Jill Bubier's Lab

RUI: Ecosystem responses to atmospheric N deposition in an ombrotrophic bog: vegetation and microclimate feedbacks lead to stronger C sink or source?

PI: Jill Bubier, Mount Holyoke College
co-PI: Steve Frolking, University of New Hampshire

Project Summary
The increase in atmospheric nitrogen (N) deposition from industrial pollution is of major concern in northern ecosystems, which are typically nutrient-limited. Previous studies have hypothesized that N deposition may increase the carbon dioxide (CO2) sink potential of northern ecosystems by stimulating plant productivity. Peatlands, in particular nutrient-limited bogs, have accumulated vast amounts of carbon (C) since deglaciation, yet the annual C balance is often a very small difference between plant production and soil decomposition. The main objective of this research program is to improve our understanding of complex feedbacks between peatland ecosystems and the atmosphere in response to increasing atmospheric N deposition and climate change. Will N deposition enhance or diminish the CO2 sink potential of nutrient-limited bog ecosystems? What are the positive and negative feedbacks of N deposition to net ecosystem CO2 exchange and climate change? How do changes in vegetation function and structure, as well as corresponding changes in microclimate (moisture, temperature, light interception), contribute to changes in the carbon balance? How will changes in leaf chemistry, phenology, and plant function affect the seasonality of CO2 exchange? The overall framework for the research addresses 1) the impacts of N deposition on global atmosphere-biosphere interactions, and 2) the vulnerability of peatland ecosystems to become C sources rather than long-term C sinks. The project builds on 10 years of research and education at a long-term fertilization experiment with varying levels of nitrogen, phosphorus, and potassium at Mer Bleue Bog in Ottawa, Ontario, Canada. The measurements and experiments include several field and laboratory components: ecosystem and leaf-level CO2 gas exchange of mosses and vascular plants at a range of light levels, leaf biochemistry to test stress responses to potential N saturation, above and belowground plant production and decomposition, and microclimate within the plant canopy and soil profile. These data will contribute to a peatland ecosystem model that will improve our ability to predict thresholds of change in these globally important ecosystems.

The broader impacts of this project include training women undergraduates at Mount Holyoke College, to prepare them for graduate school and future careers in environmental science. The plan includes a cascade mentoring model, which trains students to become research collaborators by following the sequence of trainee during the first summer, mentor to new undergraduate research assistants in the second summer, and finally designers of scientific studies and authors of honors research theses, leading to presentations at international scientific meetings and publication in peer-reviewed journals. Strong collaborations with scientists from major research universities in Canada, Finland and the U.S. are essential for training undergraduates. By involving these students in vibrant research communities of graduate students, postdoctoral fellows and faculty, they will contribute to our understanding of the complexities of carbon and nitrogen cycling in northern peatlands through interdisciplinary research.

Strategies for Understanding the Effects of Global Climate and Environmental Change on Northern Peatlands

The main objective of my research plan is to improve our understanding of feedbacks between peatland ecosystems and the atmosphere in response to global climate change and increasing atmospheric nitrogen deposition through a combination of research and educational activities with undergraduate women students at Mount Holyoke College and collaborations with peatland scientists in Canada, U.S. and Finland. I propose a Cascade Mentoring approach where students evolve from research assistants to full collaborators in furthering our understanding of three main topics: (1) the environmental controls on interannual and seasonal variability in CO2 and CH4 gas exchanges, (2) the different responses of a range of plant communities along hydrologic and nutrient gradients to climate variability, and (3) the influence of nitrogen deposition on carbon exchanges and vegetation community composition. I will build on a strong foundation of research and undergraduate student training accomplished during the last 5 years at a boreal bog and temperate fen to test hypotheses focused on two primary questions: How do changes in temperature and moisture availability on short-term (daily) and longer-term (seasonal and interannual) scales affect C cycling in different plant communities in bog v. fen ecosystems? How does atmospheric N deposition affect C cycling in northern peatlands?

The field component consists of measurements of carbon and nitrogen dynamics across wide ranges of plant community, hydrologic and nutrient gradients at a low boreal bog in Ottawa, Ontario (Mer Bleue Bog) and a temperate poor fen in southern New Hampshire (Sallie’s Fen). Comparing bog and fen, two of the most common peatland types in North America, is a unifying theme throughout this research program. Measurements include CO2 and CH4 gas exchange using manual and automatic chambers, plant production and decomposition experiments, a fertilization experiment to test the response of ecosystems to nitrogen and phosphorus additions, and monitoring plant community and environmental parameters. Preliminary data from the research thus far has raised intriquing questions that are the focus of this proposal. Undergraduate women students at Mount Holyoke College are an integral part of this research program.

