@article{SynodinosTietjenLohmannetal.2018,
  author    = {Synodinos, Alexis D. and Tietjen, Britta and Lohmann, Dirk and Jeltsch, Florian},
  title     = {The impact of inter-annual rainfall variability on African savannas changes with mean rainfall},
  series = {Journal of theoretical biology},
  volume    = {437},
  journal   = {Journal of theoretical biology},
  publisher = {Elsevier Ltd.},
  address   = {London},
  issn      = {0022-5193},
  doi       = {10.1016/j.jtbi.2017.10.019},
  pages     = {92 -- 100},
  year      = {2018},
  abstract  = {Savannas are mixed tree-grass ecosystems whose dynamics are predominantly regulated by resource competition and the temporal variability in climatic and environmental factors such as rainfall and fire. Hence, increasing inter-annual rainfall variability due to climate change could have a significant impact on savannas. To investigate this, we used an ecohydrological model of stochastic differential equations and simulated African savanna dynamics along a gradient of mean annual rainfall (520-780 mm/year) for a range of inter-annual rainfall variabilities. Our simulations produced alternative states of grassland and savanna across the mean rainfall gradient. Increasing inter-annual variability had a negative effect on the savanna state under dry conditions (520 mm/year), and a positive effect under moister conditions (580-780 mm/year). The former resulted from the net negative effect of dry and wet extremes on trees. In semi-arid conditions (520 mm/year), dry extremes caused a loss of tree cover, which could not be recovered during wet extremes because of strong resource competition and the increased frequency of fires. At high mean rainfall (780 mm/year), increased variability enhanced savanna resilience. Here, resources were no longer limiting and the slow tree dynamics buffered against variability by maintaining a stable population during 'dry' extremes, providing the basis for growth during wet extremes. Simultaneously, high rainfall years had a weak marginal benefit on grass cover due to density-regulation and grazing. Our results suggest that the effects of the slow tree and fast grass dynamics on tree-grass interactions will become a major determinant of the savanna vegetation composition with increasing rainfall variability.},
  language  = {en}
}
@article{HeinzeBergmannRilligetal.2015,
  author    = {Heinze, Johannes and Bergmann, Joana and Rillig, Matthias C. and Joshi, Jasmin Radha},
  title     = {Negative biotic soil-effects enhance biodiversity by restricting potentially dominant plant species in grasslands},
  series = {Perspectives in plant ecology, evolution and systematics},
  volume    = {17},
  journal   = {Perspectives in plant ecology, evolution and systematics},
  number    = {3},
  publisher = {Elsevier},
  address   = {Jena},
  issn      = {1433-8319},
  doi       = {10.1016/j.ppees.2015.03.002},
  pages     = {227 -- 235},
  year      = {2015},
  abstract  = {Interactions between soil microorganisms and plants can play a vital role for plant fitness and therefore also for plant community composition and biodiversity. However, little is known about how biotic plant soil interactions influence the local dominance and abundance of plant species and whether specific taxonomic or functional groups of plants are differentially affected by such biotic soil-effects. In two greenhouse experiments, we tested the biotic soil-effects of 33 grassland species differing in individual size and local abundance. We hypothesized that large plants that are not locally dominant (despite their size-related competitive advantage enabling them to potentially outshade competitors) are most strongly limited by negative biotic soil-effects. We sampled soils at the opposite ends of a gradient in land-use intensity in temperate grasslands to account for putative modulating effects of land-use intensity on biotic soil-effects. As hypothesized, large, but non-dominant species (especially grasses) experienced more negative biotic soil-effects compared with small and abundant plant species. Land-use intensity had contrasting effects on grasses and herbs resulting in more negative biotic soil-effects for grasses in less intensively managed grasslands. We conclude that biotic soil-effects contribute to the control of potentially dominant plants and hence enable species coexistence and biodiversity especially in species-rich less intensively managed grasslands.},
  language  = {en}
}