Sagebrush Rangelands in Nevada

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1 BACKGROUND INFORMATION Sagebrush Rangelands in Nevada Sagebrush Species and Their General Biology: There are at least 28 species of sagebrush and many more subspecies or varieties, found in the Intermountain West. All belong to the genus Artemisia. There are about 12 woody species common in Nevada, and they each provide important habitat and forage for wildlife and domestic livestock. These include: Basin big sagebrush, Wyoming big sagebrush, Mountain big sagebrush, low sagebrush, black sagebrush, Lahontan sagebrush, alkali or early sagebrush, three-tip sagebrush, silver sagebrush, fringed sagebrush, bud sagebrush and pygmy sagebrush. The sagebrush species you are most likely to encounter this week are: Wyoming big sagebrush: alluvial fans below the base of the mountains Basin big sagebrush: very tall sagebrush along streams and drainages Mountain big sagebrush: medium height, flat topped sagebrush in the mountains Low sagebrush: very short sagebrush on rocky sites Bud sagebrush: very short sagebrush in the valleys, particularly near the valley bottoms The most widespread sagebrushes across Nevada are Wyoming and Mountain sagebrush. They are long-lived (60+ years), evergreen shrubs, that do not sprout after a fire. They must reproduce from seed. Each mature plant, when healthy and vigorous, can produce thousands to tens of thousands of seeds. Most seeds are short-lived; lasting only one year, but a small percentage will survive up to several years. Seeds are dispersed in the fall but most remain within 3-10 feet of the mother plant. This makes the establishment of sagebrush on areas where it has been removed very slow. Sagebrush Plant Community Types in Nevada: Sagebrush species are the primary shrubs on most Nevada rangelands at elevations above 4,500 ft to 5,000 ft. Neil West identifies two distinct sagebrush regions: the sagebrush semi-desert and the sagebrush steppe. Each sagebrush region produces the same species of sagebrush, yet there are distinct differences between the regions. These differences include climatic patterns, different ratios of shrubs to grasses and forbs (non-woody flowering plants) in the herbaceous (grasses and forbs) understory, different species of grasses and forbs in the understory, and different amounts of total vegetation production each year. These differences result in each sagebrush type responding differently to disturbances. Managing sagebrush-grass rangelands in Nevada requires understanding how the sagebrush species and their associated shrubs, grasses, and forbs interact with each other, disturbances, climate, topography, and soils. The potential relationships are many and complex. Sagebrush rangeland provide important habitat for both wild and domestic animals on Nevada s rangelands. Some wildlife must have sagebrush at some time during the year to survive. These are called sagebrush obligate species. Without sagebrush they cannot exist. Examples include the sage grouse, sage sparrow and sage thrasher. Other species use sagebrush plant communities during the year, but do not require sagebrush to survive. These are called facultative sagebrush species. Examples include elk and golden eagles. Mule deer and antelope often use sagebrush for cover and food. Individual animals can survive without sagebrush, but size of their populations usually decline to low levels if most or all of the sagebrush in areas they inhabit is removed. Fire has always been a part of the sagebrush 1

2 system, but the size, frequency, and intensity of fires has changed following settlement and the introduction of non-native annual grasses, like cheatgrass. Fire has increased where cheatgrass is abundant, and decreased in areas where suppression activities are very active, and/or fine fuels have been reduced. In parts of Nevada the increase in cheatgrass and fires has resulted in the loss of sagebrush on large areas of the landscape. Sagebrush semi-desert The sagebrush semi-desert covers about 44 million acres, mostly in Nevada (Figure 1a). This area generally is north of the Nevada Test Site, and south of the Interstate 80 corridor. The sagebrush semi-desert is positioned between the salt-desert shrub vegetation that inhabits salty soils (usually on the valley bottoms) and the pinyon-juniper woodland on the lower slopes of the mountains. The typical elevation range is between 5,000 and 7,000 feet. The most common sagebrush species are Wyoming big sagebrush, basin big sagebrush, and black sagebrush. While other shrubs occur in the sagebrush semi-desert, sagebrush typically makes up over 90% of the shrub biomass on unburned and undisturbed sites. Many species of perennial grasses occur in the sagebrush semi-desert. They seldom contribute a substantial amount of biomass in mature sagebrush communities, regardless of how well the area is managed. Most, but not all, are cool season species. These include Indian ricegrass, desert needlegrass, squirreltail, Sandberg s bluegrass, and needle-andthread. Thurber's needlegrass, bluebunch wheatgrass and mutton grass become more common in the northern part of the sagebrush semi-desert and at higher elevations (>6,000 ft), where annual precipitation approaches inches. Figure 1a. Sagebrush semi-desert. Figure 1b. Sagebrush Steppe Forbs are common, but most species are annuals. These annual forbs are almost completely absent in dry years, but are abundant in wet years. They can provide important food for wildlife when present, but their variable presence from year-to-year may limit the size some wildlife populations. Forbs in the sagebrush semi-desert become dry by late spring 2

