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Mette T.,Bayerische Landesanstalt fur Wald und Forstwirtschaft LWF | Osenstetter S.,Ing Traunreut GmbH | Brandl S.,Bayerische Landesanstalt fur Wald und Forstwirtschaft LWF | Falk W.,Bayerische Landesanstalt fur Wald und Forstwirtschaft LWF | Kolling C.,Bayerische Landesanstalt fur Wald und Forstwirtschaft LWF
Waldokologie Online | Year: 2016

The assessment of the site conditions is one of the most important preconditions in forestry for the selection of site-adapted tree species. In Bavaria, the traditional site classification on the one hand gathers forestry relevant soil properties in a nominal and ordinal-scaled 3-digit code. The physiographic Bavarian Site Information System BaSIS on the other hand is based on units of the Bavarian Soil Map 1: 25,000 to which it assigns quantitative soil characteristics from soil profiles within the unit (available soil water capacity, bulk density, volumetric soil skeleton, depth profile of the base saturation, etc.). This study aims to statistically model the field expert's water balance classification (WBC), by means of measured climate and soil data (WBC model). Data basis are 1,349 profiles of the digital soil data base of the Bavarian Environment Agency, which are intersected with the site classification map and climate maps. To understand the significance of the water balance classification with respect to the site-inherent drought-risk, the WBC model is compared with two deterministic drought-stress sizes from water balance models of different complexity. The comparison clearly shows that the transpiration difference TDiff (as one of two deterministic drought-stress sizes and main determinant of the water balance in BaSIS) is much more precipitationdriven than the WBC-model. Finally-motivated by a good performance of the WBC-model-we investigate the potential of the water balance classification to derive the available water capacity as one of the most important soil characteristics. It shows that the consideration of traditional site classification in physiographic site classification systems can improve the parameter estimate. For practical implementation it is recommended to differentiate stronger between soil units or aggregated soil units, and include expert knowledge. In summary, this study establishes a bridge between a traditional and modern site classification system. It procures a knowledge gain on both sides and supports communication between users of one or the other system.

Mette T.,Bayerische Landesanstalt fur Wald und Forstwirtschaft LWF | Falk W.,Bayerische Landesanstalt fur Wald und Forstwirtschaft LWF | Uhl E.,TU Munich | Biber P.,TU Munich | Pretzsch H.,TU Munich
Austrian Journal of Forest Science | Year: 2015

Stem analyses were carried out on three common tree species in Central Europe to evaluate whether the strong drought of 2003 affected stem increment patterns in dominant and suppressed trees differently. Following Sterba (1981) we expected that dominant trees would react with an increased stem increment in the upper stem section (= acrotone) while suppressed trees would not change their stem increment pattern. Our data set included 41 Norway spruce (Picea abies [L] Karst), 46 Scots pine (Pinus sylvestris L.) and 36 European beech (Fagus silvatica L.) trees of social classes 1-4 (acc. to Kraft 1884) from stands distributed over Eastern Bavaria. To compare stem increment patterns for trees of different heights the basal area increment BAI was calculated in relative heights (10 % intervals). Drought (2003) and post-drought BAI (2004-2007) were compared with the pre-drought BAI (1999-2002). The BAI at 50 % height (BAI50) and 10 % height (BAI10) and the ratio BAI50/BAI10 were used to test increment differences between the classes. The drought in 2003 led to a loss in BAI10 of 35 % in spruce and 20 % in pine and beech. The BAI50 loss was generally weaker with 25 % in spruce, 5 % in pine and 15 % in beech. However, in terms of differences between the classes, only spruce exhibited a growth behaviour as expected: allocation pattern along the stem axis in the dominant classes 1-3 turned stronger acrotone but remained unchanged in suppressed class 4. In pine and beech, the loss in BAI10 and BAI50 during drought was higher for dominant trees than for suppressed trees, but changes in the BAI50/BAI10 ratio were independent of the social status. For all species, post-drought recovery in 2004-2007 was stronger for dominant than for suppressed trees. In spruce-which reacted strongest to drought-the more acrotone stem increment allocation in class 1-3 in 2003 is interpreted as drought stress-a reaction that has been shown also for other stress sources. Class 4 trees in spruce reacted equally strong as class 1-3 but the stem increment did not become more acrotone which indicates a high pre-drought stress level due to suppression. Pine and beech reacted less strong to drought. In contrast to spruce, increment loss increased from dominant to suppressed trees. In pine, the stem increment pattern in class 1 did not change while in class 2-4 a trend towards more acrotone increment is in correspondence with the higher drought stress in these classes. Beech, finally, did not significantly change its increment pattern in all of the classes.

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