Soil carbon storage in tropical ecosystems is important in the global carbon cycle, yet consensus is lacking on how soil organic carbon stocks are altered under anthropogenic land-use change. This thesis seeks to quantify soil carbon stocks, the associated soil carbon emissions and explores the drivers of soil respiration in managed tropical Andean lands over a 2600 m elevation gradient. It investigates: grazing and burning on high altitude montane grasslands, burning in montane forests and agriculture in premontane forests. Changes among land-uses were quantified using belowground carbon stocks, the carbon distribution among density fractions, soil carbon emissions and environmental drivers of soil respiration. Soil respiration was a good proxy of soil carbon loss in premontane pastures and montane grassland soils. The total carbon stocks on some land-uses appeared to be unaffected but the distribution of carbon within the soil had changed and even when there were no net changes in soil carbon emissions, the drivers of respiration were different. The synergistic effect of burning and grazing in montane grasslands was the most detrimental to soil carbon stocks, whereas montane forests were unaffected. In the premontane elevation, soil carbon loss was dependent on the type of agricultural practice but the succession of secondary forest allowed soil carbon to recover to similar levels measured in the mature forest. These findings highlight the fact that although land-use does not always appear to have an obvious effect on total soil carbon stocks, the loss of carbon from short-term labile pools can cause higher carbon emissions and dominate soil-atmospheric feedbacks. Furthermore, the drivers of soil respiration and the synergistic relationship between soil moisture and temperature alter under different land uses. These factors should be taken into consideration with regards to predictions of regional temperature/precipitation climate change and soil carbon management policy in order to arrive at more realistic decisions.

Zhang, Wei. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 184-203). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

He, Zhengjun. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 125-129). / Abstracts in English and Chinese. / ABSTRACT --- p.i / ACKNOWLEDGEMENTS --- p.iv / TABLE OF CONTENTS --- p.v / LIST OF FIGURES --- p.vii / LIST OF TABLES --- p.xi / NOMENCLATURE --- p.xii / Chapter Chapter 1 --- INTRODUCTION --- p.1 / Chapter 1.1 --- Issues and problems --- p.2 / Chapter 1.2 --- Objectives --- p.3 / Chapter 1.3 --- Methodology --- p.3 / Chapter 1.4 --- Significance and benefits --- p.5 / Chapter 1.5 --- Organization of the thesis --- p.5 / Chapter Chapter 2 --- BACKGROUND AND LITERATURE --- p.7 / Chapter 2.1 --- Introduction --- p.7 / Chapter 2.2 --- Daylight data measurement --- p.7 / Chapter 2.3 --- Satellite-based models to derive illuminance --- p.9 / Chapter 2.3.1 --- Irradiance derived from satellite pixel values to illuminance (indirect approaches) --- p.9 / Chapter 2.3.1.1 --- Heliosat algorithms --- p.10 / Chapter 2.3.1.2 --- Perez et al. model --- p.20 / Chapter 2.3.1.3 --- Uetani model --- p.24 / Chapter 2.3.1.4 --- Gautier et al. model --- p.25 / Chapter 2.3.1.5 --- Janjai et al. model --- p.27 / Chapter 2.3.1.6 --- Comparison of different models --- p.28 / Chapter 2.3.1.7 --- Irradiance to illuminance using luminous efficacy models --- p.31 / Chapter 2.3.2 --- Satellite pixel values to illuminance (direct approaches) --- p.34 / Chapter 2.4 --- CIE standard skies --- p.37 / Chapter 2.5 --- Sky luminance distribution and sky types prediction using meteorological data --- p.40 / Chapter 2.6 --- Sky types and sky luminance distribution prediction using satellite images --- p.48 / Chapter 2.7 --- The needs for deriving daylight data from satellite images in Subtropical southern China --- p.51 / Chapter 2.8 --- General climate information of Hong Kong --- p.52 / Chapter Chapter 3 --- USING SATELLITE-BASED METHODS TO PREDICT DAYLIGHT ILLUMINANCE --- p.55 / Chapter 3.1 --- Introduction --- p.55 / Chapter 3.2 --- Data --- p.56 / Chapter 3.3 --- Methodology --- p.62 / Chapter 3.3.1 --- Satellite pixel value to cloud index --- p.63 / Chapter 3.3.2 --- Cloud index to global illuminance: indirect approach --- p.69 / Chapter 3.3.2.1 --- Cloud index to global irradiance --- p.69 / Chapter 3.3.2.2 --- Global irradiance to global illuminance --- p.73 / Chapter 3.3.3 --- Cloud index to global illuminance: direct approach --- p.75 / Chapter 3.4 --- Model precision and results --- p.79 / Chapter 3.4.1 --- Irradiance model precision --- p.79 / Chapter 3.4.2 --- Illuminance models precision --- p.80 / Chapter 3.4.3 --- Model performance under different seasons --- p.85 / Chapter 3.5 --- Conclusions --- p.87 / Chapter Chapter 4 --- USING SATELLITE-BASED METHOD TO PREDICT SKY TYPES --- p.89 / Chapter 4.1 --- Introduction --- p.89 / Chapter 4.2 --- Data --- p.90 / Chapter 4.3 --- CIE Standard General Sky --- p.92 / Chapter 4.4 --- Sky type prediction --- p.93 / Chapter 4.4.1 --- Sample data --- p.93 / Chapter 4.4.2 --- Assessment of other approaches --- p.97 / Chapter 4.4.3 --- Formulation of a method to predict sky conditions under subtropical context --- p.101 / Chapter 4.5 --- Model precision and results --- p.105 / Chapter 4.6 --- Conclusions --- p.116 / Chapter Chapter 5 --- CONCLUSION --- p.117 / Chapter 5.1 --- Research summary --- p.117 / Chapter 5.1.1 --- The indirect approach to derive global illuminance --- p.117 / Chapter 5.1.2 --- The direct approach to derive global illuminance --- p.118 / Chapter 5.1.3 --- Sky types prediction --- p.118 / Chapter 5.2 --- Conclusion and discussion --- p.119 / Chapter 5.3 --- Research contributions and limitations --- p.122 / Chapter 5.4 --- Needs for further research --- p.123 / BIBLIOGRAPHY / APPENDIX

