• GENERAL BOTANICAL CHARACTERISTICS
• RAUNKIAER LIFE FORM
• REGENERATION PROCESSES
• SITE CHARACTERISTICS
• SUCCESSIONAL STATUS
• SEASONAL DEVELOPMENT

GENERAL BOTANICAL CHARACTERISTICS:

Pinegrass is a native, perennial, rhizomatous grass. Culms are hollow and can reach up to 44 inches (110 cm) in height, but more typically grow 11 to 20 inches (30-50 cm) tall [65,146,154]. Dense panicles are 3 to 6 inches (7-15 cm) long. Pinegrass may produce moderate-sized clumps rather than single stems  and is referred to in the literature as a sod-former [30,147,149,154], particularly when the overstory is removed [135]. Rhizomes grow mostly in the top 2 inches (5 cm) of mineral soil [30,53,72]. Seed-producing plants usually grow in the open and  are somewhat tufted and erect, differing in appearance from the stemless, drooping form that usually grows in shade [147].

RAUNKIAER [115] LIFE FORM:

Hemicryptophyte
Geophyte

REGENERATION PROCESSES:

Pinegrass reproduces primarily through the lateral extension of rhizomes [30,143,150]. Pinegrass rarely flowers except in open areas or after removal of the forest canopy [34,36,82,120,147,154]. Seedlings reach reproductive age in 1 to 2 years [72]. Seeds are wind-dispersed and apparently do not persist in the soil [30,72,134].  Seeds germinate best on mineral soil [134]; stratification or scarification are not required, which may indicate that pinegrass seeds can germinate in the fall when an adequate supply of moisture is available and other conditions are suitable  [30]. 

SITE CHARACTERISTICS:

Pinegrass grows in open areas and under forest canopies from valley floors to subalpine zones. It tolerates mesic to dry sites and is found on all aspects [30,42,70,71,82]. Pinegrass is often found growing in extensive stands [82]. Some elevational ranges have been reported in the following states and province; 8,052 to 9,058 feet (2440-2745 m) in Utah [154], 2,700 to 7,800 feet (818-2363 m) in Montana [113], and 1,980 to 6,105 feet (600-1850 m) in the Similkameen Valley, British Columbia [97].

Pinegrass is found on a wide variety of parent materials and soils within its geographic range. Most often, soils are well drained, loamy to coarse-textured Luvisols and Brunisols [30]. In the Similkameen Valley of southern British Columbia, Douglas-fir/pinegrass habitats are wide ranging and have developed mostly on glacial till, glacial outwash, and alluvium. These soils are chiefly loams to sandy loams that are well drained and are rapidly permeable [97]. On pinegrass-dominated sites in the Garnet Mountains of western Montana, pinegrass cover is highest on limestone-derived soils, and the grass is found more often on limestone than on granitic parent materials. No significant difference was found between limestone- and quartzite-derived soils [55].

Throughout interior British Columbia, pinegrass occurs on sites with nutrient regimes that range from very poor to very rich. Soils supporting dense stands of pinegrass are often low in nitrogen. Pinegrass often grows on sites that experience at least a moderate moisture deficit during the growing season. Pinegrass is most abundant in the interior Douglas-fir zone, where it occupies extremely xeric to hygric sites [30].

SUCCESSIONAL STATUS:

Pinegrass is shade tolerant [34,98,149,154] and is persistent throughout all successional stages [35,51,86,113]. In many situations, pinegrass can maintain moderate cover under moderate shade conditions, but with increased light will acquire new vigor and dominate the herb layer [27,131]. Pinegrass generally produces seedlings only in natural forest openings or in openings created by disturbance [,34,36,114,131,143]. Pinegrass is an aggressive competitor for soil moisture [13,84,86] due to the fact that it undergoes rapid growth early in the season and has high soil water usage [84,124]. It is also capable of  photosynthesis at very low leaf water potentials (-3.5 mP) [13,124]. Pinegrass is resistant to disturbance and readily invades or resprouts on sites following logging or fire, often with an increase over predisturbance canopy cover [86,102,126,142].

Pinegrass is classified by various authors as a seral to climax species throughout its range. For example, pinegrass is considered seral in Engelmann spruce/queencup beadlily habitat types in Glacier National Park [5], in some Douglas-fir stands in interior British Columbia [146], in the Douglas-fir/Rocky mountain maple type in central Idaho [132], in many lodgepole pine stands [60,113,130], and in the subalpine fir/big huckleberry (Vaccinium membranaceum)-beargrass [126] and western hemlock habitat types in Idaho [158].

Over much of its range, pinegrass occurs as a climax understory dominant with Douglas-fir [31,37,51,60,83,97,109,113,134,146], and to a somewhat lesser extent with subalpine fir [94,98,114,131,] grand fir [51,131,135], and ponderosa pine [156]. Some quaking aspen/pinegrass communities in the Intermountain Region are considered climax on sites suitable for quaking aspen dominance, or may be seral to Douglas-fir/pinegrass or subalpine fir/pinegrass habitats, especially in the absence of fire [104,157].

SEASONAL DEVELOPMENT:

Pinegrass generally initiates growth in late April or early May and typically goes into dormancy by early August [1,98]. In a study on the growth and development of pinegrass in interior British Columbia, new stem initiation was completed by mid-May, and no new stem development occurred until fall. All measures of growth (leaf number, stem height, stem weight, and leaf blade area) indicated a cessation of growth in July [143]. Regrowth takes place in late August or early September, depending on site and timing of fall rains [1,98]. Although flowering is infrequent [143,147,154], it generally takes place July and August [71,110,144].

The following phenological observations were reported for pinegrass in the northern Rocky Mountains (dates given are means; east of Continental Divide includes Montana and Yellowstone National Park; west of Continental Divide includes Montana and northern Idaho) [119]:

Location	Growth starts	Leaves fully grown	Flowering starts	Flowering stops	Seeds ripe	Seed fall starts	Leaf fall begins	Leaf fall ends	1st frost injury
East of Divide	May 6	June 22	July 2	July 22	Aug. 6	Aug. 20	Aug. 21	Oct. 5	Sept. 3
West of Divide	April 19	May 30	May 30	July 2	July 14	July 28	Aug. 28	Sept. 26	Sept. 13

Related categories for SPECIES: Calamagrostis rubescens | Pinegrass