- 05October 5, 2020
Seminar: Markus Reichstein
Machine-learning-model-data integration for a better understanding of the Earth System
This presentation will give an overview about how Machine learning can support Earth System Science. First I present an overview of the key challenges in this field of science, which addresses the complex interplay between e.g. hydrosphere, biosphere, atmosphere and cryosphere, with emphasis on the carbon cycle and climate feedbacks. This will be complemented by four examples on 1) how to infer global carbon fluxes from sparse observations, 2) how to quantify uncertainties therein including extrapolation, 3) how to model landscapes, i.e. the spatial arrangement of elements, 4) how address dynamic effects as expressed in time-series and spatio-temporal data.
- 12October 12, 2020
Seminar: Elise Pendall
Isotopic insights into plant and soil carbon metabolism and implications for climate changeClimate warming has the potential to alter the balance between photosynthetic carbon assimilation and respiratory losses in terrestrial ecosystems, leading to uncertainty in predicting their future physiological functioning. The effects of warming on plant and microbial respiration have been well studied, but effects on carbon use efficiency (CUE), allocation and mean residence time (MRT) have received less attention. In this talk I will discuss recent experiments using stable isotope tracers in native Australian systems. In the first study, we evaluated effects of warming on Eucalyptus parramattensis assimilation, sugar metabolism, transport, storage, respiration and root exudation. We applied a 13CO2 pulse to the trees in whole-tree chambers operated at ambient and ambient +3 °C temperature treatments and followed the label in plant sugars, bulk tissues and soil microbes, and in CO2 respired from leaves, canopy, roots and soil over a 3-week period in conjunction with measurements of tree growth. Although warming appeared to reduce the MRT of carbon respired from roots and soil, CUE was not significantly altered. In the second study, we evaluated soil microbial CUE and MRT across a hydrologic gradient from forest to wetland, at different soil depths, using H218O labelling of DNA during a short-term incubation experiment at two temperatures. We found that microbial CUE decreased with increasing temperature and varied with substrate C/N ratios, while the MRT and temperature sensitivity (Q10) were strongly related to soil clay content. These isotopic labelling experiments provide insights into how rising temperatures may affect the fate of assimilated carbon from the leaf to the ecosystem scale and demonstrate potential for improvements in biogeochemical models. - 19October 19, 2020
Seminar: Bill Smith
The effects of increasing water constraint on vegetation growth: Insights from novel remote sensing observations from plot to globeClimate warming is profoundly altering water availability from region to globe and these changes are impacting ecosystem functioning in complex ways, potentially resulting in strong feedbacks to future climate that are currently not well understood. Remote sensing observations present a powerful tool for high spatiotemporal monitoring of ecosystem functioning and vegetation-drought dynamics across spatiotemporal scales. In this talk, I will explore vegetation responses to a changing hydroclimate from plot to globe with a focus on novel remote sensing observations including solar-induced fluorescence, hyperspectral reflectance, and structural traits. Specifically, I will present results from: 1) a UArizona / USDA-ARS long-term, rainfall manipulation initiative; 2) a synthesis of more than 30 eddy flux tower sites distributed across the western US including a gradient of UArizona / USDA-ARS sites; 3) multi-sensor satellite observations at the global scale and spanning the last four decades. - 26October 26, 2020
Seminar: Kristen Averyt
Climate Change: What it Means for Nevada and What the State is Doing About it
Nevada is home to two of the fastest warming cities in the United States (Reno and Las Vegas) and is the driest state in the country, with statewide annual average precipitation of only 10 inches. Las Vegas just set records for most consecutive days >90oF and is in the midst of its longest stretch without any precipitation. The air quality in Las Vegas is among the worst in the country in terms of ozone exceedance days. In northern Nevada, schools were closed for days as a consequence of the poor air quality related to the fires across the Western US. Indeed, these events are focusing attention on the issues of climate change. Unlike many other states across the West, Nevada has not undertaken a comprehensive climate assessment, developed a process to evaluate climate-related risks and vulnerabilities, or implemented a state-wide climate effort—until now.
During this seminar, an overview of the impacts of climate change on Nevada will be presented, along with broader implications related to other challenges facing the state. The policy actions being implemented and those under consideration will be discussed alongside the novel approach the state has developed for its upcoming State Climate Strategy.