Sjögersten, Sofie, Cheesman, Alexander W., Lopez, Omar, and Turner, Benjamin L. (2011) Biogeochemical processes along a nutrient gradient in a tropical ombrotrophic peatland. Biogeochemistry, 104 (1-3). pp. 147-163.

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Abstract

Biogeochemical properties, including nutrient concentrations, carbon gas fluxes, microbial biomass, and hydrolytic enzyme activities, were determined along a strong nutrient gradient in an ombrotrophic peatland in the Republic of Panama. Total phosphorus in surface peat decreased markedly along a 2.7 km transect from the marginal Raphia taedigera swamp to the interior sawgrass swamp, with similar trends in total nitrogen and potassium. There were parallel changes in the forest structure: basal area decreased dramatically from the margins to the interior, while tree diversity was greatest at sites with extremely low concentrations of readily-exchangeable phosphate. Soil microbial biomass concentrations declined in parallel with nutrient concentrations, although microbes consistently contained a large proportion (up to 47%) of the total soil phosphorus. Microbial C:P and N:P ratios and hydrolytic enzyme activities, including those involved in the cycles of carbon, nitrogen, and phosphorus, increased towards the nutrient-poor wetland interior, indicating strong below-ground nutrient limitation. Soil CO(2) fluxes and CH(4) fluxes did not vary systematically along the nutrient gradient, although potential soil respiration determined on drained soils was lower from nutrient-poor sites. Soil respiration responded strongly to drainage and increased temperature. Taken together, our results demonstrate that nutrient status exerts a strong control on above and below-ground processes in tropical peatlands with implications for carbon dynamics and hence long term development of such ecosystems.

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