Publikationenhttps://hdl.handle.net/20.500.11811/7212024-03-28T22:52:10Z2024-03-28T22:52:10ZVegetation diversity in East African wetlandsBehn, KaiAlvarez, MiguelMutebi, SamuelBecker, Mathiashttps://hdl.handle.net/20.500.11811/107892023-04-28T09:30:22Z2022-12-08T00:00:00ZVegetation diversity in East African wetlands
Behn, Kai; Alvarez, Miguel; Mutebi, Samuel; Becker, Mathias
Aims: Wetlands in East Africa are important ecosystems for biodiversity conservation and ecosystem service provisioning, yet threatened by degradation and conversion into croplands. Conservation and land use management require data on vegetation structure and dynamics. The presented work is a response to a lacking consistent classification of East African wetland vegetation. Location: Namulonge valley in Uganda and Kilombero floodplain in Tanzania. Methods: We sampled 431 4 m²-plots along land use intensity and flooding duration gradients. A floristic classification using the cocktail method was performed in a two-step approach. We developed definitions for vegetation units, using plot observations from the study sites in a first step and revised them in a second step by adding data from a vegetation-plot database and complied the definitions to an expert system for classification. Resulting vegetation units were analyzed regarding their life form composition, for which we implemented a classification based on life span and growth form. Following a literature review, the identified vegetation units were assigned either to existing phytosociological associations or proposals. Results: We recognize eight units of marsh and reed vegetation (class Phragmito-Magno-Caricetea) and five units of weed and pioneer vegetation under semi-aquatic conditions (class Oryzetea sativae). Five of these associations were previously described in the bibliographic references. The remaining eight are newly described in this work. The associations contrast in their life form composition with the five Oryzetea sativae associations dominated by obligate annuals and the Phragmito-Magno-Caricetea associations dominated by either reed plants or lacking a dominating life form. Conclusions: The developed expert system enables a comparison of wetland vegetation in the East African region and will support vegetation science and informed decision making about land use management and conservation. The two-step approach of revising a classification developed for single wetlands with a database is promising for data-scarce regions. Nomenclature: Haines & Lye (1983); CJBG & SANBI (2012); The Plant List (2013); TNRS (2018). Abbreviations: DCA = Detrended Correspondence Analysis; DRC = Democratic Republic of the Congo; MRPP = Multiple Response Permutation Procedure.
2022-12-08T00:00:00ZUnusually warm winter seasons may compromise the performance of current phenology modelsFernandez, EduardoSchiffers, KatjaUrbach, CarstenLuedeling, Eikehttps://hdl.handle.net/20.500.11811/107862023-04-28T09:00:23Z2022-07-15T00:00:00ZUnusually warm winter seasons may compromise the performance of current phenology models
Fernandez, Eduardo; Schiffers, Katja; Urbach, Carsten; Luedeling, Eike
Phenology models are crucial tools for assessing climate change impacts in forestry, ecology and agriculture. Such models are typically calibrated with observational or experimental data and validated with a set of independent observations. While there have been extensive discussions about validation approaches, systematic studies assessing the effects of the calibration data on the predictive performance of the fitted model are scarce. We evaluated the impact of marginal seasons in the calibration data set on the predictive power of an integrated modeling framework (PhenoFlex) that was recently proposed to predict spring phenology in temperate trees. We calibrated PhenoFlex with phenology records of apple trees from a multi-season experiment (59 experimental seasons) that included five unusually warm winter seasons. For comparison, we excluded these marginal seasons in a second version of the analysis. We fitted the 12 model parameters to data, assessed model performance using a common validation data set and evaluated the chill and heat responses during dormancy for both versions. Despite high overall accuracy, our results indicated a better model performance (Root Mean Square Errors of 2.3 versus 5.5 days) when excluding the marginal seasons. We observed a similar shape for the chill response curve across versions but a greater chill effectiveness when including the marginal seasons. Fitted parameters suggest a hard drop in heat efficiency beyond the optimum temperature when including the marginal seasons, probably highlighting the need for more moderate conditions during model calibration. Our results demonstrate a good performance of PhenoFlex when calibration and validation data were comparable, but they also indicate risks involved in using the framework to project phenology under conditions that differ strongly from those used for calibration. Further evaluation and validation under experimentally or naturally occurring warm conditions may improve our understanding of the response of temperate trees to mild winter conditions.
2022-07-15T00:00:00Z