Our second season kicked off today with the deployment of
shade cloth to begin our snowmelt acceleration treatment.
March 29, 2011
The 2011 field season starts soon. A 2011 Toolik personnel
calendar, data from last year, recent presentations, protocols,
methods, and other relevant project documents are now being
shared using online file sharing services. While these resources
are not accessible to the public at this time, contact Anthony
if you are interested in accessing or need help accessing any of
these resources. December 7, 2010
Project meeting: Sunday December 12, in conjunction with
the AGU meeting in San Francisco. We will be sharing data from
summer 2010 and using this data to inform our scientific and
logistical plans for 2011. November 10, 2010 Article in UT
Discovers
Tundra soils are key regulators of many aspects
of the Arctic System. 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. We 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 proposed 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 rhizodeposition,
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. We 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. We 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.