The Spectral Distribution of Radiation in Two Neotropical Rainforests

The spectral quality of radiation in the understory of two neotropical rainforests, Barro Colorado Island in Panama and La Selva in Costa Rica, is profoundly affected by the density of the canopy. Understory light conditions in both forests bear similar spectral characteristics. In both the greatest changes in spectral quality occur at low flux densities, as in the transition from extreme shade to small light flecks. Change in spectral quality, as assessed by the red: far-red (R:FR) ratio, the ratio of radiant energy 400-700: 300-1100 nm, and the ratio of quantum flux density 400-700:300-1100 nm, is strongly correlated with a drop in percentage of solar radiation as measurable by a quantum radiometer. Thus, by knowing the percentage of photosynthetic photon flux density (PPFD) in relation to full sunlight, it is possible to estimate the spectral quality in the forest at a particular time and microsite.

Correspondence of historic salinity fluctuations in Florida Bay, USA, to atmospheric variability and anthropogenic changes

Florida Bay is a highly dynamic estuary that exhibits wide natural fluctuations in salinity due to changes in the balance of precipitation, evaporation and freshwater runoff from the mainland. Rapid and large-scale modification of freshwater flow and construction of transportation conduits throughout the Florida Keys during the late nineteenth and twentieth centuries reshaped water circulation and salinity patterns across the ecosystem. In order to determine long-term patterns in salinity variation across the Florida Bay estuary, we used a diatom-based salinity transfer function to infer salinity within 3.27 ppt root mean square error of prediction from diatom assemblages from four ~130 year old sediment records. Sites were distributed along a gradient of exposure to anthropogenic shifts in the watershed and salinity. Precipitation was found to be the primary driver influencing salinity fluctuations over the entire record, but watershed modifications on the mainland and in the Florida Keys during the late-1800s and 1900s were the most likely cause of significant shifts in baseline salinity. The timing of these shifts in the salinity baseline varies across the Bay: that of the northeastern coring location coincides with the construction of the Florida Overseas Railway (AD 1906–1916), while that of the east-central coring location coincides with the drainage of Lake Okeechobee (AD 1881–1894). Subsequent decreases occurring after the 1960s (east-central region) and early 1980s (southwestern region) correspond to increases in freshwater delivered through water control structures in the 1950s–1970s and again in the 1980s. Concomitant increases in salinity in the northeastern and south-central regions of the Bay in the mid-1960s correspond to an extensive drought period and the occurrence of three major hurricanes, while the drop in the early 1970s could not be related to any natural event. This paper provides information about major factors influencing salinity conditions in Florida Bay in the past and quantitative estimates of the pre- and post-South Florida watershed modification salinity levels in different regions of the Bay. This information should be useful for environmental managers in setting restoration goals for the marine ecosystems in South Florida, especially for Florida Bay.

Outdoor experiential team -building and the college adjustment and persistence of freshmen in learning communities

Student retention is a primary goal in all higher education institutions. Students who are more adjusted to college life are more likely to persist. The purpose of this research was to determine the effects of an outdoor experiential team-building program on the college adjustment of first-semester freshmen in learning communities at a diverse, urban university. The participants in this quasi-experimental study were first-semester freshmen enrolled in learning communities. A total of 123 students participated, with 61 students in the experimental group and 62 students in the comparison group. There were no significant differences between the two groups in relation to age, gender, or ethnicity. The students in the experimental group participated in the team-building program, which consisted of three events spaced three and four weeks apart. At the end of the semester, students in both the experimental and comparison groups completed the Student Adaptation to College Questionnaire (SACQ), a 67-item self-report survey. ^ Independent samples t-test of the SACQ scores (for attachment to the institution, social adjustment, and overall adaptation to college) between groups was done, and the analyses revealed no statistically significant differences. Chi-square analyses revealed no significant difference in the enrollment pattern between the two groups over a four-year period. Repeated measures ANOVAs revealed that from the first semester of enrollment to the second semester there was a significant drop in GPA for students from the comparison group and no such drop in GPA for students from the experimental group who had participated in at least two of the team building activities. A repeated measures ANOVA was conducted for the first year by semester and ethnicity. No ethnic differences were found, and no interaction was found by ethnicity and semester. ^ Should colleges and universities continue to utilize outdoor experiential team-building programs as a creative way to influence students' connection to the institution they should further investigate its value on students' adjustment to college. Future studies should also consider other variables influenced by team-building programs that affect students' college adjustment, such as collaborative learning. Faculty should be included in the planning process to increase their participation. ^

World coffee markets and national coffee parastatals since 1989: A comparative study of Colombia and Cote d'Ivoire

The International Coffee Agreements (ICA) involved the majority of nations producing and consuming coffee and provided relative economic stability to the coffee sectors of the exporting Third World countries. This study focuses on the serious impact of the 1989 collapse of the ICA on the domestic coffee sectors of Colombia and Côte d'Ivoire. In particular, the dissertation examines the role of the Colombian and Ivoirian coffee parastatals, the Federacion Nacional de Cafeteros de Colombia and the Caisse de Stabilisation et Soutien des Prix des Produits Agricoles, during the crisis and their transformation by it. ^ The theoretical framework employed in this study is borrowed from the literature on state-society relations. The methodology includes: in-depth analysis of the historical roles of the parastatal agencies in coffee production, state-society relations and economic development in Colombia and Côte d'Ivoire; interviews with parastatal administrators, producers and other knowledgeable informants in both countries; and a comprehensive review of newspaper articles and official statements of coffee policy published in Colombia and Côte d'Ivoire. prior to, during, and after the crisis. ^ The Colombian and Ivoirian coffee sectors and their producers faced serious economic and social problems following the drop in coffee prices. The coffee parastatals in Colombia and Côte d'lvoire first lost some of their responsibilities following the world coffee crisis. The Caisse was in the end eliminated while FEDECAFE struggled to remain in existence. Along the way, both entities faced protests from disgruntled coffee producers, who organized politically for the first time in their nations' histories. I argue that the outcome for the parastatals depended in part on the conditions of their formation, particularly the level of societal involvement in their creation. I also posit that the country's dependence on foreign aid played a key role in the fate of the parastatals. ^ This dissertation concludes that developments in the Colombian and Ivoirian coffee sectors have significantly contributed to the creation of the difficult political and economic conditions of both countries today. ^