Sea surface temperature (SST) reconstructions from the low latitudes indicate the tropics/subtropics warmed significantly before glacial-interglacial decreases in global ice volume, suggesting the importance of tropical and subtropical climate in driving glacial terminations. ODP Site 625, drilled at a water depth of 889 m near De Soto Canyon in the Gulf of Mexico (GOM), provides continuous records of marine isotope stages (MIS) 1-6 sampled at a mean temporal resolution of 400 years. Age control is based on 8 AMS radiocarbon dates, marine isotope stratigraphy, and Foraminifera datum levels. Results from Globigerinoides ruber (white variety) Mg/Ca-SST indicate a rise of 4.4 °C from last glacial maximum to modern conditions and a 3.2 °C rise from the penultimate glaciation to the last interglaciation. However, model results suggest reduced thermohaline circulation (THC) causes salt and heat build-up in the Atlantic Warm Pool. Paired G. ruber Mg/Ca-SST and δ18O provide evidence of sub-millennial scale variability in GOM SST and SSS that is probably influenced by the strength of NADW production, as also observed in the Western Caribbean Sea. We test the idea that widespread abrupt climate change during the last glaciation caused by millennial scale fluctuations in the intensity of THC was modulated by Laurentide ice sheet (LIS) meltwater routed to the North Atlantic. To understand LIS melting dynamics and test the Meltwater Routing Hypothesis, we investigate the phasing of GOM SST and LIS freshwater events in relationship to high latitude climate. Estimated salinities from our multi-proxy approach suggest three freshwater events with a major freshwater influx from that occurred during Heinrich Event 2. This result confirms previous studies that suggested LIS summer melting during warmings in Antarctica. We also find a climate reversal during termination II from 130.4-128.4 ka. The initial rise in GOM SST at 132.1 ka of 2.9 °C is followed by a cold reversal of 1.5 °C at 130.4 ka for 2 ky and final increase to full interglacial warmth. The reversal in GOM SST is consonant with a pause in sea level rise and reduced NADW, suggesting a reduction in THC may have caused a global two-step deglaciation.

No description available.

