Response of soil communities to experimental warmingI am working with Dr. Chris Schadt as part of the Spruce and Peatland Responses Under Climatic and Environmental Change (SPRUCE), a large-scale a large-scale ecosystem manipulation experiment designed to examine the response of peatlands to increased temperature and carbon dioxide. The initial phase of this experiment began over the summer of 2014 by heating deep subsurface peat to +2.25, +4.5, +6.75, and +9.0 °C above ambient plots with a target heating zone of 1.5-2 meters depth. My role in this project is to assess the impact of warming on the function and structure of soil microbial communities. Using molecular techniques including next generation sequencing through the Joint Genome Institute I am examining the in-situ response of microbial communities. Peat cores were collected in June 2014, September 2014 and June 2015, and microbial communities were examined at eleven discrete depths across the peat profile to a depth of 200 cm. One year of warming, microbial community structure and abundance of bacterial, archaeal, fungal, and methanogenic populations show strong vertical stratification across the peat depth profile yet no clear response to the temperature treatments.
In an effort to identify factors that may be limiting decomposition and microbial community change, we conducted a microcosm incubation of deep peat (150-200 cm depth) at 6 and 15 °C to mimic ambient and +9 °C SPRUCE conditions. Additional treatments included elevated pH and the addition of N and P. Incubation microcosms were monitored for CO2 and CH4 production, and microbial community dynamics were assessed using qPCR and amplicon sequencing. Increasing temperature elevated both CO2 and CH4 production while elevated pH only resulted in greater CH4 production. Although temperature had little effect on the overall microbial community structure, there was a shift in the size of bacterial and archaeal populations. In contrast, elevated pH and N additions seemed to have the largest influence on community structure and suggest that response in the deep peat may be limited by factors other than temperature. Microbial communities and soil carbon cyclingSoil microbes are drivers of biogeochemical cycling, however they have been largely absent from global carbon (C) models until recently, largely because it is difficult to account for the many factors that influence microbially-mediated C processes. To address this, I am conducting a series of short and long-term incubation experiments with 13C labeled substrates to examine how plant communities (forest vs. grassland), edaphic properties, and microbial communities influence C cycling and the long-term fate of C in soil systems. In addition to improving the conceptual understanding of microbially-facilitated decomposition, I designed these experiments such that ORNL C-cycle modelers, Drs. Melanie Mayes and Gangsheng Wang, can use the resulting data to improve the Microbial ENzyme Decomposition (MEND) model by incorporating C source complexity and turnover rates in various soil types.
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Reducing the impact of agriculture through wetland restorationWetlands provide a number of important ecosystem services including: water quality improvement; wildlife habitat; carbon sequestration; and flood control. One of the ways that wetlands are able to improve water quality and reduce the impact of agricultural runoff is through denitrification, the conversion of nitrate into nitrogen gas. This microbially mediated process is common in low oxygen, carbon rich environments such as wetlands. However, the greenhouse gas nitrous oxide can be produced if denitrification is not carried through to completion.
The Wetlands Component of the NRCS Conservation Effects Assessment Project (CEAP) aims to reduce the impact of agriculture on environmental quality by restoring wetlands in agricultural areas. However, it is important to monitor how wetland restoration influences denitrification and nitrous oxide production. To do this, I am working with a team of scientists to monitor gas emissions, soil properties, and microbial communities in Mid-Atlantic wetlands, converted wetlands (currently farm land), and restored wetlands. Initial findings from this multi-state assessment underscore the complex influences regional soil properties, land use, and environmental conditions have on the structure and function of soil microbial communities (Kluber et al. 2014). Photos: Natural wetland (top), converted wetland (middle), restored wetland (bottom). All photos by collaborator Jarrod Milller. |
Soil biology and ecosystem ecologyFrom 2010 to 2012, I worked with Kurt Smemo, David Burke, and Jared Deforest on an NSF funded project to examine the impact of acid deposition and acid-induced phosphorus (P) limitation on deciduous forest ecosystems. This large-scale manipulation experiment involved the application of lime and P to forested plots on glaciated and unglaciated soils. One year after the establishment of treatments, ectomycorrhizal communities shifted in response of phosphorus application. However, arbuscular mycorrhizal communities were influenced by soil pH and location rather than P availability (Kluber et al. 2012, Carrino-Kyker et al. 2016a). To follow up on the initial findings, the team initiated a study to examine the temporal variation in biogeochemical processes and soil communities under these treatments. Findings from the biogeochemical portion of this work indicate widespread P limitation that is not entirely acid-induced. Furthermore, C limitation in the northern, glaciated, sited indicate N saturation as well (Smemo et al. in preparation). I also teamed with Sarah Carrino-Kyker on a project that examined the in-situ regulation of an arbuscular mycorrhizal phosphorus transporter (Carrino-Kyker et al. 2016b).
