| This dissertation examines the effects of Monterey pine (Pinus radiata) plantations on nutrient cycling and water retention in páramo grasslands in the Ecuadorian Andes. Pine plantations constitute a growing land use in the páramo grasslands of Ecuador, driven in large part by national-level government policies, as well as the social and economic conditions of páramo landowners. However, while research exists on the effects of pine plantations on ecosystems in temperate regions, little is known about their effects on high altitude, equatorial ecosystems. The main objective of this research was to address this issue.; I examined changes in nutrient cycling and water retention in a chronosequence of pine stands in Cotopaxi province. The chronosequence consisted of 14 stands ranging from 0 to 24 years of age, which I classified into four age groups: grassland (control), young pine (5–10 years old), intermediate-aged pine (15–20 years old), and old pine (20–25 years old). Large and significant declines in soil carbon, total nitrogen, and water retention capacity with stand age were evident in the chronosequence, along with a smaller but also significant decline in pH. These results demonstrate that the change in vegetation cover causes changes in soil properties on a decadal time scale.; I also investigated the influence of harvesting and slash-burning of the pine stands in Cotopaxi. A transect was established that covered four sites: a 24 year old P. radiata stand, a post-harvest site, a post-harvest and slash-burn site, and a site in a grassland at the edge of the harvested site. Significant changes in soil temperature, field moisture, and dissolved organic carbon concentrations were evident after harvesting and burning. There was also a tendency towards lower soil carbon and nitrogen following these practices. Additional monitoring of these properties will allow for a better understanding of how these variables change with time since harvesting and burning.; The results of this research are significant for policies related to watershed management and carbon sequestration. This research can contribute to better management of the páramo, an area of great importance in terms of biological diversity as well as in the provision of livelihoods for its inhabitants, who are dependent upon its sustainable use and management. |
