3.2.3 Cumulative Effects (Riparian) - a123.g.akamai.neta123.g.akamai.net/7/123/11558/abc123/forestservic.download.akamai.com/... · 3.2.3 Cumulative Effects (Riparian) Other events

Grand River Ranger District – Allotments 1- 5 Vegetative Management Environmental Assessment

61

3.2.3 Cumulative Effects (Riparian)

Other events within the cumulative-effects area may also influence riparian conditions on the project

area’s National Forest System lands. The location of those events would largely determine their

impact, with actions happening immediately upstream having the greatest influence, while actions

happening downstream, far away, or in different watersheds having less influence. The impact of

those events would also be determined by pre-existing stream condition, as streams that are in Proper

functioning condition are better able to handle increased impacts than are streams in poor condition.

For example, a particularly violent thunderstorm might cause only minor changes to a stream in

Proper functioning condition, but severely degrade an already impaired stream.

The past and present factors that have had the most influence on project area riparian areas are:

upstream reservoir creation (which has changed downstream hydroperiod, sediment transport, ion

balance, etc.), livestock grazing

(which has a variety of effects as

already discussed), and land

conversion.

The reasonably foreseeable events

with the greatest potential to

degrade project area stream

habitat quality would be the

additional conversion of

surrounding private lands from

native prairie to cropland; or from

Conservation Reserve Program

fields to cropland. As already

noted (p. xx), the likely extent of

additional land conversion within

the cumulative-effects area is

unknown, so only qualitative

conclusions can be made

regarding its likely impacts to

local streams. Any additional loss

of perennial grass cover would

result in increased soil erosion and

decreased soil moisture in the uplands and riparian areas; and decreased hydroperiod, increased

turbidity, and increased average water temperatures in the streams themselves. These impacts

would be particularly evident under Alternative A, as that alternative proposes no remedial actions to

reduce the similar impacts currently occurring on National Forest System lands from livestock

grazing. Conversely, the impacts from additional land conversion would be less evident under

Alternatives B and C, and least evident under Alternative D, as those alternatives propose extensive

remedial actions (ranging from creating riparian exclosures to ceasing livestock grazing; see p. xx to

xx) for the intermingled National Forest System lands.

Figure 42. Beaver dam. Beaver dams have increased the hydroperiod, enhanced

infiltration of streamflow into the banks, and improved growing conditions for

riparian plants. Humphrey Draw Wildlife Area, Grand River National Grassland,

Perkins Co., SD. May 2008. Photo by Mark Gonzalez.


62

Another particularly important reasonably foreseeable event regards the role of beaver (Figure 42).

Beaver have an overall beneficial effect on streams by stabilizing banks, raising water tables,

increasing above- and below-ground water storage, extending the hydroperiod, decreasing stream

power, and slowing sediment transport. Beaver populations are likely to continue to increase in the

project area under all alternatives, due to relatively low trapping levels (Doug Backlund, South

Dakota Game, Fish, and Parks Department, pers. comm.). However, beaver are not now, and will

not be, evenly distributed throughout the Allotments 1-5 project area. Beaver are most likely to

impact the largest and most-watered streams and stream segments in the project area. For example:

beaver colonization in Allotment 2A is more likely to occur along mainstem Horse Creek than it is

along either of the unnamed tributaries in Section 18 (Figure xx).

Just as beaver affect the quality of riparian habitat available for other land uses, other land uses

affect the quality of riparian habitat available to beaver. For example, beaver occupancy of streams

containing few riparian shrubs, high sediment loads, and widely fluctuating hydroperiods, will be

shorter than their occupancy of streams containing extensive riparian shrubs, low sediment loads,

and stable hydroperiods. Because of this, the interaction between beaver and Alternative A is

expected to result in lower riparian habitat quality on the project area’s National Forest System lands

than would the interaction between beaver and Alternatives B, C, and, especially, Alternative D.

This is due to the beneficial direct and indirect impacts to riparian habitat quality that are anticipated

under Alternatives B, C, and D (see discussion, p. xx to xx).

It is considered very likely that present livestock grazing would continue on neighboring land

ownerships under all alternatives. In general, that grazing is not focused on maintaining or

improving Proper functioning condition along project-area streams. Nevertheless, a cursory

examination of such streams from public roadways indicates many likely are in Proper functioning

condition. We have no indication that significant changes in that management would occur within

the reasonably foreseeable future under any alternative. Therefore, private land grazing is expected

to continue to make a relatively minor cumulative impact to project area stream habitat quality under

all alternatives.