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The ecology of ectomycorrhizal mats in Douglas-fir forestsWorking in the laboratory of Dr. David Myrold at Oregon State University, my dissertation research investigated how mycorrhizal fungi interact with the soil environment and other soil-dwelling microbes. As part of the H.J. Andrews Microbial Observatory, I examined the microbial and biochemical dynamics of dense hyphal mats formed by some ectomycorrhizal fungi. I found that ectomycorrhizal mats can alter biogeochemical processes (Kluber et al. 2010) and create a unique microhabitat that fosters distinct fungal and bacterial communities (Kluber et al. 2011) in Douglas-fir forest soils.
To further investigate the role of mycorrhizal fungi in forest C cycling, I teamed with Claire Phillips on a project to quantify the contribution of ectomycorrhizal mats to forest soil respiration (Phillips et al. 2012). Additionally, I worked with Lydia Zeglin to investigate the importance of chitin turnover to C and N cycling in mat and non-mat forest soils (Zeglin et al. 2012). |
Soils, fire, and forest managementI collaborated with Jane E. Smith of the US Forest Service to examine how the presence of down wood at the time of a forest fire impacts soil properties and microbial communities (Smith et al. 2017) and to assess the recovery of soil fungi in areas that have undergone salvage logging after a fire. Because soil status and fungal communities impact on tree health and post-fire forest regeneration, findings from these projects could have direct implications for forest management practices.
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Soil management and plant-microbe interactions
Corn residue after harvest
Soil tillage is a common agricultural practice used to reduce weeds and prepare soils for planting. However, tillage is also known to compact subsoil, and contributes to erosion and the loss of soil carbon. Conservation tillage is a broad term to describe the practice of reduced soil tillage and leaving plant residue on the soil surface after harvest. This soil management practice is credited with reducing soil erosion and increasing soil carbon. Additionally, conservation tillage has the potential to improve habitat for soil organisms, such as rhizosphere bacteria and mycorrhizal fungi, that in turn could increase drought resistance and decrease fertilizer inputs.
I worked with other scientists at the USDA-ARS Coastal Plains Research Center to examine the effect of soil management practices on plant-microbe interactions. This project is utilized plots that were established in 1978 to compare conventional and conservation tillage and are currently undergoing a corn-cotton rotation. Plants, roots, and rhizosphere soils were harvested five times during each of the 2012 and 2013 growing seasons. Molecular techniques are being used to examine the community composition and abundance of rhizosphere bacteria and arbuscular mycorrhizal fungi. By correlating microbial communities and colonization rates with plant nutrients and soil properties, findings from this study will further our understanding of how soil management practices impact plant-microbe relations and plant productivity. Findings from this project were presented at the Beltwide Cotton Conference in January, 2013 and 2014.
I worked with other scientists at the USDA-ARS Coastal Plains Research Center to examine the effect of soil management practices on plant-microbe interactions. This project is utilized plots that were established in 1978 to compare conventional and conservation tillage and are currently undergoing a corn-cotton rotation. Plants, roots, and rhizosphere soils were harvested five times during each of the 2012 and 2013 growing seasons. Molecular techniques are being used to examine the community composition and abundance of rhizosphere bacteria and arbuscular mycorrhizal fungi. By correlating microbial communities and colonization rates with plant nutrients and soil properties, findings from this study will further our understanding of how soil management practices impact plant-microbe relations and plant productivity. Findings from this project were presented at the Beltwide Cotton Conference in January, 2013 and 2014.
Publications and data products
Smith, J.E.*, L.A. Kluber*, T.N. Jennings, D. McKay, Greg Brenner, and E.W. Sulzman. (2017) Does the presence of down wood at the time of a forest fire impact soil recovery? Forest Ecology and Management, 391, 52-62.
