KROOF Gradient
Kroof gradient was established in 2014 and is composed of a transect of forest sites along a precipitation gradient from northern Bavaria (dry) to southern Bavaria (wet).
The transect consists of seven sites with triplets (pure stand of spruce or beech and mixed stand of beech-spruce, and pine or beech and mixed stand of beech-spruce) from humid southeastern Bavaria to dry northwestern Bavaria, ranging from colline to submontane with comparable soil properties, with mean growing season temperatures of 13.8 -14.0 °C and mean seasonal precipitation of 310 -780 mm. The precipitation gradient provides ideal conditions for hypothesis analysis with respect to water availability as a driving factor. The triplet plots are comparable in terms of location and stand age, fully stocked, single-layered, and located in spatial proximity to each other. (Pretzsch et al. 2014)
KROOF Experiment
Kranzberger Forst (longitude: 11° 39′ 42″ E, latitude: 48° 25′ 12″ N, elevation 490 m a.s.l.) is located in southern Germany, about 35 km northeast of Munich. The experimental area is about 0.5 ha and lies 490 m above sea level. The annual average precipitation is 750-800 mm per year, including 460-500 mm during the growing season (May-September). The annual average air temperature is 7.8 °C, with a seasonal average of 13.8 °C. At the site, pure and mixed stands of spruce and beech grow on Luvisol of loess over Tertiary sediments, which provide high nutrient and water supply (Göttlein et al. 2012; Pretzsch et al. 1998). From about 1 m soil depth, a relatively dense layer of sandy-silty loam almost completely prevents deeper root growth and thus water uptake (Häberle et al. 2012).
The forest test plot is part of the long-term Bavarian yield research network (Bavarian State Ministry of Food, Agriculture and Forestry), accordingly stand structure and yield data are recorded tree-individually and spatially explicit (since 1992 permanent observation plot). Since 1998, several large-scale projects have been carried out on the forest test site.
In addition, a crane (45 m high, crane jib 50 m) has been located on the experimental plot since 2001, which allows direct access to the tree crowns for sampling and physiological measurements. The Kranzberger Forst test site is integrated into a worldwide canopy crane research network (International Canopy Crane Network, ICCA, Basset & Wright, 2003).
