Acid Peatland

Description

Moss cover is very indicative for this site, driving the successional dynamics and species diversity. Sphagnum sp. absorb dissolved mineral cations, and release organic acids, which lowers the pH of stagnant surface water below 5.0 (MN DNR 2003). Sphagnum tends to form carpets of hummocks, which creates an acidic environment cut off from groundwater and on-site ponding. In recently developed bogs, on sites mostly in the western range of the MLRA where soils are less continuously saturated, on sites where water table fluctuations are less variable, or on inclusions of sites where there are upwellings of groundwater, isolated minerotrophic species (i.e. creeping sedge or bluejoint) may be present. Other ground cover includes fine-leaved graminoids, and minimal presence of forbs. Occasionally, seedlings of deciduous tree species associated with adjacent sites (i.e. red maple or paper birch) may become established on Sphagnum hummocks but typically do not survive to become saplings or trees (MN DNR 2003). The overstory usually consists of scattered, stunted (<30ft [10m] tall) black spruce or tamarack (<50% cover) where Sphagum hummocks provide relief from surface flooding (MN DNR Forestry). Most vascular plants associated with Acid Peatlands have a strong association with mycorrhizal fungi, depending on them to obtain minerals and nutrients in this depauperate and harsh environment (MN DNR 2003). These fungi are more diverse on this ecological site than on other sites throughout the region.

Submodel

Description

In this state, the vegetation usually exhibits a structural pattern of “hard” edges which does not mimic the patch-scale distribution of canopy gaps we see from natural disturbances. Compositional changes in this state, as a diversion from reference, can be concerning, most notably the reversal of abundance of tamarack and black spruce (MN DNR Forestry). Tamarack regeneration has proven problematic for management, and can be susceptible to devastating outbreaks of larch sawfly and larch beetles. Tamarack regeneration in this state could be accomplished by leaving some tamarack seedtrees rather than always clear-cutting and seeding just black spruce (MN DNR Forestry). Harvesting should always be done in this state when the entire peat surface is frozen, although even then just a few passes with heavy equipment can damage the structural integrity of the site, or damage standing trees, thus prohibiting tree regeneration or maintenance on-site. In the field, areas identified by the presence of broad-leaved sedges and rough alder have far less structural integrity than the Sphagnum mat and should be avoided at all costs by heavy equipment. When dwarf mistletoe is present, control of the disease through broadcase burning, or by use of the “5 foot cutting rule”, can eradicate the disease, but success is dependent on total elimination of all living black spruce, and treatments (hand cutting, winter shearing, herbicides, combination treatments) need to be continued for 10 years after the initial harvest (MN DNR Forestry).

Description

In this state, the excess of water on-site for longer than normal duration typically results in the killing off of tamarack and spruce trees, and the establishment of invasive species such as Typha sp. or reed canary grass (Phalaris arundinacea). Sometimes, other graminoids (Carex sp.) can remain on site and form floating mats. Sometimes alder and willow shrubs will remain or establish on the edges.

Description

Possible open water. Develops where the peat becomes isolated from mineral rich runoff or groundwater. Mineral and nutrient inputs come from precipitation and deposition. The saturated conditions and quick accumulation of Sphagnum prevent or inhibit establishment/growth of black spruce and tamarack. Variation in species composition in the community occur.