The broader impacts of the plan include a Cascade Mentoring model, which trains students to become research collaborators by following the sequence of trainee during the first summer, mentor to new undergraduate research assistants in the second summer, and finally designers of scientific studies and authors of honors research theses leading to presentations at major scientific meetings and publication in peer-reviewed journals. Evaluation of student learning is a critical aspect of the process. The collaborations with scientists from major research universities in Canada and U.S. are also critical for training undergraduates, exposing them to vibrant research communities of graduate students, postdoctoral fellows and faculty, and improving our knowledge of the complexities of carbon cycling in northern peatlands through interdisciplinary research. I propose to foster collaborations with colleagues from University of Helsinki and University of Kuopio in Finland to exchange ideas on carbon and nutrient cycling in peatlands across the boreal and subarctic region, and to begin a new research and education program with a consortium of Finnish scientists on the effect of UV-B radiation and atmospheric ozone on CO2 and CH4 flux in peatlands. The plan also involves development and revision of core and advanced courses such as Environmental Science and Biogeochemistry of Northern Ecosystems. These courses are inquiry-based and involve student-directed research, hypothesis testing, data collection and analysis, and writing. With improvements to these courses with new laboratory components and equipment, I plan to build a strong foundation for students to participate in interdisciplinary research.

	Bianca Young '11 *The Role of Sphagnum* Mosses in Methane Oxidation in a Temperate Fen** Abstract or the Paper Presented to the Faculty of Mount Holyoke College in Partial Fulfillment of the Requirements for the Degree of Bachelors of Arts with Honor (prepared under the direction of Professor Jill Bubier), May 2011. Peatlands are a global source of atmospheric methane (CH4); however oxidation of CH4 by methanotrophic microbes residing in the moss layer provides the potential for mitigation of CH4 emissions (Bubier and Moore, 1994). Determining the controls on CH4 oxidation in Sphagnum mosses will increase our understanding of CH4 dynamics in wetlands, and will allow a better understanding of the influence of climate change on these ecosystems. Studies have shown that the primary controls of oxidation are environmental, i.e. water table and temperature; however little is known about the role of moss species in controlling CH4 oxidation (Basiliko et al., 2004; Larmola et al., 2010). A Sphagnum transplantation experiment was conducted at Sallie’s Fen, a temperate peatland in Barrington, New Hampshire, to observe the effect of environmental conditions on CH4 oxidation rates in Sphagnum fallax and Sphagnum magellanicum and to investigate the relative importance of species versus environment in controlling CH4 oxidation. The mosses were sampled four times over a 28 day period. Triplicate control and transplanted samples were incubated in the lab at two concentrations of CH4, 1000 parts per million (ppm; limiting to low affinity methanotrophs) and 10,000 ppm (non-limiting). Averages of the potential CH4 oxidation of all four sampling days show that when CH4 is limiting there is an interaction between Sphagnum species and the environment. The effect of environment on the microbes of S. magellanicum was evident when host rates of potential CH4 oxidation (0.4 mmol g dw-1 d-1 s.e. 0.10) in the hummock increased significantly (p < 0.05) upon transplantation to the hollow (1.8 mmol g dw-1 d-1 s.e. 0.38). The Sphagnum species effect is supported by the response of S. fallax, which, after transplantation, exhibited potential CH4 oxidation rates that were not significantly different (p > 0.05) from the host rates (1.5 mmol g dw-1 d-1 s.e. 0.20) in the hollow. There was no difference between the sites or species when CH4 was not limiting (p > 0.05). These results indicate that there is a joint control of the environment and Sphagnum species on CH4 oxidation; however the particularly dry summer may have confounded the results.
	Chrissy Kobyljanec '11 Microbial respiration and substrate utilization across a nutrient gradient at Mer Bleue Bog Abstract or the Paper Presented to the Faculty of Mount Holyoke College in Partial Fulfillment of the Requirements for the Degree of Bachelors of Arts with Honor (prepared under the direction of Professor Jill Bubier), May 2011. Atmospheric nitrogen (N) deposition is increasing in North America and Europe owing to fossil fuel burning and agricultural practices. This study was part of a long-term investigation at Mer Bleue Bog, Ontario, Canada, to test whether peatlands, which are typically N-limited, will become stronger or weaker carbon (C) sinks. I measured the CO2 production potential from microbial communities under different substrate additions in peat samples harvested from an ombrotrophic bog that has been fertilized for the past 9 years. Fertilization treatments include control, 5 N+PK, 10 N+PK, and 20 N+PK, where the constants represent how many times higher the added N is from ambient N flux (0.8 g N m-2 yr-1), and PK is added at a constant rate across treatments (6.3 g P m-2 yr-1 and 5.0 g K m-2 yr-1). Substrates included both synthetic (p-coumaric acid, lignin, glucose, cellulose, and amino acids) and plant-derived (Chamaedaphne, Ledum, Vaccinium, Sphagnum, Eriophorum, and a Chamaedaphne/ Vaccinium leachate) carbon compounds. The CO2 production did not increase across the 4 fertilization treatments under control conditions (i.e. no substrates added). However, the addition of substrates increased respiration rates 3, 17, 30, and 23 times over the controls across fertilization treatments. Synthetic C substrates induced lower respiration rates than substrates made from the dominant plant species at the site. Significant preferential utilization of substrates was restricted to amino acids, which was higher in the fertilized plots compared to control, and p-coumaric acid, which was lower in the control than the fertilized plots. These results indicate that when labile C substrates are available, CO2 production potential will increase along a nutrient gradient, potentially increasing CO2 emissions to the atmosphere. Microbial communities appear to respond similarly to substrate additions regardless of fertilization levels, which suggests that they will adapt well to vegetation changes that may take place due to increased nutrient deposition.
	Genevieve Noyce '09 THE ROLE OF SEDGES IN METHANE EMISSIONS FROM A TEMPERATE FEN Abstract or the Paper Presented to the Faculty of Mount Holyoke College in Partial Fulfillment of the Requirements for the Degree of Bachelors of Arts with Honor (prepared under the direction of Professor Jill Bubier), May 2009. Peatlands are the largest single natural source of methane (CH4) to the atmosphere, which has the next largest radiative forcing potential of any greenhouse gas after CO2. Sedges (e.g. Carex spp.) play a critical role in the production, oxidation, and emission of CH4 from these systems. This study examined the effect of Carex rostrata on belowground methane storage and net methane flux from a temperate fen through a vegetation removal experiment. We also studied the effect of sedge removal on responses to environmental variables. During the summer of 2008 we established an experiment in Sallie's Fen, Barrington, NH where we removed sedges and sealed the stems in three replicate experimental plots, while three control plots were kept intact. Methane fluxes, pore water CH4 concentrations, and C. rostrata biomass, along with temperature and water table depth, were measured throughout the growing season. We observed a strong positive correlation between seasonal averages of C. rostrata biomass and CH4 fluxes. Methane emissions increased by 30% throughout the summer in the control plots, but decreased by 22% in the experimental plots. In addition, the average 18 cm (C. rostrata rooting depth) pore water CH4 concentrations in the clipped plots were significantly higher than in the unclipped plots, suggesting increased methanogenesis, decreased methane transport or oxidation, or a combination of any of the above. The 60 cm pore water CH4, which is well below the rooting zone, was not affected by clipping. This suggests that Carex are very influential in methane dynamics.
	Rose Smith '09 Rose has been working for Jill for the past two summers. During the summer of 2007, she worked on developing a way to measure biomass non-destructively. This past summer, she did research for her honors thesis, measuring leaf-level photosynthesis from different species in the experimental fertilization plots. After graduation, she will continue to work with Jill, with efforts to turn her honors thesis into a publishable paper. Abstract Effects of Nitrogen, Phosphorous, and Potassium (N and NPK) Fertilization on Leaf Morphology and Photosynthesis for Evergreen and Deciduous Shrubs in a Boreal Peatland Rose M Smith 1, Sari Juutinen 1, Jill L. Bubier 1, Tim R. Moore 2 1 Environmental Studies Program Mount Holyoke College, South Hadley, MA, 01075 2 Department of Geography, McGill University, Montreal, Quebec H3A 2K6 Atmospheric nitrogen deposition may have serious implications for the species composition, primary production, and carbon dioxide exchange in northern peatlands. Our previous results after five years of fertilization at the Mer Bleue Bog indicated that high N (+PK) supply may reduce net ecosystem carbon uptake as a result of reductions in ecosystem gross photosynthesis (Pg). The present study examines possible mechanisms for this photosynthetic draw down by measuring leaf photosynthesis rates and morphology of the three dominant dwarf ericaceous shrubs including the deciduous Vaccinium myrtilloides, and evergreen Chamadaphane calyculata and Ledum groenlandicum. Treatments included low (1.6g N y-1) and high (6.4g N y-1) N with and without PK. We measured leaf photosynthesis for individual leaves and calculated Vcmax in order to estimate the effects of fertilization on Rubisco enzyme activity. Morphometric measurements included length, width, thickness, area, mass and specific leaf area (SLA, cm2/g). Species responded differently to fertilization in Vcmax as well as morphology. Ledum groenlandicum had significantly higher Vcmax in low N and low NPK but not high N or high