Effect of land use on forest floor and soil of a Quercus suber L. forest in Gallura (Sardinia, Italy)

Abstract

In order to determine the e ect of land use on forest ¯oor and soil, two adjacent sites with di erent land use were investigated in Gallura (northern Sardinia, Italy). One site is a Quercus suber L. forest mainly used for cork production and the other is an open Quercus suber L. forest where livestock is put out to graze. In each site one soil pro®le was studied to characterize the mineral soil, and ®ve humus pro®les were opened along a vegetation transect, were studied to characterize the forest ¯oor. Samples of L, F and H horizons of the forest ¯oor and of the A mineral horizons were collected and analysed for each pro®le. In the site mainly used for cork production well-developed ectorganic (L, F and H) horizons are always present, with a total thickness ranging from 5.2 to 9.5 cm. Humus pro®le is of the Moder type, while mineral soils have an A±C pro®le, generally 50 cm deep. Organic matter content in the forest ¯oor ranges from 1.76±3.72 kg mÿ2 and nutrients content in the mineral soil is high. In the site used chie¯y for grazing the ectorganic horizons are very poorly developed, with a total thickness ranging from 1±3 cm, except for some islands under the Quercus suber L. canopy where the total thickness may reach 5.3 cm. Humus pro®le is of the Mull type, but the used classi®cation system seems not appropriate when the tree density is below a critical limit. Mineral soils have an A±C pro®le 20±25 cm deep. The organic matter content in the forest ¯oor ranges from 0.45 to 1.84 kg mÿ2 , while nutrient content in the mineral soil maintains at high level, even higher than in the former case for C, N and Ca, probably in relation with higher supply of cattle excreta. Sheet erosion is evident in the site. It is concluded that cork production will maintain a sustainable forest ¯oor development in cork±oak forest ecosystem, whereas cattle grazing, ®res and ploughing in cork±oak forests may be considered to trigger o severe soil degradation processes.