What keeps these ancient critters around? These are white rhino which graze on grasses. Black rhinos, in contrast, are browsers and feed on woody plants. Savannas are defined by the unusual mix of trees and grasses allowing both grazers and browsers to coexist. Though many hypotheses have been developed, it is still not clear why grasses do not outcompete trees or vice versa. In research supported by the Mellon foundation, I am using a pulse-label technique to measure how trees and grasses share soil resources, providing a potential explanation for how they coexist. An understanding of tree and grass coexistence is necessary in order for predictions of the effects of climate change on tree and grass abundance to be made.

Plant Invasions

Recent theoretical and empirical research suggests that plant-soil feedbacks (PSFs) may be a critical but underappreciated factor that can explain plant community development.  Most research on PSFs, however, has been performed on over-simplified theoretical or experimental systems.  My research uses field, laboratory, and theoretical approaches to measure PSFs, typically in invaded plant systems.  Furthermore, through my research, I determine the relative importance of PSF mechanisms to other mechanisms that have been suggested to explain plant growth (e.g., competition, propagule pressure).

Using a large, multi-factor field experiment in a shrub-steppe system in Washington, I found that soil history was more important to the distribution of native and exotic plants than competition from established or germinating plants, shading, tillage, or propagule addition.  Exotic plants in this system appear to facilitate their own growth by maintaining high mycorrhizal infection rates despite suppressing total fungal biomass.  In addition to plant-microbe interactions, I have found that nematode populations are smaller and net nitrogen mineralization rates are faster in exotic- than native-dominated soils.  Despite a historical emphasis on resource competition within plant generations in the field of ecology, my work suggests that plant community development can be best described by the PSFs that develop over multiple plant generations and/or the disturbances that fundamentally alter soil biology and chemistry. This work was made possible by funding from the USDA NRICGP, the Switzer Foundation, and the Utah State Agricultural Experimental Station.

Where PSFs are important to exotic plant growth, it may be possible to use an understanding of these feedbacks to develop species-specific approaches to exotic plant management.  As a first attempt to follow this line of research, I performed an activated carbon addition experiment.  Activated carbon addition was expected to sever plant-soil communication and decrease the benefit of plant-soil feedbacks realized by exotic plants.  In support of this prediction, activated carbon addition reduced microbial abundance and diversity and the growth of two dominant exotic species.  Activated carbon addition also increased the growth of two dominant native grasses (Fig. 1).  This management approach has gained attention and is being replicated at a larger scale by other researchers and land managers.

Most PSF studies have been performed under greenhouse conditions using plant monocultures so the importance of PSFs to plant communities under field conditions remains a major question.  To address this question, I have established paired PSF experiments in the field and in the greenhouse.  These experiments will assess PSFs for individual plant species, as has been done in other studies.  These experiments will also produce the first explicit tests of PSFs for plant communities.  Data from these experiments will determine if current theoretical and greenhouse-derived data overestimate or underestimate the importance of PSFs in field conditions.

Fig. 1. My research on plant-soil feedbacks in invaded systems led me to develop a novel native plant restoration technique that utilizes activated carbon as a soil amendment to inhibit plant-microbe communication.  In this picture native grasses are seen growing vigorously in an activated carbon treated plot that is surrounded by untreated soil.  The untreated soil is dominated by exotic-invasive plants (e.g., Poa bulbosa and Centaurea diffusa). 

Theoretical models have suggested that plant-soil feedbacks may be a driving factor in plant community development, but these models are limited to two annual plant species systems.  I am currently working with a mathematician to develop three-species ordinary difference equations and a spatially-explicit, multi-species integro-difference model that will improve conceptual understanding of plant-soil feedbacks in plant communities.  We have requested funding to develop these models.  As a part of the same proposal, I am collaborating with a microbial ecologist to perform genetic analyses of the microbial communities created by plant monocultures and plant communities.  I am very excited by this research and believe that testing predictions from our mathematical models using field experiments will provide great advances in our understanding of the role of plant-soil interactions in plant community development. 