NPK treatments. V. myrtilloides had significantly lower Vcmax in low N plots, but no response in the other treatments. C. calyculata did not respond significantly to treatment. Of the three species, V. myrtilloides had the lowest Vcmax values in all treatments. Differences between Vcmax values for these species were smaller in high-N and high NPK plots than in controls. Morphology of L. groenlandicum and V. myrtilloides leaves showed significant responses to treatments. V. myrtilloides increased in leaf area in low-NPK treatments and L. groenlandicum increased in SLA in low NPK treatments. Treatments did not affect C. calyculata leaf morphology. The differences in species responses may be explained by leaf nitrogen concentrations. None of the species measured showed significant increases in Vcmax in the high N or NPK treatments, but moderate N addition might increase photosynthetic capacity of L. groenlandicum. Preliminary results indicate that species at Mer Bleue may be nitrogen-saturated with high-N and NPK treatments.
	Paliza Shrestha '10 I have been working with Jill since summer 2008 on her research at Mer Blue bog, Ottawa, Canada. Last summer I measured net CO2 exchange to investigate the effects of nutrient addition on photosynthesis and ecosystem respiration in the long-term fertilization plots. I quantified the above ground biomass among the control and nutrient treatment plots. This coming summer, I will continue net CO2 exchange measurements and investigate litter decomposition.
	Elizabeth Szarkowski '08 has been working with Professor Jill Bubier doing independent research at Mount Holyoke College since spring of 2007. Over the summer of 2007 she worked with Dr. Ruth Varner at the University of New Hampshire in Sallie’s Fen, a poor fen near UNH. There she took CO2 and CH4 gas exchange measurements, phenology measurements, and percent coverage data to form a vegetation map of the Fen. In the fall of 2007, Libby used the percent coverage data to create a vegetation map of Sallie’s Fen and compared it to a similar map created in 1995. Her future projects will include multivariate analysis of the vegetation data.
	Lisa Brunie'06 Last summer I started working for Professor Bubier at Sallie's Fen in New Hampshire. I worked on measuring CO2 and CH4 emissions from the fen. I was also given the opportunity to become familiar with the LiCor 6400.which is used to investigate leaf level photosynthesis. This summer (2005) I will continue to work for Professor Bubier and will begin collecting data for my thesis at Mere Bleue Bog in Ottawa, Ontario, Canada. I am currently working on defining my thesis project but might be interested in using the 6400 again to compare the functioning of different plant species. Plant Response to Fertilization at a Cool Temperate Peatland Abstract or the Paper Presented to the Faculty of Mount Holyoke College in Partial Fulfillment of the Requirements for the Degree of Bachelors of Arts with Honor (prepared under the direction of Professor Jill Bubier), May 2006. Peatlands are nutrient-limited ecosystems. Human activities are causing an increase in nitrogen (N) deposition, which may lead to fertilization of bogs and alter vascular plant densities and biomass. N deposition affects ecosystem function, and potentially alters the system’s ability to sequester carbon. In the summer of 2005 we measured this effect in an ombrotrophic bog, Mer Bleue, near Ottawa, Canada with a fertilization experiment established in 2000. We measured leaf-level CO2 exchange with a LI-6400 portable photosynthesis system. We used these data to calculate the maximum rate of photosynthetic capacity (Vmax) between the high fertilization (20NPK, 20 times the ambient summer N deposition, or 6.4 g N m-2 as NH4NO3, and 6.3 g P m-2, 5.0 g K m-2 as KH2PO4) treatment plots and control plots. We quantified above ground vascular plant biomass through non-destructive measurements of stem height and stem number within the 0.6 x 0.6m quadrat where we measured net ecosystem CO2 exchange. We destructively measured shrub biomass, number of leaves, leaf size, number of stems, C: N ratio of the leaves, and stem length for clipped plant samples collected from outside the CO2 measurement quadrats. We also measured leaf area index, the mass of litter and litter cover with in the 0.6x 0.6m quadrats. After five years of nutrient addition, above ground biomass of shrubs significantly increased between the control and high fertilization plots (20NPK). This pattern is perhaps explained by the increase in both stem length and leaf area with the fertilizer addition. A decrease in C: N ratio suggests that plants in the fertilizer treatments are taking up the added nutrients. However, an important difference was found in the leaf level photosynthesis data, which showed a significant decrease in Vmax between the control and the high fertilization treatment. These results have important implications for the ecosystem response to environmental changes. The increase in biomass and litter production of vascular plants will have effects on carbon storage as a result of the decomposability of this matter. The increase in biomass may be offset by decreases in leaf-level photosynthesis, potentially altering the carbon uptake within the system.

