Long-Term Ecosystem Ecology
How does global and local environmental change affect plant populations, communities and ecosystem functioning? Palaeoecological data allow us to extend our ecological “observations” to millennia and beyond. This long-term view offers an essential perspective on how ecosystems change in response to both slow and fast drivers. We use a variety of statistical modelling approaches to test hypotheses about the mechanisms underlying long-term ecosystem dynamics from palaeoecological data.
Palaeo-Trophic Cascades. We use probabilistic network models to assess the impact of environmental change and species extinctions on biotic interactions and nutrient cycling from palaeoecological time series spanning the Late Pleistocene – early Holocene transition.
Plant Population Responses to Environmental Change. We use a maximum likelihood-based model-fitting and model-selection method to infer the mechanisms by which plant populations in ancient ecosystems responded to multiple environmental changes. This novel approach has allowed us to infer differences between populations within a community in terms of their susceptibility to herbivory and burning, growth response to warmer growing seasons and rising nitrogen availability, and response to plant-plant interactions from millennial-scale palaeoecological time series. Furthermore, these approaches allow us to determine the relative importance of biotic and abiotic processes for structuring plant communities, and how this changes over time with respect to shifting environmental conditions.
Progressive Nitrogen Limitation. The progressive nitrogen limitation hypothesis suggests that carbon fertilization can lead to declines in N availability and ultimately reduce plant productivity. We are testing this hypothesis by using probabilistic state-space models to reveal how N-dependent population growth rates of selected plant taxa varied over time under different CO2 concentrations from long-term records of terrestrial N availability and above-ground plant biomass.
Jeffers, E.S., M.B. Bonsall, C.A. Froyd, S.J. Brooks and K.J. Willis (2015) Relative importance of biotic and abiotic processes for structuring plant communities through time. Journal of Ecology, 104, 459-472. http://dx.doi.org/10.1111/1365-2745.12365
Jeffers, E.S., M.B. Bonsall, J.E. Watson and K.J. Willis (2012) Climate change impacts on ecosystem functioning: evidence from an Empetrum heathland. New Phytologist, 193, 150-164. http://dx.doi.org/10.1111/j.1469-8137.2011.03907.x
Jeffers, E.S., M.B. Bonsall, S.J. Brooks and K.J. Willis (2011) Abrupt environmental changes drive shifts in tree-grass interaction outcomes. Journal of Ecology, 99, 1063-1070. http://dx.doi.org/10.1111/j.1365-2745.2011.01816.x
Jeffers, E.S., M.B. Bonsall and K.J. Willis (2011) Stability in ecosystem functioning across a climatic threshold and contrasting forest regimes. PLoS One, 6, e16134. http://dx.doi.org/10.1371/journal.pone.0016134
Lizzy completed her DPhil in 2010 for her work in MERG and the Oxford Long Term Ecology Lab using a statistical modelling approach to infer how ecosystems functioned in the past and how this varied over time. She is currently Lecturer in Long Term Ecology in the Department of Zoology and continues to use mathematics to unravel the complex drivers of ecosystem dynamics based on evidence in the fossil record.