It is likely that severe weather events would occur in the cumulative-effects area during the next 15

years. These events, while natural and considered part of the baseline conditions, would nonetheless

exacerbate any existing degradation occurring as a result of proposed activities. Furthermore, any

expected improvements in riparian conditions as a result of the remedial actions proposed under

Alternatives B, C, and D could be retarded by drought or accelerated by above-average precipitation.

As discussed above, the effects of severe weather events would be most apparent under Alternative

A (because it would result in the lowest extent of Proper functioning condition streams), and least

apparent under Alternative D (because Alternative D would result in the greatest extent of Proper

functioning condition streams at the fastest pace, and thus provide the greatest ―buffering‖ possible).


63

3.3 Key Issue: Native Vegetation

During scoping, several

comments were received about

the project area’s vegetation.

Several hundred vegetative

species occur within the

Allotments 1-5 project area

(Hansen 2008), including both

native and non-native taxa. The

following discussion will focus on

the native graminoids (i.e. grasses

and sedges) and native trees and

shrubs. See p. 83 to 96 for

discussion of non-native

vegetative species.

3.3.1 Existing Condition (Native Graminoid Composition)

As noted earlier, the project area’s native vegetation (Figures 1, 9, 10, 21, 44) is typical of northern

mixed-grass prairie. Graminoids characterize the majority of the area, with cool-season species

being the most abundant.

The potential native climax

vegetation in the project area varies

by soil type. For example, on sandy

soil sites, prairie sandreed

(Calamovilfa longifolia),

needleandthread (Hesperostipa

comata), and little bluestem

(Schizachyrium scoparium) are

usually dominant. Clay and silty (or

―loamy‖) sites are typically

dominated by western wheatgrass

(Pascopyrum smithii),

needleandthread, and green

needlegrass (Nassella viridula).

Little bluestem is dominant on

shallow soil sites; whereas big

Figure 43. Native grasses and forbs. Humphrey Draw Wildlife Area,

Grand River National Grassland, Perkins County, June 2007. Photo by

Mark Gonzalez.

Figure 44. Native northern mixed-grass prairie. Grand River National

Grassland, Perkins Co., SD. Undated. File photo.


64

bluestem (Andropogon geradii) and western wheatgrass are dominant on overflow sites (see

Grasslands Plan p. 2-4 to 2-6 for more information). These mid-height and tall graminoid species

are desired for ecological, biological, pedalogical (i.e. soils), and forage production reasons.

A variety of graminoid composition data has

been collected in the project area since the

Grand River National Grassland was

designated in 1960 (Figure 45). Range

vegetative community maps, for example,

were created for most of the project area’s

grazing allotments in the 1970s or 1980s.

These maps delineated the major vegetative

communities and identified the dominant and

co-dominant species present (Figure 46).

Figure 45. Vegetative sampling plot, Allotment 1A, Grand River

National Grassland, Perkins Co., SD. August 1968. File photo.

Figure 46. Excerpt of a range vegetative community map created in May 1981

by Steve Kerpan, Grand River Ranger District. Map shows a part of Allotment

2C - east. Four-letter codes refer to scientific names of dominant and

codominant species [Agcr: crested wheatgrass (Agropyron cristatum), Agsm:

western wheatgrass, Bogr: blue grama (Bouteloua gracilis), Dist: inland saltgrass

(Distichlis spicata), Stco: needleandthread, Stvi: green needlegrass]. Single letter

codes refer to vegetation and soil conditions and trends: E: excellent, G: good, F:

fair, P: poor. Numerator describes vegetative condition, denominator describes

soil condition. Up arrow denotes improving trend, down arrow denotes

degrading trend, horizontal arrow denotes static trend.


65

In the early 1980s an ecological study of the Grand River Ranger District’s vegetation was

conducted (Hansen and Hoffman 1985) to classify habitat types based on soil and climatic data. The

following habitat types were found and described: needleandthread/threadleaf sedge, western

wheatgrass/threadleaf sedge, little bluestem/threadleaf sedge, prairie sandreed/sun sedge, green

ash/chokecherry, western snowberry, and buffaloberry. Hansen and Hoffman (1985) determined

that in heavily grazed areas, the graminoid vegetation was at a low to mid-successional state, with

blue grama, buffalograss, and threadleaf sedge dominant. Such sites contrasted markedly with non-

grazed or lightly grazed areas, which were dominated by mid-height to tall grasses (Hansen and

Hoffman 1985).

