Jeffrey Welker - US grants

Welker - 0612534

Funds are provided for a detailed, mechanistic investigation of how shrubs become dominant in response to snow depth increases - a process that has been observed to occur in Alaska. This study will quantitatively document how increases in shrubs have altered the abiotic environment and caused a fundamental change in the functional attributes of these systems in arctic Alaska.

The specific goals of this project are to:
1. quantitatively document how shrub increases affect the year-long temperature and water regimes of arctic tundra and how shrub increases change the energy balance of the system;
2. delineate the processes controlling shrub increases, especially soil and plant nitrogen cycling and the physical protection of shrub meristems and branches by deeper snow; and
3. quantitively describe how shrub density increases have affected the patterns and magnitudes of carbon [C] cycling [C gain, C loss and C allocation], water sources and growth, both aboveground and belowground.

Observed shrub expansion within portions of arctic Alaska may have significant consequences, including shifts in the albedo-climate feedback, altered animal abundances, and changes in carbon and nitrogen cycling processes. As warming is progressing at a rapid rate in Alaska, a mechanistic understanding of the biotic response is needed, if informed land use decisions are to be made and if accurate forecasting models are to be developed.

This project will use the sampling power of the International Tundra Experiment (ITEX) Network to quantify changes in phenology, vegetation, and ecosystem properties that have occurred in tundra over the past 10-15 years in response to climate change and experimental warming, and to use the Network as the foundation for monitoring and prediction of future changes. Among the earliest signals of climate warming in the Arctic have been changes in the seasonal timing of life cycle events (phenology). Plants are leafing, flowering, and fruiting earlier than ever recorded. Because phenology and physiology are tightly coupled, ecosystem functions such as primary production, as well as the outcome of competition depend on phenological responses. Species phenological and physiological responses to warming differ, causing changes in community composition, biodiversity, and ecosystem function. However, in contrast to phenology, change in community composition is difficult to detect and ascribe to a particular phenomenon. Changes in phenology and species abundance being reported across the Arctic are consistent with the findings of the long-term experimental warming of the ITEX network, a plot-scale, nondestructive, warming experiment conducted across the tundra biome beginning in 1990. Remote sensing analyses have also detected earlier greening and increased biomass across polar regions, but cannot readily identify the basis for changes in community composition, can only infer function, and can say nothing about community trajectories.

The ITEX network was specifically designed to study phenology and community composition, and has also been used effectively to study ecosystem processes. It is perfectly positioned for an intensive, comprehensive study of decadal-scale changes in phenology, community composition, and ecosystem function in response to background climate change, and has the added value of long-term experimental warming. The baseline data and sampling power of the ITEX network and its experimental approach are unparalleled. This effort will compare the results of a renewed field campaign of phenology and plant community composition measurements on warmed and control plots during the IPY with historical data from 10-15 years ago. The PIs will hold two workshops to synthesize the long-term phenological and community changes observed across the network. Furthermore, a new suite of minimally invasive measurements will cross compare indices of ecosystem function - including: leaf, litter, and soil nutrients; isotopic composition; and secondary chemistry - in the control and warmed plots across the network. The long-term nature of these experiments and the global coverage of the coordinated network will lead to unique insights regarding the tundra response to past, ongoing, and future climate changes.

With this award from the Major Research Instrumentation program (MRI), Birgit Hagedorn and colleagues Marc C. Perry, Donald E. Spallinger and Jeffrey M. Welker from the University of Alaska Anchorage (UAA) Campus will acquire high performance liquid chromatography coupled to a tandem mass spectrometer (LC/MS/MS). Mass spectrometry provides powerful compound identification and quantification based on the masses of various fragments as well as for determining the molecular weight of the components of complex mixtures such as lipids, persistent organic pollutants, and tannins which are currently research topics of UAA faculty and students. Furthermore, the mass spectrometer will be combined with an ion chromatograph (IC) to separate anions, such as toxic perchlorate at low concentration in complex matrixes, which is another active research topic at UAA. The spectrometer is ideal because it provides different modes of ionization with a sensitivity of 250 femtograms over a wide mass range (m/z 50-2200). The instrument will be hosted in the Applied Science, Engineering, and Technology (ASET) Laboratory at UAA where a laboratory manager and chemist will provide the knowledge and skills needed to establish methods, maintain the performance of this instrument, and train faculty and students.