Gareth Crosby'05 has been working with advisor Jill Bubier for the past two summers on climate change research at Mere Bleue Bog in Ottawa Canada. With data taken from the past two summers she is working on a thesis on peatland vegetation patterns in response to water table gradient changes and the implications of climatic change on methane emissions. It has been found that some species actually aid in methane release from bogs. Since methane is an important greenhouse gas, a loss of a certain type of vegetation could have an important impact on methane accumulation in the atmosphere.

Bubier, J., T. Moore, and G. Crosby*. 2006. Fine-scale vegetation distribution in a cool temperate peatland. Can. J. Bot., 84, 910-923. [Full text]

Claire Treat'05
    This year, I am looking at the environmental controls on interannual and seasonal variability of methane emissions from the fen. I’m trying to pin down more concrete trends both between different seasons and during the growing season, trends by vegetation types, and also trends in relationships with net ecosystem exchange and its components, photosynthesis and respiration.
       Claire with Dr. Jill Bubier (MHC) and Dr. Ruth Varner (University of New Hampshire) presented "Variations in Methane Emissions and Net Ecosystem Exchange in a Temperate Peatland, 2000-2004" in Washington, DC in 2004 meeting, for the Research and Discover Program, at NASA-Goddard Space Flight
Center.
      Abstract: Global climate change has the potential to greatly affect carbon storage in peatlands, which store about 30% of the pool of global soil carbon. Increasing temperature may cause peatlands to function either as a sink or a source of C to the atmosphere. Whether the ecosystem will store or lose carbon is uncertain: climate change may lead to increased plant productivity and C storage, while it could also lead to increased respiration and C loss as both CO2 and methane. This ecosystem dynamic can be measured by net ecosystem CO2 exchange (NEE), which is the sum of two components: photosynthesis and respiration. This study examined the seasonal and interannual variations in NEE and methane emissions and possible links between the two processes in an attempt to determine the environmental controls responsible for the variations. This past summer, we collected and used NEE, methane fluxes, water table level, and meteorological data from the summer (1 May-31 August) for 2000-04, we were able to determine seasonal and interannual patterns for NEE, photosynthesis, respiration, and methane emissions. We observed that photosynthesis and respiration values become larger as the summer progressed. Methane fluxes also became greater in magnitude and variability due to higher peat temperatures and episodic events as the season progressed. Additionally, methane emissions had a positive relationship with photosynthesis and respiration, suggesting that plants exert control over methane emissions and that similar environmental factors control both respiration and methane production.

