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Mountain woodsorrel. Creative Commons image by Jason Hollinger.



SPECIES: Oxalis montana
AUTHORSHIP AND CITATION: Pavek, Diane S. 1992. Oxalis montana. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: []. Revisions: On 1 June 2018, the common name of this species was changed in FEIS from: common woodsorrel to: mountain woodsorrel. Images were also added.
ABBREVIATION: OXAMON SYNONYMS: Oxalis acetosella L. Oxalis acetosella f. montana Raf. Oxalis acetosella var. rhodantha (Fern.) Knuth. NRCS PLANT CODE: OXMO COMMON NAMES: mountain woodsorrel common woodsorrel white woodsorrel wood shamrock TAXONOMY: The scientific name of mountain woodsorrel is Oxalis montana Raf., in the woodsorrel family (Oxalidaceae). There are no recognized subspecies or varieties. Mountain woodsorrel is closely related to the European species Oxalis acetosella. Some earlier authors included mountain woodsorrel as a variety of O. acetosella [10]. Two forms based on flower color are infrequently used [10]: Oxalis montana forma montana Oxalis montana forma rhodantha Fern. LIFE FORM: Forb FEDERAL LEGAL STATUS: No special status OTHER STATUS: NO-ENTRY


SPECIES: Oxalis montana
GENERAL DISTRIBUTION: In Canada, mountain woodsorrel occurs from Manitoba east to southern Labrador and south to Nova Scotia [32]. In the United States, its range extends from Minnesota across the North Central States to New England [22]. Its range continues south along the Appalachian Mountains to North Carolina and Tennessee [10,22].
Distribution of mountain woodsorrel. Map courtesy of USDA, NRCS. 2018. The PLANTS Database. National Plant Data Team, Greensboro, NC [2018, June 1] [40].

   FRES11  Spruce - fir
   FRES14  Oak - pine
   FRES15  Oak - hickory
   FRES18  Maple - beech - birch
   FRES19  Aspen - birch
   FRES23  Fir - spruce

     CT  DE  IL  IN  KY  ME  MD  MA  MI  MN
     NH  NJ  NY  NC  OH  PA  RI  TN  VA  WV
     WI  MB  NF  NS  ON


   K096  Northeastern spruce - fir forest
   K097  Southeastern spruce - fir forest
   K102  Beech - maple forest
   K104  Appalachian oak forest
   K106  Northern hardwoods
   K107  Northern hardwoods - fir forest
   K108  Northern hardwoods - spruce forest

     1  Jack pine
     5  Balsam fir
    12  Black spruce
    13  Black spruce - tamarack
    15  Red pine
    16  Aspen
    17  Pin cherry
    18  Paper birch
    19  Gray birch - red maple
    21  Eastern white pine
    22  White pine - hemlock
    23  Eastern hemlock
    24  Hemlock - yellow birch
    25  Sugar maple - beech - yellow birch
    28  Black cherry - maple
    30  Red spruce - yellow birch
    31  Red spruce - sugar maple - beech
    32  Red spruce
    33  Red spruce - balsam fir
    34  Red spruce - Fraser fir
    35  Paper birch - red spruce - balsam fir
    37  Northern white-cedar
    60  Beech - sugar maple
   107  White spruce


Mountain woodsorrel  is a dominant understory species in red spruce (Picea
rubens) and balsam or Fraser fir (Abies balsamea or A. fraseri) forests
of the Appalachian Mountains, which are part of the boreal forest
formation [29,34].  Mountain woodsorrel  is an indicator for several forest
habitat types or site types in the balsam and Fraser fir phases

Mountain woodsorrel  is dominant in the northern hardwoods forest, red or
sugar maple-yellow birch-American beech (Acer rubrum or A.
saccharum-Betula lutea-Fagus grandifolia) [7,24].  It is also a dominant
species in the transition plant associations between the boreal forest
and the northern hardwoods [19,37].  It is a minor component of the
riparian communities in the northern hardwood forests [6].

Mountain woodsorrel  is subdominant in seral communities of black cherry
(Prunus serotina)-red maple [36].  In northern Wisconsin, mountain
woodsorrel is a dominant forb in the association of eastern
hemlock-false lily-of-the-valley-goldthread (Tsuga
canadensis-Maianthemum canadense-Coptis groenlandica) [13,20].  In white
cedar (Thuja occidentalis) communities, mountain woodsorrel  is a minor
component with a corresponding low importance value of 0.4 [28].

Frequent herbaceous codominants are false lily-of-the-valley,
goldthread, starflower (Trientalis borealis), and woodferns (Dryopteris
spp.) [8,29,31,37,41].

