Plant-soil feedbacks and invasion in sagebrush steppe ecosystems

Invasion by non-native species is a serious ecological threat and the susceptibility of ecosystems to invasion is often highly correlated with soil resource availability. Understanding the role of plant-soil feedbacks in invaded ecosystems could provide insight into community successional trajectories following invasion and could improve our ability to manage these systems to restore native diversity. My dissertation examined how plant-soil feedbacks and resource availability influence the success of both cheatgrass and native species with three interrelated studies. In a large-scale observational study, I evaluated plant community characteristics as well as soil and plant nutrients associated with progressive cheatgrass invasion in a broadly distributed sagebrush ecological site type. I found that although many nutrient pools did not differ among levels of invasion, soil ammonium (NH4+) was negatively affected by increases in cheatgrass cover. Also, cheatgrass nutrient content did not differ across sites indicating that cheatgrass may alter plant available soil nutrients to the detriment of competitors while maintaining its own nutritional content via high nutrient use efficiency and/or soil mining. I also conducted a field experiment to provide a more mechanistic understanding of the role of disturbance on nutrient availability and invasion and to address potential management approaches. I evaluated the effects of 4-5 years of repeated burning, in combination with litter removal and post-fire seeding, on nutrient dynamics and plant responses. Results from my field experiment indicated that repeated burning is unlikely to decrease soil N availability in cheatgrass-dominated systems due to cool fire temperatures that do not volatilize biomass N and strong effects of weather on plant growth and soil processes. Repeated burning and litter removal, however, did have negative effects on litter biomass and C and N contents which negatively influenced cheatgrass biomass, density and reproduction. In addition, post-fire seeding with common wheat decreased cheatgrass abundance, likely due to competition. Integrated restoration approaches that decrease litter biomass and seed banks and increase competitive interactions may be more effective at reducing annual grasses and establishing desirable perennial species than approaches aimed at reducing soil nutrients. Together, the observational and experimental components of my dissertation indicate that plant-soil feedbacks in arid sagebrush shrublands are complex and that understanding these feedbacks requires both spatial and temporal variability in sampling. Furthermore, the results from these studies provide valuable information on techniques that could facilitate the restoration of cheatgrass-dominated systems to more diverse plant communities

Aquatic Animal Health Subprogram: Investigation of an emerging bacterial disease in wild Queensland groper, marine fish and stingrays with production of diagnostic tools to reduce the spread of disease to other states of Australia : final report

This project describes how Streptococcus agalactiae can be transmitted experimentally in Queensland grouper. The implications of this research furthers the relatedness between Australian S. agalactiae strains from animals and humans. Additionally, this research has developed diagnostic tools for Australian State Veterinary Laboratories and Universities, which will assist in State and National aquatic animal disease detection, surveillance, disease monitoring and reportin

Geographic Variability in the Life History and Demography of Canary Rockfish, Sebastes pinniger, Along the U.S. West Coast

Marine fishes that persist across broad geographic ranges experience gradients in environmental and oceanographic conditions, anthropogenic stressors, and ecological factors that influence their population dynamics Understanding the spatial and temporal scale at which life history characteristics and demographic patterns vary is essential for successful management and long term sustainability of marine fisheries The Canary Rockfish is a commercially and recreationally valuable groundfish species along the West Coast of North America. After being declared overfished in 2000, several restrictions were put in place to constrain commercial and recreational fishing opportunities These restrictions coupled with favorable ocean conditions led to the recovery of the Canary Rockfish stock to a rebuilt status of 40% unfished biomass in 201 5. Despite being an important species in the management of U.S. West Coast fisheries, the life history of Canary Rockfish across untrawlable habitat s have rarely been described, including latitudinal patterns in life history traits and population demography. From 2017 through 2019, 1,567 Canary Rockfish were collected from 13 port locations along the U.S. West Coast, to investigate latitudinal patterns in size and age structure, growth, maturity, condition, and mortality, as wells as to identify biologically relevant population breakpoints along the coast. Sex specific differences in life history parameters were al so investigated coastwide. Canary Rockfish exhibited strong latitudinal patterns in life history parameters; Canary Rockfish from colder, northern port locations exhibited larger sizes at age, lived longer had variable condition, matured at larger sizes a nd older ages and had lower mortality rates than Canary Rockfish from warmer, southern port locations. Male Canary Rockfish exhibited smaller sizes at age, lived longer, were in similar condition and matured at similar sizes in comparison to female conspecifics. Trends in life history parameters related to size, age and maturity were negatively correlated with coastwide patterns in sea surface temperature a nd positively correlated with coastwide patterns in primary productivity (chlorophyll a Cluster analysis using life history traits indicated central Oregon as a biologically relevant break point for Canary Rockfish populations along the U.S. West Coast and should be considered in future stock assessment models. Further research should explore stock structure through genetic analysis and compare hook and line data from untrawlable habitats with fishery independent bottom trawl surveys to assess habitat based differences in Canary Rockfish life history and demography

