Now, two decades later, a team of scientists at Northern Arizona University, Lawrence Livermore National Laboratory, Pacific Northwest National Laboratory and West Virginia University have received a new $3.4 million award from the U.S. Department of Energy to conduct a deeper dive into what these buckets of soil have to say about the future. Mapping and better understanding the interplay of soil microbes and how they control nutrients like carbon and nitrogen will help researchers predict and potentially manage soil microbial communities to keep more carbon out of the air and in the soil—a critical piece of the climate puzzle. 

The experiment, located along an elevation gradient in the San Francisco Peaks in northern Arizona, is arrayed across four life zones found in temperate climates: mixed conifer forest at the highest elevation, then ponderosa pine forest, pinyon-juniper woodland and desert grassland. By moving the intact community of plants and soil microbes in a carefully preserved pail of soil down the mountain to a new home in the next life zone, scientists can simulate climate warming and drying and compare what happens to soil communities left at higher elevations. 

This low-tech design has been one key to the success of the experiment, said Bruce Hungate, Regents’ professor of biology, director of the Center for Ecosystem Science and Society (Ecoss) and designer of the initial experiment in 2002. Compared to other warming experiments that rely on manipulating temperatures through mechanical means, Hungate said part of the elegance was the simplicity: “You could just pick up an ecosystem and move it downslope.” This meant that the treatment was sustainable to maintain over a long period of time, allowing Hungate’s team to accrue longitudinal insights into what was happening belowground.  

And such long-term data are vital to answering one of the big questions that has guided Hungate’s research since coming to NAU. “Will different ecosystems respond to change in qualitatively similar ways,” he said, “or will we have to tell just-so stories about every ecosystem we care about to learn what is going to happen to it as the climate changes?”  

The new project builds on what Hungate and collaborators have learned from 15 years of warming, and the signals are complex, he said. Significant amounts of carbon were lost to the atmosphere in most ecosystems. In the pinyon-juniper plots, some carbon was gained. As nutrients grew scarcer over time, the team saw dynamics familiar from aboveground food webs: diversity fell, microbial interactions became more antagonistic and a few predators became more relevant in what happened to nutrients. They wondered: what if these microbial relationships hold keys to the fate of soil nutrients in a warmer world?  

Ember Morrissey, assistant professor of environmental microbiology at West Virginia University and a lead investigator on the new award, said this project could expand a frontier of soil microbiology. “Soil contains a wealth of microbial species that interact with each other. And while we understand a few of these interactions, most of them remain entirely undescribed by science.” 

“My team is asking how climate change influences cooperative and competitive interactions during decomposition,” Morrissey said. “By studying simple and complex root carbon inputs, we hope to see how mutualism and competition influence the decomposition and stabilization of these important carbon inputs to soil.” 

“We are taking a holistic approach in which we consider all microbial groups, from bacteria and archaea to fungi and protists, and associations among them, such as prey-predator interactions,” said Javier Ceja-Navarro, an associate professor of biology at Ecoss. “This work has the potential to improve current and future ecological models that aim to understand the influence of microbes on biogeochemical cycling and climate change.” 

The established warming experiment and the development of high-precision sequencing tools in the two decades since it began are adding up to a unique opportunity to ask these new questions of familiar soil. Using ‘omics tools and a state-of-the-art technique called quantitative Stable Isotope Probing, or qSIP, the team of researchers can assemble not just a picture of who lives in the soil at a given point, but a kind of molecular time-lapse that reveals who is growing, who is interacting and who disappears over time. 

The award was made as part of a $178 million investment by the Department of Energy into bioenergy and microbiome and climate-related research. “These projects will continue to advance the boundaries of biotechnology and support the emergence of a thriving U.S. bioeconomy that creates good-paying jobs and helps us meet our climate goals,” said U.S. Secretary of Energy Jennifer Granholm.  

