Four-wing saltbush seed and seedling predation by granivorous rodents on Great Basin Rangelands

Authors: Clements, Darin - Charlie; Harmon, Daniel - Dan

Submitted to: The Progressive Rancher
Publication Type: Popular Publication
Publication Acceptance Date: 12/14/2023
Publication Date: 1/4/2024
Citation: Clements, D.D., Harmon, D.N. 2024. Four-wing saltbush seed and seedling predation by granivorous rodents on Great Basin Rangelands. The Progressive Rancher. 24(1):30-33.

Interpretive Summary:

Technical Abstract: Four-wing saltbush (Atriplex canescens), native to western North America, extends from Canada to Mexico and from the Great Plains to the Pacific Coast. Shrubby species of Atriplex are in the family Chenopodiacea, which contains other important shrubs such as winter fat (Krascheninnikovia lanata), and often dominate landscapes in many arid and semi-arid regions, particularly in habitats that combine high soil salinity with aridity. Four-wing saltbush is an important browse species to wildlife and livestock and has been reported to provide as much as 11.4 % to 13.6% crude protein. The use of four-wing saltbush in restoration and land rehabilitation plantings is well documented and increasingly popular. Four-wing saltbush is a common species to be seeded on Great Basin rangelands, especially in the more xeric Wyoming big sagebrush (Artemisia tridentata) and salt desert shrub plant communities. Granivorous rodents are important in the ecology of plant communities as well as the management practices that occur in those communities. Granivorous rodents have been reported to be an important seed dispersal mechanism for numerous Great Basin plant species, such as antelope bitterbrush (Purshia tridentata) and Indian ricegrass (Achnatherum hymenoides), as well as an active seed and seedling predator on Great Basin plants species. We constructed portable live-trap enclosures in which we recorded granivorous rodent activities with four-wing saltbush seeds and seedlings. Granivorous rodents captured in the portable enclosures did not harvest four-wing saltbush in their cheek pouches nor did they cache any seeds in the soil substrate within these portable enclosures. Rodents did however excavate embryos from four-wing saltbush seeds ranging from 34-55%. Four-wing saltbush seedlings were preyed upon heavily by granivorous rodents ranging from 75-99%. It is important that critical browse species, such as four-wing saltbush, are vigorous and healthy as to experience good flowering and produce substantial seeds to the environment. The more seeds that are available to germinate and emerge, the less the total effect of rodent predation on the recruitment of seedlings to sustain the plant population. Although this research was conducted using portable live-trap enclosures, granivorous rodents in this study avoided caching four-wing saltbush seed while still excavating the embryo from the seed. The seedling predation may well be higher than in natural conditions, yet the fact that such a high level of seedling predation occurred when an alternative millet seed food source was available suggest a preference for these seedlings at this young phenology stage. This research yielded that four-wing saltbush seed is not highly preferred as the rodents at this site are not harvesting and caching the seed for future consumption. The high consumption of four-wing saltbush seedlings at this site is alarming and may be an explanation of poor success at given sites following the seeding of four-wing saltbush. The clipping of seedlings by granivorous rodents is more detrimental to shrub seedlings than grass seedlings due to the removal of the hypocotyl or epicotyl. The importance of four-wing saltbush for wildlife and domestic livestock as well as its’ role in improving functional plant communities only enhances the desire to successfully rehabilitate/restore degraded rangelands. The results from this study would suggest that resource managers cannot depend on granivorous rodents to harvest, disperse and cache four-wing saltbush seed, therefore drill seeding of four-wing saltbush seed may be necessary to get the seed into the ground where the seed has a higher chance of germination and emergence. The fact that four-wing saltbush seedlings were consumed at a high level allows resource managers the understanding of that perhaps transplanting of older seedlings coul