Publications that list mountain woodsorrel  as a dominant herb are:
(1)  Field Guide: Habitat classification system for Upper Peninsula of
       Michigan and northeast Wisconsin [4]
(2)  Ground vegetation patterns of the spruce-fir area of the Great Smoky
       Mountains National Park [5]
(3)  The principal plant associations of the Saint Lawrence Valley [7]
(4)  Field guide to forest habitat types of northern Wisconsin [20]
(5)  Habitat classification system for northern Wisconsin [21]
(6)  Soil-vegetation relationships in northern hardwoods of Quebec [24]
(7)  A comparison of virgin spruce-fir forest in the northern and southern
       Appalachian system [29]
(8)  Vegetation, soil, and climate on the Green Mountains of Vermont [34]
(9)  Communities and tree seedling distribution in Quercus rubra- and Prunus
       serotina- dominated forests in southwestern Pennsylvania [36].


SPECIES: Oxalis montana
IMPORTANCE TO LIVESTOCK AND WILDLIFE: While mountain woodsorrel has not been investigated, other members of the woodsorrel family (Oxalis pes-capre and O. corniculata) form concentrations of soluble oxalates lethal to livestock under specific grazing conditions [18]. PALATABILITY: No information was available on this topic. NUTRITIONAL VALUE: No information was available on this topic. COVER VALUE: No information was available on this topic. VALUE FOR REHABILITATION OF DISTURBED SITES: Mountain woodsorrel is a soil stabilizer; it has extensive clonal growth and the ability to grow on steep ground, poor soil, and in deep shade [5,27,38,39]. In a Canadian northern hardwood-boreal transition forest, disturbed ground was mulched to suppress red raspberry (Rubus idaeus) growth [16]. Mountain woodsorrel appeared during the second growing season, despite the oat (Avena sativa) mulch. Because only plants with 10 percent or greater cover were recorded, it is likely that mountain woodsorrel was present the first year in low amounts [16]. OTHER USES AND VALUES: No information was available on this topic. OTHER MANAGEMENT CONSIDERATIONS: No information was available on this topic.


SPECIES: Oxalis montana
GENERAL BOTANICAL CHARACTERISTICS: Mountain woodsorrel is a native woodland perennial with well-developed clonal growth [1]. It is a small evergreen plant (less than 4 inches [10 cm] high) that has scaley rhizomes [23]. Mountain woodsorrel does not have a main stem. Leaves, with three cloverlike leaflets, are basal. The fruit is a round capsule [10,32]. RAUNKIAER LIFE FORM: Geophyte REGENERATION PROCESSES: Reproduction usually involves episodes of seedling recruitment as a result of disturbance, such as fire and logging, followed by long periods of vegetative clonal growth [1]. Mountain woodsorrel forms extensive colonies in boreal spruce-fir forests; however, its colonies rarely exceed several feet in diameter in the northern hardwood forests [35]. Mountain woodsorrel reproduces both sexually and asexually. Asexual flowers (cleistogamous) produce greater amounts of seed compared to sexual flowers [14]. Total fruit set per plant is low because there is only one flower per stalk, with a recorded maximum of 34 flowers per plant [1]. Mature capsules dehisce seeds forcefully, flinging them outward from the plant [14]. SITE CHARACTERISTICS: Mountain woodsorrel has wide ecologic amplitude and occurs commonly throughout the northern hardwood and spruce-fir (Picea rubens-Abies balsamea) forests of the Appalachian Mountains [35]. Some authors have stated that mountain woodsorrel occurrence is not correlated with any particular suite of site features [27,35]. Mountain woodsorrel is on the glaciated uplands of the Canadian shield [24]. The shallow soils are sandy loams to loamy tills [20]. Saturated soils may be poor to moderately well-drained [6,7]. However, soils are generally poorly developed and often consist only of an organic mat on top of bedrock [27,31]. Soil pH is strongly to moderately acidic [15,34,38]. Mountain woodsorrel occurs on level to steep slopes and any aspect [5]. Plants occur at 500 feet (152 m) in Maine coastal forests to 5,000 feet (1,524 m) in the Smoky Mountains of Tennessee [24,34,37]. The growing season throughout its range is from 110 to 140 days and is cool with ample moisture [8]. Snowpack in the subalpine zones can extend from November to May [31]. The average annual temperatures are less than 60 degrees Fahrenheit (16 deg C) [41]. Average annual precipitation is 90 to 140 inches (2,286-3,556 mm) per year [5]. The moisture regime is perhumid to humid [31]. Rainfall is equitable in all summer months. Fog drip from evergreen needles increases precipitation amounts [34]. Moss coverage can be low to high, and very high fern coverage reduces mountain woodsorrel populations [5]. Associated understory species include lowbush blueberry (Vaccinium angustifolium), witherod (Viburnum cassinoides), hobblebush (Viburnum alnifolium), and bunchberry (Cornus canadensis) [5,8,15]. Overstory species also include white ash (Fraxinus americana) and paper birch (Betula papyrifera) [31]. SUCCESSIONAL STATUS: Mountain woodsorrel is a climax understory species. It is a tolerant species under mature fir canopy [38,39]. Mountain woodsorrel is present in, although not characteristic of, early or mid- seral stages in New England's northern hardwood or spruce-fir boreal forests [35]. Disturbance occurs as severe winds, hurricanes, and fire [31]. SEASONAL DEVELOPMENT: Plant growth mainly occurs before flowers are out [14]. Sexual flowers on mountain woodsorrel bloom from late May to August throughout its range [10,23]. In a population, the flowering period lasts approximately 30 days with individual flowers open for about five days [14]. Fruits mature in about 12 days, requiring warm days before dehiscence [14]. Seed is shed from June to September throughout its range [14].