Hungate, Morrissey and Ceja-Navarro are joined by NAU investigators professor Egbert Schwartz, senior research scientist Ben Koch, Regents’ professor Michelle Mack, assistant professor Toby Hocking, Jennifer Pett-Ridge and Steve Blazewicz at Lawrence Livermore National Laboratory and Kirsten Hofmockel and Bram Stone at Pacific Northwest National Laboratory. 

But that’s only one possible future for the vast stores of carbon locked in the formerly perennially frozen but now-thawing ground in the Arctic. Using more than a decade of synthesis science and region-based models, a new study led by Northern Arizona University and the international Permafrost Carbon Network and published in Annual Review of Environment and Resources forecasts cumulative emissions from this “country of permafrost” through 2100 under low, medium and high warming scenarios.  

“We hope that these forecasts of future Arctic carbon emissions not only update the scientific picture but act as new guide rails for policymakers who are working to stabilize the climate and avoid exceeding temperature targets,” said Ted Schuur, Regents’ professor in the Department of Biological Sciences and Center for Ecosystem Science and Society at NAU and lead author of the study.  

The team estimates that under a low warming scenario—one that could be achieved if the global community limited warming to 2 degrees Celsius or below by reducing fossil fuel emissions—permafrost would release 55 petagrams (Pg) of carbon by the end of the century in the form of greenhouse gases carbon dioxide (CO2) and methane (CH4). If nothing is done to mitigate climate warming, the study estimates the Arctic could release 232 Pg of carbon by the end of the century. 

The team’s projections go beyond previous international forecasts by accounting for hydrological and biogeochemical dynamics and tipping points unique to the permafrost zone.  

For instance, scientists are witnessing abrupt thaw in many permafrost regions, where rapid melting of ground ice in permafrost causes the land surface to collapse, forming lakes or other changes to surface hydrology. Once formerly frozen ground erodes or subsides, the carbon stored there can enter the atmosphere via microbial respiration or methane. Such rapid, non-linear shifts quickly and permanently change permafrost’s ability to store carbon and could toggle large swaths of the Arctic region from carbon sinks to carbon sources. Recent estimates suggest that one-fifth of current permafrost terrain is vulnerable to abrupt thaw.  

“Once permafrost carbon emissions increase in response to climate warming as some models predict, there won’t be a way for us to stop that process,” said Roisin Commane, assistant professor of Earth and environmental sciences at Columbia University and co-author of the new study. “We may need to reduce our fossil fuel emissions much sooner than currently planned by many governments to avoid triggering possible tipping points in Earth’s climate.” 

The potential to cross both regional and systemwide tipping points is one reason the story of Arctic carbon and its future security remains only partially written. The new study describes nine different futures based on how climate warming progresses and what actions global leaders take to reduce fossil fuel emissions. 

“Permafrost emissions will be a large and substantial contributing factor to atmospheric greenhouse gases, no matter which of the possible scenarios becomes reality,” said Guido Grosse, head of the permafrost research section at the Alfred Wegener Institute in Potsdam, Germany, and co-author of the study. “But there will be huge differences between mitigation scenarios that matter to the overall global carbon budget.”  

Curbing human-caused emissions, Grosse said, will help ensure permafrost makes a smaller contribution to global climate warming, while “doing business as usual” will guarantee that the “nation” of permafrost will have a sizable role in warming and represent a higher hurdle for mitigation efforts to clear.  

Because the Arctic is not regulated by any one state and its remoteness makes terrain hard to monitor comprehensively, the authors emphasize that international emission reduction efforts must account for this “country of permafrost” in climate targets and actions going forward. The study also underscores the importance of monitoring this quickly changing region using collaborative networks like the Permafrost Carbon Network and scientific tools like remote sensing technology.  

“Remote sensing products can really help us see and track what is happening to permafrost in a physical way,” Commane said. “High-resolution sensors can see evidence of thermokarst soil collapse, how water bodies are changing and even how wet or frozen the soils are. But satellites that tell us how much carbon from permafrost ends up in the atmosphere are limited, and there needs to be investment from space agencies in these capabilities as soon as possible.”  

Schuur said his research team is seeing evidence of rapid change on the ground, as well.  

