The goal of this research is to understand how and why tree diversity changes during 200 years of shifting cultivation in a tropical rainforest. To determine the relative importance of dispersal and nutrient limitation to tree diversity, I collected data on changes in the struct…
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The research presented in this dissertation examines how the relative dominance of silicate versus carbonate weathering varies both spatially and temporally in two rapidly uplifting, young orogenic belts—the Himalaya Mountains and the New Zealand Southern Alps. Silicate rocks in…
Surface horizon samples from two Vertisols, an Andisol, and an Alfisol were collected from farmers' fields, research station farms, and uncultivated/non-fertilized areas to characterize the organic and inorganic forms of P, to describe the equilibrium P sorption-desorption chara…
Analyses of concentration, and absorption and fluorescence spectroscopy of the dissolved organic carbon were performed on waters collected during cruises to the West Florida Shelf (WFS), eastern Caribbean, and the Arabian Sea. The cruise to the WFS was designed to measure the ef…
The limited timespan (several decades) of dissolved oxygen (DO) instrumental records precludes a complete picture of how DO in seawater have changed in the past, and thus high-resolution paleo-DO reconstructions are essential for revealing DO variability on centennial to millenn…
Forests play a central role in global biogeochemical cycling by storing carbon (C) and retaining nutrients. Yet, we have limited understanding of how shifts in forest composition (owing to global environmental changes) will affect ecosystem functioning. A long history of researc…
Pteropods (pelagic snails) are ubiquitous zooplankton in the Southern Ocean and abundant along the Western Antarctic Peninsula (WAP), one of the most rapidly warming regions on the planet. They are important prey for higher trophic levels, grazers of phytoplankton, and contribut…
The oceaographic characteristics of the Arabian Sea are closely linked with the Asian monsoon dynamics, its existence as a geographic cul-de-sac, and inputs of water from the marginal Red Sea and Persian Gulf. Surface productivity in the Arabian Sea is some of the highest in the…
Copepod fecal pellets can be an important vector for transporting organic carbon and amino acids from the surface waters to deep water and the sediments. Understanding the processes, e.g., fecal pellet production, organic carbon composition and concentration along with dissolved…
A mooring time series of physical and bio-optical variables and complimentary data were collected during the Arabian Sea Process Study in 1994-1995. The mooring data-set was collected continuously for one year. This allowed observation of two mixed layer (ML) deepening events, d…
I have developed a computer model, called GEOMOD, to simulate land use change and its consequences on biotic carbon exchanges between terrestrial ecosystems and the atmosphere, using a spatial modeling approach. Land use change is a most important part of the anthropogenic distu…
Changes in carbon dioxide concentration and/or ocean circulation are generally invoked to explain both equable early Miocene climates and subsequent rapid East Antarctic ice sheet (EAIS) expansion in the middle Miocene. However, pCO\sb2 trends and absolute magnitudes must be inf…
The accuracy of past climate estimates utilizing planktonic foraminifera is limited by our knowledge of their habitats, which determine the stable isotopic (\delta¹⁸O, \delta¹³C) signals carried by their tests. This study refines habitat estimates of the species Globigerinoides …
Ağır metal kirliliği, farklı endüstriyel alanlardaki artan kullanımlarından dolayı günden güne artış göstermektedir. Özellikle pil, boya ve metal endüstrisi ile maden faaliyetlerinden dolayı doğaya salınan ağır metal miktarı oldukça fazladır. Sanayi atıkları ile ekosistemlere ve…
This dissertation examines biogeochemical dynamics of organochlorine (org-Cl) and organobromine (org-Br) in coastal ecosystems impacted by sea level rise. Global warming results in thermal expansion of oceans and subsequent saltwater intrusion into coastal ecosystems. As previou…
This study was designed to develop a model to describe the spatial distribution of organic components within tropical domed peats in the coastal lowlands of Southeast Asia. To this end, a series of thick, domed peat deposits were examined in similar prograding deltaic settings i…
Investigations of depositional environments, paleogeographic evolution, source rock potential/maturity, and petroleum generation, expulsion, migration and accumulation were performed on the Oligocene to Middle Miocene deposits in the Ardjuna Basin, offshore Northwest Java, using…
The semi-continuous activity of Merapi volcano threatens the residents of the villages on its slopes as well as the residents of Yogyakarta, the second largest city in Java. Although Merapi behavior is scarcely predictable, its current eruptive episode lasting since the end of t…