These mosses occur in wetland sites, specifically, within wet woods in the wettest portions of what are called "extreme rich fens" (i.e., fens having surface waters with high pH and calcium concentrations). Montagnes describes this species as a "rich fen indicator of high fidelity." Associates include Scorpidium spp. and Drepanocladus revolvens.
The fire ecology of this plant is not known; however, fens rarely burn. Excess soot from a nearby fire, however, might negatively affect habitat quality. Fire return intervals in conifer bogs, a somewhat similar mire-type habitat, are estimated to be about once every 150-200 years. Fire does significant damage to peat, but the bog must be dry (as during a drought year) in order to burn; typically, bogs are not dry enough.
U.S. Forest Service Pacific Southwest Region Sensitive Species.
California Native Plant Society List 4.2
NatureServe California State Rank: S2.2; Global Rank: G5
Fens are delicate habitats susceptible to impacts from livestock grazing, hydrologic alteration, construction and continued use of roads, and peat mining. Rich fen habitats are especially susceptible to modification. The surface water chemistry of rich fens is sensitive to climatic and anthropogenic influences. This species has reached near extinction in Europe.
M. triquetra is easily recognized by its distinct three-ranked leaf arrangement and for being dioicous. It may be distinguished from M. uliginosa by: its squarrose leaves; its narrow costa relative to the size of the leaf base; its serrate, planar leaf margins; and acute leaf tips; these as opposed to the wide (up to 1/3 of the leaf base) costa, the entire, revolute leaf margins, and the blunt apices of M. uliginosa; other Meesia species also have blunt apices..