The green python Morelia viridis is a most striking animal. Individuals are born either brick red or bright yellow and both colours change to green as adults. These colours and the remarkable colour change have long made them of interest to biologists and in demand for the pet trade. Despite this interest nothing is known of their distribution, biology or ecology in the wild. Here I address this knowledge gap by presenting results from the first detailed study of the species, at Iron Range on eastern Cape York Peninsula, Australia.¶ Individual growth was described by the von Bertalanffy growth curve, with a maximum predicted size of 1.35 metres snout-vent length. Males matured at 2.4 years and females at 3.6 years, and growth was indeterminate after approximately 12 years. The colour change from yellow to green occurs at 55 centimetres, which corresponds to individuals approximately a year old. There was no sexual dimorphism in adults, however juvenile females had larger heads than juvenile males. Adult sized individuals comprised ~50% of the population.¶ Females had a home range of 6.2 ± 1.9 ha (mean ± SE), which was positively correlated with their snout-vent length. Males adopted a roaming strategy through suitable habitat while juveniles were restricted to areas where more light reached the ground. There was overlap between multiple female home ranges, and between female home ranges and the movement paths of males. There were no differences in the distances moved by males and females of any size, although the variation in movement distances was greater in the dry season than the wet season.¶ Green pythons are obligate ambush predators which eat a variety of prey. They show an ontogenetic shift from invertebrates and terrestrial, diurnal reptiles to birds and terrestrial, nocturnal mammals. This diet change is concurrent with a shift in the time of hunting, and the location and characteristics of ambush sites. Yellow individuals were usually found within ten metres of the ground, while green individuals used the full vegetation strata and were often found in the canopy.¶ The three colour morphs of the green python appear to be adaptive for camouflage rather than intraspecific communication, as conspicuousness of each morph was always greater to a predator than to that of a conspecific. Using advanced light analysis techniques I show that each colour morph is adaptive for camouflage from visually orientated avian predators under different environmental conditions. Yellow and red morphs are half as conspicuous as green individuals would be in locations near the ground where juveniles hunt during the day. Green was the least conspicuous morph in only the canopy, where it was half as conspicuous as either the red or yellow morph. In both leafy and non-leafy sub-canopy environments green individuals were more conspicuous than both yellow and red morphs. Red morphs were least conspicuous in only the non-leafy sub-canopy environment. The conspicuousness of green males decreased with age, but this was not the case with green females. Predation of plasticine models of the three colour morphs showed that red models were ten times more likely to be predated than either green or yellow morphs, however the model colours did not always match the real morph colours.¶ There is a large predicted global distribution in Papua New Guinea, including some offshore islands, however the Australian range is restricted to small areas of eastern Cape York Peninsula. In Australia green pythons occurred in nine regional ecosystems, with most records for the closed semi-deciduous mesophyll vine forest ecosystem. A mark-recapture study at Iron Range captured 101 individuals 147 times over two wet seasons, which equates to a population size of 227 ± 81 individuals in the study area of 51 hectares. Based on the known population structure at this site only 114 (or 50%) of these individuals are adult. Although green pythons have a high density at the one intensely studied site and are predicted to occur over a large geographic area, my data are insufficient to conclude that the species is not vulnerable.

No description available.

Rainforests are of great importance to global carbon cycling, but the importance of deforestation and change in land use is poorly understood due to a lack of studies quantifying the difference in carbon fluxes between original rainforest and agricultural land. Furthermore, the aquatic outgassing of neotropical systems have been proven to have greater impact on global carbon cycling than previously anticipated (Richey et al 2002).In this study we investigated the aquatic concentration and daily diffusive gas flux of CO2 and CH4 from 4 pristine sites and 4 impacted sites, respectively, in 4 streams running along a gradient of anthropological impaction in the Atlantic Rainforest, Brazil. Statistically significant differences between pristine and impacted sites were found in all streams for both CO2 and CH4. On average, the impacted sites were found to be emitting almost three times as much C into the atmosphere as the pristine sites, mainly owing to CO2 emissions (14172±5226 mg C m-2 d-1). Exploring an area of the neotropical carbon cycle that is not yet fully understood, the study draws attention to the significant difference in aquatic outgassing from rivers observed at different impaction levels and highlights the need for further field studies.

