Determining the effect of climate change on the carbon dynamics of the high elevation tropical humid puna
Recent scientific evidence shows that global temperatures are increasing. The effects of increased temperatures are expected to be more dramatic in polar regions, however, the tropics may also be especially susceptible to warming as a result of the specialization of tropical species to a narrow range of climatic conditions coupled with rapid rates of warming. Nevertheless, investigation of the potential effects of warming in tropical ecosystems has been extremely limited. Humid puna lands - grasslands located at high elevations in the Andes Mountains of South America - harbor fragile ecosystems with a high level of endemism; puna areas also are under high pressure as a result of fire, grazing, and climate change. Human populations, such as native Quechua, depend on puna ecosystems for subsistence. To better understand potential responses of high elevation tropical ecosystems to climate change, a thermal and hydrological manipulation experiment will be conducted to determine the potential effects of climate change on the high elevation humid puna ecosystem of the tropical Andes.
During the tenure of the fellowship, the Fellow will focus effort on the development and strengthening of quantitative skills, statistical analysis and model development. The Fellow will work on establishing experiments, and training and mentoring local Peruvian technicians and undergraduate and graduate students from the USA. Additionally, the proposed sponsoring institution, The Fairchild Tropical Botanic Garden (FTBG), represents a unique outreach opportunity by translating research into activities and programs that can be used for environmental education of K-12 students and the general public.
Determining the effect of climate change on the carbon dynamics of the high elevation tropical humid puna Recent scientific evidence shows that global temperatures are increasing. The effects of increased temperatures are expected to be more dramatic on polar regions; however, the tropics may also be susceptible to warming as result of the specialization of tropical species to a narrow range of climatic conditions, and with rapid rates of warming occurring there. Investigation of the potential effects of warming in tropical ecosystems has been extremely limited. To increase our understanding about how high elevation grasslands will respond to environmental change, I carried out a scientific investigation that determined the effect of warming and changes in water availability on the puna grasslands. Tropical highland ecosystems are of particular concern because the predicted increases in temperatures are expected to shift the distributions of species and affect soil carbon dynamics. Previous experiments showed that heterotrophic respiration (microbial activity) in the puna grasslands presented one of the highest sensitivities to warming. Because of the high sensitivity to warming, ecosystem processes could quickly change in response to environmental alterations. I conducted an experiment that measured how environmental change (warming and water availability changes) affects ecosystem respiration. To determine ecosystem respiration response to environmental change, I used two experimental approaches: 1) in situ warming + water changes, and 2) ex situ sod translocation. For the in situ experiments, passive warming was used to warm the surface of intact vegetation at two elevations (3700, 3350 m.a.s.l.). Also, water + temperature manipulation experiments were conducted at the middle elevation puna site (3350 m.a.s.l.). For the ex situ translocations, sections of sod were collected and moved to the middle and lower elevation sites (3350, 3000 m.a.s.l.) to simulate warming of +2 and +4°C. Results The range in elevation allowed me to assess the response of puna ecosystem respiration to warming. By transplanting sections of puna from cold- (Tres Cruces) and warm-adapted (Acjanaco) environments to lower elevations in and out side of the natural range, I determined that puna grasslands could survive and function under moderate (within natural range) and extreme warming (outside of the natural range). The transplants from cold-adapted areas (Tres Cruces) presented a large increase in ecosystem respiration with temperature. The warm-adapted puna (Acjanaco) also experienced an increase in ecosystem respiration, but proportionally the increase was not as large. In Tres Cruces, the in situ warming presented lower ecosystem respiration than expected. Similarly, the combination of warming and water treatments in Acjanaco also presented lower ecosystem respiration than expected. Season did not have an effect on these responses. Water treatments alone in Acjanaco presented responses that were unexpected. The ecosystem respiration in water addition and reduction treatments was higher than expected. Season did not affect the response to the treatments. Intellectual merit. My investigation found that high elevation grasslands presented higher ecosystem respiration to increased temperatures at least in the short-term, which can be associated with higher productivity. The results of this project have important implications for the expected environmental changes in the puna ecosystems and the local human communities. Local human communities can see the increase in productivity of the puna grassland as beneficial in particular for cattle grassing. Additionally, with warming it is expected that lower elevation species of trees should be able to colonize the higher elevation grassland, however more productive grasslands could become a barrier for the uphill movement of tree species. Additionally, this project produced a unique data set that serves as a baseline for monitoring seasonal variations in carbon dynamics (puna productivity). To the best of my knowledge, this is the first data set that reports the magnitude and variation (spatial and temporal) of carbon emissions for the humid puna ecosystems. Broader impacts. One key outcome of the project is that I was able to increase the interest of the undergraduate students, park guards, and park officials in climate change research and the potential responses of the puna grasslands to environmental change. I expect that with the infrastructure (field sites) created and didactic material (large poster at the main entrance of the park), the local community, tourists, and students that visit the park will become interested in learning about the research findings. In addition to scientific journals and meetings, I have also prepared a news article for the Tropical Garden, which is a general audience magazine produced by Fairchild Tropical Botanic Garden. This magazine is of high impact for a general audience in South Florida and beyond because it goes out to all members of Fairchild (about 40000).