“Changes we are witnessing in the field show the urgent need to curb emissions and keep permafrost carbon in the ground. This summer, at my study site in Eight Mile Lake, Alaska, we saw widespread permafrost thaw after a winter with record snowfall, and carbon losses four times larger than the average over the past several decades,” he said. “These observations match predicted tipping points in permafrost and carbon that we expect to see as human-caused emissions from elsewhere on Earth rapidly warm the Arctic.” 

The study was authored by an international team of scientists from NAU, Alfred Wegener Institute, Columbia University, Brigham Young University, University of New Hampshire, University of Alaska-Fairbanks, Stockholm University, U.S. Geological Survey, Lawrence Berkeley National Laboratory, National Center for Atmospheric Research, Colgate University, University of Texas-El Paso, University of Alberta, Woodwell Climate Research Center, Oak Ridge National Laboratory and University of Colorado-Boulder. The Permafrost Carbon Network synthesis work is supported by a grant from the National Science Foundation. 

Permafrost Carbon Network

Thousands of researchers worldwide are studying how global change affects ecosystems. Using models and field experiments, they add to our understanding of this area each day. However, individual studies sometimes only tell part of the whole story. By combining results from large numbers of studies, we can discern large-scale patterns across ecosystems, and make better estimates of how global change will affect our environment. Our work on global change synthesis combines several statistical techniques with modeling approaches.

Meta-Analysis

Over the past several decades, scientists have conducted hundreds of experiments investigating responses of ecosystems to global environmental change. Ecoss synthesizes many of these responses using a statistical technique called meta-analysis. This approach considers all the measurements together and quantifies the overall response, testing whether responses vary among ecosystems, climate regimes, and management practices (for instance, fertilizer addition). For more detailed information about specific meta-analysis topics click here.

Confronting Ecosystem Models with Experiments: Data Assimilation

Using a technique called data-assimilation, we can inform existing ecosystem models with measurements from field experiments. In combination with meta-analysis, this approach becomes a powerful statistical tool to improve our predictions of ecosystem responses to global change. We recently used data-assimilation to study the effect of warming and CO₂ enrichment on ecosystem carbon dynamics. Details can be found here.

Permafrost Carbon Network

The Permafrost Carbon Network is part of the Permafrost Action Team of the Study of Environmental Arctic Change (SEARCH) project. The SEARCH project, headed by the University of Alaska Fairbanks as the lead institution and Northern Arizona University as one partner, is a system-scale, cross-disciplinary research program that seeks to connect the science of Arctic change to decision makers. The objective of the Permafrost Carbon Network is to link biological carbon cycle research with networks in the physical sciences focused on the thermal state of permafrost. The network has produced multiple synthesis products that can be assimilated by biospheric and climate models which will contribute to future global environmental assessments, including the Intergovernmental Panel on Climate Change. More details to the network can be found here.

Using a technique called data-assimilation, we can inform existing ecosystem models with measurements from field experiments. In combination with meta-analysis, this approach becomes a powerful statistical tool to improve our predictions of ecosystem responses to global change. We recently used data-assimilation to study the effect of warming and CO₂ enrichment on ecosystem carbon dynamics.

Do Soils Store more Carbon in a Warmer World?
Field warming experiments have been set up worldwide to address whether climate warming will reduce soil carbon storage. Why is his important? Because when soils release more carbon than they take up, more ends up in the atmosphere. Thus, soils, through losing more carbon, could in fact accelerate the pace of climate change. Using a combination of data assimilation and meta-analyses we synthesized and evaluated plant and soil responses to warming using data from field experiments. Our study is currently in review. For more information, contact Natasja van Gestel.

In a related study, we combined data-assimilation with meta-analysis to synthesize published research on soil C dynamics under elevated CO₂. We combined measurements of plant production, microbial respiration, and soil C stocks to estimate CO₂ effects on soil C turnover, thereby providing insight into the mechanisms determining long-term soil C storage. We derived effect sizes from a one-pool biogeochemical model of soil C cycling, the same form used by several global C cycling models. We found that elevated CO₂ increases the decomposition rate of soil carbon, thereby limiting the potential for soil C storage.

