Gully erosion rate by means of anatomical changes in exposed roots tree rings in the Proboszczowicka Platou (southern Poland)

Network of gullies can increase above 300 % during about 80 years (Swanson et all., 1989). More often the rate of gully erosion is 0,2-0,8 m/year (Martinez-Casasnovas, 2003). The analyze of precipitation, valley morphology and sites where erosion occurs can be use to building the local erosion models. The models allow estimate future gully erosion and very often we can estimate local thresholds to erosion occurs. One of the main factors conditioning gully erosion is the quantity and intensity of precipitation. In wet periods gully erosion may occur several times faster. However, studies conducted in Canada prove that natural processes associated with climatic fluctuations are insufficient to cause gully initiation, but may contribute to ongoing gully expansion. According to (Stankowianski, 2003) gullies are formed during periods of extensive forest clearance and expansion of farmland, but the triggering mechanism of gullying are extreme rainfall events. Local hill slopes gradient and drainage-basin area are the most important topographic parameters affecting gully erosion. Also lithological conditions as well as the thickness of dusty sediments and the underlying rock structure can be significant factors affecting the development of gully erosion. Studies of gully erosion velocity are often based on the comparison of gully lengths on maps produced in different centuries or on aerial photos (Burkard and Kostaschuk, 1995). Another method of measuring the velocity of gully erosion includes continuous monitoring of headcuts. Also a dendrochronological method ha