Mass spectrometry (MS) is a technique used to probe intimate structural details and to obtain the molecular compositions of a vast array of organic, bioorganic, and organometallic molecules. It is one of the fastest growing and most widely used analytical instrumentation techniques. Because of this, it is important for undergraduate and master students to be exposed to the technique. To a first approximation a tandem mass spectrometer can be thought of as two mass spectrometers in series connected by a chamber that can break a molecule into pieces.

0923571: MRI Acquisition: Detecting and monitoring changes in the arctic using stable isotope techniques

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).

The University of Alaska at Anchorage has been awarded a grant to purchase two stable isotope mass spectrometers plus a tunable diode laser system to quantify the processes of change in high latitudes. The instruments will be used to measure the natural abundance of isotopes of carbon, nitrogen, hydrogen and oxygen (C-13, N-15, H-2 (deuterium), O-18), in studies involving plants, soils, water, and animals. The instruments are also capable of measuring samples that have been enriched with these isotopes, in labeling experiments designed to study plant water sources and field metabolic rates of small mammals. The intellectual merit and the scientific motivation for acquiring this instrumentation package derives from the fact that the Arctic is changing rapidly, and there is a great need for using tools that are integrative in time and space, and tools that can unravel the complexity of linkages between the biosphere-atmosphere and aquatic systems and the intricate nature of food webs. The instruments will facilitate quantification of the consequences of vegetation change, of shifting patterns in the field metabolic rates of small mammals, of the water sources of vegetation as permafrost melts, quantification of precipitation geochemistry at local to regional scales, and food web ecology of marine mammals. In addition to the impact on the research productivity of numerous scientists in Alaska, the new instruments will support the emerging needs of NEON (National Ecological Observatory Network) in Alaska, the International Polar Year, and citizen science with the Anchorage Waterways Council. This award will also allow the enhanced educational preparation of students in state-of-the-art instrumentation, including the training of undergraduates, graduate students, and Alaska Native students in the Alaska Natives Science and Engineering Program (ANSEP). Information on the study can be obtain in this website http://www.uaa.alaska.edu/enri/usnip/index.cfm

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).

The goal of this project is to maintain the existing ITEX AON and increase the applicability of the data collected to the greater scientific community. The International Tundra Experiment (ITEX) network has collected data on phenology, plant growth, community composition and ecosystem properties as part of a greater effort to study environmental arctic change. The network, started in early 1990?s, has played a key role in advancing knowledge related to the likely impacts of a warmer arctic through the use of experimentally warmed and un-manipulated plots (i.e., the controls) across a range of sites and ecosystems that span the major vegetation types of the Arctic. While of great value, most ITEX measurements are labor intensive and time consuming, which limit the frequency and spatial extent of sampling. Recent advances in sensor technology hold the promise to allow sampling of surrogates of these manual measurements rapidly and over larger areas. This work will continue the ITEX AON observations and initiate a suite of related, non-intrusive measurements using robotic sensor platforms (networked infomechanical systems, NIMS). These new measurements will enable scaling of measurements to the regional level by linking to existing 1 km2 sample grids and satellite imagery. These data are urgently needed to improve our capacity to monitor the impacts of changing tundra vegetation on the arctic system. This work should improve our understanding of the exchange of carbon and water across the land atmosphere interface and provide information on forage quality for herbivores.

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).

The Arctic is undergoing structural and functional changes that appear to be the result of climate change, including shifts in vegetation distribution, increases in CO2 and CH4 efflux from ecosystems to the atmosphere, and the acceleration of dissolved organic carbon (DOC) export from land to oceans. Research in NW Greenland has produced four lines of evidence that climate change is affecting the High Arctic C cycle in ways we do not fully understand. First, soil organic C pools in polar semi-deserts, which occupy 1 x 106 km2 of the Arctic land surface, may be at least 6× greater than previous estimates, and ancient (>30 ky BP) and young soil C pools are present in the active layer. Second, CO2 ecosystem exchange measurements have consistently shown net C losses during the growing season; these C losses are, however, reversed under warmer and wetter conditions and with modest snow depth increases during the previous winter. In situ ecosystem respiration has been found to increase by 25 and 35% with experimental summer warming of 1.3 and 2.4°C, respectively, but by 50% when the higher level of warming was combined with irrigation. Third, soil CO2 efflux measurements indicate that ancient soil C is being degraded by microbes before vegetation leaf-out. Losses are expected to continue throughout the growing season, but masked by high rates of plant respiration (recently-fixed C) during the mid-summer. Forth, interannual and temporal patterns of riverine DOC are not explained by simple differences in summer weather conditions. Articulating the magnitudes of CO2 and CH4 exchange and DOC export along with the ages of soil respired CO2 and DOC in soil solution and rivers, and determining the sensitivity of microbial degradation of different soil C pools to temperature and moisture will transform our understanding of environmental change, ecosystem function and C cycling in the Arctic. This study will address these questions:

