Mosses have 2 phases in their
life cycle: the gametophyte (n) and sporophyte (2n) generations. Each generation is morphologically distinct.
Gametophytes Ribbed bog moss stems comprise most of ribbed bog moss's
biomass and are easily visible. Stems are erect and spreading in habit, forming clumps or lawns. They range from long; most stems are vegetative but some bear reproductive organs. Short vegetative stems may end in a stalk-bearing clusters of
gemmae. Ribbed bog moss is heterothallic, with male and female reproductive organs borne on separate reproductive shoots. Male and female stems develop
antheridia and
archegonia, respectively, at their tips. Approximately the top of both vegetative and reproductive stems is alive; lower stem tissue is usually dead. Ribbed bog moss leaves are bright yellowish-green to green; their bright color sometimes gives ribbed bog moss an incandescent appearance ("glow moss"). Bright leaves that contrast starkly with the reddish-brown stems typically make ribbed bog moss the most conspicuous species in moss assemblages. The leaves are lanceolate in shape and often tomentose, becoming twisted and brown when dry. They range from 3 to 5 mm long. Ribbed bog moss anchors to the substrate with
rhizoids. Because ribbed bog moss lacks vascular tissue, water uptake occurs by
osmosis and
capillary action. A network of capillary spaces between stems and rhizoids enhances water uptake; ribbed bog moss usually absorbs water more efficiently than associated sphagnum mosses.
Sporophytes Sporophytes grow out of archegonia. The sporophyte consists of a foot that anchors the sporophyte to the archegonia, a stalk, and a spore capsule. Ribbed bog moss stalks are vertically straight and about long. Ribbed bog moss is named for its distinct spore capsule, which is strongly ribbed, cylindrical, and about 4 mm long. The capsule is capped with a
calyptra.
Regeneration processes Ribbed bog moss regenerates
sexually and
vegetatively.
Gametophyte dispersal and establishment A
spore is the first growth stage of a developing gametophyte. When the spore capsule matures, ribbed bog moss's calyptra splits along the side, exposing spores. Release of the exposed spores requires dry weather and is governed by a row of "teeth" that ring the capsule's top. The capsule teeth are
hygroscopic, bending outward when air is dry and permitting spores to fall. Wind
disperses ribbed bog moss spores long distances by shaking the capsule. When air is moist, the teeth bend inward, holding the spores within the capsule. The spores require a moist substrate to
germinate. A germinated spore develops into a
protonema (a branched, threadlike structure). Rhizoids grow down from the protonema and penetrate the substrate. Stems arise from buds that develop on the protonema surface. As stems grow, they develop their own rhizoids and become independent of the protonema. Mature male and female stems develop antheridia and archegonia, which produce sperm and eggs, respectively. Ribbed bog moss antheridia do not develop synchronously on the same stem. Mature and immature antheridia are intermixed on individual male shoots; therefore, sperm cells on the same stem do not all develop at the same time. However, sperm cells within a single antheridium have synchronous development. Fertilization requires a moist or saturated environment. Before fertilization, the antheridium absorbs water and swells, forcing the spore cap off. Rain may splash sperm into the archegonium, or sperm may swim to the archegonium.
Spore banking Ribbed bog moss may germinate from spores stored in the substrate, but banked spores are probably less important to ribbed bog moss regeneration than freshly dispersed spores. Ross-Davis and Frego found that annual dispersal deposited a far greater number of moss spores on boreal substrates compared to the number of spores buried in the spore bank.
Breeding system Ribbed bog moss is
dioecious.
Sporophyte development Ribbed bog moss's sporophyte generation develops from the fertilized egg. Eggs are fertilized within the archegonium. The sporophyte
embryo grows rapidly, differentiating into foot, stalk, and capsule tissue. Spores develop within the capsule.
Vegetative regeneration Ribbed bog moss
reproduces asexually from specialized gametophyte tissues and from plant breakage. It reproduces frequently from gemmae. Ribbed bog moss may also regenerate when
paraphyses (minute filaments arising from ribbed bog moss's antheridia) detach. In the laboratory, 12.5% of detached ribbed bog moss
paraphyses developed into
propagules. Ribbed bog moss establishes readily when chunks of ribbed bog moss shoots are moved to new sites by soil movement or transplanting. Ribbed bog moss is apparently competitive in its ability to establish from stem chunks. In a laboratory experiment, ribbed bog moss that was collected from an
Alberta peatland, shredded, and placed on a peat substrate showed greatest frequency (100%) of 4 moss species so treated. Ribbed bog moss also showed fastest growth relative to the other mosses throughout the 125-day experiment.
Growth Ribbed bog moss growth is robust. It showed a "tall and dense growth habit" in a greenhouse common garden; ribbed bog moss,
juniper hair cap moss (
Polytrichum juniperinum), and
papillose sphagnum (
S. papillosum) crowded out 3 other moss species. Dry climate slows or stops ribbed bog moss growth. On the Boreal Ecosystem Research and Monitoring Sites study area in
Saskatchewan, ribbed bog moss had a negative mean annual growth rate in a
drought year (2003). Mean annual growth rate in a wet year (2004) was 2.7 mm. Ribbed bog moss was sensitive to saturated conditions in the wet year; stem lengths were greatest on relatively drier microsites, and ribbed bog moss growth rate increased slightly with increasing depth to the water table.
