THE STUDY OF ANTHROPOGENIC DISTURBANCE ON GEOPEDOGENETIC PROCESS AT THE LOWER SLOPE OF MT. UNGARAN, INDONESIA

Volcanic rocks mining activity will undoubtedly remove vegetation cover and cause the physical environment changes. Revegetation effort as part of land rehabilitation program then often found many obstacles because it was mostly conducted without adequate knowledge of detailed morphology and soil characteristics at the post-mining area. This study investigates the geopedogenetic changes, including land surface morphology, recent geomorphic processes, and soil properties caused by andesite rocks exploitation at the northern flank of Mt. Ungaran, Central Java Province of Indonesia. A digital terrain model was firstly generated from small format aerial photography acquired by an unmanned aerial vehicle (UAV) to identify the surface morphology changes due to the mining. Soil observation on field and laboratory test were conducted from samples at the affected and unaffected mining areas in order to analyse the changes on pysiochemical properties. This research exhibits that the mining activities have altered a single convex hill into a complex land surface morphology consisting of sloping zone, basins and flat area. Human disturbance on pedogenetic process at the mining area are in the form of parent material alteration that make them return to the early stage of soil development and top soil reduction that modify its genetic horizons. In addition, the changes on surface morphology and the absence of vegetation cover right after the mining ends also triggered new geomorphic processes in the form of incision and deposition on slopes and basin respectively. The finer deposit layers then become a new parent material at the basin zone. Soil laboratory data demonstrate that the affected soils tend to have a high level of base saturation, but lower C-organic and N-total levels, which result in a less favourable environment for supporting vegetation growth. A precise surface morphology design, extra soil surface protection and organic matter enhancement could be wise recommendations for land managers to control soil incision and support vegetation growth at the andesite post-mining area.