1. How does the age (recently-fixed vs. older) of soil respired CO2 and DOC change over the course of a year, to what extent is this influenced by inter-annual variability in temperature and precipitation, and how does it correspond with the patterns of CO2 and CH4 fluxes?

2. To what extent do long-term experimental increases in temperature (+2 and + 4oC), and in water inputs (summer rain and winter snow) alter the ages, magnitudes, and patterns of C fluxes (CO2, CH4, and DOC)?

3. Are there differences in the extent of microbial degradation of young as opposed to older soil C pools and how sensitive are the degradation rates to changes in climate?

Linking Belowground Phenology and Ecosystem Function in a Warming Arctic ? Non-technical abstract (E. Post, PI)
This project comprises a four-year, passive warming experiment of low-Arctic tundra vegetation at a long-term study site in Greenland, with the primary aim of measuring the response of plant roots to warming, and the role of this response in ecosystem carbon exchange. Phenology, the annual timing and progression of events such as aboveground plant growth, is a well-studied an important component of the ecology of climate change, but remains under-studied belowground. This study will estimate and compare above- and belowground responses of plant phenology to warming and their respective contributions to ecosystem function, specifically the exchange of carbon between the atmosphere and tundra. It will furthermore determine which plant types, e.g., shrubs or grasses, show the greater belowground response to warming and contribution to ecosystem carbon exchange.
Novel insights into the expected response of the Arctic to climate change will emerge from this experiment, which will also expand the infrastructure for field-based experimental and observational research in the Arctic. This research will promote the involvement of under-represented groups by recruitment of students through Penn State?s Minority Undergraduate Research Experience program, and promote education and dissemination of its results through a summer field ecology module at the study site and in courses at Penn State and the University of Alaska-Anchorage. Results will also be published in peer-reviewed journals and presented at international conferences by participating students and the Principal Investigators.

The hydrological cycle has a central role in Arctic climate change, and is coupled to alterations of terrestrial, aquatic and cryosphere processes, including shifts in biogeochemical cycles. Monitoring these changes is a central part of the NSF Arctic Observing Network (AON), a consortium of projects with site-specific responsibilities and measurement packages. The next frontier for AON is facilitation of approaches that better quantify landscape and regional ecohydrological process by employing new analytical technologies (laser spectroscopy based water isotope analyzers) and integration of platforms, such as aircraft and satellites. This transformation of AON will initiate studies that quantify and integrate the heterogeneous landscapes of the Arctic tundra, while developing parallel capabilities to the NEON (National Ecological Observatory Network) program, thereby extending the relevance of AON to the continental-scale. We propose an EAGER project that applies a novel interdisciplinary approach by combining isotope geochemistry with boundary layer processes and measurements to monitor and measure the ecohydrology of tundra ecosystems and landscapes. This is a high-risk approach because it is a novel use of this particular instrument and it will change how Arctic ecohydrology is monitored and assessed. EAGER is the correct venue for our project because this novel application of water isotope spectroscopy in an aircraft is ?high risk, high reward? research and represents a radically different approach from laboratory-based studies that are the status quo. The intellectual merit of this project will be accomplished by addressing these primary questions: a) What are the spatial and temporal patterns in water vapor isotopes during the growing and shoulder seasons across the tundra ecosystems in the Arctic Foothills and Foothill-Coastal Plain boundary in Northern Alaska? To a more limited extent, we also ask: b) What is the ET isotope signature associated with different ecosystem types and disturbances (fire and thermokarst) relative to background moisture? c) What is the strength of the ecosystem ET signal in the overlying atmosphere (above the ecosystem boundary height)? The first question focuses on flight measurements, the second on ecosystem tower easurements, and the third on integrating the two measurement scales. The broader impacts and outreach of our project will be accomplished by initially sharing our findings with the scientific community at the fall meeting of the American Geophysical Union and with students as part of our teaching and seminars at the University of Alaska Anchorage (UAA) and the University of Alaska Fairbanks (UAF). We will also collaborate with AON colleagues on data sharing and data posting after post-processing our flight data and information. Our primary aim with this AON EAGER is to take the transformation step in our capacity to quantify hydrological processes at the landscape and region scale by: a) collaborating with Picarro Inc. (http://www.picarro.com/) in modifying the L2120-i for aircraft and thus landscape scale purposes and b) conducting a series of field/aircraft campaigns on the North Slope of Alaska. Our program would transform the measuring and monitoring of the terrestrial hydrological cycle beyond the point-based measurements of the past and that are currently in place with AON support (ie. Oberbauer and Welker at Toolik, Bret-Hart and Shaver at Imnaviat Creek). Our EAGER project would also provide a critical linkage between AON and NEON as the Alaska network of sites are planned to come on-line in 2013. Landscape-scale monitoring is critical for stitching together the intricacies of the changing ecohydrolgy in the north.

