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

Background/Question/Methods

Peatlands at high elevation in the northern Andes cover less than 1% of the landscape but regulate water for most of the population of Colombia and Ecuador. Peatland plant communities in the northern Andes have recently come to the attention of the scientific community due to their relevance in the global Carbon cycles, globally peatlands store nearly 600 Gt of Carbon, and water regulation properties, they store nearly 10% of the global fresh water supply. Peatlands accumulate carbon due to their low decomposition rates; rates that can be increased by warmer temperatures and higher nutrient inputs. Andean mountains are expected to be affected by global warming at the same rate than boreal regions, and anthropogenic disturbances are predicted to increase upward following milder temperatures at high elevations with direct effect on the function of peatlands. In the present study we describe peatland vegetation patterns and recent Carbon accumulation trends across an elevation range of 2,200 m from 2,500 m to 4,700 m, and across a gradient of anthropogenic disturbances covering 120 peatlands in the Northern portion of the Andes Cordillera.

Results/Conclusions

Vegetation surveys evidenced an altitudinal shift in species composition from Sphagnum dominated at lower elevations to cushion plant dominated peatlands at the upper limit of the vegetation; Distichia muscoides was the dominant species in cushion plant dominated peatlands. At low elevations novel vegetation types dominated by sedges and herbaceous vascular plants had a positive correlation with human disturbance intensity and pH replacing Sphagnum dominated peatlands. ²¹⁰Pb chronologies revealed lower total Carbon accumulated during the last 50 years in sites with high (5 kg C/m²)  than in sites with low human disturbance intensity (15 kg C/m²). Vegetation type was the most important predictor of carbon accumulation rates during the last 100 y. Peat accumulation in cushion plant dominated peatlands had a twofold increase during the last 25 y in sites fed by glacier melt waters. Climate has a strong control on vegetation types and peat productivity; the threat of extinction faced by cushion plant dominated plants is highlighted by the absence of habitats above their current distribution range. However, recent excess of water supply from glacier melt had help cushion plant ecosystems to proliferate. Human disturbances are the most urgent threat to Andean peatlands since peatland ecosystemic functioning reacts swiftly to changes in water chemistry.