Nutrient Sequestration Oligotrophification

Peat forms due to slow decompositional processes that allow organic materials to be deposited as peat. As organic material is deposited, it contains within its carbon matrix

Figure 11 A longitudinal view of the canopy of Sphagnum; each stem is terminated by a capitulum of young branches. The branches along the stem are covered with numerous overlapping leaves and organized into fascicles that have branches that hang down along the stem as well as branches that spread outward from the stem allowing the individual stems to be evenly spaced from one another.

Figure 11 A longitudinal view of the canopy of Sphagnum; each stem is terminated by a capitulum of young branches. The branches along the stem are covered with numerous overlapping leaves and organized into fascicles that have branches that hang down along the stem as well as branches that spread outward from the stem allowing the individual stems to be evenly spaced from one another.

nutrients, especially nitrogen and phosphorus, which were originally incorporated in the cell structure of the living plants, especially those of Sphagnum and brown mosses. Relatively rapid decomposition in the acrotelm mineralizes only a portion of the total nutrients tied up in the plant material, making these available for further plant growth as well as fungal and bacterial processing. However, upon entry to the catotelm, almost all decom-positional activity stops and the nutrients become tied to organic materials in unavailable forms. Thus, rather than being recycled and remaining available for new plant growth, nitrogen and phosphorus become part of long-term unavailable nutrient pools. The lack of ability to utilize this unavailable pool of nutrients causes peatlands over time to become more oligotrophic at their surface yet also having large amounts of stored nitrogen and phosphorus. For example, Sphagnum peat is generally about 1% nitrogen; however, almost all of this catotelmic nitrogen is unavailable for plant and microorganism use while in place in the peat deposit. When exposed to the atmosphere (e.g., as a garden amendment), the carbon is oxidized to CO2 and the nitrogen is mineralized to NO3-and NH^ and available for plant uptake. Although the actual percent of nitrogen, and other nutrients, may not be as high as that in inorganic soils, the total amount in the soil within any one square meter surface area of the peat-land is greater in peat soils due to the depth of the peat present. This oligotrophification, and consequently nutrient storage, is autogenetically enhanced through the buildup of the peat column, placing the peat surface farther from the source of the nutrient inputs. The long-term result of oligotrophication is the regional storage of large pools of both carbon as well as important nutrients, especially nitrogen and phosphorus.

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