Hydrologic modelling and dendrochronology as tool of site-species adequation assessment in a changing climate context

A hydrologic model is related to dendrochronological measurements performed in a 52 years old Spruce stand. The site is situated on a hillside with shallow and acid brown soil in the ecoregion of Ardenne (Wallonia, Southern Belgium).

Hydrologic modelling
The hydrologic simulation runs from 1971 to 2005 at daily time step. The model is based on an EPIC code, adapted to the site concerning soil reservoirs depth, characteristic water contents, root profile and water uptake. Weather data come from the Royal Meteorological Institute.
Outputs from the model are real evapotranspiration, surface runoff; interflows, deep percolation and soil moisture at daily time step.

Dendrochronological study
Tree ring thickness is measured on 24 core samples extracted from 12 dominant trees of the stand. Annual increments are standardised by the ARIMA function in order to produce the annual deviation of ring thickness. Means of annual deviation for the 12 trees are then related to annual soil drought intensities.

Results
Years 1976 and 1996 are emphasised by both the modelling outputs and the dendrochronological measurements as very dry. Model shows a severe drought and tree ring shows a very low growth. Years like 1990, 1992, 1994 and 2004 shows a less severe drought event but a drought that occurs in June-July, which seems to penalize spruce’s growth. On the other hand, years 1981 and 1998 show an important growth and a high value of mean soil moisture during June and July.
The poster will show how the time evolution of the ARIMA index is related to some meaningful hydrologic indexes.
These considerations will allow us to progress towards forecasting forest trees reaction to climate events and change. With this in mind, we will use a climate scenario build up in the frame of the AMICE interreg project.