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Friedrich Franz (Fig. 1) obtained his PhD degree in 1957 at the Eberswalde Institute of the Humboldt University Berlin for his research on Scots pine growth in NE Germany, and his habilitation degree in 1968 at the Ludwig-Maximilians-University in Munich for his thesis on site-tree growth relationships. He held the Chair for Forest Growth and Yield Science at the latter university from 1973 to 1994. The impetus of Friedrich Franz ( *5. August 1927, †11. July 2002) to forest growth and yield science extends from forest mensuration and inventory to modelling and knowledge transfer to practical forestry. On the occasion of the 10th anniversary of his death we review his approach to research, biography, and his impact on forest science and practice. Friedrich Franz represents a model of a scientist who combined science and knowledge application. His biography includes an apprenticeship as a woodsman, basic research into tree and stand growth of Central European tree species, and development of data processing-based information systems for efficient knowledge feedback between science and practice (Fig. 2). His close contacts with practical forestry stimulated his research on the growth of pure and mixed species stands, modeling and simulation, resource inventory and decision support for planning and operational control of forest management. His works were always based on sound data from longterm experimental plots and inventories at estate or state level and were relevant for both theory development and practical application. Through his own research and his very specific influence on his students, Friedrich Franz was able to create an impetus on forest growth and yield science and forest practice which reaches far into the future.

Ulbricht M.,Lehrstuhl fur Waldwachstumskunde | Uhl E.,Lehrstuhl fur Waldwachstumskunde | Biber P.,Lehrstuhl fur Waldwachstumskunde | Pretzsch H.,Lehrstuhl fur Waldwachstumskunde
Allgemeine Forst- und Jagdzeitung | Year: 2012

While fertilisation is an effective practice for improving soil quality and stand productivity, it has been rarely applied in recent years. It could, however, play a role as a supporting measure to protective forest restoration. In this context, this study reports the results of a melioration experiment with two organic fertilisers, Biosol and Frisol, in a highland forest in the Bavarian Alps. Because of their prominent protective functions, the stability and vitality of high mountain forests is of particular importance. At the same time, many such forest stands cannot sufficiently fulfil their protective functions due to degradation, ageing and lacking natural regeneration. As an accompanying research measure within the restoration programme for protective forests in Bavaria, the experiment FUS262 has been established in 1986, and since then it is continuously maintained and observed by the Chair for Forest Growth and Yield at Technische Universität München, Germany. The experiment is located in an altimontane Norway spruce (Picea abies [L.] Karst.) forest in the Bavarian Alps near the town of Fussen. Research questions are (i) whether the increment can be increased by organic fertiliser application, (ii) whether this enhances forest vitality, and (iii) whether a higher mechanical stability of forest stands can therewith be achieved. Biosol is an organic fertiliser, which mainly contains the nutrients N, P and K. It is a granulate made from penicillin production residues. When Biosol is enriched with the organic sugarphosphoramide ACS it is called Frisol. According to the manufacturer, it improves water and nutrient uptake by plants and a general activation of the soil organisms. The experiment FUS262 consists of six parcels which are attributed to three application variants (Biosol variant, Frisol variant and 0- or control variant, each with two repetitions). Table 1 shows site and treatment information on parcel level; Table 2 presents growth and yield data on stand level, while Table 3 contains growth and yield data on single tree level based on cored trees. The main results are as follows: (i) On tree level, an explicit reaction to Frisol application appears shortly after the fertilisation. Within the entire period from 1988 to 2009 the highest radial increment is observed for the Frisol variant. In the same period, compared to the control variant, the Biosol variant also shows an increased radial increment. In contrast, the radial increment of the control variant behaves rather indifferently. Marginally increased increments can be observed at the end of the observation period only (Figures 1 and 2). On stand level, total volume production (GWL) and average periodic increment (MPZ) react analogously: The increment of the Frisol variant is located clearly above the other both other variants, while the increment of the Biosol variant contrasts with the control variant to a minor extent only (section 3.2 and Figure 3). These results indicate that tree and stand increment can be increased by the application of Biosol and Frisol, at which Frisol is by far the more potent fertiliser. (ii) Taking foliage percentage as an indicator for vitality, the most auspicious development can be found on the Frisol variant. With approx. 70 % it remains nearly constant since 1986. The foliage percentage on the Biosol variant is approximately on a level with the Frisol variant at the beginning, but decreases over time. At the end of the observation (2009), however, it is barely below the foliage percentage of the Frisol variant. The control variant shows the most adverse development. Its foliage percentage keeps consistently below both other variants. Thus, the foliage percentage shows a positive reaction to the fertilisation, similar to the radial increment (Figures 4 and 5). Another proxy for vitality, the leaf area index (LAI), was adjusted with absolute foliage percentage (Table 4). The adjusted LAI and the correlation between tree-wise radial increment and foliage percentage indicate that especially the dominant and relatively vital spruces profit from the fertilisation; this results in a decreasing crown transparency (Figures 6 and 7). (iii) Selected crown shape parameters that were used as stability indicators do not show any noticeable influence of the fertilisation with Biosol or Frisol (Table 6). In summary, the application of Biosol and Frisol is an option for a long-term revitalisation of high-altitude Norway spruce forests. This finding is in accordance with several other studies that report a positive influence of organic-ecological fertilisation on growth and vitality in degraded high-altitude Norway spruce forests.

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