The effects of climate on the growth and physiology of tropical rainforest trees

Tropical rainforests account for more than a third of global net primary production and contain more than half of the global forest carbon. Though these forests are a disproportionately important component of the global carbon cycle, the relationship between rainforest productivity and climate remains poorly understood. Understanding the link between current climate and rainforest tree stem diameter increment, a major constituent of forest productivity, will be crucial to efforts at modeling future climate and rainforest response to climate change. This work reports the physiological and stem growth responses to micrometeorological and phenological states of ten species of canopy trees in a Costa Rican wet tropical forest at sub-annual time intervals. I measured tree growth using band dendrometers and estimated leaf and reproductive phenological states monthly. Electronic data loggers recorded xylem sap flow (an indicator of photosynthetic rate) and weather at half-hour intervals. An analysis of xylem sap flow showed that physiological responses were independent of species, which allowed me to construct a general model of weather driven sap flow rates. This model predicted more than eighty percent of climate driven sap flow variation. Leaf phenology influenced growth in three of the ten species, with two of these species showing a link between leaf phenology and weather. A combination of rainfall, air temperature, and irradiance likely provided the cues that triggered leaf drop in Dipteryx panamensis and Lecythis ampla. Combining the results of the sap flow model, growth, and the climate measures showed tree growth was correlated to climate, though the majority of growth variation remained unexplained. Low variance in the environmental variables and growth rates likely contributed to the large amount of unexplained variation. A simple model that included previous growth increment and three meteorological variables explained from four to nearly fifty percent of the growth variation. Significant growth carryover existed in six of the ten species, and rainfall was positively correlated to growth in eight of the ten species. Minimum nighttime temperature was also correlated to higher growth rates in five of the species and irradiance in two species. These results indicate that tropical rainforest tree trunks could act as carbon sinks if future climate becomes wetter and slightly warmer. ^

World coffee markets and national coffee parastatals since 1989: a comparative study of Colombia and Cote D'ivoire

The International Coffee Agreements (ICA) involved the majority of nations producing and consuming coffee and provided relative economic stability to the coffee sectors of the exporting Third World countries. This study focuses on the serious impact of the 1989 collapse of the ICA on the domestic coffee sectors of Colombia and Cote d'Ivoire. In particular, the dissertation examines the role of the Colombian and Ivoirian coffee parastatals, the Federacion Nacional de Cafeteros de Colombia and the Caisse de Stabilisation et Soutien des Prix des Produits Agricoles, during the crisis and their transformation by it. The theoretical framework employed in this study is borrowed from the literature on state-society relations. The methodology includes: in-depth analysis of the historical roles of the parastatal agencies in coffee production, state-society relations and economic development in Colombia and Côte d'Ivoire; interviews with parastatal administrators, producers and other knowledgeable informants in both countries; and a comprehensive review of newspaper articles and official statements of coffee policy published in Colombia and Côte d'Ivoire prior to, during, and after the crisis. The Colombian and Ivoirian coffee sectors and their producers faced serious economic and social problems following the drop in coffee prices. The coffee parastatals in Colombia and Côte d'Ivoire first lost some of their responsibilities following the world coffee crisis. The Caisse was in the end eliminated while FEDECAFE struggled to remain in existence. Along the way, both entities faced protests from disgruntled coffee producers, who organized politically for the first time in their nations' histories. I argue that the outcome for the parastatals depended in part on the conditions of their formation, particularly the level of societal involvement in their creation. I also posit that the country's dependence on foreign aid played a key role in the fate of the parastatals. This dissertation concludes that developments in the Colombian and Ivoirian coffee sectors have significantly contributed to the creation of the difficult political and economic conditions of both countries today.

Navigating racial boundaries: The one-drop rule and mixed-race Jamaicans in South Florida

Like many West Indians, mixed-race Jamaican immigrants enter the United States with fluid notions about race and racial identifications that reflect socio-political events in their home country and that conflict with the more rigid constructions of race they encounter in the U.S. This dissertation explores the experiences of racially mixed Jamaicans in South Florida and the impact of those experiences on their racial self-characterizations through the boundary-work theoretical framework. Specifically, the study examines the impact of participants’ exposure to the one-drop rule in the U.S., by which racial identification has been historically determined by the existence or non-existence of black forebears. Employing qualitative data collected through both focus group and face-to-face semi-structured interviews, the study analyzes mixed-race Jamaicans’ encounters in the U.S. with racial boundaries, and the boundary-work that reinforces them, as well their response to these encounters. Through their stories, the dissertation examines participants’ efforts to navigate racial boundaries through choices of various racial identifications. Further, it discusses the ways in which structural forces and individual agency have interacted in the formation of these identifications. The study finds that in spite of participants’ expressed preference for non-racialism, and despite their objections to rigid racial categories, in seeking to carve out alternative identities, they are participating in the boundary-making of which they are so critical.^