Seagrass ecosystems are intense carbon sinks, but they can also emit greenhouse gases (GHG), such as carbon dioxide (CO2) and methane (CH4), to the atmosphere. Yet, GHG emissions by seagrasses are not considered when estimating global CH4 production rates by natural sources, although these estimations will help predict future scenarios and potential changes in CH4 emissions. In addition, the effect of warming on GHG emissions by seagrasses has not yet been reported. The present study aims to assess the CO2 and CH4 production rates by vegetated and adjacent bare sediment of a monospecific seagrass meadow (Halophila stipulacea) located in the central Red Sea. We measured CH4 and CO2 fluxes and their isotopic signatures by cavity ringdown spectroscopy on chambers containing vegetated and bare sediment. The fluxes were measured at temperatures from 25 °C (winter seawater temperature) to 37 °C to cover the natural thermal range and future seawater temperatures in the Red Sea. Additional parameters analyzed included changes in the sediment microbial community composition, sediment organic matter, organic carbon, nitrogen, and phosphorus concentration. We detected up to 100-fold higher CH4 (up tp 571.65 µmol CH4 m−2 d−1) and up to six-fold higher CO2 (up to 13,930.18 µmol CO2 m−2 d−1) fluxes in vegetated sediment compared to bare sediment, and an increase in CH4 and CO2 production with increasing temperature. In contrast, CH4 and CO2 production rates decreased in communities that were maintained at 25 °C, while communities that were exposed to prolonged darkness showed a decrease in CH4 and an increase in CO2 production rates. However, only minor changes were seen in the microbial community composition with increasing temperatures. These results show that GHG emissions by seagrasses might be affected by natural temperature extremes and warming due to climate change in the Red Sea. The findings will have critical implications for the estimation of natural GHG sources, especially when predicting future changes in the global CH4 budget.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第17964号 / 農博第2032号 / 新制||農||1019(附属図書館) / 学位論文||H25||N4808(農学部図書室) / 30794 / 京都大学大学院農学研究科農学専攻 / (主査)教授 白岩 立彦, 教授 奥本 裕, 教授 稲村 達也 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

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Anthropogenic global change is altering food web dynamics. Global change comprises factors, like temperature, sound, light and more. In this dissertation, I evaluate how two factors, sound and temperature, alter prairie communities. In Chapter 1, I test if sound influences grasshopper respiration rate, thereby altering diet. Some sound frequencies increased grasshopper respiration rate while others decreased respiration rate. Frequencies that elevated respiration rate led to grasshoppers consuming more carbohydrate-rich foods compared to protein-rich foods. This diet change stems from a carbon deficit due to increased respiration rate and could act as a mechanism by which sound pollution indirectly alters plant communities. In Chapter 2, I test the hypothesis that sound can alter grasshopper movement. In response to sound-induced stress grasshoppers may alter their movement in one of two ways: in situ and displacement. I found no evidence that grasshoppers, nor non-Orthopteran insects alter their movement in the presence of sound. This chapter provides foundational methods to evaluate sound for applications in conservation and management. Further research will improve techniques for grassland or agricultural systems. Temperature is another driver of community change. What is less understood is how warming influences predator-pollinator relationships. In Chapter 3, I ask if warming alters a spider that consumes pollinators in a prairie system. My results indicate that pollinators benefit when spiders are not on the flower. Warming shifts spiders down the plant, thus positively impacting pollinator-plant interactions. In addition, warming may benefit plants two-fold if spiders shift their diet to herbivores. This requires additional research, but it is evident that warming generates a positive indirect effect on plants. These chapters contribute to a growing understanding of how global change is restructuring ecosystems. While global change may alter population dynamics or lead to evolutionary change over longer time scales, behavioral responses happen rapidly and can drive ecological dynamics in the short term. My dissertation demonstrates that sound and temperature alter animal behavior that cascades to lower trophic levels. Thus, in addition to demonstrating the indirect effects of global change, these experiments contribute to growing literature on the importance of top-down control in shaping ecosystems.

