land use change and forest transition in sierra de san javier, tucuman

GUTIERREZ, J; GRAU, HR; GASPARRI, NI; CASAVECCIA, C

Merida, Mexico

Congreso; Ecology in an Era of Globalization; 2006

Ecological Society of America

Forest transition is the process of forests recovery associated to socioeconomic changes promoted by population urbanization, industrialization, agriculture intensification and abandonment of marginal lands. This process has been well documented for Europe and North America and more recently in tropical countries. In this study we quantified the changes of land cover in a period of 50 years in the Sierra de San Javier (Tucuman), analyzing aerial photographs of 1949, 1968 and 2001. The Sierra de San Javier (600 - 1800 msnm) is an area dominated by subtropical mountain forests located 15 km west of San Miguel de Tucuman, the largest urban center in subtropical Argentina, with a population of 918.806 inhabitants. Tucuman experienced a strong rural-urban migration in second half of 20th century. Between 1980 and 1991 rural population decreased by 0,56%/yr whereas urban population increased by 2,28%/yr. The forest cover of the study area decreased from 20.366 to 20215 has (-0,03%/yr) between 1949 and 1968, and increased to 21,210 has (+0,11%/yr) between 1968 and 2001. The expansion of the forested area occurred mainly in foothills, associated to abandonment agricultural areas and in high elevation areas, associated to decreasing grazing over pasturlands. A percent of the new forests are dominated by exotic species, particularly Ligustrum lucidum, which is characterized by much lower diversity than native secondary forest. Urban areas expanded over agricultural and forested areas. These changes in the land cover respond to the model of "forest transition" and potentially have great implications for the conservation of the ecological services of these ecosystems (watershed protection, biodiversity, recreational uses, carbon sequestratoin), although the invasion by exotic species can slow down the fast recovery of the local biodiversity.