Non-technical abstract:
The water cycle has a central role in Arctic climate change, and is coupled to alterations of land, rivers and lakes as well as permafrost processes, including shifts in the cycles of nutrients. Monitoring these changes is a central part of the NSF Arctic Observing Network (AON), a consortium of projects with site-specific responsibilities and measurement packages. The next frontier for AON is facilitation of approaches that better quantify landscape and regional eco-hydrological process by employing new analytical technologies (laser spectroscopy based water isotope analyzers) and integration of platforms, such as aircraft and satellites. This transformation of AON will initiate studies that quantify and integrate the heterogeneous landscapes of the Arctic tundra, while developing parallel capabilities to the NEON (National Ecological Observatory Network) program, thereby extending the relevance of AON to the continental-scale. We propose an EAGER project that applies a novel interdisciplinary approach by combining isotope geochemistry with boundary layer processes and measurements to monitor and measure the ecohydrology of tundra ecosystems and landscapes. This is a high-risk approach because it is a novel use of this particular instrument and it will change how Arctic ecohydrology is monitored and assessed. Our primary aim with this AON EAGER is to take the transformation step in our capacity to quantify hydrological processes at the landscape and region scale by: a) collaborating with Picarro Inc. (http://www.picarro.com/) in modifying the L2120-i for aircraft and thus landscape scale purposes and b) conducting a series of field/aircraft campaigns on the North Slope of Alaska. Our program would transform the measuring and monitoring of the terrestrial hydrological cycle beyond the point-based measurements of the past and that are currently in place with AON support at Imnaviat Creek. This project would also provide a critical linkage between AON and NEON as the Alaska network of sites are planned to come on-line in 2013. Landscape-scale monitoring is critical for stitching together the intricacies of the changing ecohydrolgy in the north.

Terrestrial high-latitude ecosystems are experiencing dramatic increases in temperature, changes in precipitation, and advancement of the growing season with important implications for trophic interactions. Uncoupling of the temporal relationships between migratory animals and the phenology of the forage they rely on for energy, nutrition, and rearing of young is one of the most glaring consequences of these changes. Furthermore, herbivores in high latitudes are likely to mediate biogeochemical responses to climate change substantially altering ecosystem function. However, little is known about how changes in the synchrony of herbivore-vegetation interactions will influence biogeochemical cycles.

This project will be conducted on the Yukon-Kuskokwim (Y-K) Delta in western Alaska, where there is strong evidence that climate change is driving temporal decoupling of the evolved linkage between the phenology of plants and the timing of goose migration. There is an urgency to the research because: some of the most rapid climate changes in the world are underway in Alaska, leaving migratory geese and the ecosystem processes they influence vulnerable to new conditions, and with the rapid advancement of the growing season, migratory goose feeding ecology is lagging substantially, threatening an irreplaceable subsistence resource for Native communities.