In 2002 and 2003, a floristic survey was completed for the entire Grand River Ranger District,

including the Allotments 1-5 project area (Kopp 2004). Several years later, that work provided the

data for the compilation of an annotated plant checklist (Hansen 2008).

The most intensive vegetative inventory

performed in the project area was

conducted by researchers (Figure 47)

from North Dakota State University-

Hettinger Research Extension Center,

which is located approximately 4 miles

north of the project area. Funding for that

collaborative project was provided by the

USDA Forest Service’s Dakota Prairie

Grasslands, the Grand River Cooperative

Grazing Association, and North Dakota

State University (NDSU).

The NDSU researchers collected baseline

information on the project area’s native

graminoid vegetation at numerous sample

plots in summers 2006 (a pilot-study

year), 2007, and 2008 (Figure 47). A

wide variety of measurements were

taken, including, but not limited to: basal cover data (Figure 47), frequency, ―indicators of rangeland

health,‖ and use-pattern mapping. Each of these varying methods provides information helpful to

describing the current composition of native graminoid communities in the Allotments 1-5 project

area and so is discussed separately below. Overall, however, these different methods generally

confirm the IDT’s conclusions from extensive field visits and examination of past range vegetative

inventory data that the project area is currently below Grasslands’ Plan objectives for late seral

composition.

Note: NDSU data were used, in part, to describe project area conditions and assess current

versus desired conditions. That assessment was conducted by the IDT. Conclusions are

those of the IDT and do not necessarily reflect those of NDSU personnel.

Figure 47. NDSU researcher using a 10-point frame to collect

vegetative basal cover data, Dakota Prairie Grasslands. Little

Missouri National Grassland, McKenzie Co., ND. Summer 2008.

Photo courtesy of Amanda Gearhart.


66

Figure 48. Location of NDSU vegetative sampling points measured in summer 2007 and 2008. Figure courtesy of

Amanda Gearhardt.


67

Basal Cover - Bare Ground & Vegetative Litter

One of the useful applications of basal cover data is the measurement of bare ground and vegetative

litter. A site might have too much or too little of either parameter. In the project area, however, the

management concern is focused on the high extent of bare ground and low extent of litter (Figure

49), the two parameters often being highly inversely related.

The desired level of bare ground varies

by ecological site. In highly productive

areas, such as on loamy ecological sites,

bare ground should not exceed 15% (J.

Printz, NRCS State Range Specialist,

Ecological Reference Worksheets, 4-20-05

drafts). On less productive sites, such as

on shallow claypan ecological sites, bare

ground should not exceed ~20% (ibid).

Monitoring data collected in the project

area indicates that the extent of bare

ground is excessive at numerous locations

throughout the project area (Table 15).

Some sites have particularly high levels of

bare ground. For example, the loamy

ecological site in the northeast pasture of

Allotment 4B had 64% bare ground.

The interdisciplinary team, using

monitoring data and/or field visits

conducted over several years, identified excessive bare ground and paucity of vegetative litter as

management issues in the following allotments: 1A (Figure 49), 1B, 2A, 2B, 3A (especially on the

southwest pasture’s clayey ecological site, where up to 28% of the ground was bare), 4B, 5A

(especially on the clayey ecological site in the northwest pasture, where 29% of the ground was bare

and on the loamy ecological site in the southwest pasture, where 22% of the ground was bare ), 5C,

and Dyson (Figure 50).

Figure 49. Abundant bare ground and a lack of vegetative litter

increases vulnerability to erosion from overland flow, disrupts

nutrient cycling, lowers forage production, increases evaporation,

and increases soil temperature. Note 9‖ x 13‖ clipboard for scale.

Allotment 1A, Grand River National Grassland, Perkins Co., SD.

June 2007. Photo by Mark Gonzalez.

.

Figure 50. Heavy grazing by

livestock on the right side of the

fence has lead to excessive bare

ground, retention of very little

litter, and excessive loss of soil

moisture. Such conditions were

not present to the left of the

boundary fence. At the time of

this photo, there were 27% more

livestock per acre in the

allotment to the right of the

fence, than in the adjacent

allotment. Sections 23/26,

Dyson (right) and Krisle (left)

Allotments, Grand River

National Grassland, Perkins Co.,

SD. September 2006. Photo by

Mark Gonzalez.