Treat*, C., J. Bubier, R. Varner and P. Crill. 2007. Time scale dependence of environmental and plant-mediated controls on CH4 flux in a temperate fen. Journal of Geophysical Research-Biogeosciences,112, G01014,1-9, doi:10.1029/2006JG000210. [Full text]

Kathryn McKain'05 has been working with thesis advisor: Dr. Steve Wofsy (Harvard University), MHC advisor: Dr. Jill Bubier, Mount Holyoke College and project mentor: Elizabeth Hammond-Pyle (Harvard University) on "Carbon Accumulation at the Harvard Forest: A Comparison of Measurement Methods and an Investigation of Spatial and Temporal Trends".
Although an abundance of data about local forest carbon cycling dynamics exists from the Prospect Hill tract, the relevance of this data depends on our ability to scale individual sites to the larger forested region. From 2000-2002, the Big Foot Project monitored an array of ecological measurement plots centered on the EMS tower over a 25 km2 area with the purpose of linking the ground-based measurements to Landsat ETM+ data and validating MODLand science products. The continued monitoring of the Big Foot plots by the Wofsy research group will provide a valuable opportunity to increase the scale of the Wofsy group’s area of study. However, an initial comparison of the Big Foot and Wofsy plots revealed that while the Wofsy plots yielded an average of 108 ± 33 MgC/ha as of 2002, the Big Foot plots yielded an average of 73± 26 MgC/ha. This discrepancy could have resulted from the different measurement methods employed by the two groups, or may reflect true spatial differences in forest composition. Whereas the Wofsy group uses fixed-radius plots, the Big Foot project used a prism method and variable-radius plots. A resurvey of the Big Foot plots using both fixed and variable radius plots has allowed for an additional comparison of the two methods. Preliminary results reveal that both methods yield equivalent biomass figures, numbers which also correspond with that calculated from the Prospect Hill tract, but not with that of the original Big Foot survey. Further investigation of the 2004 Big Foot data, including the incorporation of mortality and recruitment, will allow for the better use of existing data and thus for regional extrapolation.

Articles in refereed journals
Larmola, T., Alm, J., Juutinen, S., Koppisch, D., Augustin, J., Martikainen, P.J. & Silvola, J. 2006. Spatial patterns of litter decomposition in the littoral zone of boreal lakes. Freshwater Biology 51, 2252–2264.

Kortelainen, P., Rantakari, M., Huttunen, J.T., Mattsson, T., Alm, J., Juutinen, S., Larmola, T., Silvola, J. & Martikainen, P.J. 2006. Sediment respiration and lake trophic state important predictors for the large CO2 evasion from small boreal lakes. Global Change Biology 12, 1554–1567.

Juutinen, S., Alm, J., Larmola, T., Saarnio, S., Martikainen, P.J. & Silvola, J. 2004.
Stand-specific diurnal dynamics of CH4 fluxes in boreal lakes: Patterns and
controls. Journal of Geophysical Research 109 (D19313), doi:10.1029/2004JD004782.

Larmola, T., Alm, J., Juutinen, S., Huttunen, J.T., Martikainen, P.J. & Silvola, J. 2004. The contribution of vegetated littoral zone to winter fluxes of carbon dioxide and methane from boreal lakes. Journal of Geophysical Research 199 (D19102), doi:10.1029/2004JD004875.

Larmola, T., Alm, J., Juutinen, S., Saarnio, S., Martikainen, P.J. & Silvola, J. 2004. Floods can cause large interannual differences in littoral net ecosystem productivity. Limnology and Oceanography 49: 1896–1906.

Juutinen, S., Alm, J., Larmola, T., Huttunen, J.T., Morero, M., Martikainen, P.J. & Silvola, J. 2003. Major implication of the littoral zone for methane release from boreal lakes. Global Biogeochemical Cycles 17(4), 117, doi:10.1029/2003GB002105.

Juutinen S, Alm J, Larmola T, Huttunen J, Morero M, Saarnio S , Martikainen PJ & Silvola J. 2003. Methane (CH4) release from littoral wetlands of boreal lakes during an extended flooding period. Global Change Biology. 9 (3), 413–424.

Juutinen, S., Larmola, T., Remus, R., Mirus, E., Merbach, W., Silvola, J. & Augustin, J. 2003. The contribution of Phragmites australis litter to methane (CH4) emission in planted and non-planted fen microcosms. Biology and Fertility of Soils 38:10-14. Doi:10.1007/s00374-003-0618-1.

Larmola, T., Alm, J., Juutinen, S., Martikainen, P.J. & Silvola, J. 2003. Ecosystem CO2 exchange and plant biomass in the littoral zone of a boreal lake. Freshwater Biology 48:1295–1310.

