Doctoral Dissertation Research: Impacts of Exotic Pine Plantations on Paramo Grasslands in the Ecuadorian Andes

University Of Colorado At Boulder, Boulder CO

Investigators

Abstract

The introduction of exotic species has had significant impacts on a broad range of ecosystems throughout the globe. While ecologists, biogeographers, and other scientists continue to develop and refine broader theories regarding interactions among biotic, physical, and human systems when humans introduce new species to a region, these theoretical developments have been fueled by the careful analyses of the dynamics of ecosystem change in specific locales. This doctoral dissertation project will examine the ecological impacts of Monterey pine (Pinus radiata) plantations in alpine grasslands in the Ecuadorian Andes. The project will address how pine plantations are affecting a high-elevation, equatorial ecosystem that plays an important role in regional and local hydrology and in which soil carbon storage is high. The focus of the research will be on changes in soil properties and in water retention, especially the changes in soil physical and chemical properties associated with exotic pine plantations as compared to adjacent grasslands. Attention also will be given to assessing how these properties change with plantation age. The general hypothesis is that pine plantations will cause changes in chemical, physical, and biological processes in soils, which will be reflected in altered physical and chemical properties of the soil. These changes are anticipated to become more severe as plantations age, possibly leveling off at later stages of stand development. In order to examine these questions, a chronosequence of pine plantation plots will be compared to control plots of native grasses. Random sampling of surface soils will be conducted as well as sampling in soil pits, where zero-tension lysimeters will also be installed. Analyses will made of a range of variables, including total carbon, available phosphorus, total and available nitrogen, pH, bulk density, soil moisture content, and water retention, as well as dissolved carbon, nitrogen, and phosphorus in the solution samples. The theoretical context for this research draws on Jenny's state-factor approach, which states that the soil or any soil property is a function of five soil-forming factors: climate, biota, topography, parent material, and time. In order to analyze the role of any one of these factors, the others must be held constant or minimized. The characteristics of the study site allow for an assessment of soil properties as a function of vegetation type (pines vs. grasses) and as a function of time of occupation by the exotic vegetation. Research on the impacts of pine plantations on the carbon and water cycles is particularly necessary in regions like the tropical Andes. These types of studies in these locales are especially important because the fragility of the ecosystems being altered may be much greater than lower-elevation and temperate systems that have been studied more intensively. If carbon losses from these soils are greater than the rates of carbon sequestration following the introduction of tree plantations, policies aimed at decreasing atmospheric carbon concentrations may have the opposite effect. The potential for drying out of these soils under plantations could also have profound impacts for the provision of water to lower elevations. This project will provide a better understanding of impacts of pine plantations at the ecosystem level, information that is important for policy makers and landowners who will make decisions about land uses. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.