Environmental Limiting Factors

The initiation, development, and succession of peatland ecosystems are influenced by a number ofregional, external factors. Especially important are hydrological and landscape position, climate, and substrate chemistry. These regional allogenic factors determine a number of site-specific factors that influence individual peatland sites. These local factors include rate of water flow, quantity of nutrient inputs, the overall chemistry of the water in contact with the peatland, and the amount of water level fluctuation. Additionally, there are a number of internal, or autogenic, processes that help regulate peat-land form and function (Figure 2). These allogenic and autogenic factors operate in an everchanging world of disturbance that includes natural disturbances, especially wildfire, as well as anthropogenic disturbances such as mining, forestry, and agriculture.

Peatland form and function are dependent on the process of peat accumulation and the pattern of loss or gain of carbon from habitats. Peat accumulation is dependent on the input of organic matter produced by photosynthesis. This organic matter is first accumulated in the upper, aerobic (or acrotelm) peat column wherein relatively rapid rates of decomposition occur. The rate at which this partially decomposed organic matter is deposited into the water-saturated, anaerobic peat column (the catotelm), wherein the rate of decomposition is extremely

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Figure 1 Estimated global distribution of peatlands. Areas colored in light green are those having >10% peat cover. The orange areas in North America and Siberia are the world's largest peatland complexes. The dot in western Siberia is the location for the Vasyugan peatland.

Figure 1 Estimated global distribution of peatlands. Areas colored in light green are those having >10% peat cover. The orange areas in North America and Siberia are the world's largest peatland complexes. The dot in western Siberia is the location for the Vasyugan peatland.

Decomposition ^Production^

Figure 2 Substrate, position, and climate are regional factors that influence six local factors that are shown in boxes in the diagram. These local drivers direct both the form and function of bogs and fens. Adapted from Vitt DH (2006) Peatlands: Canada's past and future carbon legacy. In: Bhatti J, Lal R, Price M, and Apps MJ (eds.) Climate Change and Carbon in Managed Forests, pp. 201-216. Boca Raton, FL: CRC Press.

Figure 2 Substrate, position, and climate are regional factors that influence six local factors that are shown in boxes in the diagram. These local drivers direct both the form and function of bogs and fens. Adapted from Vitt DH (2006) Peatlands: Canada's past and future carbon legacy. In: Bhatti J, Lal R, Price M, and Apps MJ (eds.) Climate Change and Carbon in Managed Forests, pp. 201-216. Boca Raton, FL: CRC Press.

slow, largely determines the amount of carbon that will accumulate at a given site. Thus, the amount of carbon, and hence the quantity of peat, that is deposited at a peatland site is dependent on photosynthesis, aerobic decomposition within the acrotelm, and subsequent anaerobic processes in the catotelm, including methenogenesis and sulfate reduction.

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