UAV RGB,thermal infrared and multispectral imagery used to investigate the control of terrain on the spatial distribution of dryland biocrust

Biocrusts (topsoil communities formed by mosses, lichens, bacteria, fungi, algae, and cyanobacteria) are a key biotic component of dryland ecosystems. Whilst climate patterns control the distribution of biocrusts in drylands worldwide, terrain and soil attributes can influence biocrust distribution at landscape scale. Multi-source unmanned aerial vehicle (UAV) imagery was used to map and study biocrust ecology in a typical dryland ecosystem in central Spain. Red, green and blue (RGB) imagery was processed using structure-from-motion techniques to map terrain attributes related to microclimate and terrain stability. Multispectral imagery was used to produce accurate maps (accuracy > 80%) of dryland ecosystem components (vegetation, bare soil and biocrust composition). Finally, thermal infrared (TIR) and multispectral imagery was used to calculate the apparent thermal inertia (ATI) of soil and to evaluate how ATI was related to soil moisture (r² = 0.83). The relationship between soil properties and UAV-derived variables was first evaluated at the field plot level. Then, the maps obtained were used to explore the relationship between biocrusts and terrain attributes at ecosystem level through a redundancy analysis. The most significant variables that explain biocrust distribution are: ATI (34.4% of variance, F = 130.75; p < 0.001), Elevation (25.8%, F = 97.6; p < 0.001), and potential solar incoming radiation (PSIR) (52.9%, F = 200.1; p < 0.001). Differences were found between areas dominated by lichens and mosses. Lichen-dominated biocrusts were associated with areas with high slopes and low values of ATI, with soil characterized by a higher amount of soluble salts, and lower amount of organic carbon, total phosphorus (P_tot) and total nitrogen (N_tot). Biocrust-forming mosses dominated lower and moister areas, characterized by gentler slopes and higher values of ATI with soils with higher contents of organic carbon, P_tot and N_tot. This study shows the potential to use UAVs to improve our understanding of drylands and to evaluate the control that the terrain has on biocrust distribution.     

From rainfed agriculture to stress-avoidance irrigation: I. A generalized irrigation scheme with stochastic soil moisture

With vast regions already experiencing water shortages, it is becoming imperative to manage sustainably the available water resources. As agriculture is by far the most important user of freshwater and the role of irrigation is projected to increase in face of climate change and increased food requirements, it is particularly important to develop simple, widely applicable models of irrigation water needs for short- and long-term water resource management. Such models should synthetically provide the key irrigation quantities (volumes, frequencies, etc.) for different irrigation schemes as a function of the main soil, crop, and climatic features, including rainfall unpredictability. Here we consider often-employed irrigation methods (e.g., surface and sprinkler irrigation systems, as well as modern micro-irrigation techniques) and describe them under a unified conceptual and theoretical framework, which includes rainfed agriculture and stress-avoidance irrigation as extreme cases. We obtain mostly analytical solutions for the stochastic steady state of soil moisture probability density function with random rainfall timing and amount, and compute water requirements as a function of climate, crop, and soil parameters. These results provide the necessary starting point for a full assessment of irrigation strategies, with reference to sustainability, productivity, and profitability, developed in a companion paper [Vico G, Porporato A. From rainfed agriculture to stress-avoidance irrigation: II. Sustainability, crop yield, and net profit. Adv Water Resour 2011;34(2):272-81].     