Related publications

Van Groenigen KJ, Qi X, Osenberg CW, Luo Y, Hungate BA, 2014. Faster decomposition under increased atmospheric CO₂ limits soil carbon storage. Science 344, 508-509.

Van Gestel N, Shi Z, van Groenigen KJ, Luo Y, Osenberg C, Dukes JS, Andresen LC, Michelsen A, Schuur T, Hungate BA. Little change in soil carbon storage with warming. Under review.

Over the past several decades, scientists have conducted hundreds of experiments investigating responses of ecosystems to global environmental change. Ecoss synthesizes many of these responses using a statistical technique called meta-analysis. This approach considers all the measurements together and quantifies the overall response, testing whether responses vary among ecosystems, climate regimes, and influences of human management, like fertilizer addition. Here are some topics that we studied using meta-analysis:

Climate Change and the Terrestrial Carbon Cycle
Plants may store more carbon as CO₂ in the atmosphere rises and stimulates plant growth, slowing climate change. Or, soils may release more carbon in response to warming, which speeds up microbial decomposition and CO₂ release back to the atmosphere. Changes in rainfall can also affect the balance of carbon uptake and release by the Earth’s land ecosystems. In a recent study, we summarized published results on the sensitivity of the terrestrial carbon cycle to climate change, focusing on plant growth, respiration, and net carbon balance. We found that warming and increased precipitation stimulated the carbon cycle, whereas reduced precipitation suppressed it. Changes in carbon input tended to be compensated by changes in carbon loss, resulting in little change in net carbon fluxes. For more information, see Wu et al. (2010).

Do Soils Store More Carbon as CO₂ in the Atmosphere Increases?
Ecosystems are expected to soak up much of the CO₂ emitted from fossil fuel burning and deforestation, but these expectations may be too optimistic. In this study, we showed that soil carbon storage only increases with rising CO₂ when enough extra nitrogen is also available – far more than what is normally available in most ecosystems. For this reason, future carbon storage by land ecosystems may be smaller than previously thought, and therefore not a very large part of a solution to global warming. For more information, see van Groenigen et al. (2006, 2014), de Graaff et al. (2006), Hungate et al. (2009).

Responses of Soil Biota to Environmental Change
Soils are a biological cosmos, from extremely diverse bacterial and archaeal communities to nematodes, mites, collembola and springtails, key players in the most complex food webs on earth. Yet, we know little about how these biological networks respond to environmental change. In a recent study, we synthesized results from over 75 manipulative experiments to test for effects of elevated CO₂, warming, and altered precipitation on the abundance of soil biota. Elevated CO₂ initially stimulated the abundances of soil biota, but the effects were short-lived. Warming initially suppressed soil biota abundances, but these recovered over time. Increased precipitation caused sustained increases in soil biota. Our results suggest that responses of soil biota to global change are initially predictable but vary over time, indicating that long-term experiments are essential for understanding responses of these food webs to global environmental change. For more information, see Blankinship et al. (2011).

Microbial Feedbacks to Increased Atmospheric CO₂
In a recent study, we gathered results from 49 different experiments, mostly from North America, Europe and Asia, and conducted in forests, grasslands, wetlands, and agricultural fields, including rice paddies. The common theme in the experiments was that they all measured how extra carbon dioxide in the atmosphere affects how soils take up or release the gases methane and nitrous oxide. Using meta-analysis, we found that more CO₂ boosted soil emissions of nitrous oxide, and that extra CO₂ caused soils to release more methane from wetlands and rice paddies.

Why? The culprits are specialized microscopic organisms in soil that produce methane, a greenhouse gas 25 times more powerful than carbon dioxide, and nitrous oxide, 300 times more potent than carbon dioxide. With more CO₂, photosynthesis by plants speeds up, soaking up carbon dioxide from the atmosphere, and, the hope is, locking away carbon in wood and soil. But our work shows that at least some of that extra carbon also provides fuel to microorganisms whose byproducts, nitrous oxide and methane, end up in the atmosphere and counteract the cooling effects of more plant growth. It’s an ecological surprise, one that climate models will need to reckon with as they further refine pictures of the climate of the future. By overlooking the key role of these two greenhouse gases, previous studies may have overestimated the potential of ecosystems to mitigate the greenhouse effect. For more information, see van Groenigen et al. (2011).

