been to understand the mechanisms and feedback consequences of shrub increases in northern Alaska using experimental, observational and expedition research.
We have undertaken studies at Toolik Lake, Alaska and across the north slope along the Colville and Noatak rivers and in the Chandalar River drainage. Our studies have implement new snow manipulation experiments and we have utilized a snow experiment that was initiated by NSF OPP in 1994. We implemented the first wind turbine powered research at Toolik Lake that powered our CO2 sensors over winter allowing for winter-long quantification of C losses in areas where shrubs have been increasing and in ambient areas. We conducted vegetation surveys along the major river drainages and have characterized areas with expanding and stagnate shrub growth which appear to be related to disturbance history, subsequent soil properties, plant water and nutrient relations and growth. We have also used 14C measurements to depict the loss of ancient C to the atmosphere as snow accumulates when shrubs become an increasing large component of the landscape.
Our most important papers from this work are:
- Nowinski, N, Taneva, L., Trumbore, S., and Welker, J. M. 2010. Decomposition of old organic matter as a result of a deeper active layer in a snow manipulation experiment. Oecologia 163: 785-792.
- Sullivan, P. F., Arnes, S., Sveinbjornsson, B. and Welker, J. M. 2010. Modeling the seasonality of belowground respiration along an elevational gradient in the Chugach Mountains, south central Alaska. Biogeochemistry 101: 61-75.
- Taneva, L., Sullivan, P. F., and Welker, J. M. 2011. Identifying the cause and biogeochemical consequences of high shrub abundance in low arctic tundra. Global Climate Change (under author review).
- Post, E., Forchhamer, M., Welker, J. M., et al. 2009. Ecological dynamics across the Arctic associated with recent climate change. Science 325: 1355-1358.
- Sullivan P. F., Welker, J. M., Arens, S.J.T., Sveinbjörnsson, B. 2008. Continuous estimates of CO2 efflux from arctic and boreal soils during the snow-covered season in Alaska. J of Geophysical Research 113: G04009.
- Oberbauer, S, Tweedie, C., Welker, J. M. et al. 2007. Tundra CO2 fluxes in response to experimental warming across latitudinal and moisture gradients. Ecological Monographs 77: 221-238.
- Schimel, J., Fahnestock, J., Michaelson, G., Milkan, C., Ping, C, Romanovsky, V and Welker, J. M. 2006. Cold-season production of CO2 in Arctic soils: Can laboratory and field estimates be reconciled through a simple modeling approach. Arctic, Antarctic and Alpine Research 33: 120-125.
- Tape, K., Verbyla, D. and Welker, J. M. 2011. Shrub expansion along arctic streams and Gullies reduces erosion since 1980 (in co-author review).
- Tape, K., D., Hallinger, M., Reuss, R. and Welker, J. M. 2011. Disturbance regime Accountable or landscape heterogeneity of shrub expansion in Arctic Alaska (in co author review).