68

Table 15. Extent (%) of bare ground in project area allotments for the most common ecological sites, compared to

desired levels. Note: percentages are simple (not weighted) averages of values per allotment. Data courtesy of NDSU.

---------------------------------ECOLOGICAL SITES-----------------------------------------

ALLOTMENT CLAYEY LOAMY THIN

LOAMY

SANDY SHALLOW

LOAMY

1A 33 35 42 48

1B 24 21

2A 30 28 25

2B 22 16 23 36

2C - west 15 21

2C- east 6 16

3A 20 12 15 9

3B – outside of

Humphrey Draw

Wildlife Area

11 14

3B – Humphrey Draw

Wildlife Area

7 4

4A 15 16 22

4B 15 38 35

5A 18 15 13

5B- north 10 13 11

5B- south 19 24

5C 12 40

Dyson 13

Hermann 4 13

Krisle 11

DESIRED* 5%-15% 10%-15% 20%-25% 15%-20% 25%-40% *(Source: Ecological Reference Worksheets, prepared and reviewed by J. Printz, NRCS State (ND) Range Specialist, 4-

20-05 drafts)

Basal Cover - Vegetative Composition Basal cover data also provides a basis to describe vegetative composition, recognizing, however, that

bunch grasses are more likely to be recorded than rhizomatous grasses (Dr. Kevin Sedivec, NDSU

Range Extension pers. comm.). For example in Allotment 1A, western wheatgrass, a late mid-seral

and late seral species, which is the desired dominant graminoid on at least 50%* of the loamy

ecological sites, is the dominant species on none (Table 16). In fact, it is only the fifth or sixth most

common native species (Table 16). Conversely, blue grama was the first or second most widespread

species (Table 16). Similar patterns can be noted in data from most of the other grazing allotments

in the project area. These data indicate that desired levels of late seral graminoid vegetation are not

currently present in the project area.

*Based on the Grasslands Plan objective for desired seral stages being: Early: 10-15%; Mid: 65-

75%; Late: 15-20%, where western wheatgrass is the dominant species on one-half of the mid-sere

(i.e. the ―late mid-seral‖) as well as on all of the late-sere plant communities [(70%/2) + 18% = 53%].

Mid:65-75%25

Mid:65-75%25


69

Table 16. Percent (and rank*) of native dominant/co-dominant plants, by ecological site and pasture, as measured by

basal cover at sample plots in Allotment 1A, Grand River National Grassland, Perkins Co., SD. Data courtesy of NDSU.

Northeast Pasture Southeast Pasture West Pasture

Clayey Loamy Sandy Loamy Sh. Loamy Clayey Loamy Number of monitoring sites: 3 3 3 3 3 3 4

Blue grama 3.50 (3) 5.83 (1) 5.67 (2) 7.67 (1) 5.11 (2) 0.89 (3t) 2.58 (2)

Threadleaf + sun sedge 5.28 (1) 2.06 (3) 9.78 (1) 1.50 (4) 10.56 (1) 0.89 (3t) 1.71 (4)

Western wheatgrass 1.17 (5) 1.28 (5) 1.28 (4) 0.67 (6) 0.72 (5) 0 0.71 (5)

Needleandthread 0.67 (6) 1.22 (6) 0.50 (6) 4.72 (2) 1.56 (3) 0 0

*Rank of 1 represents the native species with greatest basal cover at each ecological site. Each higher rank represents

the species with the next greatest amount of basal cover. Numerical ties with other species indicated with ―t‖.

Frequency – Vegetative Composition

Vegetative monitoring in the project area included recording species frequency. Frequency indicates

the percentage of sample frames that contained a given graminoid species (i.e. frequency is a

measure of how widespread each species is). Frequency is not a measure of vegetative species

density (i.e. frequency is not a measure of how many of each species there is); nor is frequency a

measure of forage productivity (which is the parameter used by the USDA Natural Resources

Conservation Service to define seral stage). Nevertheless, frequency data does provide useful

insight into existing vegetative composition (Dr. Kevin Sedivec, NDSU Range Extension pers.

comm.). This can be illustrated by an examination of the data (Table 17) collected on two of the

project area’s most common ecological sites, i.e. clayey and loamy.

