Thinning effects on pine-spruce forest transpiration in central Sweden |
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| Authors: | Fredrik Lagergren Harry Lankreijer Jiří Kučera Emil Cienciala Meelis Mölder Anders Lindroth |
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| Institution: | 1. Department of Physical Geography, Geobiosphere Centre, Lund University, Sölvegatan 12, SE-223 62 Lund, Sweden;2. Environmental Measuring Systems, Turisticka 5, 62100 Brno, Czech Republic;3. Institute of Forest Ecosystem Research Ltd., Jílové u Prahy 1544, 254 01 Jílové u Prahy, Czech Republic |
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| Abstract: | This study analyses the effects of thinning on stand transpiration in a typical mixed spruce and pine forest in the southern boreal zone. Studies of transpiration are important for models of water, energy and carbon exchange, and forest management, like thinning, would change those processes. Tree transpiration was measured by the tissue heat-balance sapflow technique, on a reference plot and a thinning plot situated in a 50-year-old stand in central Sweden. Sapflow was measured during one season (1998) on both plots before thinning, to establish reference values. In winter 1998/1999 24% of the basal area was removed from the thinning plot. Thinning was done so as to preserve the initial species composition and the size distribution. The measurements continued after thinning during the growing seasons of 1999 and 2000. The climate showed remarkable differences between the 3 years; 1998 was wet and cool, with frequent rain, and the soil-water content was high throughout the year. In contrast, 1999 was dry and warm, and the soil-water content decreased to very low values, ca. 5–6% by volume. In 2000, the weather was more normal, with variable conditions. Stand transpiration was similar on both plots during the year before thinning; the plot to be thinned transpired 6% more than the reference plot. After thinning, transpiration was initially ca. 40% lower on the thinned plot, but the difference diminished successively. When the following drought was at its worst, the thinned plot transpired up to seven times more than the reference plot. During the second season after thinning, the thinned plot transpired ca. 20% more than the reference plot. The increased transpiration of the thinned plot could not be attributed to environmental variables, but was most probably caused by changes in biological factors, such as a fertilization effect. |
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| Keywords: | Pinus sylvestris Picea abies Thinning Sap flow Forest management Drought |
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