TY - JOUR A1 - Massie, Thomas Michael A1 - Ryabov, Alexei A1 - Blasius, Bernd A1 - Weithoff, Guntram A1 - Gaedke, Ursula T1 - Complex transient dynamics of stage-structured populations in response to environmental changes JF - The American naturalist : a bi-monthly journal devoted to the advancement and correlation of the biological sciences N2 - Stage structures of populations can have a profound influence on their dynamics. However, not much is known about the transient dynamics that follow a disturbance in such systems. Here we combined chemostat experiments with dynamical modeling to study the response of the phytoplankton species Chlorella vulgaris to press perturbations. From an initially stable steady state, we altered either the concentration or dilution rate of a growth-limiting resource. This disturbance induced a complex transient response-characterized by the possible onset of oscillations-before population numbers relaxed to a new steady state. Thus, cell numbers could initially change in the opposite direction of the long-term change. We present quantitative indexes to characterize the transients and to show that the dynamic response is dependent on the degree of synchronization among life stages, which itself depends on the state of the population before perturbation. That is, we show how identical future steady states can be approached via different transients depending on the initial population structure. Our experimental results are supported by a size-structured model that accounts for interplay between cell-cycle and population-level processes and that includes resource-dependent variability in cell size. Our results should be relevant to other populations with a stage structure including organisms of higher order. KW - chemostat experiments KW - Chlorella vulgaris KW - environmental changes KW - population dynamics KW - stage structure KW - transient dynamics Y1 - 2013 U6 - https://doi.org/10.1086/670590 SN - 0003-0147 SN - 1537-5323 VL - 182 IS - 1 SP - 103 EP - 119 PB - Univ. of Chicago Press CY - Chicago ER - TY - JOUR A1 - Schibalski, Anett A1 - Körner, Katrin A1 - Maier, Martin A1 - Jeltsch, Florian A1 - Schröder, Boris T1 - Novel model coupling approach for resilience analysis of coastal plant communities JF - Ecological applications : a publication of the Ecological Society of America N2 - Resilience is a major research focus covering a wide range of topics from biodiversity conservation to ecosystem (service) management. Model simulations can assess the resilience of, for example, plant species, measured as the return time to conditions prior to a disturbance. This requires process-based models (PBM) that implement relevant processes such as regeneration and reproduction and thus successfully reproduce transient dynamics after disturbances. Such models are often complex and thus limited to either short-term or small-scale applications, whereas many research questions require species predictions across larger spatial and temporal scales. We suggest a framework to couple a PBM and a statistical species distribution model (SDM), which transfers the results of a resilience analysis by the PBM to SDM predictions. The resulting hybrid model combines the advantages of both approaches: the convenient applicability of SDMs and the relevant process detail of PBMs in abrupt environmental change situations. First, we simulate dynamic responses of species communities to a disturbance event with a PBM. We aggregate the response behavior in two resilience metrics: return time and amplitude of the response peak. These metrics are then used to complement long-term SDM projections with dynamic short-term responses to disturbance. To illustrate our framework, we investigate the effect of abrupt short-term groundwater level and salinity changes on coastal vegetation at the German Baltic Sea. We found two example species to be largely resilient, and, consequently, modifications of SDM predictions consisted mostly of smoothing out peaks in the occurrence probability that were not confirmed by the PBM. Discrepancies between SDM- and PBM-predicted species responses were caused by community dynamics simulated in the PBM and absent from the SDM. Although demonstrated with boosted regression trees (SDM) and an existing individual-based model, IBC-grass (PBM), our flexible framework can easily be applied to other PBM and SDM types, as well as other definitions of short-term disturbances or long-term trends of environmental change. Thus, our framework allows accounting for biological feedbacks in the response to short- and long-term environmental changes as a major advancement in predictive vegetation modeling. KW - Baltic Sea KW - hybrid model KW - Lolium perenne KW - model coupling KW - Scirpus maritimus KW - transient dynamics Y1 - 2018 U6 - https://doi.org/10.1002/eap.1758 SN - 1051-0761 SN - 1939-5582 VL - 28 IS - 6 SP - 1640 EP - 1654 PB - Wiley CY - Hoboken ER -