Kathrin Schwarz

Plant phenology, i. e. the timing of life cycle events, is related to individual fitness and species distribution ranges. Temperature is one of the most important drivers of plant phenology together with day length. The adaptation of their phenology may be important for the success of invasive plant species. The present study aims at understanding how the performance and the phenology of the invasive legume Lupinus polyphyllus vary with latitude. We sampled data across a >2000 km latitudinal gradient from Central to Northern Europe. We quantified variation in phenology of flowering and fruiting of L. polyphyllus using >1600 digital photos of inflorescences from 220 individual plants observed weekly at 22 sites. The day of the year at which different phenological phases were reached, increased 1.3–1.8 days per degree latitude, whereas the growing degree days (gdd) required for these phenological phases decreased 5–16 gdd per degree latitude. However, this difference disappeared, when the day length of each day included in the calculation of gdd was considered. The day of the year of the earliest and the latest climatic zone to reach any of the three studied phenological phases differed by 23–30 days and temperature requirements to reach these stages differed between 62 and 236 gdd. Probably, the invasion of this species will further increase in the northern part of Europe over the next decades due to climate warming. For invasive species control, our results suggest that in countries with a large latitudinal extent, the mowing date should shift by ca. one week per 500 km at sites with similar elevations.

Bush encroachment is reported from savannah regions worldwide. Different management strategies are used to rehabilitate these areas. In this context, the mutual interaction between vegetation and large herbivore's distribution is evident. We studied effects of land management on vegetation structure in regard to encroaching species and the subsequent habitat use of two grazing (oryx, Oryx gazella L.; common warthog, Phacochoerus africanusGmelin) and one browsing (greater kudu, Tragelaphus strepsicerosPallas) herbivore species. We assumed that (i) cleared areas will be favoured by grazers and (ii) noncleared areas will be favoured by browsers. Specifically, we asked: Which factors determine the habitat use of these different feeding guilds? Consistently with our expectations, we found that warthog favoured sites with high grass cover. For oryx, surprisingly shrubs with a height of 80–150 cm influenced their distribution positively, whereas for kudu, only the interaction of site and grass cover was significant in our models. However, this was related to the occurrence of shrubs of 80–150 cm height. We conclude that the management of encroachers, resulting in differences in vegetation, did not influence herbivore distribution as expected. Other factors like human impact and vegetation cover among others are discussed as additional drivers of habitat use.