Application DAPT cell line to analysis of I. typographus population density The forests growing in the Świętokrzyskie Mountains were subjected to the fluctuating actions of many stress factors (e.g. wind) causing an intensive mortality of trees (Podlaski 2008a). In the investigated stands, I. typographus colonised all P. abies windfalls in the first year after damage from wind. The studies indicate that the colonisation of trees damaged by wind can take up to 2 years (Annila and Petäistö 1978; Göthlin et al. 2000;

Eriksson et al. 2005). The length of the colonisation period depends on various climatic factors such as the degree of insolation on the sites with windfalls and population size (Jakuš 1998). In the Świętokrzyskie Mountains intermediate-scale disturbances increased the number of windfalls (Podlaski 2008b). The occurrence of a large number of windfalls creates favourable conditions

for the development of bark beetles and spread of the population in the stand. The following year, when the number of windfalls is lower, the attacks on standing trees are found to be stronger (Lindelöw and Schroeder 1998; Göthlin et al. 2000; Grodzki et al. 2006b). In 2008, the breeding Procaspase activation base for bark beetles in the Świętokrzyskie Mountains was extended to include fresh windfalls from the late autumn of 2007 and early spring of 2008. In 2009, I. typographus attacked fresh windfalls from the late autumn of 2008, as well as single standing trees both on exposed sites and trees in the forest interior where insolation was reduced. A similar I. typographus progradation pattern was observed in other areas affected by wind damage both in Poland (e.g. Grodzki 2004) and in other European countries (e.g. Forster 1998; Lindelöw and Schroeder 1998, 2001; Göthlin et al. 2000). The studies show that with a high availability of breeding material (e.g. a large number of broken trees and high stumps), the windfalls whose roots have contact

with the ground are less attacked by I. typographus and colonised mainly in the second year after wind damage (Lekander 1955; Butovitsch 1971; Göthlin et al. 2000). Due to the partially retained contact of tree roots with the ground, the windfalls maintain humidity for a longer time, thus their Phospholipase D1 resistance to beetle attacks is also maintained. With the low availability of the breeding material suitable for colonisation and high population numbers of the I. typographus, the windfalls whose roots retain the contact with the ground are also heavily attacked in the first year after wind damage (Göthlin et al. 2000). The investigated I. typographus population is in the progradation phase as evidenced by the sex ratio indicating an approximately twofold higher number of females in the population. The study by Lobinger (1996) shows that during the progradation phase this index increased far beyond 50%, while during the retrogradation phase it drops to below 50%.