Sediment trace metals and PCB input history in Lake Anna, Virginia, USA

Damming of the North Anna River in 1972 created Lake Anna, a cooling water source for the Dominion nuclear power plant as well as a popular recreation site in Spotsylvania and Orange counties, Virginia, USA. Previously dated (210-Pb) sediment cores from seven locations within the lake and three locations in the adjoining Waste Heat Treatment Facilities (WHTF) were analyzed for trace metals (Al, Ba, Zn, Cd, Cu, Fe, Mn and Pb) and polychlorinated biphenyls (PCBs) to examine the environmental evolution of the reservoir system. The reservoir has a history of mining activities in its watershed and unusually elevated concentrations of PCBs were found in fish tissues from previous studies. Therefore, dated sediment cores provided the framework for both the temporal and spatial analysis of possible sources and flux histories for both trace metals and PCBs. The trace metals results suggest that, though the upper reaches are relatively less impacted, the old mine tailings from the now ceased mining activities in the watershed of Contrary Creek tributary continue to dominate the sediment chemistry of the lower portion of the lake basin, signified by sediment enrichment of Pb, Cd, Cu, and Zn. Lagoon-2 of the WHTF also seems to be receiving unusually high loadings of Cd (12.5 ± 1.07 μg/g) that is probably associated with waste materials from the nuclear power plant that maintains the lagoons. PCB sediment concentrations were relatively low in the lower sections of the basins with values typically being <3.5 ng/g. The upper reaches of the basin had several PCB hotspots, with the surface sediments of Terry’s Run tributary having values as high as 53.13 ng/g. The spatial distribution of PCBs seems to suggest the upper reaches of the basin as the probable source, with the unusually high concentrations near bridges suggesting a possible link between the PCBs and old bridge fill materials. The oldest lacustrine sediments also had relatively high trace metals and PCB values signifying a probable role of soil disruption and sediment reconcentration during reservoir construction.     

Seasonal snow cover decreases young water fractions in high Alpine catchments

Estimation of young water fractions (F_yw), defined as the fraction of water in a stream younger than approximately 2–3 months, provides key information for water resource management in catchments where runoff is dominated by snowmelt. Knowing the average dependence of summer flow on winter precipitation is an essential context for comparing regional drought severity and provides the hydrological template for downstream water users and ecosystems. However, F_yw estimation based on seasonal signals of stable isotopes of oxygen and hydrogen has not yet explicitly addressed how to parsimoniously include the seasonal shift of water input from snow. Using experimental data from three high-elevation, Alpine catchments (one dominated by glacier and two by snow), we propose a framework to explicitly include the delays induced by snow storage into estimates of F_yw. Scrutinizing the key methodological choices when estimating F_yw from isotope data, we find that the methods used to construct precipitation input signals from sparse isotope samples can significantly impact F_yw. Given this sensitivity, our revised procedure estimates a distribution of F_yw values that incorporates a wide range of possible methodological choices and their uncertainties; it furthermore compares the commonly used amplitude ratio approach to a direct convolution approach, which circumvents the assumption that the isotopic signals have a sine curve shape, an assumption that is generally violated in snow-dominated environments. Our new estimates confirm that high-elevation Alpine catchments have low F_yw values, spanning from 8 to 11%. Such low values have previously been interpreted as the impact of seasonal snow storage alone, but our comparison of different F_yw estimation methods suggests that these low F_yw values result from a combination of both snow cover effects and longer storage in the subsurface. In contrast, in the highest elevation, glacier dominated catchment, F_yw is 3–4 times greater compared to the other two catchments, due to the lower storage and faster drainage processes. A future challenge, capturing spatio-temporal snowmelt isotope signals during winter baseflow and the snowmelt period, remains to improve constraints on the F_yw estimation technique.     

Sensitivity of the multiannual thermal dynamics of a deep pre‐alpine lake to climatic change

The study of the multiannual thermal dynamics of Lake Iseo, a deep lake in the Italian pre‐alpine area, is presented. Interflow was found to be the dominant river entrance mode, suggesting future susceptibility of the lake thermal structure to the overall effects of climate change expected in the upstream alpine watershed. A lake model employed the results of a long‐term hydrologic model to simulate the effects of a climate change scenario on the lake's thermal evolution for the period 2012–2050. The model predicts an overall average increase in the lake water temperature of 0.012 °C/year and a reinforced Schmidt thermal stability of the water column in the winter up to 800 J/m². Both these effects may further hinder the deep circulation process, which is vital for the oxygenation of deep water. Copyright © 2014 John Wiley & Sons, Ltd.     

Unified structural classification of AB2 molecules and solids from valence electron orbital radii

We present structural plots for AB₂ molecules and solids with sp-bonding based on parameters derived from valence electron orbital radii. We show that the same schemes that allow one to classify crystals with different structures, are also able to distinguish molecular shapes into linear and bent. Our picture is consistent with the existence of a critical numberN _c =16of valence electrons, in agreement with the Mulliken-Walsh rule, and accounts for many exceptions to the latter in the caseN≤16. We discuss critically our findings and announce new results on AB₃ molecules. We also discuss preliminary results of model calculations on AB₂ molecules.     

