Investigating dune-building feedback at the plant level: Insights from a multispecies field experiment

Coastal foredunes provide the first line of defense against rising sea levels and storm surge and for this reason there is increasing interest in understanding and modeling foredune formation and post-storm recovery. However, there is limited observational data available to provide empirical guidance for the development of model parameterizations. To provide guidance for improved representation of dune grass growth in models, we conducted a two-year multi-species transplant experiment on Hog Island, VA, U.S.A. and measured the dependence of plant growth on elevation and distance from the shoreline, as well as the relationship between plant growth and sand accumulation. We tracked total leaf growth (length) and aboveground leaf length and found that Ammophila breviligulata (American beachgrass) and Uniola paniculata (sea oats) grew more than Spartina patens (saltmeadow cordgrass) by a factor of 15% (though not statistically significant) and 45%, respectively. Our results also suggest a range of basal/frontal area ratios (an important model parameter) from 0.5-1 and a strong correlation between transplant growth and total sand deposition for all species at the scale of two years, but not over shorter temporal scales. Distance from the shoreline and elevation had no effect on transplant growth rate but did have an effect on survival. Based on transplant survival, the seaward limit of vegetation at the end of the experiment was approximately 30 m from the MHWL and at an elevation of 1.43 m, corresponding to inundation less than 7.5% of the time according to total water level calculations. Results from this experiment provide evidence for the dune-building capacity of all three species, suggesting S. patens is not a maintainer species, as previously thought, but rather a moderate dune builder even though its growth is less stimulated by sand deposition than A. breviligulata and U. paniculata. © 2019 John Wiley & Sons, Ltd.     

The state of water resources in major Mediterranean islands

This work analyses the state of water resources in six Mediterranean islands: Corsica, Crete, Cyprus, Mallorca, Malta and Sicily. The analysis is focused on the prevailing social, economic and hydroclimatological characteristics of these islands in order to identify the main common features affecting water availability, demand and use. A detailed analysis of the state of water resources in all the considered islands has been carried out. A background of current conditions relating to freshwater availability, quality and use has been established. Different strategies to face water scarcity and enhance water quality in theislands have been assessed in a context of climate change which is a common threat. The identification of similar problems for all the islands highlights the importance of strengthening inter-islands co-operation in the field of sustainable water resources management.     

Kernel distributed residual function in a revised multiple order autoregressive model and its applications in hydrology

ABSTRACT

This paper describes a new approach to fill missing data in hydrologic series. Based on a multiple-order autoregressive model, our algorithm represents the random term with an empirical distribution function that includes different parameters for the low, medium and high ranges of the modelled hydrologic variable. The algorithm involves a corrective mechanism that preserves the original statistical distribution of the series that are filled, while also eliminating the possibility of obtaining negative values for low flows. The algorithm requires multiple correlated hydrologic time series with sufficient data to permit accurate calculation of their statistical properties. It ensures that both the original statistical dependence among the data series and the statistical distribution functions will be preserved after the missing data had been filled. The model has been tested using 15 streamflow series in the Upper Bow River watershed in Alberta, Canada.     

A conceptual model of water yield effects from beetle‐induced tree death in snow‐dominated lodgepole pine forests

In regions of western North America with snow‐dominated hydrology, the presence of forested watersheds can significantly influence streamflow compared to areas with other vegetation cover types. Widespread tree death in these watersheds can thus dramatically alter many ecohydrologic processes including transpiration, canopy solar transmission and snow interception, subcanopy wind regimes, soil infiltration, forest energy storage and snow surface albedo. One of the more important causes of conifer tree death is bark beetle infestation, which in some instances will kill nearly all of the canopy trees within forest stands. Since 1996, an ongoing outbreak of bark beetles (Coleoptera: Scolytidae) has caused widespread mortality across more than 600,000 km² of coniferous forests in western North America, including numerous Rocky Mountain headwaters catchments with high rates of lodgepole pine (Pinus contorta) mortality from mountain pin beetle (Dendroctonous ponderosae) infestations. Few empirical studies have documented the effects of MPB infestations on hydrologic processes, and little is known about the direction and magnitude of changes in water yield and timing of runoff due to insect‐induced tree death. Here, we review and synthesize existing research and provide new results quantifying the effects of beetle infestations on canopy structure, snow interception and transmission to create a conceptual model of the hydrologic effects of MPB‐induced lodgepole pine death during different stages of mortality. We identify the primary hydrologic processes operating in living forest stands, stands in multiple stages of death and long‐dead stands undergoing regeneration and estimate the direction of change in new water yield. This conceptual model is intended to identify avenues for future research efforts. Copyright © 2012 John Wiley & Sons, Ltd.     