SPECIES: Oxalis montana
FIRE ECOLOGY OR ADAPTATIONS: Burning conditions are usually poor in the spruce-fir boreal forests in which mountain woodsorrel grows due to the presence of water throughout the year [17]. Droughts can make the areas more susceptible to fire. Fires may occur in the southern boreal forests every 50 to 150 years, and in the northern boreal forests, fire frequencies are every 100 to 300 years [17]. Mountain woodsorrel fire survival strategy is that of a perennial with underground rhizomes; surviving rhizomes sprout. However, it often grows in humus on bedrock in spruce-fir forests [27,31]. The organic layer does not give much protection from fire. No information was found about mountain woodsorrel seed surviving fire. FIRE REGIMES: Find fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find Fire Regimes". POSTFIRE REGENERATION STRATEGY: Rhizomatous herb, rhizome in soil Secondary colonizer - off-site seed


SPECIES: Oxalis montana
IMMEDIATE FIRE EFFECT ON PLANT: No fire studies have been done on mountain woodsorrel . Fire would top-kill this plant. Growing in mainly organic or shallow soils, its rhizomes probably would not survive a fire of moderate severity. DISCUSSION AND QUALIFICATION OF FIRE EFFECT: NO-ENTRY PLANT RESPONSE TO FIRE: Surviving rhizomes will sprout. Existing patches can expand to colonize open areas. Vegetative reproduction allows the population flexibility in initiating or stopping plant development. Since mountain woodsorrel can reproduce by asexual flowers, seed set is highly probable, despite a possible low initial population size. Dissemination by explosive dehiscence provides the ability to colonize open disturbed areas. When open ground has closed with vegetation, mountain woodsorrel colonies will continue to expand by rhizome growth (see SUCCESSIONAL STATUS). DISCUSSION AND QUALIFICATION OF PLANT RESPONSE: The Research Project Summary Effects of surface fires in a mixed red and eastern white pine stand in Michigan provides information on prescribed fire and postfire response of plant community species, including mountain woodsorrel, that was not available when this species review was written. FIRE MANAGEMENT CONSIDERATIONS: No information was available on this topic.


SPECIES: Oxalis montana
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Manual to accompany the map of potential vegetation of the conterminous United States. Special Publication No. 36. New York: American Geographical Society. 77 p. [1384] 23. Lakela, O. 1965. A flora of northeastern Minnesota. Minneapolis, MN: University of Minnesota Press. 541 p. [18142] 24. Lemieux, G. J. 1963. Soil-vegetation relationships in northern hardwoods of Quebec. In: Forest-soil relationships in North America. Corvallis, OR: Oregon State University Press: 163-176. [8874] 25. Lyon, L. Jack; Stickney, Peter F. 1976. Early vegetal succession following large northern Rocky Mountain wildfires. In: Proceedings, Tall Timbers fire ecology conference and Intermountain Fire Research Council fire and land management symposium; 1974 October 8-10; Missoula, MT. No. 14. Tallahassee, FL: Tall Timbers Research Station: 355-373. [1496] 26. Maguire, D. A.; Forman, R. T. 1983. Herb cover effects on tree seedling patterns in a mature hemlock-hardwood forest. Ecology. 64(6): 1367-1380. 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