<p> This dissertation examines the competitive and cooperative strategies of male mantled howlers (<i>Alouatta palliata</i>) living within a fragmented habitat at La Pacifica (LP), Costa Rica. Mantled howlers exhibit considerable intraspecific variation in their social behavior, and there remains much to learn regarding the nature of their sociality and the proximate mechanisms that underlie it, particularly among males living in multimale groups. In contrast to males at other mantled howler study sites, males at LP had higher rates of within-group agonism, and exhibited clear dominance hierarchies. Both groups inhabited a fragmented forest, which may exert greater pressure to compete for both food and reproductive resources than mantled howler males living in more intact forests. However, data from this dissertation also suggest that males may adjust competitive relationships as forest fragment characteristics within the same population vary. The group inhabiting the larger forest fragment experienced higher intergroup competition but lower intragroup competition than the group inhabiting the smaller fragment, allowing higher-ranking males to be more tolerant of subordinates accessing key resources, including females, in order to cooperate in group defense. Despite clear hierarchies, males at LP nevertheless form both preferred and avoided associations with specific males, which suggest that cooperative relationships among males have adaptive value. Neither rank nor age emerged as clear drivers shaping competitive and cooperative relationships. Collectively, these results suggest that male mantled howlers show considerable flexibility in their social relationships that are likely dependent on a complexity of ecological, social, and demographic factors.</p>

Abstract Not Available.

Increasing levels of atmospheric CO2 threaten to change the earth's climate and diversity in numerous adverse ways. This thesis explores aspects of two potential types of terrestrial sinks in East Texas, plantation rotation management and reforestation. I used a simple method of employing government GIS and tabular data for calculating and visualizing the size of those sinks, which could store an additional 2.3 to 98 million Mg C aboveground. The uncertainty of these values is high because of data inadequacies and also uncertainty about future land use trends. The mitigative powers of these sinks are discussed, as is their potential application in newly forming carbon credit programs such as the Chicago Climate Exchange.

Three experiments focused on the contribution of rice productivity to methane emission were conducted in Texas flooded rice paddy soils during 1994-95 growing seasons. Measurements of methane emission from different rice paddy soils during 1991-92 growing seasons (Sass et al., 1994) and from ten different cultivars in 1993 growing season (Willis, 1995; Sass and Fisher, 1995) were cited to quantify the relationships of methane emission with soil, rice cultivar and grain yield. Under the similar soil sand content and agronomic management regime, total seasonal methane emission was positively correlated with rice grain yield and aboveground biomass at harvest. Linear relationships of daily methane emission with aboveground vegetative biomass and root biomass were also observed. On a carbon to carbon basis, the ratio of methane emission to rice net primary productivity was dependent on soil and rice variety, and increased with rice plant development. Models emphasized the contributions of rice plants to the processes of methane production, oxidation and emission and also the influence of environmental factors were developed to predict methane emission from flooded rice fields. Relative effects of soil texture, soil temperature and rice variety on methane production/emission were quantified by three dimensionless indices: soil index, temperature index and variety index, respectively. Model validation against observations from various regions of the world, including Italy, China, Indonesia, Philippines and USA demonstrated that methane emission can be predicted from rice growth and development, cultivar character, soil texture and temperature, and organic matter amendments. Of these, rice growth and development is a principal parameter governing the processes of methane production, oxidation and emission in irrigated rice paddies. Model estimates suggest that annual amount of methane emitted from Chinese rice fields ranges from 7.03 to 13.32 Tg CH$\sb4$ yr$\sp{-1}$ with an average value of 9.45 Tg CH$\sb4$ yr$\sp{-1}$ under permanent irrigation and the majority of methane was emitted in the region located at latitude between 25$\sp\circ$ and 32$\sp\circ$ N. Comparisons of estimated with the observed emissions show that the estimates were in general close to the measurements at most locations.

Lying in the wake of accelerated technological advancement is a landscape of economic and environmental consequence. As older industrial facilities become obsolete, newer technologies look towards virgin land for growth. In turn, the industrial city, once the recipient of generous corporate taxation and stable work force, is saddled with social unrest, economic stagnation, and vast tracts of infrastructure-laden land. Such is the case with the vacated Bethlehem Steel plant in Bethlehem, Pennsylvania. At the root of this thesis is a conviction that regeneration of this site needs to be approached as a multidimensional phenomenon which touches upon the organic, the economic, and the chemical. As such, a kind of petri dish can emerge where physical entropy and the erosion of memory coexist with economic and ecologic growth. This thesis attempts to define a new beginning by bridging the cleft between growth and decay. The history of this site, its entropic future, and the beginnings of a new history are conflated into a single continuum.

Humans are inextricably linked to the ecosystems they inhabit. The making of artifacts in our environment invariably changes the trajectory of already mutable systems, affecting change in both nature and culture. This change is sometimes calculated and deliberate, at other times it is unintentional and unforeseen. Where humans have caused blight to ecosystems, restoration ecologists attempt to assuage human-induced losses by copying or even re- inventing nature. Copying or re-inventing nature is as natural as nature itself. Nature itself copies. Nature copies itself. Artifacts of Nature is an investigation into the vestiges of human making, the disposition of materials and (in) time, and the dynamic and ever-changing order that is nature. The design component for the project, a trout hatchery, is for the purpose of reintroducing an extirpated cutthroat species into 18 miles of native stream in east-central Nevada.