Water Use

Interactions between plants and soil organisms are not the only way in which plant effects on soils may feedback to affect plant growth: plants may differ in the timing or extent of resource extraction.  Plant species differ, for example, in the timing and extent of use of soil water.  Differences in water use are likely to be especially important in semi-arid systems.  A second theme in my body of research examines water use by different plant species.

To measure differences in water use between exotic and native plants in the shrub-steppe of Washington State, I have used measures of soil moisture and isotopic composition to demonstrate that exotic plants extracted shallow soil water before most native plants became active in the spring.  This suggests that exotic plants may maintain dominance by altering the timing of shallow water use. 

I am now pursuing a similar line of research in South Africa.  In this research I am using several techniques to determine the timing, location, and extent of water-use by grasses, tree seedlings, shrubs, and trees in an effort to define niche space in a savannah system. Historically, it has been difficult to measure root activity because the fragile fine roots that absorb water are buried in dense soils and difficult to observe. To resolve this problem, we are injecting (Figs. 2 and 5) deuterated water into specific soil depths at specific times of the year. 

Fig. 2. While the wildlife do cause some delays in our research, we have had great success in determining root activity in the savanna systems in Kruger National Park using a pulse-labeling approach. The lower photo shows Karen Beard, Lauren Hierl, and Shane Heath injecting deuterium oxide into the soil in a trial plot.

Fig. 3. A rainout shelter designed to create fewer but larger precipitation events (a real engineering feat - for beginners).

In a second experiment in South Africa I am testing the predicted effects of climate change on the savannah ecosystem.  To do this, I have assembled 8m x 8m rain-collecting shelters that will deposit precipitation as large events.  This will simulate the predicted effect of fewer, larger precipitation events.  Tree, grass, and soil moisture responses to these changes will be monitored.  

Fig. 4. Installing soil water potential and water content probes. I'm really a professional hole digger.

In addition to my own work, I have enjoyed collaborating with others.  My role in these collaborations is typically as an ecosystem ecologist.  While at Yale I worked with researchers on the effects of coarse woody debris and a terrestrial vertebrate on ecosystem processes in Puerto Rico.  Also with Kristiina Vogt and others, I worked on the effects of nitrogen saturation on forest ecosystems in the northeastern US.  While at USU, I worked with Karen Beard and graduate students on the long-term effects of native ungulate herbivory on nutrient cycling and on the role of gopher activity and soil compaction in exotic plant growth in Washington.  Most recently I have collaborated with a Karen Mock at USU to determine whether the invasive Phragmites australis has hybridized with a EurAsian strain.  I am now also collaborating with a mathematician, Justin Heavilin, on a model of plant-soil feedbacks, a statistician, John Stevens, on a Bayes model for the meta-analytical review of ecological data, and with a microbial ecologist, Jenny Norton, on genetic analyses of soil microbial communities. I look forward to extending my collaborations with researcher here in Alaska. 

 Fig. 5. Reason, Isaac, Wasani, and Rudolph applying deuterated and rinse water in some of the 5,000 injection points that go into every plot.

Biogeochemistry (A485/A685)

Principles of Ecology (A271)

Kulmatiski A., K.H. Beard, J. Stevens, S.M. Cobbold. 2008. Plant-soil feedbacks: a meta-analytical review. Ecology Letters. 11(9): 980-992.

Kyle, G.P., K.H. Beard, A. Kulmatiski. 2008. Pocket gophers change plant species composition in a shrub steppe ecosystem. Western North American Naturalist.68(3): 374-381.

Kulmatiski A., K.H. Beard. 2008. Decoupling plant-growth from land-use legacies in soil microbial communities. Soil Biology and Biochemistry. 40(5): 1059-1068.

