Transpiration and hydraulic conductivity in three Scots pine (Pinus sylvestris L.) stands with different air pollution histories
✍ Scribed by S. Rust; D. Lüttschwager; R. F. Hüttl
- Publisher
- Springer Netherlands
- Year
- 1995
- Tongue
- English
- Weight
- 316 KB
- Volume
- 85
- Category
- Article
- ISSN
- 0049-6979
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✦ Synopsis
As p,'u-t of a project studying the effects of massive reductions in the output of air pollutants in eastern Gerlnany we monitored st,mad la'anspiratiou rates and water stress and analyzed the hydraulic architecture of Scots pine in three stands with different air pollution histories. Sap flow densities were continuously zneasured in 15 trees per stand with a thermoelectric method. The sap flow densities were scaled up to the stand transpiration rate via the conductive xylem area, which was me,~sured with computer-tomography in the s,'mae ts'ees. Radiation (PAR), humidity mid tempe,'ature were monitored at tlu-ee levels in the stands, water stress is ,assessed by predawn water potentials. Ks a parameter of hydraulic architecture we studied leaf specific conductivity (LSC). The proportion of the heartwood area did not sigaaificantly vary along the gradient of air pollution. The variation of sap flow densities within the stands was large. The ratios of sap flow densities in the inner ,and outer xylem were site-specific and significantly different between the stands. In the stand with the highest rate of air pollution there was a sharp decline in the sap flow densities towards the heartwood. Stand tr,'mspiration in the site with the lowest pollution was siglaific,'mtly higher than in the two more polluted sites. LSC in 2 years old twigs was significantly higher in the low pollution stand. In the dry sununer of 1994 predawn water potentials fell to extreme values of below 1.6 MPa. At that stage transpiration ceased until the next substantial rainfalls.