Importance of Shrub Restoration on Great Basin Rangelands By Charlie D. Clements, Mark Freese, Mike Scott, Jeff White and Dan Harmon Rangeland Scientist, Great Basin Rangelands Research Unit, US Department of Agriculture, Agricultural Research Service, 920 Valley Road Reno, NV 89512 charlie.clements@ars.usda.gov Habitat Supervisory Biologist and Supervisory Wildlife Biologist, Nevada Department of Wildlife, Vice President, Elko Land and Livestock, and Agricultural Research Science Technician, US Department of Agriculture, Agricultural Research Service
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he recognition of brush species and the browse these plants provide as an important component of rangeland production was often overlooked in land management for some time. Even after the birth of range management in the early twentieth century, herbaceous species were considered the basic component of rangeland forage. Arthur Sampson, one of the founders of scientific range management, was among the first to describe and discuss native range shrubs as components of the basic forage supply on ranges in 1924. By 1931, USDA, Forest Service Ecologist William A. Dayton published Important Western Browse Plants. Dayton was in charge of the range forage investigation for the USDA, Forest Service when the agency published the Range Plant Handbook in 1937. Among the contributors to this publication was Odell Julander, who became a very noted mule deer researcher, and in the handbook stressed the importance of antelope bitterbrush as a critical shrub on winter ranges for deer, elk and antelope as well as recognizing this shrub species as palatable at all seasons and preferred by all classes of domestic large animals, except horses. By the 1940s, there was a growing concern over the use of range plants by domestic livestock and its effect on wildlife habitats, especially that for deer. In 1945, Utah State researchers L. A. Stoddart and D. I. Rasmussen entered the wildlife/livestock conflict debate with the publication Deer Management and Livestock where they shared the view that deer and domestic livestock could co-exist on the same rangelands. The debate over the influences of domestic livestock grazing on wildlife habitats is perhaps as robust and controversial as ever in the history of range management as many grazing permit renewals are challenged in court directly due to possible impacts to wildlife species such as sage grouse, mule deer, pygmy rabbits, and an array of other species. Joe DiTomaso, Department of Plant Sciences University California Davis noted that rangeland and pasture comprise about 42% of the total land area in the United States and that about 75% of domestic livestock depend on those grazing lands for survival portion of their life cycle. Currently, there are more than 300 species of rangeland weeds in the United States. Western rangelands that were previously dominated by big sagebrush/bunchgrass species are now largely influenced by one of the most notorious aggressive invasive weeds, cheatgrass. The accidental introduction, subsequent establishment, and invasion of cheatgrass on rangelands has resulted in an increase in the chance, rate, spread, and season of wildfires. This in turn has increased wildfire frequencies from an estimated 60-110 years down to as little as every 5-10 years, simply too short of a time period to allow for the recovery of critical shrub species (Figure 1). In 1999, 1.8 million acres of Great Basin rangelands burned in Nevada alone, many of these acres were critical shrub communities that provided thermal and hiding cover as well as nutritional forage. Early researchers, such as Emor Nord, pointed out that antelope bitterbrush was such a critical browse species that it was referred to as a ‘keystone species’ for mule deer and other wild ungulates in late fall and early winter for its nutritional values. Bruce Welch, U.S. Forest Service plant physiologist reported on the importance of big sagebrush not only as winter forage for wild ungulates and domestic sheep but its importance to species such as sage grouse, black-tailed jack rabbit, pigmy rabbit, dark-eyed junco and white-crowned sparrow. Following the 1999 catastrophic wildfire season, 4,322,610 pounds of seed was purchased and drill or aerially seeded on these burned Nevada rangelands. Four 8 July-August 2016
Figure 1. Burned antelope bitterbrush community providing an empty plate scenario for wildlife and grazing resources.
wing saltbush and big sagebrush were some of the shrubs seeded on many burned habitats, yet due to past reports of unsuccessful antelope bitterbrush seeding efforts, not a single pound of antelope bitterbrush was purchased, much less planted. In this paper we focus on two shrub species, antelope bitterbrush and big sagebrush to shed some light as to better understand methods by which to restore these critical shrub species in Great Basin plant communities. Antelope bitterbrush flowers on second-year wood and depends on seed production, dispersal and recruitment to successfully sustain the population. Some bitterbrush shrubs resprout following wildfire, but this attribute is rare across the range of this species. Vigorous antelope bitterbrush plants produce nearly 100,000 seeds per shrub, while old decadent shrubs produce less than 1,000 seeds per shrub. The USDA, Agricultural Research Service, Great Basin Rangelands Research Unit (GBRRU) aged a variety of antelope bitterbrush stands that ranged from 36 to 98 years of age and recorded the forage and seed production of these shrub stands. Antelope bitterbrush productions starts to decrease after it reaches 60-70 years of age, which significantly influences seed production and its’ ability to recruit and sustain the population. In southern Oregon, researchers reported that an antelope bitterbrush population of 473 bitterbrush plants/acre only needed the successful recruitment of 6.7 bitterbrush seedlings/year, yet they were only getting 0.7/year. These old decadent stands simply cannot recruit without active management. The GBRRU also recorded as much as 52% insect damage on seeds, while granivorous rodents like deer mice, pocket mice and kangaroo rats harvested as much as 85% of the seeds within a 24 hour period. Many researchers have reported on the benefits of rodents to harvest and scatter-hoard cache antelope bitterbrush seeds at optimal depths for seed germination and recruitment. Granivorous rodents exhibit two types of caching; a) “larder-hoard caching” is when the rodents take the seed back to their deep burrows (homes) and store the seeds, which are too deep for germination and emergence, and b) “scatter-hoard caching” is when these rodents harvest the seed and bury
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