<p>Human activity has resulted in significant increases in air temperature over the last century, and air temperatures are expected to continue rising at an accelerating rate over the next 100 years (IPCC 2007). The warming that has already occurred has had significant impacts on the worlds biota: species ranges are shifting north (or upslope), seasonal phenological events are occurring earlier, disease dynamics are changing, and populations are going extinct (Walther et al. 2002; Parmesan & Yohe 2003; Parmesan 2006; Walther 2010; Pau et al. 2011). Understanding the temperature-dependent biological mechanisms that lead to such changes is a major priority: only with such understanding can we hope to make a concerted effort to mitigate the effects of continuing climatic change. </p><p> There are three general biological mechanisms by which organisms can respond to, and potentially buffer themselves from, the direct effects of climate change: 1) physiological plasticity, 2) behavior, and 3) evolution. Here, I refer to physiological plasticity as changes in thermal reaction norms, which include sensitivity to thermal change and tolerance for thermal extremes (Huey & Stevenson 1979). These plastic responses can be reversible (acclimation) or be fixed by developmental or cross-generational non-genetic processes (West-Eberhard 2003; Ghalambor et al. 2007; Angilletta 2009). There appear to be global patterns of plasticity in thermal physiology, as temperate ectotherms tend to be more plastic than tropical ectotherms (Feder 1978; Tsuji 1988; Ghalambor et al. 2006). This difference is hypothesized to result from differences in seasonality: temperate ectotherms can experience a much wider range of thermal conditions than tropical ectotherms, and thus temperate environment might select for plasticity to track changing conditions. If physiological plasticity can buffer organisms from warming (Stillman 2003; Somero 2010), then tropical ectotherms may be at a disadvantage in the face of climate change (Huey et al. 2009). </p><p> In general, behavioral responses to thermal challenges can be thought of as occurring on either local or regional scales. At the local scale ectotherms can engage in behavioral thermoregulation, seeking out thermally suitable microhabitats within their home ranges (Bogert 1949; Huey et al. 2003; Kearney et al. 2009). At the regional scale, organisms may shift their ranges by migrating along elevation or latitudinal thermal gradients (usually up or north, respectively) to escape warming (Buckley et al. 2013). The degree to which local- and regional-scale behavioral responses can buffer populations from warming depends on numerous factors. For example, behavioral thermoregulation requires fine-scale thermal variation within the environment. However, habitats such as heavily shaded tropical forests have little thermal heterogeneity, precluding behavioral thermoregulation as an effective buffering mechanism (Huey et al. 2009). On the other hand, range shifts can be hindered by factors such as inherent mobility and natural and man-made barriers (Forero&#8208;Medina et al. 2011). Both behavioral thermoregulation and migration can be hindered by the presence of competitors or antagonistic species such as predators or parasites in thermally favorable locations (Araújo & Luoto 2007). </p><p> Most work on the evolution of thermal physiology focuses on the evolution of thermal tolerance limits (i.e., the lower and upper lethal temperature thresholds) (Stillman & Somero 2000; Angilletta et al. 2007; Barrett et al. 2011). Broad-scale comparative analyses have demonstrated that upper thermal limits vary less than lower thermal limits, suggesting that upper thermal limits may be evolutionarily constrained (Kellermann et al. 2012; Araújo et al. 2013; Grigg & Buckley 2013). This pattern is particularly strong looking over terrestrial latitudinal gradients; cold tolerance increases with latitude, but heat tolerance does not change appreciably (Sunday et al. 2012). Artificial selection experiments have demonstrated that the upper thermal tolerances of animals can evolve, but there may be limits to how much they can change (Huey et al. 1991; Loeschcke & Krebs 1996).</p><p> Physiology, behavior, and evolution are of course not mutually exclusive mechanisms. As noted above, physiological traits such as tolerance to extreme temperature can evolve, as can behavioral mechanisms. In addition, behavior may promote or inhibit the evolution of physiology. For example, behavioral thermoregulation can potentially inhibit the evolution of thermal physiology because it allows organisms to buffer themselves from thermal change (Huey et al. 2003). Furthermore, the physiological state of an organism can dictate how it behaviorally responds to a given stimulus (Atkins-Regan 2005). For example, lizards that are dehydrated seek out cooler microclimates (Crowley 1987). </p><p> My dissertation focuses on the physiological, behavioral, and evolutionary axes of organismal response to climatic challenges, and their interactions, using the arboreal Caribbean lizard Anolis cristatellus as a model system. The general approach that I take throughout each chapter is to consider climatic data and organismal responses to climate at a fine-scale. A recent review and meta-analysis of climate change studies found that, on average, researchers consider climatic data at a scale 10,000X larger then the animals they study (Potter et al. 2013). In other words, we frequently consider the climatic environment very coarsely relative to our focal organisms. Such an approach can yield broad patterns of warming vulnerability over large geographic scales. Nonetheless, much of the climatic variation important to organisms occurs at the scale of meters rather than kilometers (Helmuth et al. 2010). Similarly, broad-scale studies must typically make assumptions about how organisms respond to climatic variation, rather than actually measuring responses. Throughout, I highlight the benefits of working at the scale of the organism. </p><p> Chapter 1 is the only chapter that does not deal directly with thermal biology. In it, I investigate whether or not A. cristatellus from mesic and xeric habitats differ in their water loss rates, and ask whether the differences that I observe can be explained by plasticity (Gunderson et al. 2011). In the second chapter, I explore the vulnerability of A. cristatellus to climate warming by integrating behavior and physiology with fine-scale measurements of the thermal environment (Gunderson & Leal 2012). In the third chapter, I investigate the ability of thermal tolerance limits to evolve rapidly in response to climatic change using the recent introduction of A. cristatellus to Miami from Puerto Rico (Leal & Gunderson 2012). In the final chapter, I focus solely on behavior and use A. cristatellus to ask how well current models of thermal constraint on activity predict observed patterns at a fine scale in the field (Gunderson and Leal, in review).</p> / Dissertation

Thesis (Ph. D.)--University of Hawaii at Manoa, 1995. / Includes bibliographical references (leaves 202-237). / Microfiche. / xvi, 237 leaves, bound ill., photos. 29 cm