CHANGES IN SOIL CHEMICAL AND BIOCHEMICAL PROPERTIES ASSOCIATED WITH REPLACEMENT OF NATURAL GRASSLANDS BY PINUS RADIATA D. DON AND AGRICULTURAL ROTATIONS

Abstract

The replacement of native vegetation of grasslands by agriculture, or by afforestation, causes changes in the properties of the soil, affecting its productivity. The objective of this research was to study the changes in some edaphic properties generated by the following changes in land use: 1) Natural grassland (PN) to agriculture (AGR); 2) PN to afforestation with pines (MP); 3) Strips thinned within MP: secondary grassland (PS). Soil samples were taken from each system, and both chemical and biochemical properties were analyzed. All the systems recorded a reduction of the pH and an increase in the H+ saturation of the soil. An increase in the total organic carbon (COT) was observed in MP and PS. The anaerobic N mineralization potential (Nan) of these sites was much lower than that of PN, probably due to differences in the quality of their organic matter. PS generated a decrease in soil acidity, and an increase in Nan and P extractable. Acidification was lower in AGR, but it recorded the highest reduction in COT, Nan and P extractable. The changes observed indicate that the original characteristics of the soil tend to recover quickly in places where introduced vegetation was replaced.