Abstract
[1] Very little information exists on Amazonian peatlands with most studies on tropical peatlands concentrating on Southeast Asia. Here we describe diversity of Amazonian peatland ecosystems and consider its implications for the global diversity of tropical peatland ecosystems. Nine study sites were selected from within the most extensive wetland area of Peruvian Amazonia: the 120,000 km2 Pastaza-Maranon basin. Peat thickness was determined every 500 m from the edge toward the center of each site, and peat samples were collected from two cores per site. Samples from the entire central core and surface samples from the other core were analyzed for nutrient content. Topography of four peat deposits was measured. In order to study differences in vegetation, pixel values were extracted from a satellite image. The surface peat nutrient content of the peatlands varied from very nutrient-rich to nutrient-poor. Two of the peatlands measured for their topography were domed (5.4 and 5.8 m above the stream), one was gently sloping (1.4 m above the stream), and one was flat and occurred behind a 7 m high levee. Five different peatland vegetation types were detected on the basis of pixel values derived from the satellite image. The peat cores had considerable variation in nutrient content and showed different developmental pathways. In summary, the Pastaza-Maranon basin harbors a considerable diversity of previously undescribed peatland ecosystems, representing a gradient from atmosphere-influenced, nutrient-poor ombrotrophic bogs through to river-influenced, nutrient-rich swamps. Their existence affects the habitat diversity, carbon dynamics, and hydrology of the Amazonian lowlands, and they also provide an undisturbed analog for the heavily disturbed peatlands of Southeast Asia. Considering the factors threatening the Amazonian lowlands, there is an urgent need to investigate and conserve these peatland ecosystems, which may in the near future be among the very few undisturbed tropical ombrotrophic bogs remaining in the world.
Highlights
[2] Peatlands are characterized by the accumulation of partially decomposed organic matter under anaerobic conditions created by water‐logging
These peatlands are influenced by large annual variations in the water level of the Amazon River and its tributaries
[32] Our results show that the Pastaza‐Marañón basin harbors (1) several previously unstudied peat deposits and (2) a considerable diversity of peatland ecosystems, indicated by differences in surface peat nutrient content, topography and vegetation
Summary
[2] Peatlands are characterized by the accumulation of partially decomposed organic matter under anaerobic conditions created by water‐logging. Some of the thickest and oldest of these peatlands have evolved through minerotrophic conditions to form domed, up to 6 m thick nutrient‐poor ombrotrophic bogs, and their surface peat layers (e.g., 0–175 cm, including the critical rooting zone for vegetation) currently depend entirely on atmospheric inputs of water and nutrients, despite their location in the floodplain of the Amazon River [Lähteenoja et al, 2009a, 2009b]. The aim of the paper is to answer the following questions: (1) Do the wetlands of the Pastaza‐Marañón foreland basin harbor peat deposits?
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