Conducting Slug Tests in Mini‐Piezometers

Slug tests performed using mini‐piezometers with internal diameters as small as 0.43 cm can provide a cost effective tool for hydraulic characterization. We evaluated the hydraulic properties of the apparatus in a laboratory environment and compared those results with field tests of mini‐piezometers installed into locations with varying hydraulic properties. Based on our evaluation, slug tests conducted in mini‐piezometers using the fabrication and installation approach described here are effective within formations where the hydraulic conductivity is less than 1 × 10^?3 cm/s. While these constraints limit the potential application of this method, the benefits to this approach are that the installation, measurement, and analysis is cost effective, and the installation can be completed in areas where other (larger diameter) methods might not be possible. Additionally, this methodology could be applied to existing mini‐piezometers previously installed for other purposes. Such analysis of existing installations could be beneficial in interpreting previously collected data (e.g., water‐quality data or hydraulic head data).     

The role of chronic and episodic disturbances on channel–hillslope coupling: the persistence and legacy of extreme floods

Landscape form represents the cumulative effects of de‐stabilizing events relative to recovery processes. Most geomorphic research has focused on the role of episodic rare events on landscape form with less attention paid to the role and persistence of chronic inputs. To better establish the interplay between chronic and episodic extreme events at regional scales, we used aerial photography and post‐flood sediment sampling to assess stream and hillslope response and recovery to a 100–300 yr. flood caused by Tropical Storm Irene in New England. Within a 14 000 km² study area, analysis of aerial photographs indicated that the storm initiated (n = 534) and reactivated (n = 460) a large number of landslides. These landslides dramatically increased overall estimates of regional erosion rates (from 0.0023 mm/yr. without Irene to 0.0072 mm/yr. with Irene). Similarly, Irene‐generated LWD inputs of 0.25–0.5 trees/km exceeded annual background rates in a single event, and these concentrated inputs (10¹–10² of trees/landslide) are likely to result in large jams and snags that are particularly persistent and geomorphically effective. Finally, we found that landslide scars continue to provide elevated sediment inputs years after the event, as evidenced by sustained higher suspended sediment concentrations in streams with Irene‐generated landslides. Overall, our results indicate that infrequent, high‐magnitude events have a more important geomorphic role in tectonically stable, more moderate‐relief systems than has been previously recognized. Understanding the role of these events has particular relevance in regions such as New England, where the frequency and magnitude of extreme storms is expected to increase. Further, these effects may force reconsideration of conservation and restoration targets (for example in channel form and large wood loading and distribution) in fluvial systems. Copyright © 2016 John Wiley & Sons, Ltd.     

The Impact of Climate Change on Wildfire Severity: A Regional Forecast for Northern California

We estimated the impact of climatic change on wildland fire and suppression effectiveness in northern California by linking general circulation model output to local weather and fire records and projecting fire outcomes with an initial-attack suppression model. The warmer and windier conditions corresponding to a 2 × CO₂ climate scenario produced fires that burned more intensely and spread faster in most locations. Despite enhancement of fire suppression efforts, the number of escaped fires (those exceeding initial containment limits) increased 51% in the south San Francisco Bay area, 125% in the Sierra Nevada, and did not change on the north coast. Changes in area burned by contained fires were 41%, 41% and –8%, respectively. When interpolated to most of northern California's wildlands, these results translate to an average annual increase of 114 escapes (a doubling of the current frequency) and an additional 5,000 hectares (a 50% increase) burned by contained fires. On average, the fire return intervals in grass and brush vegetation types were cut in half. The estimates reported represent a minimum expected change, or best-case forecast. In addition to the increased suppression costs and economic damages, changes in fire severity of this magnitude would have widespread impacts on vegetation distribution, forest condition, and carbon storage, and greatly increase the risk to property, natural resources and human life.     

Petroi Metabasalt: Alkaline within‐plate mafic rocks from the Nambucca Slate Belt,northeastern New South Wales

The Petroi Metabasalt comprises approximately 2000 m of massive and pillowed metabasalt flows, breccias, and metadolerite sills that overlie and are intercalated with Early Permian epiclastic rocks of the Nambucca Slate Belt. Both the basaltic rocks and associated sedimentary material were multiply deformed and metamorphosed to pumpellyite‐actinolite facies grade at about 255 Ma. Metamorphism and earlier sea‐floor alteration of these mafic rocks have led to hydration, carbonation and oxidation and considerable redistribution of the major elements and the more labile traces, notably Rb, Ba and Sr. However, abundances of TiO₂, the high field strength trace elements, Ni, Cr and V, the light rare earths and yttrium are interpretable as being the largely unmodified magmatic abundances of mildly alkaline within‐plate basalts. This interpretation is supported by the composition of relic Ca‐rich pyroxenes in the metadolerites which fall in the fields of mildly alkaline basalts. The field relationships, age and composition of these rocks suggest either eruption on oceanic crust covered by a thick sequence of epiclastic rocks and subsequent incorporation into an accretionary subduction complex, or generation during rifting of the eastern part of the New England Fold Belt and accumulation, together with the associated sedimentary rocks, in a graben. The chemical and mineral characteristics of the igneous rocks indicate that the volcanism was not related to magmatic arc activity, and their presence demonstrates the rocks of the Nambucca Slate Belt are neither fore‐arc basin nor slope‐basin deposits.