3 and provide almost no summer forage. The shrubs and perennial grasses provide better continuity for food from year-to-year. Sagebrush steppe: The sagebrush steppe covers over 11 million acres in Nevada, and tens of millions of acres in other states (Figure 1b). In resides in two distinct areas: one loosely defined by latitude and the other by elevation. In northern Nevada, the sagebrush steppe occupies the mountains, hills, plateaus and mesas just above the valley bottoms that often are vegetated with plants tolerant of high salt content in the soil. Farther south, it occupies the upper elevations of mountain ranges where a sagebrush zone occurs above the pinyon-juniper woodland. The lower elevation limit for the sagebrush steppe in extreme Northern Nevada and northwestern Nevada is about 4,500 feet to 5,000 feet. In central and eastern Nevada it typically occurs in the mountains above 6,500 feet to 7,500 feet, depending on aspect. Wyoming big sagebrush is most common at the lower elevations on droughty soils. Mountain big sagebrush is typical where annual precipitation is more than about 12 inches. Low sagebrush typically inhabits shallow soils with high clay content. Black sagebrush is most common in the high elevation phase of the sagebrush steppe, where soils are shallow and calcium content is high. The sagebrush steppe either has, or has the potential to produce many perennial grass and forbs when sagebrush is abundant. Roughly equal amounts of shrubs and herbaceous species occur on undisturbed and/or properly managed sites. In contrast with the sagebrush semi-desert, the sagebrush steppe often has a high abundance of other shrubs in mature plant communities. These include bitterbrush, snowberry, mountain mahogany, Douglas rabbitbrush, currant, and serviceberry. These species often occupy areas that accumulate drifting snow. Common, widespread grasses include bluebunch wheatgrass, beardless wheatgrass, Sandberg=s bluegrass, Canby bluegrass, Thurber=s needlegrass, Idaho fescue, squirreltail, western needlegrass, Columbia needlegrass, Letterman=s needlegrass, mutton grass, mountain brome and Cusick=s blue grass. Forbs are a much more common and dependable in the sagebrush steppe, than the sagebrush semi-desert. Many are perennial and provide forage for wildlife every year. During wetter years many remain green well into the summer or fall. Important perennial forbs include Arrowleaf balsamroot, buckwheats, Penstemon, lupines, wild onions, desert parsley, phlox, loco weeds, daisy, evening primrose, rosy everlasting, false dandelion, tapertip hawksbeard, and waterleaf. Task Specific Background: During this task you will visit two sites inhabited with sagebrush plant communities. One will be on an alluvial fan near the valley bottom (i.e., sagebrush semi-desert), and one near the top of the Toiyabe Mountains (high elevation sagebrush steppe). Both sites include areas that were burned by the same wildfire fire in During this task you will visually compare the vegetation, soils, and other components of these two sites. These comparisons will be for the burned and unburned areas at each site, and then for the burned and unburned areas between each site (compare low elevation areas with the high elevation site). Our goal is to learn about differences in sagebrush plant communities, that different sagebrush plant communities benefit different animals, and that sagebrush communities respond to disturbances differently and the response of each community will influence how animals use the community. 3

4 Location Number 1, Sagebrush Semi-desert: 1. The General Setting: Look at the environment around you. Record observations about the landforms, soils, plants, and animals you see. Think about similarities and differences with the locations of other tasks you have completed the past several days. Landform: Soils: Plants: Animals: 2. Plant Community Types in the Sagebrush Zone. How Many Different Plant Communities do you see on our study area and in the visible vicinity? What do you think are the reasons these different communities exist? Study Site: 4

5 Vicinity of the Study Site: 3. Land Uses. What land uses do you think are possible on this sagebrush rangeland? 4. Disturbances What disturbances have taken place in this sagebrush plant community and what has been their effect? Think about how this may influence or change land uses on the site both shortterm (next 5 years) and long-term (over next 20 years). 5. Habitat. Each species of wildlife uses a landscape to obtain water, food and shelter. Specific locations with water may be common or infrequent. Also, the amount available may vary throughout the year. Fire and other disturbances can affect the availability of food and/or cover for many species. What is the seasonal availability of water at our work site, and how is it likely to affect the use of this area by humans, livestock and wildlife? Humans: Livestock: 5