Site characteristics Ribbed bog moss is a habitat generalist. It was, for example, 1 of 6 mosses having broad
ecological amplitude in a survey of bryophyte habitats on peatlands across Alberta's
Mackenzie River basin. Ribbed bog moss tolerates a wide range of moisture levels, substrates, nutrient loads, terrain, and climates.
Moisture regime Ribbed bog moss generally grows on wetlands including fens, bogs, marshes, pond margins, streambanks, wet meadows, and riparian shrublands. In subalpine fir forests of central
Idaho, ribbed bog moss occurs on seeps and springs that remain moist throughout the fire season. Ribbed bog moss is an
indicator species of wet to very wet soils in Canada. In northern British Columbia, ribbed bog moss is an indicator species of undisturbed wet conifer sites. The white spruce/field horsetail/ribbed bog moss association occurs on the wettest white spruce forests in subboreal British Columbia; the
water table is near the soil surface for most of the growing season. In a
geothermal meadow in
Haida Gwaii, British Columbia, ribbed bog moss occurred on sites with high local
humidity (31-66%) due to nearby
thermal pools. Ribbed bog moss did not grow on dry sites, although drained microsites may favor ribbed bog moss growth on otherwise saturated substrates. Ribbed bog moss does not tolerate salt spray, which prevents its establishment on coastal dunelands. Ribbed bog moss is not confined to wet sites in all areas. Some forests with ribbed bog moss dry in late summer, and ribbed bog moss grows on relatively xeric hummock mounds on bogs in
Birds Hill Provincial Park,
Manitoba. Ribbed bog moss occupies both dry and wet sites on the Boreal Ecosystem Research and Monitoring Sites study area. It dominates relatively dry, shaded microsites in the area; the water table is below ground, and there is 30% to 60% black spruce and/or tamarack cover.
Substrates Ribbed bog moss is primarily a ground-layer species, but it does not require a particular substrate to establish and grow. It is most common on peat but also grows on thinner organic soils and other substrates. Ribbed bog moss frequently grows on peat overlying permafrost in Alaska and northern Canada. On northern peatlands, the peat layer generally ranges from thick, and organic content of the soil layer is high. Studies on peatlands in Quebec showed ribbed bog moss "preferred sites with high organic matter depth" (P2 inches (0.63–5 cm)). Ribbed bog moss grew on peat of all particle sizes but was most frequent on small () peat particles.
Water and substrate chemistry The
pH of water, peat, and/or soil is usually acidic to neutral in mires with ribbed bog moss, although ribbed bog moss tolerates mildly alkaline conditions. For example, ribbed bog moss grows in extremely acidic peatlands overlying permafrost in spruce taiga of Alaska but also grows in calcareous bogs in Birds Hill Provincial Park. In Minnesota, ribbed bog moss is reported from bogs ranging from 5.0 to 7.3 in pH. A survey of bryophytes on peatlands across Alberta's Mackenzie River basin found ribbed bog moss was abundant on sites ranging from 4.5 to 7.5 in pH. Mires are classified on pH and mineral gradients from extreme-poor (very strongly acid and low in
calcium and
magnesium) to extreme-rich (neutral to alkaline and high in calcium and magnesium). Fens are richer than bogs. Ribbed bog moss occurs in poor and rich mires. On mires across British Columbia and Alberta, ribbed bog moss grows in mires with broad ranges of water pH and
electrical conductivity, but is most common on strongly acidic peatlands (water pH ) sites that remain snow-free most of the year.
Climate Ribbed bog moss occurs in arctic, subarctic, boreal, and subboreal zones with cold meso-thermal,
oceanic,
continental, or cold-humid climates. It is more common in arctic, subarctic, and boreal than subboreal zones. A survey of bryophytes on peatlands across Alberta's Mackenzie River basin found optimal ribbed bog moss growth occurred on sites with annual temperatures ranging from . In interior arctic, subarctic, and boreal zones, climate is strongly continental in the west, becoming more humid to the east. Climate shift from continental to humid generally occurs near
Hudson Bay and
Lake Superior. In a study of moss habitats across British Columbia, Alberta, and Manitoba, ribbed bog moss was an indicator species for continentality of climate: it was the only moss common to all continental peatlands surveyed. On sites from coastal British Columbia to central Alberta, ribbed bog moss was most common on subcontinental sites (intermediate between coastal and continental climates). Ribbed bog moss was intermediate on gradients ranking breadth of moss habitat
niches. Climate factors evaluated included length of growing season, amount of precipitation during the growing season, temperature, and aridity.
Feather mosses (Hylocomiaceae) and sphagnum mosses generally had wider niches and dominated more sites than ribbed bog moss. Ribbed bog moss's rarity on all but cold sites in the lower 48 states suggests that ribbed bog moss does not tolerate long periods of warm weather. In a geothermal meadow on Queen Charlotte Island, British Columbia, ribbed bog moss was absent from sites where nearby thermal pools raised local soil temperatures above . ==Uses==