Effects of simulated drought stress on Norway spruce clones

Abstract

We monitored the effects of the drought stress on 20-year old clones of Norway spruce (Picea abies) by using a range of instrumental methods. On two experimental plots (Hoxmark, Norway, 59°40'14"N, 10°47'36"E) the drought was induced in a period between May and October 2009 by removing the throughfall using the rain shelters and trenching.

We collected data on soil moisture, stem and branch sap flow, xylem diameter, anatomical and calorimetric analysis of the needles, fine root biomass and dynamics and resistance to pathogens. Standard meteorological data were collected locally throughout the whole period.

Here we present the preliminary analysis of sap flow and xylem diameter in a period 1-17 august 2009. The sap flow was measured on stems in the breast height by using the method of stem tissue heat balance (THB, EMS Brno). The values were measured once in 2 minutes and saved as the average of 10 minutes. The fluctuations in xylem diameter was monitored by using the automatic dendrometers DR26 (EMS Brno). We evaluated both diurnal and seasonal dynamics.

Preliminary results show a significant difference in shape of diurnal curves of transpiration as well as different time lag among the sap flow and the potential evapo-transpiration. Also the differences in diurnal dynamics of the stem circumference suggested different xylem water potential in stressed and control trees. In the drought-stressed trees the diurnal fluctuation in stem diameter was about 4 times higher and the total stem increment one third lower, com-pared to the control trees.

Referanse

Børja, I., Urban, J., Gebauer, R. & Krokene, P. 2010. Effects of simulated drought stress on Norway spruce clones. In: Brunner, I. (ed.): Belowground carbon turnover in European forests - State of the art, p. 55. COST Action FP0803 Conference, 26-28 January 2010. Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland.