Hopland Research and Extension Center
University of California
Hopland Research and Extension Center

Animal Science & Rangeland Science

#43-88 Scaling Effects of Nitrogen Addition on Spatial Heterogeneity in Grassland Community Composition

Dr. Valerie Eviner, Plant Science UC Davis

Human-derived nitrogen deposition is recognized as a major threat to the stability of natural systems worldwide, noted particularly for its negative effect on the abundance of stress-adapted species. However, current approaches to evaluating N deposition effects on grassland community structure often use small plots and short durations, which may translate poorly to the broader ecosystem—California grasslands, in particular, are characterized by rapid turnover in community composition through space and time. While N addition has generally been found to decrease diversity in small plots, due to changes in local competition between plants, it is unclear whether these same diversity losses will occur uniformly across the landscape and over time. As a key contributor to ecosystem resilience and stability, maintaining a shifting mosaic of diverse species which fluctuate in their abundances in response to annual variation in climate may be an increasingly important goal for effective land management. By using a combined approach that incorporates long-term datasets and sampling at Hopland REC, Sierra Foothill REC, and McLaughlin Natural Reserve, we aim to characterize general patterns describing how grassland community composition varies across the landscape and between years. Following establishment of these patterns, we will evaluate the effect of nitrogen deposition on the underlying processes driving shifts in grassland composition through nutrient addition treatments. Doing so will present a refined picture of N-driven biodiversity change in California grasslands, informing potential management practices to enhance long-term ecosystem resilience and productivity in the face of human-derived pressures of nitrogen deposition and climate variability.

#44-16 The effect of semen prepared with various methods on conception rates following laparoscopic artificial insemination in Targhee ewes

Catalina Cabrera, Veterinary Medicine Teaching Hospital, UC Davis

Artificial insemination greatly increases the ability to establish new genetics in sheep flocks.

Targhee lambs
 Multiple methods for semen freezing have been described with different freezing curves, extenders and cryoprotectants. The objective of this study is to evaluate the effects of these methods on conception rates in commercial targhee ewes. Semen from a pool of rams will be collected, extended and chilled of frozen under the following different proposals 1:TRIS and nitrogen vapor, 2: TRIS and a controlled freezing curve, 3: ANDROMED and nitrogen vapor, 4: ANDROMED and a controlled freezing curve, 5: CHILLED semen. Laparoscopic Artificial Insemination (LAI) will be performed on all ewes (beginning with 75 ewes) responding to the CIDR, Prostaglandin and PG600 sychronization treatment. Pregnancy rate, lambing rate and fecundity will be evaluated and analyzed between groups. The results of this study will be immediately available to veterinarians and sheep producers.

#47-14 Effects of Progesterone Intra-Vaginal Devices, PG-600, and Ram Effect on Hastening Onset of Cyclicity and Fecundity in Ewes

Catalina Cabrera and Bret McNabb, Livestock Herd Health & Reproduction, School of Veterinary Medicine, UC Davis

Effects of Progesterone Intra-Vaginal Devices, PG-600, and Ram Effect on Hastening Onset of Cyclicity and Fecundity in Ewes
While sheep are seasonal polyestrous breeders, cycling in late summer and early autumn when daylength is decreasing, breeding as early as possible in the season has many management and economic benefits.  This study evaluates the effectiveness of using a recently- approved intravaginal progesterone device (CIDR). The objective is to determine the most effective protocol for inducing cyclicity in Targhee ewes and synchronizing lambing, while at the same time maximizing economic return for the flock.

#42-12 Spatial Methods for Low-Cost Restoration of Rangeland Ecosystem Services

Emilio Laca, Dept. of Plant Sciences, UC Davis

Spatial Methods for Low-Cost Restoration of Rangeland Ecosystem Services
Rangelands have been degraded or lost due to removal of woody species, invasion by noxious exotic plants, overgrazing, and development.  Restoration is hindered by high costs and low returns because the entities that pay for restoration do not capture most of the benefits resulting from increased ecosystem services.  This project aims at promoting restoration of rangelands by testing and disseminating spatial methods to reduce cost and improve the success of revegetation and seeding of native species.  We hypothesize that restoration success per unit cost can be improved by careful selection of sites at the landscape scale and custom spatial seeding patterns at the site scale.  At HREC, we will conduct a controlled manipulative experiment at a small scale where we can do intensive sampling in 16 pre-existing 17 × 35-m bounded runoff plots.  Four treatments [1) 100% area seeded with a seed mix recommended for restoration of native grasses and forbs, 2) 75% area seeded, 3) 50% area seeded, 4) 25% area seeded] will be replicated three times and compared to untreated controls.  In addition to measuring forage production, vegetation and insect diversity, and weed abundance, we will intensively measure total runoff, sediment, soil moisture, and N and C fractions leaving the plots with belowground lateral water flow at the bottom of the slope.

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