The changing face of Andean peatlands: the effects of climate and human disturbance on ecosystem structure and function

Author

Juan C. Benavides, Southern Illinois University CarbondaleFollow

Date of Award

5-1-2013

Degree Name

Doctor of Philosophy

Department

Plant Biology

First Advisor

Vitt, Dale

Abstract

Peatlands store nearly one third of the soil global carbon, and approximately 10% of the world's drinkable water on only 3% of the land surface. Peatlands store large amounts of carbon from the organic matter due to the reduced decomposition rates in the soil allowing the accumulation of new plant growth each year. Rising temperatures and increasing nutrient inputs from human activities can accelerate decomposition rates in the soil transforming peatlands from sinks to sources of carbon, and reducing their ability to regulate the local hydrological cycles. To identify how rising temperatures and increasing human originated disturbances have peatlands, I studied the current vegetation patterns and related them to elevation, temperature and disturbance environmental gradients, explored the recent history (last 200 years) of the peatland vegetation, and built models that described the past rates of gains by primary production and losses due to decomposition; finally I constructed a forecasting model to describe the dynamics of northern Andean peatlands. Past vegetation and historic production and decomposition rates were estimated from 210Pb chronologies. Results indicate a strong effect of the interaction between elevation and the intensity of human disturbance; superficial carbon stocks were negatively affected by human disturbances that at the same time favored the encroachment of upland vascular species. Elevation was an important gradient with lower peat accumulation rates at higher elevations, except when water from glacial meltdown was supplied in which case production reached extremely high values. Modeling of peatland dynamics indicated increasing decomposition rates in sites with high human disturbance, an effect that propagated towards the future in the form of net losses of carbon in the upper part of the peat column. Conversely, sites with low human disturbance or at high elevations but receiving water from glacial meltdown become larger carbon sinks. In conclusion, climate change is having a direct and measurable effect on the dynamics of northern Andean peat dynamics; however, the effects become less predictable when interactions with the climatic or human systems are included. The rate of peat degradation due to modifications in the environment indicates the urgency to better understand the northern Andean peatland ecosystems. In conclusion: high elevation peatlands in the Northern Andes are ecosystems that offer extremely important ecological services but that may have started an irreversible decline.