Date of Award:
Master of Science (MS)
A series of experiments evaluated: 1) the influence of seed intake and gut
retention time on seed passage , recovery , and germinability; 2) fecal seeding and
broadcast /trampling as techniques to incorporate seeds into a well-established
Agropyron desertorum (Fisch.) Schult. stand in Skull Valley , Utah; 3) intensive
grazing as a means to reduce Agropyron biomass and increase establishment and
survival of seeded species; and 4) the recovery and germinability of seed extracted
from dung collected from the field. Two shrubs (Artemisia tridentata Nutt. ssp.
wyomingensis Beetle & Young and Atriplex confertifolia Torr. & Frem.), a grass
(Elymus elymoides (Raf.) Swezey) , and a forb (Sphaeralcea grossulariaefolia (H. &
A.) Rydb.) were selected as representative native species. Holstein heifers were fed
15,000 , 30 ,000 , and 60,000 seeds of Artemisia , Sphaeralcea, and Elymus. Elymus
recovery was negatively correlated to seed intake. Sphaeralcea had the highest
percentage of recovered, undamaged seed, followed by Elymus and Artemisia.
Sphaeralcea and Artemisia seed passage was highest on Day 1 then dropped sharply.
Elymus passage and recovery were more consistent through time. Post-passage
germjnability was highest for Elymus and Sphaeralcea on Day 1. Artemisia
germjnation was neghgible.
In the fall seeding, Sphaeralcea emerged in 6% of the subplots (half were
volunteers). Overall seedling mortality was 93%. Elymus emerged in 63% of the
dung pats, with 86% mortality. No Artemisia emerged. Drought and Anabrus
simplex herbivory contributed to low seedling emergence and survival. In April
2003, similar treatments were applied, except Atriplex seed was substituted for
Artemisia, and a third treatment was added (broadcast seeding/raking). No
emergence was observed. Sphaeralcea had the highest seed recovery from dung
collected in the field trials, followed by Elymus, Atriplex, and Artemisia.
Sphaeralcea germinability was similar for seeds collected from both trials (11 %) and
Elymus germination was highest in the fall seeding (13%).
These studies indicate that: 1) physical seed properties (size, shape, density,
seed coat) influence seed passage , recovery, and germination; 2) intensive grazing
can reduce Agropyron biomass by 50% for 2 years; 3) broadcast/trampling may be
effective for Sphaeralcea; and 4) an average-sized dung pat (714 g) may have ample
germinable Sphaeralcea and Elymus seeds for plant establishment.
Whitacre, Marina K., "Cattle as Grazing Management and Seed Dispersal Tools for Increasing Native Species Diversity on Great Basin Rangelands" (2004). All Graduate Theses and Dissertations. 6604.