Kulmatiski A., Kardol P. 2008. Invited Submission. Getting plant-soil feedbacks out of the greenhouse: conceptual and experimental approaches. Beyschlag W. (ed) In: Progress in Botany Vol. 69.

Kulmatiski A., Vogt K.A., Vogt D.J., Wargo, P., Tilley J.P., Siccama T.G., Sigurdardottir R. Ludwig D. 2007. Nitrogen and calcium additions increase forest growth in Northeastern USA spruce-fir forests. Canadian Journal of Forest Research. 37(9):1574-1585.

Kyle G.P., K.H. Beard, A. Kulmatiski. 2007. Reduced soil compaction enhances growth of non-native plant species. Plant Ecology. 193(2):223-232.

Rexroad E., K.H. Beard, A. Kulmatiski. 2007. Soil, plant, and arthropod response to 35 and 55 years of native ungulate grazing in shrub-steppe communities. Western North American Naturalist. 67(1): 16-25.

Kulmatiski, A., K.H. Beard, J.M. Stark. 2006. Soil history as a primary control on plant invasion in abandoned agricultural fields. Journal of Applied Ecology. 43:868-876.

Kulmatiski A. 2006. Exotic plants establish persistent communities. Plant Ecology. 187(2):261-275.

Kulmatiski A., K.H. Beard, J.M. Stark. 2006. Exotic plant communities shift water-use timing in a shrub-steppe ecosystem. Plant and Soil. 288: 271-284.

Kulmatiski, A., K.H. Beard. 2006. Activated carbon as a restoration tool: potential for control of invasive plants in abandoned agricultural fields. Restoration Ecology. 14(2) 251-257.

Kulmatiski, A. 2005. Soil-mediated controls on weed establishment and growth. Ph.D. Dissertation, Biology Department, Utah State University.

Kulmatiski A., K.H. Beard, J.M. Stark. 2004. Finding endemic soil-based controls on weed growth. Weed Technology 18:115-120.

Kulmatiski A., D.J. Vogt, T.G. Siccama, J.P. Tilley, K. Kolesinskas, T.W. Wickwire, B.C. Larson. 2004. Landscape determinants of soil carbon and nitrogen storage in Southern New England. Soil Science Society of America Journal 68(6) 2014-2022.

Kulmatiski A., K.H. Beard. 2004. Reducing sampler error in soil research. Soil Biology and Biochemistry. 36:383-385.

Kulmatiski A., D.J. Vogt, T.G. Siccama, K.H. Beard. 2003. Detecting nutrient pool changes in rocky forest soils. Soil Science Society of America Journal 67:1282-1286.

Beard, K.H., K.A. Vogt, A. Kulmatiski. 2002. Top-down effects of a terrestrial frog on forest nutrient dynamics. Oecologia 133:583-593.

In review:

Kulmatiski A., R. Verweij, K.H. Beard, E. February. Redefining niche space: a long-awaited resolution for the two-layer hypothesis. Oecologia.

Kulmatiski A. Managing soils to manage plant communities: Activated carbon decreases microbial abundance and restores a native-dominated plant community. Soil Biology and Biochemistry

Kulmatiski A., K.E. Mock., K.H. Beard, L.A. Meyerson. (drafted) Reconstructing the cryptic invasion of Phragmites australis in Utah. Diversity and Distributions.

In preparation:

Kulmatiski A., J. Heavilin. (parameterizing model) Community-level plant-soil feedbacks. Ecology.

Kulmatiski A. (drafted) Short and long-term microbial community responses to exotic plant invasions in a shrub-steppe ecosystem. Soil Biology and Biochemistry.

Kulmatiski A. (data collected) Native grass seeds wait for wet years to germinate and establish in a semi-arid system. Plant Ecology.

(S. Heath photo)

Personal interests

I do a lot of climbing and I'm looking for a new partner for rock, ice, mixed, bigwall, alpine, any type of climbing.