Possibilities of Application of Relative Openness in Secondary Forest Opening of Slope Forests in Croatia

For achieving a high-quality and efficient management of forest ecosystems (Pentek et al. 2010), it is necessary to provide an optimally distributed network of primary and secondary forest road infrastructure. The openness of forest areas, the need to describe the existing situation and the tendency to rationalize the existing road network were described with traditional openness (density of forest roads). Traditional openness is a well-known parameter that has represented the size of the basis determined by the level of the achieved existing primary and secondary road density for a long time in forestry. In many previous researches, different authors described the current state with traditional openness of the secondary forest road network (Rebula 1983, Zdjelar 1990). Traditional openness is a numeric data that says little about the quality of road distribution on the observed areas. It represents only the quantity and distribution of primary and secondary forest roads. The transitional form of themodern view of the subject matter is a combination of traditional openness andmean skidding distance (Pentek et al. 2010, Pentek et al. 2007). Relative openness has, lately, (Pentek et al. 2010, Pentek et al. 2007) been increasingly used as a variable that describes more precisely and accurately the actual state of forest road infrastructure and defines the need for further opening of forests. The basic terrain characteristics (Šikić et al. 1989) such as relief altitudes, slopes and indented terrains determine the terrain configuration such as: the plain, hilly and mountainous terrains. Generally, relief and terrain can also be divided into plain and bumps, where the plains are – lowlands and plateaus, and bumps are – elevations (hills, highlands, mountains) and troughs (valleys, basins, river basins). The relative openness is both a quantitative and qualitative parameter (Pentek 2010), which gives a good insight into the spatial distribution of forest roads, and expresses the ratio of surface forest area opened by forest roads and the total forest area in percentage terms. It is the parameter that (Pentek 2002), with a good insight into the spatial distribution of forest roads, gives the possibility of establishing open and unopened areas, and offers to designers the option of choosing the most appropriate version of forest road routes. The relative openness is determined by the buffer method and the procedure consists in laying down the buffered areas around t