Arctic Field Projects

Project Title: Collaborative Research: The Changing Seasonality of Tundra Nutrient Cycling: Implications for Ecosystem and Arctic System Functioning (Award# 0902096)

PI: Weintraub, Mike N (
Phone: (419) 530.2585 
Institute/Department: U of Toledo, Department of Environmental Sciences 
IPY Project? NO
Funding Agency: US\Federal\NSF\GEO\OPP\ARC\ARCSS\CSAS
Program Manager: Dr. Neil Swanberg (
Discipline(s): | Biology\Biogeochemistry | Biology\Plant Ecology | Biology\Soil Ecology |

Project Web Site(s):

Science Summary:
This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Arctic soils have large stores of carbon (C) and may act as a significant CO2 source with warming. However, the key to understanding tundra soil processes is nitrogen (N), as both plant growth and decomposition are severely N limited. However, current models of tundra ecosystems and their responses to climate change assume that while N limits plant growth, C limits decomposition. In addition, N availability is strongly seasonal with relatively high availability early in the growing season followed by a pronounced crash. There is a need to understand the controls on this seasonality to predict Arctic System responses to climate change, but there are multiple questions that need answers: 1) What causes the seasonal nutrient crash? 2) Does microbial activity switch seasonally between C and N limitation? 3) How will a lengthening of the growing season alter overall ecosystem C and N dynamics, as a result of differential extension of the periods before and after the nutrient crash? 4) What will be the larger impacts of these patterns on the Arctic system? Addressing these questions requires following plant and soil dynamics in a very tight time frame, coupling this understanding of the timing of C and N interactions to an enhanced mechanistic understanding of why the nutrient crash occurs, and then using transect sampling and ecosystem modeling to explore the large-scale implications of this seasonal crash. This research will address our questions by: 1) Varying the length and timing of the growing season in the field by advancing snow melt and warming the ecosystem; 2) Establishing the fine scale seasonal time-courses of soil N availability, plant N content, leaf expansion, root growth and rhizo deposition, ecosystem respiration, microbial biomass and enzyme activity; 3) Conducting lab experiments to determine the extent to which microbial activity is limited by temperature, and C and N availability before and after the crash; 4) Determining how the timing of the nutrient crash and plant growth vary across a latitudinal transect; 5) Refining the Multiple Element Limitation model (MEL) that was developed for arctic ecosystems to better handle how plant and microbial systems respond to N limitation, and incorporating the specific drivers of the crash into MEL; 6) Testing the large-scale spatial and temporal effects of the seasonality of nutrient availability and how it may change in a warming Arctic with a lengthening growing season. This work will require intense mechanistic research focusing on transitions and transformations that occur over only a few weeks at most, but which have profound impacts on the tundra ecosystem. Researchers will scale this mechanistic work to the intermediate spatial scale by conducting transect measurements along a latitudinal transect to validate that patterns that occur locally are robust. They will scale to the whole Arctic system by integrating these mechanisms, and importantly, the N-effects on decomposition, into the MEL model that is designed to explore multiple limiting resource effects on ecosystem function. As an integrated package, this research will explore how the changing seasonal pattern that drives the crash in N availability in tundra soils will alter overall tundra C-cycling and its role as a source or sink of C and through this its role in the global climate system.

Logistics Summary:
This collaborative project is composed of the following: 0902096 (Weintraub, U of Toledo), 0902184 (Sullivan, UAA), 0902038 (Schimel, UCSB), 0902102 (Rastetter, MBL), and 0902030 (Steltzer, CSU). Researchers will manipulate the timing of seasonally driven processes in tussock tundra ecosystems by advancing the timing of snowmelt with radiation absorbing fabric placed over the snowpack in the late spring and by using open-top warming chambers in concert with advanced snowmelt. Researchers will follow how seasonally driven plant and soil dynamics are affected by changes in the timing of snowmelt and warming. In August of 2009 a team of 4 will visit Toolik Field Station to establish plots, install experiments, and conduct some sampling. Teams will return in 2010-2012 for ongoing work throughout the growing season. In 2010, CPS will construct ~1000m of 2' wide boardwalk to support safe and efficient access to the plots. Researchers will arrive at the station in early May. The project will have a presence at Toolik through the end of August. In 2011, CPS personnel will reinstall the project’s boardwalk and upgrades just after snowmelt. A single representative will arrive at Toolik during the last week of April to establish the experiments, which will run all summer. Additional team members will arrive in mid-May, with periodic personnel change-outs all summer. In 2012, CPS personnel will reinstall the project’s boardwalk spurs in the research plots just after snowmelt. Two representatives will arrive at Toolik during the last week of April to establish the experiments, which will run all summer. Additional team members will arrive in mid-late May, with periodic personnel change-outs all summer. In mid-May, snow machine support will be provided for one morning to deploy 20 ‘mantis’ instrument arrays to the site. Logistic details under 0902096.

In addition to boardwalk construction, CPS will provide payment of Toolik user days for all years of the award and truck and communications support from 2010-2012. Toolik on-site support, including snowmachines, will be provided by IAB. All other logistics will be paid by the investigators from the grant and the investigators are responsible for acquiring all necessary permits
SeasonField SiteDate InDate Out#People
2009Alaska - Toolik08 / 13 / 2009 08 / 20 / 20094
2010Alaska - Toolik05 / 03 / 2010 08 / 30 / 201010
2011Alaska - Toolik04 / 26 / 2011 09 / 08 / 201112
2012Alaska - Toolik04 / 27 / 2012 08 / 09 / 201211

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Parameters used to generate this report:, Grant# = "0902096", IPY = "ALL" 
     Number of projects returned based on your query parameters = 1