Ecological dynamics

Ecological Dynamics of the Site
This ecological site is found at low elevations, ranging from 1,100-1,400 meters (3,600-4,600 feet) high, on very low to moderate slopes with all aspects on terraces in valleys. The terraces mainly consist of outwash or stream terraces. This site can also occur on ground moraines. This ecological site is at lower elevations than the warmest coniferous zone dominated by ponderosa pine.

State 1.0: Historic Reference state with no weedy species present.
Richardson’s needlegrass (Achnatherum richardsonii)-rough fescue (Festuca campestris)-Idaho fescue (Festuca idahoensis)/old man’s whiskers (Geum triflorum)-sticky purple geranium (Geranium viscosissimum)

The Montane Loamy Outwash Terrace ecological site is dominated by a mixture of native, perennial, cool-season tufted bunch grasses. These grasses include rough fescue (Festuca campestris), Idaho fescue (Festuca idahoensis), Richardson’s needlegrass (Achnatherum richardsonii), bluebunch wheatgrass (pseudoroegneria spicata), timber oatgrass (Danthonia intermedia), and prairie Junegrass (Koeleria macrantha). These grasses can occur in varying amounts of cover, but generally are dominated by rough fescue, Richardson’s needlegrass, and Idaho fescue. The grasslands in western Montana, in general, are considered unique in that they have similar species to both grasslands of eastern Washington and northern Idaho (Palouse Region grasslands) as well as northern grasslands in Canada (Alberta fescue grasslands). Associated montane forbs include yarrow (Achillea millefolium), sticky purple geranium (Geranium viscosissimum), old man’s whiskers (Geum triflorum), northern bedstraw (Galium boreale), and yellow penstemon (Penstemon confertus). Shrubs with very low cover occur, including kinnikinnick (Arctostaphylos uva-ursi), serviceberry (Amalanchier alnifolia), shrubby cinquefoil (Dasiphora fruticosa), sulphur-flower buckwheat (Eriogonum umbellatum), common juniper (Juniperus communis), creeping barberry (Mahonia repens), Woods’ rose (Rosa woodsii), snowberry (Symphoricarpos albus), mountain big sagebrush (Artemisia tridentata var. vaseyana) and western snowberry (Symphoricarpos occidentalis). Only kinnikinnick occurs in any abundance, forming low-growing clumps. Some tree species occur in very low cover (1 percent canopy cover at 18 percent of the 22 sites visited). Conifer encroachment by lodgepole pine (Pinus contorta) usually occurs along the edges of the prairie.

Big Prairie along the North Fork of the Flathead River in Glacier National Park is an excellent example of this site. This prairie has the highest number of microhabitat types for a grassland in this area, due to differential accumulation of glacio-alluvial material and the mix of subtle river swales and depressions on this former glacial outwash floodplain (Koterba and Habeck, 1971). Koterba and Habeck found in their ordination study of North Fork grasslands that species distribution was grouped by available soil moisture and soil attributes. Drier sites with available soil moisture of 17.7 percent and 60-70 percent sand and 5-10 percent clay had more bluebunch wheatgrass. Bluebunch wheatgrass usually is associated with drier areas and south facing aspects, but has very broad range of osmoregulation and can grow in a variety of sites.
Areas with higher available soil moisture of 31.3 percent and less sandy soils (40-50 percent) had a higher proportion of rough fescue. Idaho fescue, timber oatgrass, and prairie Junegrass were found throughout. They surmised that the development and maintenance of the North Fork grasslands are attributed to the local climate (the “rain shadow effect” of the Whitefish Range), soil texture (coarse subsoil materials), and a long history of fire. The U.S. Forest Service (USFS) Fire Effects Information System (FEIS) evaluates the fire regime for northwestern montane and foothill grasslands with a fire interval of 9-66 years, with 43-100 percent of the fires occurring as replacement severity and 0-57 percent of fires as mixed severity, and 0-35 percent of the fires as low severity. The National Park Service (NPS) generally states that the historic mean fire return interval for the Big Prairie specifically is 9-26 years (Barrett, 1983). The policy of full fire suppression resulted in an absence of fire for 77 years, with a concomitant increase in the encroachment of lodgepole pine (Pinus contorta) upon the prairies during this period. The NPS fire management process is to actively try to return the area to close to the historic fire return interval through the prescribed fire program (NPS Fire Ecology Annual Report (2014) and Prescribed fire in the North fork Grasslands of Big Prairie poster (Fire Effects Program, Glacier NPS, ). In October of 1996, a prescribed fire was conducted. The NPS objectives are to maintain existing native species without introducing an inordinate number of non-native species, and to reduce overstory and pole sized trees by 30-70 percent within five years postburn. Post fire analysis showed there was minimal change in relative cover of native and nonnative species, the overstory and pole-sized density was reduced, but the seedling establishment increased and requires further prescribed burning.