Huttunen, J.T., Juutinen, S., Alm, J., Larmola, T., Hammar, T., Silvola, J. & Martikainen, P.J. 2003. Nitrous oxide flux to the atmosphere from the littoral zone of a boreal lake. Journal of Geophysical Research 108, doi:10.1029/2003JD002989.

Huttunen, J.T., Alm, J., Liikanen, A., Juutinen, S., Larmola, T., Hammar, T., Silvola, J. & Martikainen, P.J.. 2003. Fluxes of methane, carbon dioxide and nitrous oxide in boreal lakes and potential anthropogenic effects on the aquatic greenhouse gas emissions. Chemosphere 52: 609–621.

Juutinen, S., Alm, J., Martikainen, P.J. and Silvola, J. 2001. Effects of spring flood and water level draw-down on methane dynamics in the littoral zone of boreal lakes. Freshwater Biology 46:855–869.

Richert, M., Saarnio, S., Juutinen, S., Silvola, J., Augustin, J. and Merbach, W. 2000. Distribution of assimilated carbon in the system Phragmites australis-waterlogged peat soil after carbon-14 pulse labelling. Biology and Fertility of Soils 32:1–7.

Other Scientific Publications
Putkinen, A., Juottonen, H., Juutinen, S., Tuittila, E.-S., Fritze, H. & Yrjälä, K. 2006. Active Archaea and methane production in southern and northern boreal mire sediments. Pro Terra 29: 82–83.

Martikainen, P.J., Alm, J., Huttunen, J.T., Hyppönen, N., Jauhiainen, J., Juutinen, S., Koponen, H., Kortelainen, P., Larmola, T., Liikanen, A., Maljanen, M., Nykänen, H., Pekkarinen, N., Repo, M., Saari, A., Shurpali, N., Silvennoinen, H., Silvola, J., & Vasander, H. 2006. Greenhouse gas dynamics of terrestrial and aquatic environments: Pristine ecosystems and land-use effects, 375–381. In Kulmala, M., Lindroth, A. & Ruuskanen, T. (Eds.), Proceedings of BACCI, NECC and FCoE activities 2005. Report Series of in Aerosol Science N:o 81B, Aerosolitutkimusseura ry, Helsinki.

Juutinen, S., Alm, J., Larmola, T., Huttunen, J.T., Martikainen, P.J. & Silvola, J. 2003. Lakes and climate change; implications for CH4 emissions from littoral zone, 120–122. In Honkanen, J.O. & Koponen, P.S. (Eds.), Proceedings of Sixth Finnish Conference of Environmental Sciences. University of Joensuu, May 8–9, 2003. Finnish Society of Environmental Sciences.

Larmola, T.,Alm, J., Juutinen, S., Huttunen, J.T., Martikainen, P.J. & Silvola, J. 2003. Contribution of the littoral carbon dioxide dynamics to carbon fluxes of a boreal lake, 152–154. In Honkanen, J.O. & Koponen, P.S. (Eds.), Proceedings of Sixth Finnish Conference of Environmental Sciences. University of Joensuu, May 8–9, 2003. Finnish Society of Environmental Sciences.

Huttunen, J., Alm, J., Juutinen, S., Silvola, J. and Martikainen, P.J. 2000. Greenhouse gas fluxes in a boreal agricultural landscape. In. Pietola, L. (ed.) Soil Science in the Service of Mankind – Extended Abstracts of the 1st Finnish Soil Science Conference, Helsinki 21–22 November 2000. Pro Terra 4. University of Helsinki, 131–133.

Alm, J., Juutinen, S., Saarnio, S., Silvola, J., Nykänen, H. & Martikainen, P.J. 1996. Temporal and spatial variations in CH4 emissions of flooded meadows and vegetated hydrolittoral, 71–76. In: Laiho R, Laine J & Vasander H (eds.) Proc. of the Int. Workshop on "Northern Peatlands in Global Climatic Change", Hyytiälä, Finland 8-11. October, 1995. Publications of the Academy of Finland 1/96. VAPK.

Scientific monographs
Juutinen, S. 2004. Methane fluxes and their environmental controls in the littoral zone of boreal lakes. University of Joensuu, PhD Dissertations in Biology. No: 25. 110 p. Summary of Ph.D thesis, http://www.joensuu.fi/biologia/phd/juutinen.pdf