Inferring past zooplanktivorous fish and macrophyte density in a shallow lake: application of a new regression tree model

摘要: 1. Eutrophication has a profound effect on the biological structure and function of shallow lakes, altering composition abundance submerged macrophyte fish assemblages. Relatively little is known, however, about decadal to centennial-scale change in these important aspects lake ecology. 2. Established palaeolimnological inference models are limited reconstructing single variable. As zooplanktivorous exert dual interacting controls cladoceran assemblages variable model may contain significant error. To obviate this problem, we applied new cladoceran-based multivariate regression tree (MRT) subfossil from dated cores small (Felbrigg Lake, U.K.) assess long-term acrophyte abundance. Plant macrofossil, chironomid mollusc were also analysed track changes evaluate inferences MRT model. 3. Over 200+ year period covered by sediment cores, there was good agreement timing nature ecological reflected plant mollusc, data. The sequence divided into three zones: c. 1797–1890, 1890–1954 1954–present. Prior 1890 plant-associated indicated species-rich community; scenario confirmed macrofossil From 1954 macrophyte-associated species all invertebrate groups remained abundant but proportion pelagic cladocerans rose. Post-1954 changed associated detrital feeders taxa increased further. 4. long stability, 1790–1927,characterised macrophytes fish. 1927 1980, inferred decline density (ZF) relative stability August 1980 2000, an increase tallying well with available data population (since 1970s), which extirpation perch 1970s subsequent rudd population. until post-c. at point it decline. surface assemblage placed group A, where plants absent or very rare late summer current conditions site. 5. model, here for first time, appears have successfully tracked ZF over last 200 years Felbrigg Lake. agreed historical observations community supporting Given that multiple structuring forces shape most communities, application capable allowing represents advance palaeolimnology.