CHANGES IN LAND-USE IN NORTHERN SPAIN - EFFECTS OF FORESTRY MANAGEMENT ON SOIL CONSERVATION

The substitution of agricultural land uses and native forests in the N orth of Spain by Pinus radiata plantations was studied. The variabilit y of a set of soil samples taken in these plantations, and other types of land uses, was analyzed. The sites studied have had characteristic changes in land use, being submitted to different degrees of exploita tion and types of management practices. Clear-cutting and planting tec hniques, along with the selective logging from the main mass of trees and the clear felling of the understorey, cause an alteration of the e daphic system which is seen in its lesser ability to mobilize necromas s, recycle nutrients and increase the carbon/nitrogen ratio. Old pine plantations, forests of Fagus sylvatica and Quercus spp. and pastures also show a noteworthy variability in their edaphic characteristics de pending on the type of management. Forests with very similar appearanc e may have soils with very different necromass recycling capabilities. The same occurs with pine plantations. The usual procedure involved i n land planning, characterizing the degree of nature conservation by m eans of identification of large units of vegetation or farmland uses i s highlighted. In territories with intense human management, as here c onsidered, this degree can best be assessed through the study of the s oil characteristics. (C) 1998 Elsevier Science B.V.