6 Wildlife: Both wild and domestic animals use vegetation for cover to hide from predators and provide shelter from rain, snow and excessive heat. Not all animals use the same lifeforms (grasses, forbs, shrubs, or trees) similarly. On sagebrush rangelands, some nesting birds prefer to nest in areas with mostly perennial grasses. Others prefer to nest in areas with mostly shrubs. What types of nesting birds may use the plant communities around the study site and why? The quality of a sagebrush rangeland for habitat depends on more than just the presence or absence of certain life-forms of plants. The size, shape, and general abundance of plants can be important. We ll use sage grouse as an example to illustrate this point. Sage grouse have their best nest success when individual sagebrush plants are common. Sage grouse, however, nest on the ground beneath sagebrush where there nests are susceptible to many predators (coyotes, foxes, badgers, squirrels, ravens, eagles, and others). Think about what type of habitat structure (size, shape, and abundance of plants) would be best for a ground based, shrub nesting species like sage grouse. Write your ideas below. Wildlife and livestock also use sagebrush rangelands to obtain food. Some species prefer to consume grasses, others forbs, and still others shrubs. Animals may consume one life-form during one time of the year, and another during a different period. Sagebrush rangelands, however, can have varying amounts of grasses, forbs, and shrubs. The amount of each depends on how long it has been since the last fire (or similar disturbance) removed the sagebrush. Forbs are often abundant for several years after a fire, then decline as grasses increase. Grasses increase slowly at first, but within several years produce the most biomass of any life-from on a site. Shrubs have a slow initial increase but eventually produce the most biomass. As shrubs increase there is a corresponding decline in the amount of perennial grasses and forbs (Figure 2). 6

7 Relative Biomass of Grasses, Forbs and Shrubs Forbs Grasses Shrubs Increasing Time from Last Disturbance Figure 2. General changes in the amount of forbs, grasses, and shrubs across time in sagebrush plant communities. We ll use sage grouse, deer, antelope, cattle and sheep to understand how different stages of a sagebrush rangeland plant community can be used by different animals. Sage grouse eat forbs in the spring when they are nesting, typically move to riparian areas in the summer, and eat sagebrush in the fall and winter. Mule deer consume largely forbs in the spring and summer (if available); use increasing amounts of shrubs in the summer; and largely eat sagebrush and other shrubs in the fall and winter. Antelope will eat many forbs in the spring (and summer if available), but switch their diet to sagebrush and other shrubs in the summer, fall and winter. Cattle consume mostly grasses throughout the year if they are available. Sheep will select forbs over grasses, and typically switch to shrubs as forbs and grasses become dry and brittle in the summer, fall, and winter. On the lines below identify which plant community in our study area the animal species is likely to use in each season. The plant communities are sagebrush dominated (SB), grass dominated (G), both communities (B), or none of these (N) Spring Summer Fall Winter Sage Grouse Mule Deer Antelope Cattle Sheep 7

8 6. Vegetation Measurement. Managers of sagebrush rangelands often need to measure or quantify the composition or structure of an area to assess its quality for different land uses, its potential response following a disturbance, or to track change across time (called monitoring for trend) following a management action. Managers can measure vegetation many different ways. Can you think of a few? Describe them below. Quantitative measurements about vegetation composition and structure provide rangeland information about the current state (stage of development) of a plant community compared to other relative stages that could be present on a site. Measurement helps keep land managers from making errors that often occur when visual observations are the only information collected. For this task you will visually estimate, and then measure the canopy cover of the sagebrush and other shrubs, and the basal cover of perennial grasses in both the burned and unburned areas using a technique called line intercept. Canopy cover refers to the percent of the ground surface covered by the canopy of the shrub when you are looking toward the ground from high above. Visual estimate of cover in each community type: Burned Community Unburned Sagebrush Community Sagebrush Other Shrubs Perennial Grasses Pick a random point in both the burned and unburned areas. Stretch a 100 ft tape measure from the random point across slope. Make sure you are perpendicular to any dry stream channels, and are always within the same community type. Starting at the zero point determine how many feet of the tape measure overlap a sagebrush, another shrub, and the root crown of a grass plant. Burned Community Unburned Sagebrush Community Sagebrush Other Shrubs Perennial Grasses How do your visual estimates compare with the quantitative measurements? 8