<p> Predicting impact of oil spills on aquatic life requires a better understanding of effects on aquatic organisms, both for single hydrocarbons and for their interactions. In this study, the individual and combined effects of petroleum hydrocarbons phenanthrene (Phen) and dibenzothiophene (DBT) were assessed on the reproductive behavior of the freshwater amphipod <i>Hyalella azteca. </i> Following a 24-h exposure to single PAHs, or an equimolar mixture of Phen-DBT, mate-guarding behavior was assessed at the end of the exposure and during a subsequent 10 min behavioral observation period with the animals in clean water. The endpoints of the study during the behavior observation period were&mdash;time taken to initiate mate-guarding (TIMG), and proportion of time spent in amplexus (PTA). The study demonstrated that the exposure to Phen and DBT reduced the incidence of mate-guarding during the actual exposure period, but not during the observation period. However, whether or not pairs were involved in mate-guarding at the end of the exposure period did affect both TIMG and PTA during the observation period. Thus, the effects of Phen and DBT on amplexus status at the end of the exposure period indirectly affected TIMG and PTA during the observation period. The interaction between Phen and DBT with respect to their effects on mate-guarding varied among the mate-guarding measures. For the amplexus status at the end of the exposure period and for the effect on TIMG, the interaction did not deviate statistically from an additive effect. For PTA, the overall interaction was a synergistic one. This study's findings point out that assessments of hydrocarbon toxicity need to take into account that subtle reproductive behaviors (that may play an important role in population persistence) may be negatively affected. The results also show that the general assumption of additive effects among different PAHs may be an oversimplification.</p>

<p> What drives invasive species success? My research consists of four studies aiming to answer this question for <i>Ligustrum sinense</i>. The four projects are: (1) Synthesis of invasion literature within passenger-driver-backseat driver frameworks; (2) hydrochory investigation of water as a dispersal mechanism for invasion; (3) ecohydrology investigation of inundation effects on seed viability of <i>L. sinense</i>; (4) dendrochronology study of the effects of stream channelization and <i>L. sinense</i> invasion on bottomland oak tree growth. Results suggest that <i>L. sinense</i> initially invaded habitats that were hydrologically altered, resulting in drier conditions and a "novel niche." Dispersal <i>via</i> hydrochory allowed <i>L. sinense</i> to quickly colonize the novel niches. Once established, <i>L. sinense</i> competed with native oak species contributing to reduced growth rates, an "invasion meltdown." Control strategies should aim to remove <i>L. sinense</i> and return natural hydrologic regimes, or should consist of human-assisted re-establishment of native species that can thrive in altered conditions.</p>

<p> <i>Sinorhizobium meliloti</i> is a Gram-negative alphaproteobacterium and nitrogen-fixing symbiont, which undergoes a novel cell cycle modification during its' host-microbe interaction. I intend to monitor the transcriptional regulation of cell cycle-related genes during free-loving growth, in addition to monitoring their expression during symbiosis. Using genes known to be regulated by CtrA in <i>C. crescentus</i> or predicted to be regulated by CtrA in <i>S. meliloti,</i> I aim to show how certain cell cycle genes are regulated in <i>S. meliloti.</i> In <i>C. crescentus, </i> CtrA acts as a transcription factor that is active when phosphorylated and inactive when not phosphorylated. In <i>S. meliloti,</i> CbrA is a histidine kinase that ultimately inhibits CtrA phosphorylation. Using a &Delta;<i>cbrA</i> null mutant, which leads to increased levels of CtrA in <i>S. meliloti,</i> and the &beta;-glucuronidase (GUS) reporter gene, I can monitor the expression levels of target genes that are potentially regulated by CbrA and CtrA. Promoter regions, transcription start sites, and translation start sites of target genes have been cloned into the plasmid pVO155 upstream of the GUS gene. I measured the GUS enzymatic activity using the 4-methylumelliferyl-beta-D-glucuronide (MUG) substrate. Additionally, after infecting <i>Medicago sativa</i> seedlings with these fusions strains, I used a different GUS substrate to test for the presence of target gene expression in root nodules. Results thus far have shown some target genes with large differences in expression coinciding with the absence of <i> cbrA</i> and increased CtrA levels while some target genes show only slight differences, if any at all. Tracking the expression location and patterns of target genes in root nodules has shown that some genes are expressed ubiquitously throughout the nodule while other genes are expressed in specific locations. These results are significant because no one has looked at genes regulated by CbrA or CtrA in <i>S. meliloti,</i> which is more applicable to host-microbe interactions than <i>C. crescentus,</i> especially since <i>Agrobacterium tumefaciens</i> and <i>Brucella abortus </i> both have a CbrA homologue. Additionally, I will provide critical insight into the molecular biology of the <i>S. meliloti</i> host-microbe interaction.</p>

<p> Physical evidence of past fires, left in the form of cambial scars, suggests that low and moderate intensity fires have burned periodically for centuries in the coast redwood (<i>Sequoia sempervirens</i>) forest in California's central coast bioregion. These fires may have played an important role in shaping stand age structure and composition. Nonetheless, the ecological role of fire in shaping successional processes in the redwood ecosystem is not well understood. The extent to which both aboriginal and more recent burning practices have affected the central coast landscape is also uncertain. Standard dendrochronology techniques were used to reconstruct and analyze the fire history of the coast redwood forest in the Santa Cruz Mountains based on the fire scar record. Three hundred and seventy-three fire scars were identified in 70 cross-sections that were removed from redwood stumps, downed logs, and trees in select locations between Davenport and A&ntilde;o Nuevo, California. The earliest recorded fire occurred in 1352 and the most recent in 2009. The grand mean fire return interval (FRI) for single trees (point) was 60.6 years, and the median FRI was 40.1 years. Fire scars were found most frequently in the dormant and latewood portions of the annual growth rings, signifying that fires tended to occur in the late summer and fall. A high degree of variability in the data set suggests that cultural burning practices occurred on fluctuating temporal and spatial scales.</p>