Species Descriptions of Dominant Grasses
Rough fescue is a native, cool-season, perennial bunchgrass that produces thick mats of persistent sheath and stem bases and culms that grow to 3.5 feet, and leaf tufts that grow to 16 inches in height (Cronquist, 1977). It has extensive fibrous roots to a depth of 4 feet, 73 percent of which are concentrated in the top 6 inches of soil (Coupland, 1953). Rough fescue regenerates from seed, tillers, and sometimes creeping rhizomes (Pavlick, 1984). It is well adapted to a short growing season by initiating growth following snowmelt, and completes growth before the onset of summer drought. It is very productive and highly palatable to livestock and wildlife. Rough fescue is used by bighorn sheep, mule deer, elk, and bison. It is resistant to moderate grazing, but heavy grazing can result in severely decreased root depth and biomass (Aiken, 1990). Grazing can cause a general decline in rough fescue coverage, and it is one of the first species to decline with a concomitant increase of common increaser species, such as Idaho fescue, needlegrass species, prairie Junegrass, and Parry’s oatgrass.
Rough fescue and elk sedge are considered very resistant to human trampling due to its tough core of the tuft, according to D. Cole of the USFS in his study of recreational human trampling effects on habitat types in western Montana. The majority of the loss of cover, a reduction of 50percent, occurred in the first 400 passes. Thereafter, cover loss was stabilized from 400-800 passes. The community of rough fescue-timber oatgrass is considered very resistant to both light and heavy trampling (Cole, 1987).
Rough fescue is well adapted to periodic burning and resistant to light fire because of their dense, tufted habit. It sprouts from surviving residual plants and colonizes from off-site wind-dispersed seed. Fire may top-kill plants, but normal cover and production usually is attained in 2-3 years post-fire. Severe damage can occur by hot, mid-summer wildfires (Wright, 1982).

Idaho fescue is a long-lived native perennial cool-season bunchgrass. It is densely tufted with fine leaves. The root system is strong and can extend 16 inches deep (Hanson, 1959). In well drained soils, the root biomass is greatest at depths of 2-4 cm. Reproduction is from seeds and tillers, although seed production is variable (Stubbendieck, 1992). Idaho fescue is found in more mesic grasslands and is considered a climax species. It can survive fires of light severity, but usually is harmed by more severe fires (Smith, 1981). Fire return intervals of 10-25 years have neutral to negative effects. Rapid tillering of Idaho fescue occurs where root crowns are not suppressed and soil moisture is favorable. Plants may re-establish from seed after fire if the burn temperatures are low enough to allow for survival of seed in the soil. Idaho fescue can decrease with heavy grazing or severe fire and be succeeded by native and non-native increaser species including poa and needlegrass grass species, sagebrush, lupine, phlox, and the invasive timothy (Phleum pratense) (Eckert, 1987). Idaho fescue is an important forage species for livestock (cattle, sheep, and horses) and wildlife species including elk and mule deer (Mueggler, 1980). It is particularly important in elk diets throughout the Rocky Mountain region.