Note: as discussed in greater detail below (pp. 83-96), non-native grasses now play a major

role in the project area’s herbaceous communities. For example, even after excluding known

monocultures of crested wheatgrass, native graminoids were the two most frequent species

recorded on only 17 of 35 sampled plots on clayey ecological sites and on 62 of 105 loamy

ecological sites (Table 17).

Of the 35 plots sampled on clayey ecological sites in the project area, 17 (Table 17) had native

species as the two most frequently encountered graminoids. Of these 17, two (12%) plots (Table 17,

Allotment 1A, plot #NE2-2 and Allotment 5A, plot #SE2-1) had blue grama and upland sedge as the

two most widespread species. One (6%) plot (Table 17, Allotment 4A, plot #SW-2) recorded

western wheatgrass and a needlegrass as the two most widespread species. If sites with high

frequencies of blue grama (Figure 51) and upland sedge are considered early sere, and sites with

high frequencies of western wheatgrass and needlegrasses are considered late sere, then these data

suggest that the project area’s clayey ecological sites are meeting Grasslands Plan (p. 2-4) objectives

for early seral stages (i.e. 10-15%), but not for late seral stages (i.e. 15-20%).


70

Note: the Grasslands Plan (p. 2-5) states that early seral vegetation on clayey sites is

dominated by blue grama, annual forbs, and annual grasses. Upland sedges are not

specifically mentioned, but that does not mean that sedges are absent from that seral stage.

The Grasslands Plan does state (p. 2-5) that ―Blue grama and upland sedges primarily

dominate in earlier mid seral conditions…‖. Therefore, the blue grama/upland sedge sites

noted in Table 12 could be classified as mid-sere (albeit early mid-sere), rather than early

sere. Such an interpretation would indicate that the project area is below Grasslands Plan’s

objectives for early seral vegetation. The IDT, however, did not consider availability of

early seral vegetation limited in the project area, basing that conclusion on field trips which

encompassed the last several years.

An analysis for the loamy ecological site (Table 17) shows a similar pattern as that described above

for clayey sites. Native species were the two most frequently found graminoids on 62 of 105 plots.

Of the 62 native-dominated plots, 7 (11%) were consistent with early seral vegetation (i.e. had blue

grama and upland sedge as their most frequent species), whereas 2 (3%) were consistent with late

seral vegetation (i.e. had western wheatgrass and a needlegrass as their most frequent species). This

too indicates adequate early seral vegetation and a shortfall of the desired levels of late seral

vegetation.

Figure 51. Blue grama. This species is at or above desired levels in the project area, based on frequency data. Photo

courtesy of USDA Natural Resources Conservation Service.


71

Table 17. First and second most frequently encountered native graminoid species on clayey and loamy ecological sites

in the project area. Plots where non-native species were the first or second most frequently encountered species are

excluded. ALLOT. = allotment. NA= not applicable. I.D. = identification number. W. = western. Data courtesy of

NDSU.

CLAYEY LOAMY

ALLOT. #

PLOTS

PLOT I.D./SPECIES #

PLOTS

PLOT I.D./ SPECIES

1A

6 #NE2-1. w. wheatgrass/blue grama.

#NE2-2. blue grama/upland sedge.


#NE3-2. w. wheatgrass/blue grama.

#SE3-2. blue grama/w. wheatgrass.

#SE3-3. w. wheatgrass/inland

saltgrass.

#W3-4. w. wheatgrass/blue grama.

1B 0 NA 6 None.

2A

2 #W2-2. w. wheatgrass/blue grama.

#W2-3. needleandthread/blue grama.


#NE3-2. upland sedge/w. wheatgrass.

#NE3-3. w. wheatgrass/upland sedge.

#NW3-1. w. wheatgrass/upland

sedge.

#NW3-2. upland sedge/

needleandthread.

#NW3-3. upland sedge/blue grama.

#SE3-1. w. wheatgrass/blue grama.


#SW3-1. blue grama/w. wheatgrass.

#SW3-3. blue grama/prairie

junegrass.

2B

2 #2-3. w. wheatgrass/upland sedge. 2 #3-1. w. wheatgrass/blue grama.

#3-2. w. wheatgrass/blue grama.

