Ecosystem services from keystone species: diversionary seeding and seed-caching desert rodents can enhance Indian ricegrass seedling establishment

Authors: Longland, William - Bill; OSTOJA, STEVEN - Us Geological Society

Submitted to: Restoration Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/28/2012
Publication Date: 7/6/2012
Citation: Longland, W.S., Ostoja, S.M. 2012. Ecosystem services from keystone species: diversionary seeding and seed-caching desert rodents can enhance Indian ricegrass seedling establishment. Restoration Ecology. DOI: 10.1111/j.1526-100X.2012.00895.x.

Interpretive Summary: Indian ricegrass is a native bunchgrass that provides an important source of livestock and wildlife forage on arid western rangelands. Desert rodents, especially some species of kangaroo rats, cache (i.e., store) large numbers of Indian ricegrass seeds when mature seeds are available on or beneath plants and recover most of their caches for consumption during the remainder of the year. Even though most cached seeds are eaten, a sufficient number of seeds remain unrecovered and eventually germinate from caches that rodents account for the vast majority of seedlings produced by Indian ricegrass. We applied millet seeds, which are commonly available in wild bird food and highly preferred by desert rodents, as “diversionary foods” to plots at three Great Basin study sites in an attempt to reduce cache recovery by rodents so that more Indian ricegrass seeds would remain in soil seedbanks and potentially establish new seedlings. Although lack of sufficient precipitation resulted in no seedling production at an eastern California study site, at two Nevada sites considerably more Indian ricegrass seedlings were produced on plots where we applied diversionary millet seeds than on non-seeded plots. Diversionary seeding may thus provide a promising low-input strategy for restoring Indian ricegrass to arid rangelands.

Technical Abstract: Seeds of Achnatherum hymenoides (Indian ricegrass), a native bunchgrass on arid western rangelands, are naturally dispersed by seed-caching rodent species, particularly Dipodomys spp. (kangaroo rats). These animals cache large quantities of seeds when mature seeds are available and recover most of their caches for consumption during the remainder of the year. Unrecovered seeds in caches account for the vast majority of Indian ricegrass seedling recruitment. We applied three different densities of Panicum miliaceum (white millet) seeds as “diversionary foods” to plots at three Great Basin study sites in an attempt to reduce cache recovery so that more Indian ricegrass seeds would remain in soil seedbanks and potentially establish new seedlings. There was no seedling recruitment at an eastern California study site. However, at two sites in western Nevada, the number of Indian ricegrass seedlings sampled along transects was significantly greater on all plots treated with diversionary seeds than on non-seeded control plots. Density of diversionary seeds applied to plots did not affect recruitment significantly. Results suggest that application of a diversionary seed type that is preferred by seed-caching rodents provides a promising passive restoration strategy for target plant species that are dispersed by seed-caching rodents in nature.