The overall research objective is to quantify how an advancing growing season and changes in the synchrony of vegetation-goose interactions alter the magnitudes and patterns of C and N cycling in the Y- K Delta. Two specific questions will be addressed with an experiment: How does the timing of plant growth interact with goose arrival time to alter summer-long magnitudes of plant production, foliar chemistry, and N availability; and, How does the timing of plant growth interact with goose arrival time to alter summer-long magnitudes of net ecosystem CO2 exchange, gross ecosystem photosynthesis, and ecosystem respiration? SAVANNA-YK, a biogeochemical model that considers grazing a critical control on vegetation and trace gas processes in the Y-K Delta, will be used to predict how these ecosystem processes and plant-herbivore interactions will continue to change, altering the nature of ecosystem processes and landscape dynamics in years to come.

The intellectual merit of the research is three-fold: The focus on phenologic decoupling of migratory birds and their primary forage on ecosystem biogeochemical cycles is the first of its kind. More specifically, the research is the first to investigate how the timing of herbivory interacts with plant phenology to affect biogeochemical cycles compared to other programs that have focused on the presence or absence of herbivores and/or on herbivore density effects on these cycles; The research is the first to take an experimental approach to the issue of trophic mismatch in the western Alaskan sub-Arctic while integrating these findings with forecasting ecosystem models tailored to wet sedge systems of the north. This combination allows investigation into how climate change effects on herbivore-vegetation interactions will influence large spatial scales in years to come; and The research focuses on plant species that are critical to migratory geese, while other northern studies focusing on climate change effects have focused on tundra plant species that are not critical to migratory bird foraging ecology.

The broader impacts of the research will be realized throughh several activities. First, a citizen- science observatory will be established using protocols of the National Phenology Network. Students throughout the Y-K delta will record goose arrival times and key phenological events in grasses and woody plants. Second, students from Bethel Regional High School will be recruited to assist in the field research and be given the opportunity to develop small projects. Researchers will visit village classrooms each spring to introduce the project, climate change, and plant-animal interactions; share results of previous and ongoing research in the study area; and recruit interested students. Third, Native Alaskan undergraduate students through the Alaska Native Science and Engineering Program (ANSEP) will be recruited as field and laboratory technicians; these students may also develop their own projects. Fourth, Virtual Science will be used with local teachers to develop blogs, pod-casts, and instructional videos that can be distributed to remote classrooms throughout western Alaska and beyond. Fifth, objectives and results will be communicated to Native organizational bodies, which have representatives from each major village, to build knowledge and support for the research, and provide educational outlets for families who rely on geese for subsistence. Finally, one post-doctoral researcher, one graduate student, and several undergraduates will be provided new training, mentoring, and an opportunity to collaborate on project activities and present their findings at scientific meetings.

The International Tundra Experiment (ITEX) was chartered in 1990 to test the effects of increased temperature on tundra plant phenology, growth, species composition and ecosystem function. Since 2007, the ITEX-Arctic Observatory Network (ITEX-AON) has continued and expanded on the ITEX program across a latitudinal transect of five sites in Alaska and Greenland, collecting core ITEX data specifically designed to address the current needs outlined in the Study of Environmental Arctic Change (SEARCH) Implementation Report. The goal of this effort is to maintain the continuity of the temporally-critical datasets of the ITEX-AON in Alaska and Greenland. Core datasets include the long-term manual observations of phenology, vegetation structure and composition, ecosystem function, and surface properties on the long-term ITEX control and experimental warming plots, repeat measurement of the vegetation plots on the 1km2 ARCSS grids, and a multifactor warming-moisture experiment in Greenland. The simultaneous measurement of multiple surface properties at the small scale has allowed detection of relationships not previously recognized, e.g., in moss-dominated areas of the intensive transects, higher albedo is linked to higher temperatures. Continuation of these measurements is imperative because increasing evidence points towards the critical importance of carry-over effects of the previous growing seasons on current and future responses and the inherent variability in the system precluded determination of the system response on the basis of a few years. Data from this project are freely available on the ACADIS website. The project will continue extensive outreach activities established in the initial phase, including strong relationships between the Fairchild Tropical Botanic Garden (FTBG) and the GVSU Regional Math and Science Center and school systems in Miami, Anchorage, Grand Rapids, and El Paso.