2C - west

0 NA. 5 #H3-2. w. wheatgrass/blue grama.

#H3-3. blue grama/w. wheatgrass.

#H3-4. blue grama/upland sedge.

#H6-1. w. wheatgrass/blue grama.

#H6-2. w. wheatgrass/blue grama.

2C - east

1 #D3-1. w. wheatgrass/upland sedge. 3 #D3-2. w. wheatgrass/blue grama.

#D3-4. blue grama/upland sedge.

3A

6 #SE2-3. w. wheatgrass/upland sedge.


14 #NE3-3. w. wheatgrass/upland sedge.

#NW3-1. w. wheatgrass/blue grama.


#SE3-3. blue grama/w. wheatgrass.

#SW3-1. w. wheatgrass/blue grama.

#SW3-2. w. wheatgrass/upland sedge.


#SW3-4. upland sedge/blue grama.

3B

2 NA. 14 #E3-3. w. wheatgrass/

green needlegrass.

#E3-4. blue grama/w. wheatgrass.

#M3-1. blue grama/w. wheatgrass.

#W3-1. upland

sedge/needleandthread.

#W3-2. w. wheatgrass/upland sedge.

#W3-3. w. wheatgrass/upland sedge.


72

CLAYEY LOAMY

ALLOT. #

PLOTS

PLOT I.D./SPECIES #

PLOTS

PLOT I.D./ SPECIES

4A

2

#SW-2. w. wheatgrass/

green needlegrass.


#NE3-3. upland sedge/w. wheatgrass.

#SE3-1. upland sedge/blue grama.


#SW2-3. w. wheatgrass/upland

sedge.

#SW3-3. w. wheatgrass/blue grama.

4B

5 #NW-1. blue grama/w. wheatgrass.

#NW-2. w. wheatgrass/upland sedge.

#SE2-1. w. wheatgrass/Cusick’s

bluegrass.


#SE2-3. Cusick’s bluegrass/upland

sedge.

5 #NW2-2. w. wheatgrass/upland

sedge.


sedge.


#NW3-3. upland sedge/w.

wheatgrass.

#NE3-4. w. wheatgrass/blue grama.

5A

6 #SE2-1. upland sedge/blue grama.

#SE2-2. w. wheatgrass/upland sedge.

11 #NE2-3. upland sedge/blue grama.

#NE6-3. blue grama/w. wheatgrass.

#NW3-2. upland sedge/blue grama.

#SE3-1. upland sedge/w. wheatgrass.

#SE3-3. w. wheatgrass/upland sedge.

5B -

north

1 #SW3-1. w. wheatgrass/upland sedge. 8 #NE3-2. blue grama/w. wheatgrass.


#SW2-1. upland sedge/w. wheatgrass.

5B- south

0 NA. 6 #NE3-1. upland sedge/

needleandthread.

#NW3-1. upland sedge/w.

wheatgrass.


sedge.

#SE3-2. w. wheatgrass/

needleandthread.

5C 1 None. 1 None.

Hermann

0 NA. 1 #E3-1. upland sedge/

slender wheatgrass.

Krisle 1 None. 0 NA.

TOTAL 35 105

The interdisciplinary team reviewed the basal cover and frequency data presented above, examined

the other vegetative composition information collected within the project area since the 1960s, and

reviewed past and current field notes; based on this information, the interdisciplinary team identified

native graminoid composition as a management issue in all of the project area’s allotments except

Gunn. Departures from desired conditions ranged from moderate (example Allotment 5B - south) to

severe (example: Allotments 1A, 1B, 2A, 2B, 4A, 4B, 5A, 5C, and Dyson).


73

Figure 53. Paul Drayton, interdisciplinary team leader, examining high seedheads of green needlegrass. This species,

which produces ample forage, is below desired levels in the project area. North Community Allotment, Cedar River

National Grassland, Sioux Co., ND. September 2008. Photo by Dan Svingen.


74

Indicators of Rangeland Health – Vegetative Composition

A qualitative assessment of range health intended to supplement the other monitoring described in

this document was developed by an interagency team of scientists and managers (Pellant et al.

2005). The effort was lead by personnel from the USDA Natural Resource Conservation Service,

USDA-Agricultural Research Service, US Geological Survey, and USDI Bureau of Land

Management. The resulting ―Indicators of Rangeland Health‖ technique provides a preliminary

evaluation of soil stability, hydrologic function, and biotic integrity, and as such can be used as an

―early warning‖ system to alert managers to potential problems and opportunities (ibid). It was one

of the methods used in the project area by NDSU researchers.