Richardson’s needlegrass is a native perennial cool-season bunchgrass with fine stems. It is shallow-rooted and clay accumulation can restrict roots (Lackschewitz, 1991). Richardson’s needlegrass becomes dormant following the depletion of surface soil moisture during the latter part of the growing season (Nimlos, 1968). It reproduces by seed and is wind- and animal-dispersed (Tyser, 1990). Richardson’s needlegrass is considered an obligate climax species, meaning it is co-dominant with another grass (Koterba, 1971). In general, perennial needlegrasses are among the least fire-resistant of the bunchgrasses, especially with midsummer burns: the accumulated dead culm and leaves makes them more susceptible to burning. Perennial needlegrasses often survive low-intensity fires as the heat is not transferred below the soil surface, only top-killing plants (Wright, 1965). Richardson’s needlegrass is an important forage species for livestock and wildlife especially deer, bighorn sheep, and elk.

Hansen et al. (1995) found that Idaho fescue is good for cattle, horse, and sheep forage: it has high energy value and medium protein values in the fall and winter. Sticky geranium is good sheep forage, but only fair for cattle and horses: it has low energy and protein values in fall and winter. Sticky geranium also is considered good food value for elk and whitetail and mule deer, but poor for antelope and for bird species. Old man’s whiskers (Geum triflorum) is considered fair to poor forage for cattle, sheep, and horses. It contains low energy and protein values in fall and winter. It has fair to poor food value for elk, whitetail and mule deer, and antelope, and also for bird species.

The NPS fire effects crew has established monitoring plots pre- and post-prescribed fire burns. These also are located within Big Prairie, which is where the reference sites are for this ecological site. The NPS established thirteen plots with the same dominant bunchgrass species found within this ecological site, and it is assumed that these plots occur within this ecological site. The composition of each site varies, with some dominated by rough fescue with a lower canopy cover of associated grasses including Idaho fescue, Richardson’s needlegrass, timber oatgrass, prairie Junegrass, and bluebunch wheatgrass. There are weedy species recorded at these sites including redtop (Agrostis stolonifera), smooth brome (Bromus inermis), Canada thistle (Cirsium arvense), butter and eggs (Linaria vulgaris), hop clover (Medicago lupulina), common timothy (Phleum pratense), Kentucky bluegrass (Poa pratensis), sheep sorrel (Rumex acetosella), common dandelion (Taraxacum officinale), yellow clover (Trifolium aureum), red clover (Trifolium pratense), and common speedwell (Veronica arvensis). Of these weedy species, the only ones with cover over 10 percent were butter and eggs, hop clover, and yellow clover.

Effects of Land Management Practices On Ecological Dynamics And Invasive Species
Invasion Theory
Invasion of weedy species into native vegetation communities requires an understanding of the processes and mechanisms by which an invasion occurs. Resistance and resilience of the native community are essential elements in predicting the success of the invasion. There are two counter point theories on invasive species. The driver theory considers the invasive species to be driving species decline while the passenger model sees the invading species as filling in empty niches left by habitat alteration (Didham, 2005). The passenger model suggests that disturbance is the cause and if stopped, invasion can be reversed. Potential mechanisms of invasion include theories such as novel weapons, enemy release, competitive superiority, and manipulation of environment. Novel weapons include biological weapons or associations with micro-organisms that allow the invader species to either access new resources or steal them from indigenous plants (Tannas, 2011). Specifically, arbuscular mycorrhizal fungi may provide a substantial competitive advantage to spotted knapweed by carbon parasitism (Carey, 2004). In these cases, the invader uses these weapons to drive the invasion process. Enemy release describes the concept that once invader species are released from their native predator species or chemical warfare within their original community, they are more aggressive in their new community (Blumenthal 2006, Callaway and Aschelhoug 2000). The invader species may have characteristics that allow it to be more competitive than resident plant species such as grazing resistance, adaption to a harsh environment or another competitive ability (Tannas, 2011). Invading species can manipulate the environment to their advantage through resource competition. Mechanisms include modifying light interception, water uptake efficiency or change in soil water holding capacity, nutrient uptake and cycling (D’Antonio and Vitousek, 1992). The final outcome of invasion is establishment of the invading species which occurs as either dominance, coexistence, or exclusion from the indigenous plant community (Seabloom, 2003). D’Antonio and Vitousek (1992) stated grass invasions are particularly important because they are actively moved by humans and exotic grasses compete effectively with native species in many ecosystems. In addition, dominant grasses may change nutrient cycling, modify regional microclimates and alter fire dynamics.