Since the Pleistocene, slow organic matter decomposition has led to the accumulation of vast amounts of organic carbon in permafrost. However, while ongoing climate warming and permafrost thaw are expected to increase plant productivity (CO2 uptake), continued warming is also expected to weaken prior constraints on decomposition (CO2 emissions). The net effect of these changes on the Arctic?s carbon budget and the global climate system are poorly understood, as most observations have been made during the short growing season, when root and rhizosphere respiration dominate CO2 emissions. This project will focus on the development of a new technology for the continuous collection of CO2 emitted from arctic tundra soils. This passive diffusive sieve (zeolite) trap for measuring soil respired CO2 will be rugged, small, lightweight, low-cost, and require little in the way of power (batteries) low power. It has the potential to transform our understanding of carbon cycling in the Arctic, as it allows for the year-round CO2 collection, including during the winter and shoulder seasons when sites are often inaccessible, and over multiple weeks (3 weeks/sample), thus integrating both diffusive and episodic emissions. Outreach activities will strengthen the existing NSF-supported K-12 training programs at UC Irvine that are aimed to increase the participation of underprivileged populations in the STEM fields. THE Investigators will engage middle school students with lab tours and activities during a ?Day at College?-experience and class room visits. The project will also train a graduate student, and contribute to educating researchers (via an international summer course) in the use of 14C analysis in Ecology and Earth System Science.

The investigators will develop and deploy a novel system to continuously trap CO2 emitted from arctic tundra soils over several weeks for radiocarbon (14C) analysis. However, typical canister-based systems for measuring soil respired CO2, can be relatively large, expensive to ship, and require line power. This project will develop and deploy a novel system to continuously trap CO2 emitted from Arctic tundra soils over several weeks for radiocarbon (14C) analysis. This continuous collection system has the potential to transform carbon cycle research. Such devices would obviate the need for shipping large canisters to the Arctic as well and the need for line power. Moreover, such devices are relatively inexpensive and lightweight, and therefore, permit for high spatial resolution monitoring. These new traps, however, have never been tested in the Arctic, where the environmental conditions can be harsh, especially in winter. Thus the focus of this work is to develop, harden, and test such devices through a number of winter seasons at the Toolik Lake Long Term Ecological Station, on the north slope of Alaska. If successful, this device will provide the first year-round, quasi-continuous dataset on soil-respired 14CO2 in moist acidic tussock tundra, which is the dominant tundra type of arctic Alaska and globally accounts for over 20% of the tundra land surface. Moreover, this research will point the way for other experimental groups working in similar harsh environments throughout the Arctic.

Arctic ecosystems are changing in response to arctic warming, which is proceeding more than twice as fast as the global average. The International Tundra Experiment (ITEX) was established in the early 1990s to understand the effects of warming and environmental variability on tundra vegetation properties and ecosystem function. The ITEX program has been extremely valuable for detection of changes in tundra plant and ecosystem responses to experimental warming and to background climate change across sites that span the major ecosystems of the Arctic. In 2007, the Alaskan and Greenland ITEX sites were combined into an Arctic Observatory Network (AON). The current ITEX AON project will continue to document and understand Arctic terrestrial vegetation change and its ecosystem consequences by maintaining the long-term datasets of the ITEX-AON. The warming experiment of ITEX-AON allows us to assign the cause for observed changes in response to warming instead of relying on simple correlations. This project provides urgently needed data on changes in vegetation and the importance of these changes for ecosystem services from a variety of Arctic ecosystems. This project will provide training for postdoctoral, graduate and undergraduate students in the emerging fields of remote sensing, cybertechnology and big-data analysis. The project will include outreach activities through strong relationships with the CLEO Institute in Miami; the Grand Valley State University Regional Math and Science Center; and K-12 school systems in Miami, Anchorage, Grand Rapids and El Paso. All data from this project are and will be freely available at the NSF Arctic Data Center.

