Description of the research area Seehornwald-Davos
The area has the coordinates 46°48'55.2" N, 9°51'21.3" E and is located at 1639 m.a.s.l. in the middle elevations of the Pre-Alpine belt in the eastern Swiss Alps.
The coniferous forest is dominated by spruce (Picea abies (L.) Karst.) with an average tree height of 18.3 m in the central research plot (CP plots), and an average tree height of 9.9 m in the footprint of the eddy covariance measurements (SP plots), with the tallest trees reaching 41 m. The difference in tree height between the two plots is due to the difference in the height of the trees. The difference originates from the fact that the CP plots, which have been operated for more than 25 years, have never been thinned, while the surrounding forest is continuously harvested, thus management keeps the stand smaller and also younger. The average stem diameter at breast height is 22 cm for the CP plots, or 12.5 cm for the SP plots. The trees have an estimated average age based on stem diameter of 106 years in the CP plots, and 60 years in the SP plots. The oldest specimen is estimated to be over 350 years old. Leaf area index is about 4 m2 m-2 (a more precise figure is currently being evaluated). The average number of stems per ha is 995 (CP plots) and 1061 (SP plots). The average basal area of stems per ha is 54.7 (CP plots), and 40.6 m2 (SP plots), respectively. The average radial stem growth is 1.2 mm per year, resp. 23 µm per day (CP plots). On average, the trees grow 220 h per year, mainly at night with the highest growth at 5:00 in the morning.
The understory is rather patchy and covers about 30% of the forest floor. It consists of dwarf shrubs, mainly Vaccinium myrtillus and Vaccinium gaulterioides along with mosses.
The research plot offers a unique combination of continuous long-term measurements: Regional climate, CO2 and microclimate profiles through the forest, tree physiological measurements of sap flow and stem diameter changes, eddy covariance flux measurements, continuous measurements of atmospheric NO, NO2 and O3 concentrations, and diverse vegetation characteristics (such as crown thinning, litterfall, etc.) and soil structure. More information about the equipment of the Seehornwald-Davos research area can be found here.
The very long duration of most of the measurements predestines this area for investigations into the (missing) links between climate change and tree physiological adaptations. But it is also ideal for researching questions about the carbon balance of the ecosystem relative to soil properties and tree physiology (under changing environmental conditions).
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