How many inhabitans do have your city? Tuvalu has 12.000 and that´s not a city. It´s a country. Nine islands in south Pacific nearly date line. On first sight You may say, it´s a paradise. Air has always about 30°, sand is white, sky is blue and the sea is full of fish. On shore grows coconuts and on the sea-floor grows beautiful corals. But second lowest country in the Word cannot be a paradise. The land is missing in huge Pacific. Inhabitans don´t have money neither for build another Venice nor dubai´s palm. Global warming a sea level rise is dangerous for milions people of our planet. Maldives, Banghlades, Holland, south of USA… Many of you can have a question: „Why then Tuvalu?“ Few tausends people can move to Australia and finish. And Maldives have worse position, land has less meters over sea level, people is more… ten times. But 12.000… it´s so enough – for specimen. It´s enough people to get for them money and spend it for saving thein land, for trying some science theories. If cannot save these 12.000, you cannot save the others. They have many renewable resourcies: the wind is blowing, the sun is shining, the water is flowing. In this time they are maybe not energy-independent, but they plan to be in 2020. Energy is that wonderfull power, which can save them. Did you know, that if you set low electric energy going in iron element under sea level (which cannot harm sea life and people), at the surface is formed a layer of sediments called „biorock“?- rock, which can you use for building. The project will save only one atoll: Funafuti. It´s enough large for all contemporary and future inhabitans to living. Project is planned to year 2200 and calculated for 24.000 inhabitans. Untilll then sea level rise will grow about one meter above. On atoll Funafuti will rise eight villages with max. 3.000 inhabitans. Every village will have by average equipment (grocery, school, doctor, church) advanced nation-wide important functions (airport, hospital, parliament, university..). On biorock layer stored up in the sea by atoll Funafuti will rise shelf, where people can build stilt houses, how they did houndreds years before European arrival. Or they can live in houseboats. Between houses they wil build jetty road for light engine vehicles and bridge-like paths for pedestrians. They will meet on squares and over their heads will bloom tropical plant in colourfull steeltubes made for it. On the dry land, which is very small, will grow coconut and pandanus. This land will be under heritage, park for everyone to come end enjoy. Part of this project is a floating church. Its building represents all ideas, that Project Tuvalu has: building on water, energy-independent, offer an shelter, shade and place for meeting of people. White facade made from textile membrane reminds white sails of ships, that crossed oceans before 200 years. With these ships came Chrisitanity, that is deeply rooted in this land. Bamboo construction with steel cables will reminds to people Crown of Thorns and martyrium of Christ, but also average problem hat must people meet in their lives. This project is pure utopic and doesn´t have ambition to get real. Its aim is to make visible problem of global warming in this sight and create a discussion: what next?

A large disconnect exists between the general public's acceptance of human-caused climate change and the prevailing consensus of actively publishing scientists. Previous research has examined both political and economic motivated reasoning, media influence in print and television, conspiracy ideation as a predictor of science rejection, and the role of the social construction of scientific knowledge in science rejection. Using these previously studied justifications for climate change rejection as a starting point, this research examines 212 written responses to a prompt at Climate Etc. asking the community to explain their acceptance / rejection of climate change. Using a textual content analysis, this study finds that media choice, motivated reasoning, conspiracy ideation, and the scientific construction of knowledge all play important roles in explanations for climate science rejection. Work and educational background, as well as a reframing of the scientific consensus as a "religion," add new analytical perspectives to the motivated reasoning explanations offered in prior research. This analysis also finds that the explanations for climate science denial given by respondents are often complex, falling into two or more of the explanation types suggesting that science rejection may be a more complex social process than previously thought.