*co-first authors
R.M. Wilson and A.H. Hopple, M.M. Tfaily, S. Sebestyen, C.W. Schadt, L. Pfeifer-Meister, C. Medvedeff, K. McFarlane, J.E. Kostka, M. Kolton, R. Kolka, L.A. Kluber, J. Keller, T. Guilderson, N. Griffiths, J.P. Chanton, S. Bridgham, and P.J. Hanson. (2016) Stability of a peatland carbon bank to rising temperatures. Nature Communications, 7, 13723, DOI: 10.1038/ncomms13723
Carrino-Kyker, S.R., L.A. Kluber, K.A. Smemo, D.J. Burke. (2016) Detection of phosphate transporter genes from arbuscular mycorrhizal fungi in acidic forest soils. Symbiosis,
Kluber, L.A., J.R. Phillips, P.J. Hanson, C.W. Schadt. 2016. SPRUCE Deep Peat Heating (DPH) Peat Water Content and Temperature Profiles for Experimental Plot Cores, June 2014 through June 2015. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tennessee, U.S.A.
Carrino-Kyker, S.R., L.A. Kluber, K.P. Coyle*, S.M. Peterson, J.L. DeForest, K.A. Smemo, and D.J. Burke. (2016) Ectomycorrhizal fungal communities respond to experimental elevation of soil pH and P availability in temperate hardwood forests. FEMS Microbiology Ecology, 92, 3, DOI: 10.1093/femsec/fiw02
Kluber, L.A., J.O. Miller, T.F. Ducey, P.G. Hunt, M. Lang, K.S. Ro. (2014) Multistate assessment of wetland restoration on CO2 and N2O emissions and soil bacterial communities. Applied Soil Ecology, 75; pp. 87-94.
Kluber, L.A., S.R. Carrino-Kyker, D.J. Burke, K.P. Coyle, J.L. DeForest, A.N. Shaw, and K.A. Smemo. (2012) Response of mycorrhizal communities to experimental pH and P manipulation in acidic hardwood forests. PLoS ONE 7(11): e48946. DOI:10.1371/journal.pone.0048946
Zeglin, L.H., L.A. Kluber and D.D. Myrold. (2012) Amino sugar C and N dynamics in ectomycorrhizal mat and non-mat soils of an old-growth Douglas-fir forest. Biogeochemistry DOI: 10.1007/s10533-012-9746-8
Phillips, C.L., L.A. Kluber, J.P. Martin, B.A. Caldwell, and B.J. Bond. (2012) Contributions of ectomycorrhizal fungal mats to forest soil respiration. Biogeosciences, 9, pp. 2099-2110.
Kluber, L.A., J.E. Smith, and D.D. Myrold. (2011) Distinctive fungal and bacterial communities are associated with mats formed by ectomycorrhizal fungi. Soil Biology and Biochemistry, 43; pp. 1042-1050.
Kluber, L.A., K.M. Tinnesand, B.A. Caldwell, S.M. Dunham, R.R. Yarwood, P.J. Bottomley, and D.D. Myrold. (2010) Ectomycorrhizal mats alter forest soil biogeochemistry. Soil Biology and Biochemistry, 42; pp. 1607-161.
Submitted and in preparation
Kluber, L.A., S.A. Allen, J.N. Hendershot, P.J. Hanson, C.W. Schadt. Nutrient and temperature constraints of peat decomposition. In preparation for Global Change Biology
Smemo, K.A., S.M. Peterson, L.A. Kluber, C.R. Hewins, A.N. Shaw*, and J.L. DeForest. Soil enzyme stoichiometry reveals new insights into the nutrient economy of acidic hardwood forests. In revision.
Non-refereed publications
Smith, J.E., L.A. Kluber, and N. Parks. Nutritional Hotspots and the secret life of Forests. 2014. Science Findings 161. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 6 p.
Carrino-Kyker, S.R. & L.A. Kluber. 2012. The invisible world of soil and how we study it. Leaves Magazine, The Holden Arboretum. v10 no1. pp14-15.
Kluber, L.A. 2011. Ectomycorrhizal mats create unique micro habitat for soil fungi and bacteria. Leaves Magazine, The Holden Arboretum. v9 no4. pp18.