Many tropical trees do not form reliable annual growth rings, making it a challenge to develop tree-ring width chronologies for application to paleoclimatology in these regions. Here, I seek to establish high-resolution proxy climate records from trees without rings from the Monteverde Cloud Forest in Costa Rica using stable isotope dendroclimatology. Neotropical cloud forest ecosystems are associated with a relatively narrow range of geographic and hydroclimatic conditions, and are potentially sensitive to climate variability and change at time scales from annual to centennial and longer. My approach takes advantage of seasonal changes in the d18O of water sources used by trees over a year, a signature that is imparted to the radial growth and provides the necessary chronological control. A rapid wood extraction technique is evaluated and found to produce cellulose with d18O values indistinguishable from conventional approaches, although its application to radiocarbon requires a statistical correction. Analyses of plantation-grown Ocotea tenera reveal coherent annual d18O cycles up to 9 permil. The width of these cycles corresponds to observed basal growth increments. Interannual variability in d18O at this site is correlated with wet season precipitation anomalies. At higher elevations within the orographic cloud bank, year-to-year changes in the amplitude of oxygen isotope cycles show a relationship with dry season climate. Longer d18O chronologies from mature Pouteria (Sapotacae) reveal that dry season hydroclimatology is controlled at interannual time scales by variability in the eastern equatorial Pacific (ENSO) and the Western Hemisphere Warm Pool (WHWP), which are correlated with trade wind strength and local air temperature. A change in the late 1960s toward enhanced annual d18O amplitude may reflect low frequency changes in the Atlantic and Pacific ocean-atmosphere system. This study establishes the basis for cloud forest isotope dendroclimatology and demonstrates that the local climate of neotropical cloud forests is sensitive to interannual, and perhaps, multidecadal changes in important large-scale modes of climate variability.

<p>Costa Rica är inte vad det en gång har varit. Jaguarjägaren har lagt ner vapnet. Idag försörjer han sig på turister som vill bli ett med naturen. Svenska skolbarn samlar in pengar för att skydda regnskogen i Costa Ricas mest besökta naturreservat. Traditioner som att jaga vilda djur och att skövla dyrbar regnskog är inte längre lagliga.</p><p>Vad händer när ett land satsar på en näring som innebär stora förändringar? Ekoturism är vad turisterna efterfrågar och vad costaricanerna erbjuder.</p>

The rapid expansion of ecotourism in the Monteverde zone of Costa Rica has increased the incidence in food insecurity in the area. Changes in food preferences and availability have led to a more homogenized diet that is increasingly delocalized and reliant on processed foods. Additionally, there has been a rapid economic shift away from agricultural and dairy farming to an economy more reliant on tourism. This NSF supported study builds upon data from a longitudinal investigation (#BNS 0753017) examining the nutritional effects of this rapid economic transition. Using a mixed methods approach, a culturally appropriate scale of stress was developed and used in conjunction with the Household Food Insecurity Access Scale, the Cohen Perceived Stress Scale, and the Hopkins Symptom Check List to explore the relationship between food insecurity and mental health among residents of the Monteverde zone. Quantitative results show that food insecurity correlated positively with stress, depression and anxiety, and was found to be a significant predictor of stress and depression

Costa Rica är inte vad det en gång har varit. Jaguarjägaren har lagt ner vapnet. Idag försörjer han sig på turister som vill bli ett med naturen. Svenska skolbarn samlar in pengar för att skydda regnskogen i Costa Ricas mest besökta naturreservat. Traditioner som att jaga vilda djur och att skövla dyrbar regnskog är inte längre lagliga. Vad händer när ett land satsar på en näring som innebär stora förändringar? Ekoturism är vad turisterna efterfrågar och vad costaricanerna erbjuder.

No description available.

Disturbance in a forest’s canopy, whether caused by treefall, limbfall, landslide, or fire determines not only the distribution of well-lit patches at any given time, but also the ways in which the forest changes over time. In this dissertation, I use a 25 year record of treefall gap formation find a novel and highly patterned process of forest disturbance and regeneration, providing a local mechanism by examining the factors that influence the likelihood of treefall. I then develop a stochastic cellular automaton for disturbance and regeneration based on the analysis of this long term data set and illustrate the potential of this model for the prediction and detection of patterned forest dynamics in general. Finally, I investigate the spatial structure of a population of one of the most common gap colonist species in this forest, Didymopanax pittieri, and illustrate the effect of local aggregation of treefalls and on the population dynamics of D. pittieri in the process.

No description available.