Boreal Woodland Peat Frozen Flats

Description

The reference plant community is dwarf tree scrub woodland (Viereck et al. 1992) with the dominant tree being black spruce. There are three plant communities within the reference state related to fire.

Dominant plant species

1. black spruce (Picea mariana), tree

2. marsh Labrador tea (Ledum palustre ssp. decumbens), shrub

3. sphagnum (Sphagnum), grass

4. reindeer lichen (Cladina), grass

Submodel

Description

Thermokarst occurs due to the thermal erosion of ice-rich permafrost in soil after disturbances such as fire events or land clearing. While thermokarst can be readily observed, details related to thermokarst succession are poorly understood. After an unknown timeframe, thermokarst depressions could theoretically revert back to plant communities associated with the reference state (Myers-Smith et al. 2008). However, the timeframe for recovery is likely outside the scope of typical land management priorities. At this time, restoration back to reference conditions is not considered within the state-and-transition model.

The thermokarst plant community is open low scrub (Viereck et al. 1992). Associated soils pond and have a persistent high water table. The thermokarst state has one documented plant community.

Future data collection efforts and research would likely enhance information about existing plant communities within this state and allow for better understanding of the potential transitions from one community or state to another.

Dominant plant species

1. leatherleaf (Chamaedaphne calyculata), shrub

2. bog rosemary (Andromeda polifolia), shrub

3. water sedge (Carex aquatilis), grass

4. sphagnum (Sphagnum), grass

Submodel

Description

Palsa and peat plateau develop from the soils associated with the reference state (personnel observations of NRCS staff). A palsa is a much smaller landform feature compared to a peat plateau. A palsa is an elliptical dome-like permafrost mound containing alternating layers of ice lenses and peat or mineral soil, commonly 10-30 feet in height and 6 to 80 feet long (Schoeneberger and Wysocki 2017). A peat plateau is a generally flat-topped expanse of peat, elevated above the general surface of a peatland, and containing segregated ice that may or may not extend downward into the underlying mineral soil (Schoeneberger and Wysocki 2017).

Palsa and peat plateau can raise significantly above the water table and their peaty soils can become well drained. If these landforms raise high enough above the water table, soil temperature increases and eventually ice-lens melt. Palsa (Pielou 1994) and peat plateau (personnel observations of NRCS staff) are both prone to collapse. After collapse, the soils are thought to revert back to reference state conditions.

The alternate state community is dwarf tree scrub woodland (Viereck et al. 1992) with black spruce as the dominant tree. The plant community associated with this state has limited data (USDA NRCS 2016) and is provisional.

Dominant plant species

1. black spruce (Picea mariana), tree

2. marsh Labrador tea (Ledum palustre ssp. decumbens), shrub

3. bog rosemary (Andromeda polifolia), shrub

4. small cranberry (Vaccinium oxycoccos), shrub

5. (Flavocetraria cucullata), grass

6. reindeer lichen (Cladina), grass

7. sphagnum (Sphagnum), grass

Submodel