The core datasets of the proposed research include manual observations of phenology, vegetation structure and composition, and ecosystem function (carbon flux and nutrient cycling) on long-term ITEX control and experimental warming plots, repeat measurement of vegetation plots on the long-term 1 km2 vegetation grids, and a multifactor warming/moisture experiment in Greenland. In 2009, the sampling scheme was expanded to include a larger spatial component to amplify the value of the measurements collected. This expansion included the addition of phenocams, automated mobile sensor platforms, and medium-scale aerial imagery. The automated platforms measure a suite of vegetation surface properties with minimal effort across focal transects spanning strong moisture and microtopographic gradients at a near-daily frequency. These measurements capture the fine-scale changes in vegetation over the growing season that are missed by lower frequency manual measurements and provide a bridge between manual measurements and aerial imagery. Medium-scale aerial imagery, using Kite Aerial or Unmanned Aerial Vehicles, is acquired throughout the growing season for scaling of manual and automated measurements; satellite imagery is referenced to medium-scale aerial imagery to aid scaling of responses to the regional level. In the newest phase of AON ITEX, we are particularly focused on understanding the relationship between landscape subsidence as a result of permafrost thaw and vegetation structure and function because of the potential for significant positive feedbacks to climate change.

Terrestrial Arctic systems are the result of complex interactions between climate, vegetation, herbivores, and humans that must be studied together to understand their functional
traits. While low temperatures and short-growing seasons limit plant growth, enough plant biomass exists to support herds of migratory caribou, on which Alaska Natives depend. Any changes in the plants at the base of the food web can have cascading consequences for herbivores and human consumers and their interactions. Today, the Arctic system is in the midst of change resulting in new vegetation assemblages, changes in the nutritive value of plant tissues, and ultimately in the diets of migratory caribou and the humans that depend on them. This project examines the nutritional landscape of the Central Arctic Caribou Herd as a unifying concept, describing the nutritional landscape as caribou available protein (CAP) and caribou available energy
(CAE), integrative forage quantity measures that reflect biomass, species composition, plant
C and N content, digestibility, and secondary compounds. The core objectives are gaining understanding of the drivers of spatial and temporal patterns in the amounts of CAP and CAE across the tundra; caribou use of this nutritional landscape; how the amounts of CAP and CAE will differ in the future under likely climate scenarios and long-term experiments, and the interactions between caribou and Native communities.

The broader impacts of this study involve several groups of Alaskan stakeholders, including: harvesters of the North Slope community of Nuiqsut, the worldwide caribou community, and students at multiple stages of education. The project will embed a team member with hunters in Nuiqsut,
and develop an educational scientific documentary on the caribou - Alaska Native interactions for
high school students. The group plans to employ village students and undergraduates affiliated with the Alaska Native Science
and Engineering Program to assist with experimental work and vegetation collection at Toolik Lake. This research is significant to ecologists from the Circumarctic Rangifer Monitoring
and Assessment Network, dedicated
to caribou conservation and sustainable management in the US, Canada, and Scandinavia, who will use the data to consider how a suite of climate change scenarios affect herd fecundity and population dynamics.

The intellectual merit of this project stems from the merging of five elements to understand Arctic
System function and response to climate change: (1) A landscape-scale assessment of plant species, soil and plant C and N, digestibility, and secondary compounds that will be used
to calculate the amounts of CAP (kg m-2) and CAE (kJ m-2); (2) analysis of how closely caribou foraging is tied to the nutritional landscape throughout the year; (3) analysis of samples
from an existing long-term winter - summer climate change experiment to provide data on how
CAP and CAE will differ in the future; (4) prediction of future nutritional landscapes and
caribou foraging interactions; and (5) observations of Alaska Native hunter harvesting and attributes
of the system that determine their spatial and temporal patterns. These project components will enable an integrative understanding of how an important herbivore, caribou, interact with a landscape that is rapidly changing. This research: (1) examines the Arctic System from primary production to secondary consumers and the
influence of climate change across multiple trophic levels; (2) applies broadly by examining
the most abundant large herbivore and its food sources, both of which are distributed throughout
the Arctic; and (3) integrates experimental, observational, and modeling approaches to understanding ecological systems and climate change. The integration of observation, experimental data
and modeling to describe current and forecast future nutritional landscapes is intended to provide a
mechanistic understanding of Arctic System function and transform the understanding
of climate-vegetation-caribou-subsistence hunter interactions.

