Responses of Native and Invasive Floating Aquatic Plant Communities to Salinity and Desiccation Stress in the Southeastern US Coastal Floodplain Forests

Low-lying coastal ecosystems along the northern Gulf of Mexico are already experiencing the effects of elevated salinity from sea-level rise and are predicted to face extreme events such as extended saltwater inundation, intense Atlantic hurricanes, and episodic drought. The ability of coastal plant communities to survive stresses from these events depends largely on how these communities respond to the stresses. Our understanding of how plant communities dominated by native vs. invasive plants respond to extreme events is limited. Utilizing controlled greenhouse experiments, we assessed the responses of floating aquatic macrophyte communities, dominated by native or invasive plants, of the coastal floodplains, Louisiana, USA, to a gradient of chronic salinity, mimicking sea-level rise; a gradient of acute salinity, mimicking hurricane storm surges; and a gradient of desiccation stress, mimicking episodic drought. We found that salinity and desiccation stress effects on plant communities depended on the degree of plant invasion; plant community cover decreased precipitously as severity of stress increased. Specifically, extreme salinity led to a decrease in plant cover of >?90% when communities were dominated by invasive plants, whereas increased desiccation stress led to decreased plant cover of 100% when communities were dominated by native species. At low to moderate salinity, invasive dominated plant communities performed better than native dominated. These responses to salinity and desiccation stress may drive large-scale shifts in plant community structure, including loss of species. Our results underscore the importance of evaluating plant community responses to environmental extremes to determine the potential for future effects on dynamics and functioning of low-lying coastal floodplain ecosystems experiencing effects of climate change.     

The eccentricities of the barium stars

We investigate the eccentricities of barium (Ba  ii ) stars formed via a stellar wind accretion model. We carry out a series of Monte Carlo simulations using a rapid binary evolution algorithm, which incorporates full tidal evolution, mass loss and accretion, and nucleosynthesis and dredge-up on the thermally pulsing asymptotic giant branch. We follow the enhancement of barium in the envelope of the accreting main-sequence companion and dilution into its convective envelope once the star ascends the giant branch.
The observed eccentricities of Ba  ii stars are significantly smaller than those of an equivalent set of normal red giants but are nevertheless non-zero. We show that such a distribution of eccentricities is consistent with a wind accretion model for Ba  ii star production with weak viscous tidal dissipation in the convective envelopes of giant stars. We successfully model the distribution of orbital periods and the number of observed Ba  ii stars. The actual distribution of eccentricities is quite sensitive to the strength of the tides, so that we are able to confirm that this strength is close to, but less than, what is expected theoretically and found with alternative observational tests. Two systems – one very short-period but eccentric, and one long-period and highly eccentric – still lie outside the envelope of our models, and so require a more exotic formation mechanism. All our models, even those which were a good fit to the observed distributions, overproduced the number of high-period barium stars, a problem that could not be solved by some combination of the three parameters: tidal strength, tidal enhancement and wind accretion efficiency.     

Very short-term spatio-temporal wind power prediction using a censored Gaussian field

Wind power is a renewable energy resource, that has relatively cheap installation costs and it is highly possible that will become the main energy resource in the near future. Wind power needs to be integrated efficiently into electricity grids, and to optimize the power dispatch, techniques to predict the level of wind power and the associated variability are critical. Ideally, one would like to obtain reliable probability density forecasts for the wind power distributions. We aim at contributing to the literature of wind power prediction by developing and analysing a spatio-temporal methodology for wind power production, that is tested on wind power data from Denmark. We use anisotropic spatio-temporal correlation models to account for the propagation of weather fronts, and a transformed latent Gaussian field model to accommodate the probability masses that occur in wind power distribution due to chains of zeros. We apply the model to generate multi-step ahead probability predictions for wind power generated at both locations where wind farms already exist but also to nearby locations.     

Evaluation of hydrologic impact of an irrigation curtailment program using Landsat satellite data

Upper Klamath Lake (UKL) is the source of the Klamath River that flows through southern Oregon and northern California. The UKL Basin provides water for 81,000+ ha (200,000+ acres) of irrigation on the U.S. Bureau of Reclamation Klamath Project located downstream of the UKL Basin. Irrigated agriculture also occurs along the tributaries to UKL. During 2013–2016, water rights calls resulted in various levels of curtailment of irrigation diversions from the tributaries to UKL. However, information on the extent of curtailment, how much irrigation water was saved, and its impact on the UKL is unknown. In this study, we combined Landsat-based actual evapotranspiration (ETa) data obtained from the Operational Simplified Surface Energy Balance model with gridded precipitation and U.S. Geological Survey station discharge data to evaluate the hydrologic impact of the curtailment program. Analysis was performed for 2004, 2006, 2008–2010 (base years), and 2013–2016 (target years) over irrigated areas above UKL. Our results indicate that the savings from the curtailment program over the June to September time period were highest during 2013 and declined in each of the following years. The total on-field water savings was approximately 60 hm³ in 2013 and 2014, 44 hm³ in 2015, and 32 hm³ in 2016 (1 hm3 = 10,000 m³ or 810.7 ac-ft). The instream water flow changes or extra water available were 92, 68, 45, and 26 hm³, respectively, for 2013, 2014, 2015, and 2016. Highest water savings came from pasture and wetlands. Alfalfa showed the most decline in water use among grain crops. The resulting extra water available from the curtailment contributed to a maximum of 19% of the lake inflows and 50% of the lake volume. The Landsat-based ETa and other remote sensing datasets used in this study can be used to monitor crop water use at the irrigation district scale and to quantify water savings as a result of land-water management changes.     