AGAINST THE GRAIN: SAUDI ARABIA AND ISRAEL'S WARMING RELATIONS

Saudi Arabia and Israel have never had formal diplomatic relations. The Arab-Israeli issue of Palestinian self-determination, above all else, has kept these two Middle East states apart and at times in adversarial tension. However, the 21st century has witnessed thawing relations between Saudi Arabia and Israel, despite the continued unpopularity of Israel within Saudi society. Scholars have largely isolated one or two of the primary drivers that promote or inhibit Saudi's desire to cooperate with Israel—mutual concern with Iran, Saudi reform initiatives, and U.S. influence—without analyzing how the factors work in tandem to promote or inhibit cooperation as a whole. This thesis examines how those drivers interact to provide a more holistic understanding of why Saudi Arabia would cooperate with Israel, and the implications of those drivers on U.S. foreign policy in the Middle East. This thesis concludes that in the present configuration, the drivers of Saudi's cooperation initiatives with Israel collectively have not stimulated a viable path to normalization of relations that circumvents the barrier of Palestinian self-determination. This thesis also concludes that this barrier is predominantly the result of Saudi Arab tradition and not borne out of religion. Saudi Arabia and Israel will continue to cooperate towards mutually beneficial opportunities short of normalization for as long as the strategic context of their relationship endures.Lieutenant Commander, United States NavyApproved for public release. Distribution is unlimited

How do the movement patterns of homeless youth affect their information seeking behaviors within the systems provided to them

This work provides a reflection on the relationship between movement patterns, homeless youth, and their information seeking behaviors within the information systems they have access to in order to find help. While understudied, the relationship between the movement patterns of the homeless youth population could be used to build information systems that are customized to the way this population looks for and uses resources. We propose a two phase user study focused on homeless youth that consists of a semi-structured interview as well as a user study on a tool they use to locate resources for help

The Women Librarians of the Land-Grant Colleges in the West and Midwest, 1862-1920: A Preliminary Study

This paper focuses on the history of women librarians of the land-grant universities in the West and Midwest during the last half of the 19th century and the first two decades of the 20th century. A history of the general situation of the land-grant colleges during this time period and the new curriculum in agriculture and the mechanical arts is provided. This new curriculum required a new type of library that greatly differed from the libraries common to higher education before this time period. These changes occur alongside the emergence of Librarianship not only as a new profession, but also a new and socially appropriate vocation for educated women. The hiring practices of the land-grant college libraries, with regards to its librarians, are discussed within this historical milieu

Presynaptic partner selection during retinal circuit reassembly varies with timing of neuronal regeneration in vivo

Whether neurons can restore their original connectivity patterns during circuit repair is unclear. Taking advantage of the regenerative capacity of zebrafish retina, we show here the remarkable specificity by which surviving neurons reassemble their connectivity upon regeneration of their major input. H3 horizontal cells (HCs) normally avoid red and green cones, and prefer ultraviolet over blue cones. Upon ablation of the major (ultraviolet) input, H3 HCs do not immediately increase connectivity with other cone types. Instead, H3 dendrites retract and re-extend to contact new ultraviolet cones. But, if regeneration is delayed or absent, blue-cone synaptogenesis increases and ectopic synapses are made with red and green cones. Thus, cues directing synapse specificity can be maintained following input loss, but only within a limited time period. Further, we postulate that signals from the major input that shape the H3 HC's wiring pattern during development persist to restrict miswiring after damage

Exceptional sperm cooperation in the wood mouse

Spermatozoa from a single male will compete for fertilization of ova with spermatozoa from another male when present in the female reproductive tract at the same time. Close genetic relatedness predisposes individuals towards altruism, and as haploid germ cells of an ejaculate will have genotypic similarity of 50%, it is predicted that spermatozoa may display cooperation and altruism to gain an advantage when inter-male sperm competition is intense. We report here the probable altruistic behaviour of spermatozoa in an eutherian mammal. Spermatozoa of the common wood mouse, Apodemus sylvaticus, displayed a unique morphological transformation resulting in cooperation in distinctive aggregations or 'trains' of hundreds or thousands of cells, which significantly increased sperm progressive motility. Eventual dispersal of sperm trains was associated with most of the spermatozoa undergoing a premature acrosome reaction. Cells undergoing an acrosome reaction in aggregations remote from the egg are altruistic in that they help sperm transport to the egg but compromise their own fertilizing ability