My research focuses on the physiological responses of plants to environmental variability and water availability. Understanding physiological plant responses to changes in resource availability allows us to understand and predict community and ecosystem dynamics over time. By the nature of my field, my research is interdisciplinary, providing me the opportunity to collaborate broadly with other ecologists (population, community and ecosystem), physical scientists (geologists, atmospheric scientists, hydrologists), and evolutionary biologists
Specific examples of my current research include:
- We are examining the physiological and growth responses of tallgrass prairie plant species on Konza Prairie to changes in microclimate/soil moisture over a broad range of spatial and temporal scales using distributed sensor networks, biweekly measurements of growth, landscape energy/water exchange, and the parameterization of process models. Our results are providing more detailed assessments of spatial and temporal water and energy budgets for tallgrass prairie, as well as provide a framework to model potential responses of this grassland type to extreme climate events in the future.
- The temporal properties of tree-grass bi-stability have not been rigorously analyzed and thus, are not well-understood. Yet, temporal dynamics are largely responsible for generating the spatial patterns of bi-stability seen globally and are integral to understanding when and why state-shifts will and have occurred. To address these questions, we are measuring local drivers and consequences of encroachment at Konza Prairie and using long-term datasets from other grassland ecosystems to improve our ability to predict state transitions of ecosystems and assess the consequences of these changes.
- Explaining the mechanisms regulating tree-grass coexistence will allow us to improve predictions of existing spatial patterns and temporal shifts in tree cover (site-based, and over large gradients), as well as future trajectories under novel climate scenarios. Our research project is multi-faceted, with work focused on an environmental and edaphic gradient in Kruger National Park, South Africa, as well as on the Konza Prairie here in Kansas. We are generating mechanistic data on the physiological responses of trees and grasses to changes in water / resource availability used to drive dynamic community and ecosystem models.
Craine JM, TW Ocheltree, JB Nippert, EG Towne, AM Skibbe, SW Kembel, and JE Fargione (2013) Global diversity of drought tolerance and grassland climate-change resilience. NATURE CLIMATE CHANGE 3: 63-67 DOI: 10.1038/NCLIMATE1634
Ratajczak, Z, JB Nippert, SC Collins (2012) Woody encroachment decreases diversity across North American grasslands and savannas. ECOLOGY 93(4): 697–703 doi:10.1890/11-1199.1.
Ocheltree, TW, JB Nippert, PVV Prasad (2012) Changes in stomatal conductance along grass blades reflects changes in leaf structure. PLANT CELL & ENVIRONMENT 35: 1040-1049 doi: 10.1111/j.1365-3040.2011.02470.x
Nippert, JB, RA Wieme, TW Ocheltree, JM Craine (2012) Root characteristics of C4 grasses limit reliance on deep soil water in tallgrass prairie. PLANT & SOIL 355: 385-394 doi: 10.1007/s11104-011-1112-4
Ratajczak Z, JB Nippert, JC Hartman, TW Ocheltree (2011) Positive feedbacks amplify rates of woody encroachment in mesic tallgrass prairie. ECOSPHERE 2(11):121. doi:10.1890/ES11-00212.1
Nippert JB, TW Ocheltree, AM Skibbe, LC Kangas, JM Ham, KB Shonkwiler Arnold, NA Brunsell. (2011) Linking plant growth responses across topographic gradients in tallgrass prairie. OECOLOGIA 166: 1131-1142 doi: 10.1007/s00442-011-1948-6
Nippert, JB, & AK Knapp (2007). Soil water partitioning as a mechanism for species coexistence in tallgrass prairie. OIKOS 116: 1017-1029
Nippert, JB, & AK Knapp (2007). Linking water uptake with rooting patterns in grassland species. OECOLOGIA 153: 261-272