The overarching goal of the project is to understand tundra ecosystem change across landscape types and enable realistic forecasts of change across the Arctic. The power of the International Tundra Experiment (ITEX)- Arctic Observatory Network (AON) is founded on a capacity to synthesize and compare results across sites that use standardized sampling protocols. Specifically, this project will (1) maintain the data-streams at ITEX-AON sites in Alaska near Toolik Lake, Imnavait Creek, Utqiagvik (Barrow), and Atqasuk; (2) lead two new ITEX network syntheses focused on soil carbon and phenocam imagery; (3) increase scientific literacy; and, (4) expand citizen science opportunities across communities in northern Alaska. The project will sustain an array of large and publicly available data-streams documenting ecosystem change occurring across the Arctic and will team up with citizen scientists to expand the monitoring footprint of the network and the societal relevance of this work to communities across the North Slope of Alaska.

The ITEX network was chartered in 1990 to document and understand the ecological impacts of a warming Arctic. The US-led ITEX projects expanded their monitoring efforts across a larger spatial area with the use of automated sampling to form an Arctic Observatory Network (AON) in 2009. The ITEX-AON currently includes traditional ITEX measurements (phenology, cover, carbon flux and nutrient cycling), as well as phenocams, automated mobile sensor platforms (MISP) and mid-scale aerial imagery of 1 km2 ARCSS (Arctic System Science) grids established in the 1990s. In this phase of the project, collection of core data sets will be sustained and new data sets will be added with the aim of identifying and understanding patterns of change and feedbacks. Specifically, ITEX-AON will expand its collection of vegetation functional traits to better understand ecosystem response and predict future change. ITEX-AON will also further expand automated measurements to link plot level change (sampled by hand or with hand-held equipment) with landscape level observations (sampled by phenocams or drones) and high resolution regional imagery (sampled by aircraft or satellite). The new phase of ITEX-AON will include two synthesis efforts: (1) an examination of soil carbon dynamics across the ITEX network, and (2) a multi-scale phenological analysis using phenocam and high resolution satellite imagery to determine fine-scale spatiotemporal patterns of seasonal greening trends across the Arctic. Mentoring of postdocs, and training of graduate and undergraduate students are some of the primary broader impacts of this project. The project will continue to provide a test bed for engineering and software development that will be shared freely among the ITEX network and broader science community and will expand outreach activities aimed at improving science literacy.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

The Arctic carbon and water cycles are undergoing fundamental changes as the Arctic experiences an entire suite of new conditions. At the core of this restructuring is rapid Arctic warming, the loss of sea ice, shifting atmospheric and ocean circulation patterns, increasing precipitation, permafrost thaw, and enhanced melt of the Greenland Ice Sheet and other mountain glaciers and ice caps. These changes have resulted in the simultaneous freshening of the Arctic seas and humidification of the Arctic atmosphere due to more evaporation from what was previously ice-covered ocean. Concurrently, riverine discharges are driving the fertilization of the Arctic seas and increasing ocean water productivity by carrying ancient carbon and old nutrients from thawed permafrost into the fjords, bays, and ocean. It is urgent to monitor and quantify these new ice-ocean-land-atmosphere interactions to understand the magnitude and variability of carbon and water cycle changes across the Arctic.

This project capitalizes on an autumn 2021 research expedition of the USCGC Healy Icebreaker. The project will use continuous isotope fingerprinting to delineate key linkages between ice-ocean-land-atmosphere interactions along the west coast of Alaska, through the Northwest Passage and in Baffin Bay. The project will measure carbon and water isotopes of marine air and ocean water continuously with some spot intense sampling locations. These measurements will enable quantification of the geochemical patterns that record freshening, fertilization, evaporation, and productivity variations driven by differing degrees of ice-ocean-land-atmosphere interactions. These data will be the first of their kind in terms of coordination at this large scale with a transect spanning ~15 degrees of latitude and over 100 degrees of longitude in the western and central Arctic. This project will: 1) delineate the intensity of land-ice freshwater injections including the extent to which these freshwater plumes carry new sources of ancient (permafrost derived) carbon and nutrients that may drive productivity increases and ocean carbon exchange; 2) quantify the connectivity of and mechanisms controlling Arctic Ocean water evaporation and atmospheric humidification which may be altering precipitation patterns in the Arctic and in the mid-latitudes; and 3) determine ocean carbon gain or loss continuously across the Arctic seas with implications for marine food webs, support of subsistence hunting, and climate warming via atmospheric carbon dioxide and methane concentrations. This project will offer valuable contributions and data to studies of Arctic change by groups examining changing atmospheric, ocean, cryospheric processes, and marine and terrestrial ecosystems.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.