Related publications

Blankinship JC, Niklaus PA, Hungate BA, 2011. A meta-analysis of responses of soil biota to global change. Oecologia 165:553-565 doi: 10.1007/s00442-011-1909-0

Hungate BA, van Groenigen KJ, Six J, Jastrow JD, Luo Y, de Graaff MA, van Kessel C, Osenberg CW, 2009. Assessing the effect of elevated CO₂ on soil C: a comparison of four meta-analyses. Global Change Biology. 15: 2020-2034

Van Groenigen KJ, Osenberg CW, Hungate BA, 2011. Increased soil emissions of potent greenhouse gases under elevated CO₂. Nature, 475: 214-U121   DOI: 10.1038/nature10176

Van Groenigen KJ, Six J, Hungate BA, van Kessel C, de Graaff MA, van Breemen N, 2006. Element interactions limit soil carbon storage U.S. Proceedings of the National Academy of Sciences, 103:6571-6574, DOE:10.1073/pnas.0509038103.

Wu Z, Dijkstra P, Koch GW, Peñuelas J, Hungate BA, 2011. Responses of terrestrial ecosystems to temperature and precipitation change: a meta-analysis of experimental manipulation. Global Change Biology 17:927-942. DOI: 10.1111/j.1365-2486.2010.02302.x

Experimental array for the Jasper Ridge Global Change research project

Overview

Most global change research focuses on individual components, but the environment is changing in multiple ways simultaneously. The Jasper Ridge Global Change Experiment seeks to find out how these combined changes will affect ecosystems. Researchers tested the response of a California grassland to:

• climate change
• elevated atmospheric carbon dioxide
• increased nitrogen pollution
• disturbance by wildfire (since 2003)

Students, faculty, and staff affiliated with the Ecosystem Science and Society Center have been active at the site since the experiment began in 1997.

Learn more details about the Jasper Ridge Global Experiment.

This research has been conducted by Bruce Hungate and Paul Dijkstra.

Recent results

Researchers have found that climate change, nitrogen deposition, and wildfire together boosted soil release of nitrous oxide, a potent greenhouse gas. Soils are the major source of nitrous oxide in the atmosphere, so increased soil emissions of nitrous oxide will accelerate global warming. This research shows the importance of considering simultaneous global changes: burning fossil fuels releases reactive nitrogen and raises the concentration of carbon dioxide in the atmosphere, in turn altering climate.

In some parts of the world, like the western United States, wildfires are also becoming more frequent and more intense. Alone, the treatments had little influence on nitrous oxide emissions, but the interaction with wildfire caused a huge burst of nitrous oxide production. Why? The combination of treatments favored bacteria in soil called dentrifiers, which convert nitrate into nitrous oxide. Wetter soils, more nitrate, and more carbon together promoted growth of denitrifying bacteria, microscopic organisms with global impacts. Increasing wildfire frequency and the changing climate could cause these soil microorganisms to release more nitrous oxide into the atmosphere, accelerating global warming.

Related publications

Niboyet A, Brown JR, Dijkstra P, Blankinship JC, Leadley PW, LeRoux X, Barthes L, Barnard RL, Field CB, and Hungate BA, 2011. Global change could amplify fire effects on soil greenhouse gas emissions. PLoS ONE, DOI: 10.1371/journal.pone.0020105

Barnard R, Le Roux X, Hungate BA, Cleland EE, Blankinship JC, Barthes L, Leadley PW, 2006. Several components of global change alter nitrifying and denitrifying activities in an annual grassland. Functional Ecology, 20:557-564.

Blankinship JC, Brown JR, Dijkstra P, Hungate BA, 2010. Effects of interactive global change on methane uptake in an annual grassland. Journal of Geophysical Research, 115, G02008, doi:10.1029/2009JG001097.