Evaluating the effects of protection on two benthic habitats at Tavolara-Punta Coda Cavallo MPA (North-East Sardinia, Italy)

In this paper, two benthic habitats have been investigated in a fully protected site and two control sites at the Tavolara-Punta Coda Cavallo marine protected area (MPA) (NE Sardinia). Overall, a protection effect on the benthic assemblages was highlighted in the shallow subtidal (5 m deep) rather than at intertidal algal turf habitat. Structure of assemblages at the shallow subtidal habitat is different in the fully protected site vs. controls, while this was not true for the intertidal habitat. At the subtidal, this finding is probably linked to indirect effects due to an increase of consumers in the protected site (e.g., sea urchins), while the lack of direct impacts in the intertidal at control sites is indicative of very similar assemblages. Cover of encrusting algae was significantly higher at the subtidal protected site suggesting a possible higher grazing pressure. Possible causes underlying the inconsistency of results obtained between habitats include the possibility that trophic cascade effects have a different influence at different heights on the shore. The need to estimate the interconnection among benthic habitats through trophic links is also highlighted to provide an estimate of the vulnerability to protection of various habitats.     

Hybrid simulation of a partial-strength steel–concrete composite moment-resisting frame endowed with hysteretic replaceable beam splices

This paper deals with the seismic response assessment of a steel–concrete moment-resisting frame (MRF) equipped with special dissipative replaceable components (DRCs): the dissipative replaceable beam splices (DRBeS), which combine large energy dissipation with ease of replacement. The evaluation of the full potential of DRBeS requires a system-level investigation, that is, a six-story MRF, whereby the hysteretic effects of beam splices partial-strength joints are considered on the global response of the structural system. Therefore, an OpenSees finite element (FE) frame model, based on previous experimental campaigns with cyclic displacements on partial-strength joints, and a Matlab model validated on OpenSees, were used for a more complex experimental activity via hybrid simulation (HS). The aim of the simulations was twofold: (i) to increase knowledge of the non-linear behaviour of steel-concrete composite partial-strength MRFs; and (ii) to study the effectiveness of the DRBeS components for increasing the recovery of functionality after a major seismic event. Therefore, to appreciate the performance of the partial-strength MRF at damage limitation (DL), significant damage (SD) and near collapse (NC) within the performance-based earthquake engineering (PBEE) approach, HSs were carried out. In such instances, the ground floor was physically tested at full scale in the laboratory and the remainder of the structure was numerically simulated. Relevant results showed that the DRBeS were capable of dissipating a significant amount of hysteretic energy and of protecting the non-dissipative parts of partial-strength joints and the overall structure with an ease of replacement.     

Prospects for crowdsourced information on the geomorphic ‘engineering’ by the invasive Coypu (Myocastor coypus)

Among the most invasive species, the Coypu (Myocastor coypus) best exemplifies the widespread effect of alien species on ecosystems. Among the impacts, the induced erosion in riverbanks has an increasing economic and social importance. Despite its significance, this type of erosion is rarely quantified, and the available information is limited to local knowledge, grey literature, and maintenance reports. This research shows the potential of freely and instantly available Structure‐from‐Motion (SfM) photogrammetry to obtain crowdsourced information based on smartphone images. The results highlight how it is possible to provide a rough estimate of the damages with relatively low or null cost of application, and limited expert knowledge and expenditure of time, depending on the scale of analysis. The proposed technique provides a fresh approach to a known long‐standing issue, offering a new source of information for farmers, researchers, wildlife managers, as well as for land managers and planners. The potential applications of such a technique and its unprecedented ease of use and very low cost offer effective tools for management plans and scientific research, providing a basis to relate eroded volumes to the functioning of the drainage system and the connected agroecosystem. The method would also enable the opportunity of participatory and opportunistic crowdsourced sensing. Further scientific research on the crowd‐based data on erosion should encourage standardisation of data gathering and accessibility, together with a public involvement in information exchange, to generate a better understanding and awareness of erosion problems also for other fields of research. Copyright © 2016 John Wiley & Sons, Ltd.