9 What are the hazards of relying only on visual estimates of habitat structure? 7. Putting it all together. Sagebrush rangelands evolved with fire and other disturbances that can completely remove sagebrush cover from part or all of a landscape. In the more arid Wyoming sagebrush rangelands fire typically occurred every 30 to 100 years. In the wetter sagebrush steppe fire was more frequent, occurring on average from 12 to 50 years. Fire is not necessarily bad or good. The result depends on the frequency, intensity, and size of the fire, and the spatial relationship between very recently burned patches, unburned patches, and patches that have burned but are in various stages of recovery toward a mix of grasses, forbs, and shrubs. Large fires that remove all the sagebrush from an area will have adverse effects for species that depend on the presence of sagebrush. If perennial grasses become common after the fire some species may benefit. If our study area was burned by a large fire that removed all the sagebrush and converted it to perennial grassland which species are likely to: Benefit: Be harmed: Conversely, if fire did not occur and the sagebrush displaced the grasses and forbs across the entire areas which species would: Benefit? Be harmed? Now think about the size and shape of fires. If we had a few small fires (25 acres to several hundred acres) every few years, and unburned habitat remained between each fire, what type of patch structure would our landscape have? How do you think the different species of wildlife and livestock would respond to that type of patchwork? Would there be a very small population, a very large population, or a something in between, and why? 9

10 Sage grouse: Mule Deer: Antelope: Elk: Cattle: Sheep: 8. What did we learn. Given what you have learned about sagebrush rangelands how would you describe the quality of this sagebrush rangeland for wildlife and livestock production, and what changes would you like to see in the next 5 to 20 years. 10

11 STUDY LOCATION NUMBER 2: High Elevation Sagebrush Steppe. 9. General Setting. Look at the environment around you. Record observations about the landforms, soils, plants, and animals you see. Think about similarities and differences with sagebrush semi-desert area we looked at earlier. Landform: Soils: Plants: Animals: 10. Plant communities in the High elevation sagebrush steppe. How Many Different Plant Communities do you see on our study area and in the visible vicinity? What do you think are the reasons these different communities exist? Study Site: 11

12 Vicinity of the Study Site: How do these communities appear to differ than those in the low elevation sagebrush semidesert? 11. Disturbances What disturbances have taken place in this sagebrush plant community and what has been their effect? Think about how this may influence or change land uses on the site both shortterm (next 5 years) and long-term (over next 20 years). 12. Habitat What is the seasonal availability of water at our work site, and how is it likely to affect the use of this area by humans, livestock and wildlife? Humans: Livestock: Wildlife: 12

13 What types of nesting birds may use the plant communities around the study site and why? The quality of a sagebrush rangeland for habitat depends on more than just the presence or absence of certain life-forms of plants. The size, shape, and general abundance of plants are important. We ll use sage grouse as an example to illustrate this point. Sage grouse have their best nest success when individual sagebrush plants are common. Sage grouse, however, nest on the ground beneath sagebrush where there nests are susceptible to many predators (coyotes, foxes, badgers, squirrels, ravens, eagles, and others). Think about what type of habitat structure (size, shape, and abundance of plants) would be best for a ground based, shrub nesting species like sage grouse. How does the high-elevation sagebrush steppe compare to the low elevation sagebrush semi-desert? Remember our previous discussion about the food preferences of different animals by season of the year. On the lines below identify which plant community in our high elevation study area each animal species is likely to feed in during each season of the year. The plant communities are sagebrush dominated (SB), grass-forb dominated (G), both community types (B), or none of these (N). Spring Summer Fall Winter Sage Grouse Mule Deer Antelope Cattle Sheep 13. Vegetation Measurements Visual estimate of cover in each community type: Burned Community Unburned Sagebrush Community Sagebrush Other Shrubs Perennial Grasses 13

14 Pick a random point in both the burned and unburned areas. Stretch a 100 ft tape measure from the random point across slope. Make sure you are perpendicular to any dry stream channels, and are always within the same community type. Starting at the zero point determine how much of the tape measure (in feet) overlap a sagebrush, another shrub, and the root crown of a grass plant. Burned Community Unburned Sagebrush Community Sagebrush Other Shrubs Perennial Grasses Describe the differences and/or similarities between the sagebrush steppe and the sagebrush semi-desert. Which sagebrush system sees the quickest increase in sagebrush after a fire and why? 14. Understanding the Big Picture: How Animals May Use an Entire Landscape. Both wild and domestic animals use different types of rangeland during different times of the year, depending on their species specific needs. Integrating what you have learned about needs for cover, food, and water, determine whether the species listed below are more likely to use the sagebrush steppe (S), sagebrush semi-desert (SBSD), or both (B) during the different seasons of the year. Spring Summer Fall Winter Sage grouse Mule deer Antelope Cattle Sheep 14

15 15. What do I know now that I did not know before? 15