Brown JR, Blankinship JC, Niboyet A, van Groenigen KJ, Dijkstra P, Le Roux X, Leadley PW, Hungate BA, 2012. Effects of Multiple Global Change Treatments on Soil N₂O Fluxes. Biogeochemistry 109: 85-100. DOI 10.1007/s10533-011-9655-2

Niboyet A, Barthes L, Hungate BA, Le Roux X, Bloor J, Fontaine S, Price PM, Leadley PW, 2010. Responses of soil nitrogen cycling to the interactive effects of elevated CO₂ and inorganic N supply Plant and Soil 327: 35-47

Niboyet A, Le Roux X, Barthes L, Hungate BA, Dijkstra P, Blankinship JC, Brown JR, Field CB, Leadley PW, 2011. Testing interactive effects of global environmental changes on soil nitrogen cycling. Ecosphere 2:art56. Doi:10.1890/ES10-00148.1

Grants supporting this work

National Science Foundation, CAREER: Ecosystem responses to rising CO₂ and climate change: feedbacks through the nitrogen cycle, 2001-2006, $781,574

Low intensity fire burning through understory of a mixed conifer forest.

Fire plays an important role in controlling structure and function in many ecosystems. Fire regimes across the globe are changing as a result of human management and climate change. Research in Ecoss seeks to understand feedbacks between fire disturbance and ecosystem structure and function in multiple contexts, from savannas in South Africa to Arctic tundra and boreal forests in Alaska and Siberia. Here are some of the topics we work on:

Fire, Management, and the Global Carbon Cycle

Fire, a natural ecological disturbance, has been suppressed in U.S. forests for much of the past century. This has prevented damage to property and protected timber resources, but has caused many forests to develop in an unnatural manner, resulting in dense stands of small trees that are now poised to fuel catastrophic fires when they do ignite. A warming and drying climate exacerbates this risk. How forests function has big impacts to the global carbon cycle; when trees grow they remove carbon dioxide from the atmosphere, and when they burn, some of that is returned to the atmosphere. Read more here.

Increasing Fire Severity and the Loss of Legacy Carbon from Forest and Tundra Ecosystems

Climate warming in northern latitudes has led to an intensification of wildfire disturbance. Increased fire frequency, extent, and severity is expected to strongly impact the structure and function of northern ecosystems. As a large proportion of organic carbon (C) in Arctic tundra and boreal coniferous forests resides in the soil organic layer (SOL), combustion of this layer can lead to large C emissions. In fact, increased depth of SOL burning associated with an intensifying fire regime, might change northern ecosystems from net C sinks into net C sources. For this shift to occur, burning must release old C that escaped combustion in one or more previous fires. We term these old SOL C pools ‘legacy C’ because they are carryover of C pools sequestered prior to past disturbance events or under past climate. Our research combines SOL consumption metrics with radiocarbon techniques for aging soil C to determine the ecosystem, landscape, and regional controls on the combustion of legacy C in forest and tundra regions. Read more here.

Post-fire Carbon Dynamics of Boreal Forests

Boreal forests cover 40% of the vegetated land area above the Arctic Circle and are a critical component of arctic ecosystems. Global change models predict boreal forests will become increasingly susceptible to fire activity with climate warming. Because these forests contain a large proportion of global terrestrial C stocks, changes in the fire regime are likely to alter global C cycling. Increased fire activity will increase C emissions to the atmosphere, with a potential positive feedback to climate warming. However, an altered fire regime may also affect forest regrowth and permafrost degradation, responses that could magnify or offset this feedback. Fire effects on these ecological mechanisms remain uncertain but will ultimately determine whether Arctic ecosystems act as a C source or sink under future climate change scenarios. The primary objective of this research is to increase our understanding of post-fire C dynamics in boreal forests of the Siberian arctic by elucidating the ecological mechanisms by which increased fire severity could influence C accumulation and storage during forest succession. Read more here.