Invasive Species Descriptions
Specifically, scientific literature on invasions by Kentucky bluegrass, smooth brome, spotted knapweed, leafy spurge and Canada thistle into rough fescue grasslands in Canada and Montana will be reviewed. Kentucky bluegrass invasion into rough fescue grasslands can take multiple pathways. Heavy grazing of rough fescue which reduces litter amount combined with timing of defoliation, winter versus growing season and abiotic factors like seasonal variation in soil moisture content can make native grasslands less resistant to invasion (Douwes, 2012, Tannas, 2012). Resilience of the native grassland is dependent on vigor and density of rough fescue and restoration establishment is more successful with cuttings and plugs than seeding (Tannas, 2011). Although, seeding rough fescue as a monoculture is effective (Sherritt, 2012). A study of grazing effects on a rough fescue at Stavely grassland, a Canadian research station, found that heavy grazing pressure by cattle resulted changes in plant species composition to an increase in shallow rooted species, less productive overall, but more resistant to grazing (Dormaar, 1990). In a study of seasonal biomass changes, Willms (1996) found that with grazing intensity the vegetation community composition shifted from one dominated by rough fescue to one dominated by parry oatgrass-Kentucky bluegrass in moderately grazed pastures to Kentucky bluegrass-sedge species in heavily grazed pastures. The rough fescue dominated community had the greatest forage value compared to communities resulting from moderate, heavy and severe grazing (Willms, 1996). More than 20 years of drastically reduced stocking rates were required to enable recovery (Willms, 1985). Soils associated with heavy grazing were transformed to a soil more characteristic of a drier microclimate (Johnston, 1962 and 1971), by reducing the thickness of Ah horizon, reducing percent organic matter and soil moisture and increasing soil temperature with grazing intensity. Heavy grazing also reduced the fertility and soil water holding capacity (Dormaar, 1998). Soil organic matter, and nutrient cycling differed between grazed and ungrazed rough fescue grasslands (Willms, 1988). At a watershed scale, heavy grazing lead to larger summer storm and spring snow melt runoff compared to watersheds with less grazing (Chanasyk, 2002). The quantity and quality of surface runoff from these watersheds showed that grazing posed little risk of nutrient contamination of adjacent streams (Mapfumo, 2002). There was less snow accumulation in heavily and moderately grazed watersheds (Willms, 2006). A study on the effects of grazing on germinable seeds found that soil disturbance in fescue grassland is more likely to lead to a seral community dominated by annual broad-leafed plants, than a rough fescue dominated grassland (Willms, 1995). Skim grazing (light, once-over-spring defoliation) by cattle was not conducive to rough fescue conservation (Moisey, 2005). Rough fescue tolerated light winter-early spring elk grazing but not heavy grazing (Thrift, 2013). A rough fescue grassland in Rumsey Block, Alberta Canada tolerated moderate grazing which resulted in a community co-dominated with shortbristle needle and thread while heavy grazing and/or moderate to major oil and gas disturbance crossed a threshold requiring complete eradication of species and reseeding (Desserud, 2014). Another study of effects of human caused disturbance in rough fescue grasslands in Manitoba Canada, found it depends on invasive species introduction history (Gifford, 2013). Kentucky bluegrass tolerates grazing and can increase in abundance after heavy grazing. Therefore, Kentucky bluegrass resided in historically grazed areas, while smooth brome occurred along roads. In a study of smooth brome on rough fescue grasslands in Saskatchewan Canada, found that it is likely the combination of traits of smooth brome (higher productivity, abundant production of lower quality litter, clonal growth, and greater nutrient uptake capability) that allows it to invade native prairie (Piper, 2015). Smooth brome had a consistent negative impact on community structure and function across 8 grasslands in Alberta Canada with the impact on native species richness higher in species rich areas, while impact on native biomass was larger in productive, warmer and more variable sites (Stotz, 2016).
The noxious weed spotted knapweed was found to strongly reduce the final biomass and reproduction of native Idaho fescue grasslands. An insect biocontrol agent had little effect on spotted knapweed, while a native fungal pathogen killed it in a common garden experiment in Missoula Montana (Ridenour, 2003). Perry (2005) found that invasion of grasslands by spotted knapweed are mediated by root exudation of catechin, a potent phytotoxin. Catechin resistance was positively correlated with mean seed mass for eight species identified as resistant: Mountain brome, curlycup gumweed, needle and thread grass, basin wildrye, cicer milkvetch, boreal sweetvetch, common blanketflower, and alfalfa. Perry (2005) further found that residual soil catechin may interfere with reestablishment of native grassland species even after spotted knapweed populations are controlled.
Leafy spurge has an extensive rhizomatous root system, potential allelopathic properties and all parts contain high starch latex which seals wounds and is a possible deterrent against insect attacks. Areas with leafy spurge invasion that have been treated with herbicide application and mechanical removal still had higher bare ground area, significantly lower soil arthropod densities and lower plant species richness and cover (Pritekel, 2006). Jordan (2008) found that invasive plants, specifically leafy spurge, smooth brome and crested wheatgrass, are capable of modifying soil microbiota to facilitate further invasion by conspecifics and other invasive species. These soil alterations have the potential to impede restoration of native communities after removal of an invasive species. Successional management may require repeated treatments to achieve a desired outcome. Pokorny (2009) found that while broadleaf herbicide applications decreased hoary cress, Canada thistle and undesired forbs within a leafy spurge invaded site, the results were temporary, and seeding was necessary for native species establishment.

