Current Projects
Increased Variability and Regime Shifts Collaborators: LTER Transitions Working Group Increased climate variability and multiple perturbation might result in more difficult to reverse compositional shifts in plant communities. We are using cross-site synthesis to test and inform theory on ecosystem transitions and transient dynamics in plant communities. |
Spatial and Temporal Contributions of Plant-Soil Feedbacks During Shrub ExpansionCollaborators: Anny Chung
Shrub expansion into grasslands and savannas can result in loss of diversity and reduced ecosystem service provisioning for local communities. I am working on a model that will help us discern the potential contributions (through time and space) of plant-soil feedbacks in the grassland-shrubland ecotone at Sevilleta LTER. |
Recovery of Biodiversity Following Cessation of Nutrient AdditionCollaborators: Carmen Ebel, Chris Clark, Forest Isbell
Nutrient enrichment of ecosystems can cause persistent reductions in plant diversity. How can we overcome the mechanisms that might be reinforcing low levels of plant diversity? We are looking at long-term responses of biodiversity and productivity to common restoration strategies in an ex-arable grassland that experienced nutrient enrichment and cessation. |
Biotic Feedbacks After Long-Term Nutrient Addition and CessationCollaborators: Forest Isbell, Richard Lankau
Long term nutrient enrichment can lead to persistent reductions in biodiversity. In many cases, reducing nitrogen inputs is not sufficient to restore plant diversity, but the mechanisms behind this are still unclear. We are interested in understanding wether biotic feedbacks, such as those between plants and soil microbes, could be contributing to the lack of recovery of biodiversity we observe in our experiments. To test this, we have conducted greenhouse experiments regarding changes in plant-soil feedbacks and mutualism disruption. |
Nutrient Enrichment and DecompositionCollaborators: Forest Isbell, Sarah Hobbie
Litter accumulation and light limitation are some of the mechanisms that have been shown to contribute to the loss of plant diversity after nutrient enrichment. In our long term nutrient addition and cessation experiment we observe that litter accumulation persists even decades after increased nutrient inputs have stopped (and despite lower litter production). We are interested in understanding why this happens and are testing it with a litter bag experiment. We made a reciprocal transplant of litter from different plots in the experiment in order to understand differences in litter decomposition. |
Long-Term Irrigation and FertilizationCollaborators: Jessica Gutknecht
We are interested in understanding how changes in precipitation and nutrient inputs are affecting the function of microbial communities. We are doing this by measuring hydrolytic enzyme activities in a ten year irrigation and fertilization experiment at Cedar Creek. To make it even more interesting, we are imposing a drought (rainfall reduction) in these plots. This will allow us to test how microbial communities that have experienced a decade of increased precipitation, nutrient inputs, or both, will respond to drought. |
Drought-NetCollaborators: Many!
The Isbell lab collaborated in setting up a Drought-Net site at Cedar Creek. Our plots are located in a very diverse oak savannah, where we have crossed rainfall interception with fertilization. Along with collaborators across the world, we are imposing a 1-in-100 year drought for a period of 4 years. We are interested to see how these plant and microbial communities respond to these global change factors. |
Past Projects
Prey Visit Risky Sites at Safe TimesCollaborators: Meredith Palmer, Caitlin Potter, David Mech, Forest Isbell
Reintroduction of large carnivores can result in trophic cascades, changing the abundance of herbivores, vegetation, and even soil nutrients. After wolves briefly returned to Cedar Creek, we simulated their presence by spreading wolf pee near plots where we could monitor herbivore presence, vegetation consumption, and soil nutrients. In the first field season we did not find evidence for a tropic cascade, instead, we found that deer and other herbivores continued to visit "wolf" sites, but did so during safer times of the day, when there was more light. If you want to learn more, check out Palmer et al. 2021 |
Garlic Mustard Disrupts the Legume-Rhizobia MutualismCollaborators: Tina Van Doornik, Elizabeth H. Schultheis, and Tomomi Suwa
Garlic mustard, an exotic species in North America, is known to benefit from the production of allelochemicals which reduce the abundance of mycorrhizal fungi, an important plant mutualist. We were curious to see if these negative effects extended to other types of mutualism, namely the one between legumes and nitrogen fixing rhizobia. We found that they do! Garlic mustard allelochemicals reduced the growth of rhizobia in culture and prevented nodule formation. If you want to learn more, check out Portales-Reyes et al. 2015. |