Of the 17 parameters assessed by the Indicators of Rangeland Health technique in the project area,

two showed consistent departure from desired conditions. These parameters were: invasive species

and ―Functional/Structural Groups‖. Invasive species were recorded as a concern if ―increasers‖ (i.e.

grass species which do well under constant grazing) were above desired levels, or if exotic

vegetation (such as crested wheatgrass) were present. Both situations were present at most sample

sites in the project area (unpubl. NDSU data available in the project file).

A functional/structural group is defined as a suite or group of species that because of similar shoot or

root structure, photosynthetic pathways, nitrogen fixing ability, life cycle, etc., are grouped together

on an ecological site basis (Pellant et al. 2005). Functional composition and functional diversity are

the principal factors explaining plant productivity, plant percent nitrogen, plant total nitrogen, and

light penetration (Tilman et al. 1997).

Examples of functional/structural groups in the Allotments 1-5 project area include: mid-stature,

cool-season rhizomatous grasses (such as western wheatgrass); mid-stature, cool season bunch

grasses (such as green needlegrass); short stature, warm season rhizomatous grass (such as blue

grama); forbs, and shrubs. All allotments sampled by NDSU using the Indicators of Rangeland

Health technique had one or more sites showing more than slight departure from reference

conditions for functional/structural groups. Specifically, of the 236 sites evaluated, 146 (62%)

exhibited moderate to extreme departure from desired conditions; whereas 30 (12%) exhibited

extreme to total departure from desired condition (NDSU, unpubl. data contained in the project file).

These departures were due to the relative abundance of short stature warm season rhizomatous

graminoids and relative absence of mid-stature cool-season rhizomatous grasses.

A confounding factor in this otherwise simple interpretation, however, was the common presence of

cool-season upland sedges, which alone would raise the classification of functional/structural groups

to at least ―moderate‖ departure from reference conditions (Amanda Gearhardt, NDSU researcher,

pers. comm.). Nevertheless, as mentioned above, upland sedges are ―…primarily dominant in earlier

mid-seral conditions‖ on clayey and silty (a.k.a. loamy) sites (Grasslands Plan p. 2-5). These data,

therefore, reinforce the earlier conclusion that the project area is below desired levels for late seral

vegetative conditions.


75

Use Pattern Mapping – Livestock Distribution & Consequent Vegetative Composition

The existing vegetative composition described above has been greatly influenced by past livestock

grazing patterns, as chronic overuse by livestock often favors species such as blue grama over others

such as green needlegrass (Holechek et al. 1999). A helpful measure of current livestock grazing

was provided by NDSU researchers using the ―use-pattern mapping‖ technique (Figure 53). This

approach entailed trained observers walking or driving through a pasture, delineating various levels

of forage utilization. Patches of different use rates were mapped and coded separately. Except in

areas where early sere is desired, use rate codes should be no higher than code 3 (i.e. 41 to 60% use).

Plant health, species compositions, soil fertility, and conservation of rangeland moisture are all

adversely affected by high (i.e., >50%) utilization rates on most ecological sites and plant

communities in the project area. In most of the sites where these data were collected, however,

utilization rates of code 4 (i.e. 61% to 80% use) were noted, particularly in drainageways and in

riparian areas. Such examples included allotments: 1B, 2C - west, 3A, 4A, 4B, 5A, 5B - north, and

5B - south. Utilization rates were particularly high in Allotment 5C, where use rates of code 5 (i.e.

81% to 100%) were noted (Figure 53).

Figure 53. Use-pattern map for Allotment 5C, northwest pasture, August 2008. Red lines delineate areas of

differing forage-utilization levels. Utilization levels are coded as: (1) 0% to 20%; (2) 21% to 40%; (3) 41% to

60%; (4) 61% to 80%; and (5) 81% to 100%. Note the code 5 use levels along drainageways in the northwest and

southeast corners. North is towards the top of the map. Map courtesy of NDSU.

Documents

3.2.3 Cumulative Effects (Riparian) - a123.g.akamai.neta123.g.akamai.net/7/123/11558/abc123/forestservic.download.akamai.com/... · 3.2.3 Cumulative Effects (Riparian) Other events