STATE 1.0:
Historic Reference state with no weedy species present.
Richardson’s needlegrass (Achnatherum richardsonii)-rough fescue (Festuca campestris)-Idaho fescue (Festuca idahoensis)/old man’s whiskers (Geum triflorum)-sticky purple geranium (Geranium viscosissimum)
COMMUNITY PHASE 1.1: This community phase is dominated by rough fescue, Idaho fescue, or Richardson’s needlegrass. Other grass species that occur frequently and provide moderate cover include timber oatgrass and prairie Junegrass, and bluebunch wheatgrass in drier areas. Shrubs generally are very low and cover no more than 10percent of the site. Diverse montane meadow forbs are associated with this site. Tree encroachment is very low, mainly consisting of lodgepole pine at the edges of the prairie.

COMMUNITY PHASE 1.2: This community has sustained shrub or tree encroachment due to a lack of fire. Likely shrub species to encroach on this community include serviceberry, kinnikinnick, sagebrush, shrubby cinquefoil, common juniper, Wood’s rose, snowberry, western snowberry, and dwarf bilberry. The tree species that encroach primarily are lodgepole pine.

Community Phase Pathway 1.1.A
This pathway represents a significant time without fire, so that the historical fire return interval is lengthened and shrub and conifer species invade.

Community Phase Pathway 1.2.A
This pathway represents a resumption of historic fire return intervals, so that woody shrub and conifer encroachments are suppressed and grasslands are sustained.