Multi‐scale classification of fluvial architecture: An example from the Palaeocene–Eocene Bighorn Basin,Wyoming

Fluvial channel geometry classification schemes are commonly restricted in relation to the scale at which the study took place, often due to outcrop limitations or the need to conduct small‐scale detailed studies. A number of classification schemes are present in the literature; however, there is often limited consistency between them, making application difficult. The aim of this study is to address this key problem by describing channel body geometries across a depositional basin to ensure that a wide range of architectures are documented. This was achieved by studying 28 locations over 4000 m of vertical succession in Palaeocene‐aged and Early Eocene‐aged deposits within the Bighorn Basin, Wyoming, USA. Five different channel body geometries have been defined based on the external geometric form, and internal arrangement and nature of storey contacts. These include the massive channel body geometry, semi‐amalgamated channel body geometry, internally amalgamated channel body geometry and offset stacked channel body geometry, which are considered to be subdivisions of the sheet geometry of many other classifications. An isolated channel body geometry has also been recognized alongside splay channel and sheet sandstone geometries in the floodplain facies associations. Field evidence, including the stacking style of storey surfaces, suggests that the different geometries form a continuum. The nature and degree of amalgamation at the storey scale are important in producing the different geometries and are related to the degree of channel migration. It is speculated that this is the result of differences in sediment supply and available accommodation. In contrast to previous schemes, the classification scheme presented here recognizes the importance of transitional geometries. This geometrical range has been recognized because of the basin‐scale nature of the study.     

A review of modern treeline migration,the factors controlling it and the implications for carbon storage

Numerous studies have reported that treelines are moving to higher elevations and higher latitudes.Most treelines are temperature limited and warmer climate expands the area in which trees are capable of growing.Hence,climate change has been assumed to be the main driver behind this treeline movement.The latest review of treeline studies was published in 2009 by Harsch et al.Since then,a plethora of papers have been published studying local treeline migration.Here we bring together this knowledge through a review of 142 treeline related publications,including 477 study locations.We summarize the information known about factors limiting tree-growth at and near treelines.Treeline migration is not only dependent on favorable growing conditions but also requires seedling establishment and survival above the current treeline.These conditions appear to have become favorable at many locations,particularly so in recent years.The review revealed that at 66%of these treeline sites forest cover had increased in elevational or latitudinal extent.The physical form of treelines influences how likely they are to migrate and can be used as an indicator when predicting future treeline movements.Our analysis also revealed that while a greater percentage of elevational treelines are moving,the latitudinal treelines are capable of moving at greater horizontal speed.This can potentially have substantial impacts on ecosystem carbon storage.To conclude the review,we present the three main hypotheses as to whether ecosystem carbon budgets will be reduced,increased or remain the same due to treeline migration.While the answer still remains under debate,we believe that all three hypotheses are likely to apply depending on the encroached ecosystem.Concerningly,evidence is emerging on how treeline migration may turn tundra landscapes from net sinks to net sources of carbon dioxide in the future.     

Evidence and Implications of Recent Climate Change in Northern Alaska and Other Arctic Regions

The Arctic climate is changing. Permafrost is warming, hydrological processes are changing and biological and social systems are also evolving in response to these changing conditions. Knowing how the structure and function of arctic terrestrial ecosystems are responding to recent and persistent climate change is paramount to understanding the future state of the Earth system and how humans will need to adapt. Our holistic review presents a broad array of evidence that illustrates convincingly; the Arctic is undergoing a system-wide response to an altered climatic state. New extreme and seasonal surface climatic conditions are being experienced, a range of biophysical states and processes influenced by the threshold and phase change of freezing point are being altered, hydrological and biogeochemical cycles are shifting, and more regularly human sub-systems are being affected. Importantly, the patterns, magnitude and mechanisms of change have sometimes been unpredictable or difficult to isolate due to compounding factors. In almost every discipline represented, we show how the biocomplexity of the Arctic system has highlighted and challenged a paucity of integrated scientific knowledge, the lack of sustained observational and experimental time series, and the technical and logistic constraints of researching the Arctic environment. This study supports ongoing efforts to strengthen the interdisciplinarity of arctic system science and improve the coupling of large scale experimental manipulation with sustained time series observations by incorporating and integrating novel technologies, remote sensing and modeling.     

Engaging public for building resilient communities to reduce disaster impact

Perception about people’s behaviour during emergencies defines, to a large extent, the course of planning and resource allocation for community emergency response as well as development of mitigation measures. During the past decade, there has been a paradigm shift in the approach to disaster management. A recent trend has been to encourage more community participation as opposed to the top-down approach of the past. It is believed that community participation will bring about a comprehensive and accurate appreciation of people’s perception regarding hazards, risk, vulnerability, and resilience, and this research is an attempt to achieve just that. In order to accomplish our goal, we engaged a group of women that would typically fall into the category of “vulnerable group” in a focus group interview setting. The participants were mainly over 40 years old, the majority with little education, unemployed, facing language barriers, of low income, and reliant on public transit. Many participants identified that they lived in the vicinity of rivers, lakes, railways, or power plants, but did not seem to be aware of their exposure to potential threats—indicating a lack of education and awareness. The most common hazards and mitigation measures they were aware of, included floods (including basement flooding), fire, fire alarm, and smoke detectors. Additionally, illness and loneliness were mentioned as factors contributing to their increased vulnerability, hence reduced resiliency. With the help of the focus group members’ participation, we were able to discuss the importance of communities being aware of their surroundings, available resources and help, and permit them to voice their concerns in order to be able to cope during emergencies. We trust and hope that more community participation will lead to stronger and more resilient cities.