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Wildlife, Animals, and Plants |
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BOTANICAL AND ECOLOGICAL CHARACTERISTICS
GENERAL BOTANICAL CHARACTERISTICS:Limber pine is a slow growing, long-lived species, sometimes taking several hundred years to reach maturity [26,75]. Mature trees may exceed 1000 years of age [53,96,127]. Limber pine stands are broadly even-aged [89], though populations also occur in uneven-aged stands and on very harsh sites as widely spaced, isolated individuals [96,102,112]. Trees often have an irregular or multi-stem growth form, and rarely reach over 50 feet (15 m) [11,120,127]. At high elevations they sometimes form krummholz [11,127]. Trunks may reach 6.5 feet (2 m) in diameter [41]. The species is cold and drought tolerant. Trees are ectomycorrhizal, have deep taproots, and are very windfirm [33,120]. Cones of limber pine are cylindrical, 3 to 6 inches (8-15 cm) long. They release their seeds if not preyed upon (see Regeneration section below). The seeds are large (7-12 mm long) and sometimes have a vestigial wing [21,63,74].
RAUNKIAER [88] LIFE FORM:Phanerophyte
REGENERATION PROCESSES:Limber pine reproduces entirely from seed; it does not layer lower branches in the soil [22,122]. Seeds are not effectively dispersed by wind. Small mammals and birds, especially Clark's nutcrackers and pinyon jays, disperse limber pine seeds [63,64,66,110,125]. The minimum seed-bearing age of limber pine ranges from 20 to 40 years. There are 2 to 4 years between large seed crops [58,59,101]. Seeds from krummholz trees have low germination potential [66]. Clark's nutcrackers have co-adapted an important mutualism with limber pine
and are the primary harvester and disperser of its seeds. Limber pine regeneration
on burns is largely from germinants of Clark's nutcrackers seed caches [63,64,66,110,125].
The birds begin harvesting seeds in late August, while the cones are still green and slightly closed. They remove the cones by pecking them loose,
fly them to perches, and peck between the scales to remove the seeds. As cones begin to open on the trees in September, Clark's nutcrackers remove exposed seeds.
An individual bird can store as many as 125 seeds in its sublingual pouch, then
flies to a cache area and deposits numerous caches from its pouchful of seeds. In a burned-over area in northern Utah,
Clark's nutcrackers cached an estimated 12,140 seeds per acre (30,000/ha) in 1 year [62,101,112].
SITE CHARACTERISTICS:Limber pine grows across a wider range of elevations that any other tree species in the central Rocky Mountains [94], inhabiting some of the driest sites capable of supporting trees [11,85,102,111]. In many high-elevation sites it occupies or forms the upper treeline [30,69,83,94,122], but in northern parts of its range it is found at low elevations along plains grassland edges [22,94,96]. It typically occurs on steep, rocky, well-drained, windswept, and nutrient-poor sites on exposed ridges and summits [1,10,11,32,42]. Limber pine is often reported growing on calcareous soil [11,19,85]. It is also reported on soils derived from many other types of parent material [12,17,23,42,68,101]. Ground cover and litter accumulation in limber pine stands are often sparse, accumulating only under individual trees [11,127]. Severe sheet erosion of fine particles often occurs from summer convection storms over sparsely vegetated sites. Snowpack accumulations on limber pine sites may be light as a result of high insolation and winter winds [127]. Site preference often separates limber pine and whitebark pine, which is ecologically similar in many respects [112]. Limber pine has a wider geographical distribution and altitudinal range than whitebark pine. Relative to whitebark pine, limber pine occurs on warm, dry sites at low and middle elevations. Where their ranges overlap, the 2 species sometimes grow together on droughty soils. Occasionally, limber pine grows at higher elevations than whitebark pine. South of the range of whitebark pine in California, Colorado, Nevada, and southern Wyoming, the more drought-resistant limber pine replaces whitebark pine and may form the alpine treeline [74,112,121]. Elevations reported in the literature for limber pine are as follows: 7,500 to 11,000 feet (2,290-3,350 m) in California [80] 5,000 to 12,500 feet (1,500-3,800 m) in Colorado [27,42,49] 4,000 to 6,000 feet (1,200-1,800 m) in Montana [85,91] 6,500 to 11,500 feet (2,000-3,500 m) in Nevada [114] 5,000 to 7,000 feet (1,500-2,100 m) in Oregon [19] 6,000 to 11,600 feet (1,830-3,540 m) in Utah [123]
SUCCESSIONAL STATUS:According to Tomback and Linhart [112] limber pine (and whitebark pine) "are pioneering species that are either seral or topoedaphic climax species under different environmental conditions. In fact, seed dispersal by Clark's nutcrackers to outlying sites, treeline, and other harsh environments essentially increases the ecological niche breadth (in the Hutchinsonian sense) of these species. Clark's nutcrackers can maintain climax communities, colonize previously unforested sites, or initiate succession." The later stages of succession in xeric subalpine forests vary due to differences in sites and seed availability. In the Colorado subalpine, Rebertus and others [89] studied conifer population age structure and succession on 3 burns greater than 100 years old. The sequence of conifer colonization appeared to be consistent: 1st limber pine, then Engelmann spruce, and later subalpine fir, with a delay between the 1st limber pine and later subalpine fir of as long as 140 years. The authors suggested that the early advantage of limber pine was due to avian seed dispersal and exceptional drought tolerance in seedlings. Spatial analysis suggested that limber pine facilitated the establishment of the other 2 species by providing shade or wind protection. On the xeric to slightly xeric sites, limber pine formed broadly even-aged, non-regenerating populations that were gradually replaced by the spruce and fir. On the most extreme sites, limber pine formed all-aged, self-maintaining populations with no evidence of replacement by the other species. The authors note that in lower elevation stands along the Front Range, limber pine is successional to Douglas-fir. In the even lower Pawnee National Grasslands of Colorado, limber pine forms all-aged, self-replacing populations. "Hence, many successional pathways could be operating at different sites or stages in stand development."
SEASONAL DEVELOPMENT:Limber pine cones ripen from August to September, and seeds are dispersed from September to October [26,44,58,59]. Cones open in the fall. Observed dates for phenological events of mature in limber pine east of the Continental Divide in Montana and Yellowstone National Park, Wyoming, are given here [93]: Shoots start: April 30 to June 6 Buds burst: April 30 to June 26 Pollen starts: June 20 to July 14 Pollen ends: July 4 to July 22 Shoots end: June 22 to August 5 Winter buds formed: June 11 to August 16 Cones full size: August 15 to August 16 Cones open (seed dispersal): August 23 to August 30 Please refer also to the Regeneration Processes section above regarding pollen phenology.
Related categories for SPECIES: Pinus flexilis | Limber Pine |
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