The impact of tree species diversity on tree growth and herb-layer diversity – ecological studies and management implications at the biosphere reserve Valle del Ticino
 project descriptionThe junior scientist group is going to analyze effects of biodiversity on ecosystem functioning in the manifold woodlands of the biosphere reserve “Valle del Ticino”, Italy. Abundancy and diversity of the exotic (neophytic) tree species in the study area give the opportunity to extend the diversity approach to functional diversity and comparisons between indigenous and neophytic neighbourhoods. In this context, especially increment of certain tree individuals in the shrub and tree layer will be considered. Besides the in-situ study, a pot experiment with seedlings from the stands will complete the study. Comparisons of physiological characteristics of the different tree species, results of tree ring analyses and calculations of utilizable neophytic biomass will be used to develop recommendations for the treatment of neophytic species in the biosphere reserve. study area The study area is located in the biosphere reserve ‘Parco Naturale Valle del Ticino’, south of the Lago Maggiore in the region of Lombardy, Italy. The biosphere reserve is characterized by the river Ticino, which originates in the Swiss Alps, flows through the Lago Maggiore and then continues its course southwards bordered by the biosphere reserve. The biosphere reserve has a length of approximately 100 km and a width between 5 and 15 km. Woodland is the dominant landscape element and covers about 3500 ha (60 %) of the park's area. The Querco-Carpinetum forms the natural vegetation of this area, i.e. mixed stands of oak (Quercus robur) and hornbeam (Carpinus betulus) with an essential proportion of sweet chestnut (Castanea sativa) and conifer (Pinus spp.), mainly in the northern part, as well as poplar (Populus spp.) and alder (Alnus glutinosa) in the southern part. At the end of the nineteenth century, several exotic woody species (Prunus serotina, Robinia pseudoacacia, Quercus rubra) were introduced to the area. The abundance of these species has increased strongly since then, so that the natural forest ecosystem is endangered today. subproject A Impact of alien plant species on diversity and growth of native tree species in the Biosphere reserve „Valle del Ticino“- Ecosystem functions and management implications person in charge Peter Annighöfer This subproject deals with the possibilities of containment and use of alien tree species in a biosphere reserve in northern Italy. In a first step the horizontal and vertical stand structure is measured and described with special focus on the occurrence of the alien (and partly invasive) tree species black locust (Robinia pseudoacacia) and black cherry (Prunus serotina). A subsequent factor analysis of the tree species (non-) occurrence should demonstrate the silvicultural possibilities to use and contain the species. These results should lead to management implications for the biosphere reserve. Furthermore, the abundance of the neophytes should be explained in a cause study along a North-South gradient in the biosphere reserve. The special focus of this subproject is on the stand structure as found in the park, like tree species composition and species distribution, dbh and height distributions, stand stratification and light regime connected to it within the stand, and also the pedological starting conditions. In connection with this, the use potential of neophytes should be evaluated. The aim of the potential analysis is to estimate the biomass of the alien tree species occurring within the park. The estimation should be based on biomass functions which are to be deduced. The potential monetary use of the biomass should be evaluated, considering also the consequences for the ecosystem related to harvest (e.g. nutrient extraction). Study methods: subproject B Investigation of the competition mechanisms of native and exotic tree species person in charge Heike Kawaletz This project aims to investigate the competition mechanisms of native and exotic tree species. For this purpose we established a pot experiment on the area of the faculty of forest science in Göttingen to compare the physiological attributes of the different woody species. The tree species planted in the pots correspond with the prevalent vegetation of the study area ‘Valle del Ticino’, Italy. This means in particular oak (Quercus robur) and hornbeam (Carpinus betulus) for the native species and black cherry (Prunus serotina) and black locust (Robinia pseudoacacia) for the exotic species. The different species will be arranged in all possible combinations mostly four trees in one pot (i.e. one species: four individuals in one pot or just one individually, two species: each pot with two individuals of two different species, four species: each pot with one individual of every species). In a total of 760 pots the differences in growth and other physiological attributes (leaf area, rate of photosynthesis etc.) between the four tree species will be documented over a time of two years. Since their introduction to the study area the abundance of the two exotic species has increased strongly, so that the natural forest ecosystem is endangered today. The objective of this project is to find out what is the competitive advantage of the exotic species in comparison to the native species. To define the competitiveness in detail, we distinguish between above- and belowground competition, that means competition by the shoots or by the roots. For this purpose we separated some of the plants by partition walls. There are four different treatments regarding competition: partition walls are installed either belowground, aboveground, above- and belowground, and or no partitions at all (investigation of shoot, root, no or full competition). In the second year two different types of watering will be conducted. Thus the impact of water availability on the competitiveness can be described more precisely. By means of different measurements the effects of competition will be estimated:  |