Long Term Ecological Research in Alaska

Vegetation composition and other structural aspects of the ecosystem and landscape modulate climate sensitivity of disturbances and associated ecosystem responses to those disturbances. For example, the distribution of conifers and hardwoods on the landscape influences both fire severity and the outbreak behavior of insects and pathogens, which influence the likelihood that the system will shift to a new resiliency cycle. However, changing disturbance regimes also influence the climate sensitivity of species, plant communities and landscape functional types. The impacts of permafrost thaw on soil water content, for example, strongly affect vegetation responses to climate warming. Moreover, important thresholds may be manifested through interactions between changing disturbance regimes. How increased fire severity is influencing the vulnerability of permafrost to thaw, and how insect and pathogen outbreaks will affect fire regimes and associated successional pathways are two prominent examples. Understanding the underlying mechanisms for these interaction pathways is essential for predicting whether climate-driven changes will contribute to ecosystem and landscape resilience or cause abrupt shifts to a new landscape mosaic with fundamentally different dynamics. Read more here.

Research outlined above is being conducted by Michelle Mack, George Koch and others.

Early morning at the Carbon in Permafrost Experimental Heating Project (CiPEHR) in Alaska

Global change affects plants and soil in ecosystems across the globe. By doing so, it can alter the composition of ecosystems and the functions they provide. For instance, even small changes in plant growth and soil properties can have a large impact on the amount of CO₂ and other greenhouse gases in the atmosphere. At Ecoss, we use field experiments to manipulate the temperature, rainfall and other environmental factors in various ecosystems. This allows us to mimic future conditions, and helps us understand how future ecosystems will differ from the ones today.

Zone Jumping: Downhill Transplants Simulate Future Climate Change

Northern Arizona supports a wide range of ecosystems, from deserts to alpine tundra. Will these ecosystems respond the same way to altered climate? To find out, we are conducting a climate change experiment in four different ecosystems, from high desert grassland to subalpine meadow, using experimental treatments that simulate the expected future climate in 50-100 years.

Modification of Multiple Environmental Factors at Jasper Ridge

Most global change research focuses on individual components, but the environment is changing in multiple ways simultaneously. The Jasper Ridge Global Experiment seeks to find out how these combined changes will affect ecosystems. Researchers tested the response of a California grassland to:

• climate change
• elevated atmospheric carbon dioxide
• increased nitrogen pollution
• disturbance by wildfire (since 2003)

Students, faculty, and staff affiliated with the Ecosystem Science and Society Center have been active at the site since the experiment began in 1997.
This research has been conducted by Bruce Hungate and Paul Dijkstra. Learn more details about Ecoss research at Jasper Ridge.

Carbon in Permafrost Experimental Heating Research

The Carbon in Permafrost Experimental Heating Research (CiPEHR) project is an ecosystem warming experiment that was established in 2008 to test hypotheses about changes in the carbon cycle that are expected as a result of warming temperatures and permafrost thaw. The experiment is located close to Healy, Alaska. The CiPEHR project uses snow fences coupled with spring snow removal to increase soil and permafrost temperatures and open-top chambers to increase growing season air temperatures. Details about this project can be found here.

Deep Nitrogen Acquisition in Warming Permafrost Soils

As permafrost soils thaw, organic matter that has been protected from decomposition for centuries to millennia is released as greenhouse gasses, resulting in an important feedback between the biosphere and climate. However, nitrogen released from deep, thawing soils may stimulate productivity and thus regulate the pace and magnitude of the permafrost carbon (C) feedback to climate. This regulatory role of N is predicated on the opportunistic capacity of arctic plants and their obligate mycobionts to forage as seasonally unfrozen ground deepens. We are using a suite of field experiments and observational studies coupled with model development and modeling experiments to investigate whether tundra plants can acquire deep permafrost N as soils thaw and whether this influences regional carbon balance. This research is a collaborative effort between Northern Arizona University (Michelle Mack and Rebecca Hewitt), University of Alaska Fairbanks (Dave McGuire and Hélène Genet), and University of New Mexico (Lee Taylor). More information about this project can be found here.