Planned grazing management in rangelands may improve carbon sequestration potential of soils by increasing plant biomass and the rate of nutrient cycling, which might mitigate global warming. The effects of high-intensity, short-duration planned grazing of sheep on several soil and ecosystem properties were investigated on a mixed grassland in San Luis Obispo, CA. The objectives of this study were to (a) identify soil properties related to soil C sequestration in rangelands; (b) determine if planned grazing improved soil carbon sequestration; (c) quantify changes in identified variables in grazed and rested plots; and (d) analyze any changes in plant species composition attributable to grazing. Total rest exclosures and short-duration grazing by sheep at average stocking densities of 115,000 pounds per acre were applied at two sites with clay-loam soils: a rangeland site that had been rested for over 50 years (REX), and an adjacent site that was previously rested for over 50 years, and subsequently grazed for six years (GR). Bare soil, live plants, plant litter, and perennial and annual plant densities were not different between sites. Soil organic carbon (SOC) was higher at the GR site, but total nitrogen was not different between sites, resulting in higher C:N ratios at the GR site. Soil pH was lower at the GR site, moisture was higher at the GR site, and bulk density and aggregate stability were not different between sites. There was a higher incidence of black soils at the REX site, suggesting perhaps a difference in soil mineralogy which may impact SOC. Treatment did not have an effect on any of the variables investigated except perennial plant diversity, in which grazed plots had lower species diversity than rested plots. Site aspect may have an effect on the results, as the GR site was northwest-facing while the REX site was south-facing. It is possible that higher SOC at the GR site is due to topography, rather than grazing management. Further investigation is required, but if grazing can be used in California as a strategy for increasing soil carbon sequestration, the rates of desertification may be slowed and damage caused to the ecosystem by global warming may be reduced.

With a warming climate and the usage of monocultures in food production it is possible we may face more issues concerning food insecurity in the future as pollinators struggle to find food in agricultural landscapes. Therefore, it is of value to know whether common agricultural weeds are important sources of food for pollinators. Pollinators are vital in the growing of food-crops and may depend on different agricultural weeds during their flying season. This study is based on observational citizen science data on the flowering of 24 agricultural weeds classified as useful to pollinators in the years 2008-2022. Data on first flowering and length of flowering was compared between life history classifications based on life span and time of germination. The results showed that while there is variation both between groups and within groups among the selected species, summer annuals are among the last to start flowering. Species classed as “summer and winter annuals”, i.e that can germinate either in spring or autumn, had a longer flowering period than the other classes. Winter annuals were first to flower while the perennials and “summer and winter annuals” differed more among each other. Weather dependency was also addressed by comparison over years. Overall, the selected species were not significantly affected by mean winter temperature, mean summer temperature or mean summer precipitation.

As a temperature-delineated boundary, Arctic treeline is predicted to shift poleward and tree growth is expected to increase in response to rapid warming. The massive scale of the Arctic treeline magnifies these changes to impact energy balance, carbon balance, and climate-related feedbacks at local, regional, and global scales. Yet, not all sections of the Arctic treeline are reporting growth, suggesting factors other than temperature may be becoming more limiting as the climate continues to change. This dissertation investigates how water availability and tree size may modify the response to climate change of a dominant conifer species (white spruce, Picea glauca) growing at an Arctic treeline site in the Brooks Range, Alaska, USA. The first chapter examines the influence of temperature and water availability on population regeneration and individual tree growth during the 20th century. A climatic shift towards a warmer and drier climate after 1975 caused divergent responses of sapling regeneration and mature tree growth, suggesting that, while individuals have grown, this section of treeline has remained relatively stationary. The second chapter explores the present-day relationships between tree size, temperature, moisture availability, and tree growth by examining the response of intra-annual radial stem growth rate to changing environmental conditions at the Arctic treeline. Tree size and water availability play important roles in moderating the growth response to increasing temperature. Finally, in the third chapter, the environmental cues which trigger the onset of radial stem growth in spring are identified. The results suggest a combination of winter chilling and subsequent spring heat accumulation initiates onset, like trees growing at lower latitudes. However, the chilling and heating thresholds at this Arctic treeline site were far colder than those identified at lower latitudes, suggesting local adaptation to harsh Arctic winters and springs. Through these new findings, this dissertation advances our understanding of Arctic treeline dynamics and will help to predict the future of the Arctic treeline more accurately in a rapidly changing climate.