Bachelor Thesis

Untersuchung des Einflusses des Borkenkäferbefalls auf die Betadiversität im Nationalpark Bayerischer Wald.

David Kienle (07/2011-09/2011)

Support: Carl Beierkuhnlein, Manuel Steinbauer

In the Bavarian Forest National Park are storm felling areas and large scaled bark beetle attacked forests of Norway Spruce in the focus of public and science. The local population discusses about conservation policy in view of tourism and forestry while ecologists see disturbances as ubiquitous and unavoidable. National parks are for scientists interesting because of the possibility to research natural dynamics without, as possible, human influence. Scientists think of disturbances are indispensable for biotic diversity. It's suggested that a gradient of different intensity of disturbance tends to heterogeneity of vegetation. To quantify disturbances is often difficult and needs large effort. Mortality is defined by dead standing Norway Spruces (snags) in proportion of all standing trees (dead or alive) and could be used as measurable size of the influence of bark beetles. Storm felling is taken from a stand density estimation method (Bitterlich method). A higher heterogeneity of vegetation is hypothesized by changes in resources availability by bark beetle attacs. Interaction of slope can increase this effect. In kind of this argumentation storm felling is positive for heterogeneity. The hypothesis were tested by the ordination methods „Detrended Correspondence Analysis“ and „Canonical Correspondence Analysis“ and linear models about matrices of the Sorensen Index. Linear models were build with distances between all sampling plots and neighbor plot distances (distances of same length). In all kind of models more environmental and geographical variables were used. Main result of analysis is that most of the heterogeneity of vegetation is explained by geology and altitude. If we view just on neighborhood distances geology is not more important. In all methods mortality has no large part of explained variance. Interaction between slope and mortality is not measurable. Also for the Bitterlich method no explanation part of variance was found. Interpretation of the mortality results is difficult because of the large influence of altitude. Maybe it is feasible to solve this problem by a new sampling design without altitude gradient. Maybe it's also possible to argue that the variability of mortality is small scaled and not covered by the sampling grid. There is no result of interaction of mortality and slope, so this hypothesis could be refused. Maybe also the values of the Bitterlich method will have an higher part of explanation by an smaller sampling grid. Empirical verification of mortality and Bitterlich method values as quantitative sizes for bark beetle attacks and storm felling will be useful. The assumption of small scaled patterns of disturbances argues for the zoning concept of the national park management. The proposed next research steps to snags is very interesting for questions to biodiversity and ecosystem services.

last modified 2015-04-10