This National Science Foundation Minority Postdoctoral Fellowship will examine land use effects on, and ecological limits to, tropical montane forest recovery in RÃo Abiseo National Park, Peru. Here, centuries of livestock grazing and burning, introduction of exotic African grasses for improved pasturing, and temperature variation have resulted in a patchwork mosaic of advancing and receding forest-grassland boundaries. However, the mechanisms controlling forest-grass ecotone location across this landscape remain poorly understood. In this study, environmental history data, observations from natural regeneration monitoring, and experimental manipulations will together be used to test the hypothesis that under conditions of fire and grazing exclusion, elevation and grass species interact to control rates and patterns of forest recovery within native alpine and exotic kikuyu-dominated grasslands. By investigating whether or not these bottlenecks can be overcome, this project will reveal the role of co-occurring ecological processes in mediating regional forest dynamics, and hence potential vegetation response to climate variability, on tropical mountains.
The Fellow will perform her research at the University of Texas at Austin, under the sponsorship of Dr. Kenneth R. Young in the Department of Geography & the Environment. The University of Texas has a strong research tradition in Latin American geography. It houses the Nettie Lee Benson Latin American Collection and Plant Resources Center, both with significant materials from Peru. The Fellow will also benefit from access to the Environmental Information Systems Laboratory in the host department. Dr. Young has conducted academic and consulting research in Peru since the 1980s. His research focuses on the biogeography, ecology, and conservation of Peru?s humid eastern montane forests in the context of landscape and climatic change.
In addition to contributing to theory on grass-tree vegetation shifts, this project will have far-reaching implications for protected areas management, restoration, climate change, and ecosystem services. Peru?s humid montane forests, the world?s leading biodiversity hotspot, are integral to the long-term environmental sustainability of the Andean-Amazon basin. An assessment of the factors driving contemporary resource use within and outside the park will serve to re-evaluate threats to conservation in this region and to generate practical policy recommendations related to land use and economic development. By evaluating the most promising methods and species for forest restoration, this project will supply land managers with practical guidelines for degraded lands rehabilitation. Experimental manipulations will potentially indicate species-specific responses to global warming, as well as the suitability of these forests and key species as indicators of climate change. Lastly, an understanding of the factors controlling tree establishment in grasslands will be important for assessing the sensitivity of ecosystem services, such as water regulation, to distinct land-use legacies. The training objectives are to enhance the Fellow?s expertise in land use and global change, expand the Fellow?s knowledge of experimental methods, and improve her analytical skills. First, postdoctoral training will allow the Fellow to continue studying the influence of anthropogenic disturbance on tropical mountain forests, but in a remote region that has received little attention despite its worldwide conservation importance. Second, field research will allow the Fellow to design and conduct a suite of experiments needed to test historical land use effects on forest dynamics. Third, data acquired from this project will provide the foundation for future research comparing forest recovery across degraded landscapes in Mexico, Peru and similar environments elsewhere. In addition to providing innovative and important research contributions, an NSF Minority Postdoctoral Fellowship will improve the Fellow?s qualifications for a tenure track faculty appointment at a major research institution.
Pattern and process of woody plant establishment above treeline: land-use legacies and forest recovery in the equatorial Andes Treeline is a boundary between forest and grassland that exists at high altitudes and latitudes around the world. Essentially, it is the limit to which forests can grow before being replaced by grasses. In the U.S., many studies have shown that treeline forests are growing to ever-higher elevations due to climate change. However, we still know very little about the effects of climate change on treeline forests in the Andes Mountains of South America, where temperatures have risen approximately one degree Celsius over the past century. Are these forests also growing to higher elevations? If so, why or why not? This research project examined these questions in a small valley in Rio Abiseo National Park, Peru, where unlike the U.S., people have been grazing cattle for hundreds of years and burning grasslands for millennia. As trees grow very slowly, the growth and survival of tree seedlings rather than adult trees was monitored over a two-year period. The research revealed that seedlings of very few forest species grew from seed in grasslands above treeline forests. Most woody species were shrubs that re-sprouted from roots. In addition, the abundance of forest seedlings found growing in grassland was variable throughout the valley. To understand these patterns, temperature and soil fertility were examined in the same areas where plant establishment was monitored. Nighttime temperatures were much lower in grasslands than in forest, resulting in more frequent frost episodes in grasslands. As well, levels of such essential plant nutrients as nitrogen and phosphorus were much higher and lower, respectively, in grassland than in forest, likely to due to cattle grazing and fire. Based on these results, the research suggests that differences in temperature and soil fertility associated with land use may limit the establishment of forest seedlings above treeline. These findings are important, because they indicate that the sensitivity of forests to climate change on tropical mountains will likely vary from location to location depending on local climate factors and land-use intensity. Where human impacts are high and long lasting, climate change effects on treeline forests may not be evident for some time. In protected areas, such as Rio Abiseo National Park, where fire is prohibited and grazing is slowly being phased out, the research supplies information on the most promising methods and species for use in cloud forest restoration projects. Moreover, the study contributes to knowledge in the fields of geography, ecology, botany, and related disciplines by showing how treeline forests are simultaneously responding to changes in human impact and climate. This project provided numerous opportunities for research, teaching, and mentoring in science. A total of 10 individuals, including the principal investigator, worked on the project during various stages of the research, including undergraduate students, a postdoctoral fellow, and junior and senior faculty. In addition, six local workers played an active role in data collection. The research team was also diverse in terms of gender and ethnicity. Women were well represented, comprising six of the ten team members, and the team included people from various countries, including the U.S., Mexico, Peru, and Argentina. As a result of the collaborative nature of the project, the research created new and also strengthened existing partnerships between U.S. universities, including the University of Texas at Austin and the University of North Texas, a Peruvian non-governmental organization, and the Peruvian Natural History Museum. The plant collection, which will be archived in the Natural History Museum in Lima, and the additions to the existing plant species lists that will result from the project are major resources for research and education in Peru and internationally. The scientific findings and strengthened collaborations that resulted from this research are of benefit to society as a whole. Understanding the impact of humans and global climate change on treeline forests in the Andes Mountains of South America is of social and ecological significance. The Andes is the longest continental mountain chain on Earth. Changes in the position of treeline forests could have major effects on the distribution of plant and animal species, many of which are used by Andean societies. Because trees and grasslands have distinct effects on the hydrologic cycle, it is probable that a moving treeline will also affect the supply of water to downstream areas. Finally, forests absorb carbon dioxide and store large amounts of carbon not only in trunks, branches, and leaves, but also in roots and soil. An expansion of treeline forests along the length of the Andes could potentially reduce the effects of increasing carbon dioxide in the atmosphere.