STATE 2.0:
Current Reference state with weedy species present at a very low canopy cover value.
Richardson’s needlegrass (Achnatherum richardsonii)-rough fescue (Festuca campestris)-Idaho fescue (Festuca idahoensis)/old man’s whiskers (Geum triflorum)-sticky purple geranium (Geranium viscosissimum)

COMMUNITY PHASE 2.1:
This community phase is dominated by rough fescue, Idaho fescue, or Richardson’s needlegrass. Other grass species that occur frequently and provide moderate cover include timber oatgrass and prairie Junegrass, and bluebunch wheatgrass in drier areas. Shrubs generally are very low and cover no more than 10percent of the site. Diverse montane meadow forbs are associated with this site. Tree encroachment is very low, mainly consisting of lodgepole pine at the edges of the prairie.

COMMUNITY PHASE 2.2: This community has sustained either severe drought or heavy grazing, which has reduced the cover and vigor of rough fescue and increased the cover of Idaho fescue, needlegrass species, and prairie Junegrass. If these native bunchgrasses decreased significantly, then a transition would occur out of this State 1.

COMMUNITY PHASE 2.3: This community has sustained shrub or tree encroachment due to a lack of fire. Likely shrub species to encroach on this community include serviceberry, kinnikinnick, sagebrush, shrubby cinquefoil, common juniper, Wood’s rose, snowberry, western snowberry, and dwarf bilberry. The tree species that encroach primarily are lodgepole pine.

Community Phase Pathway 2.1.A
This pathway represents heavy grazing or improper grazing management for sustained periods of time.

Community Phase Pathway 2.2.A
This pathway represents a ceasing of heavy grazing or improper grazing management for sustained periods of time.

Community Phase Pathway 2.1.B
This pathway represents a significant time without fire, so that the historical fire return interval is lengthened and shrub and conifer species invade.

Community Phase Pathway 2.3.A
This pathway represents a resumption of historic fire return intervals, so that woody shrub and conifer encroachments are suppressed and grasslands are sustained.

TRANSITION 1:
This represents the pathway from the historic Reference state in which there were no weedy species present in the vegetation community (State 1.0), to the introduction and establishment of weedy species, even at very low canopy cover values, within the vegetation community of State 2.0.

TRANSITION 2:
This pathway represents weed infestation from human, animal, or transportation corridors that allow non-native species to invade and establish within the grassland to the degree that native grass species decline.

STATE 3.0:
This state represents the community with significant increase in weedy species and concomitant decrease in native grass species.
COMMUNITY PHASE 3.1:
This community phase is dominated by the weedy species phleum pratense, poa pratensis, taraxacum offinale and Centaurea stoebe with less amounts rough fescue, Idaho fescue, or Richardson’s needlegrass. Other grass species that occur frequently and provide moderate cover include timber oatgrass and prairie Junegrass, and bluebunch wheatgrass in drier areas. Shrubs generally are very low and cover no more than 10percent of the site. Diverse montane meadow forbs are associated with this site. Tree encroachment is very low, mainly consisting of lodgepole pine at the edges of the prairie.

COMMUNITY PHASE 3.2:
This community has sustained shrub or tree encroachment due to a lack of fire, and is dominated by the weedy species phleum pratense, poa pratensis, taraxacum offinale and Centaurea stoebe with less amounts of the native vegetation community of this ecological site found in 2.1. Likely shrub species to encroach on this community include serviceberry, kinnikinnick, sagebrush, shrubby cinquefoil, common juniper, Wood’s rose, snowberry, western snowberry, and dwarf bilberry. The tree species that encroach primarily are lodgepole pine.

Community Phase Pathway 3.1.A
This pathway represents a significant time without fire, so that the historical fire return interval is lengthened and shrub species invade. Weedy species are still present within the community.

Community Phase Pathway 3.2A
This pathway represents a resumption of historic fire return intervals, so that woody shrub and conifer encroachments are suppressed and grasslands are sustained.

RESTORATION 1:
This pathway represents proper grazing management that allows the cover and vigor of native bunchgrass, particularly rough fescue, to be restored. Other means such as chemical, mechanical, or biological may be needed to restore native bunchgrass species to dominance.