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In this article, an open channel flow resistance equation, deduced applying dimensional analysis and incomplete self-similarity condition for the flow velocity distribution, was tested using measurements carried out in a full-scale channel equipped with three types of riparian plants (Salix alba L., Salix caprea L. and Alnus glutinosa L.). In the experimental channel, having banks lined with boulders, the vegetation branches were anchored in a concrete bottom. For each species, the measurements were carried out with plants having different amounts of leaves, different plant density and plant area index. The relationship between the scale factor Γ of the velocity profile and the Froude number was separately calibrated by measurements carried out without and with vegetation. The component of Darcy-Weisbach friction factor corresponding to the riparian vegetation fv was calculated as the difference between the measured friction factor value (channel grain roughness + vegetation) and that calculated for the channel without vegetation in the same hydraulic conditions. Using these fv values, the relationship between the scale factor Γ and the Froude number was calibrated. In this last relationship, a scaling coefficient a varying with the investigated vegetation type was introduced. This coefficient, as expected, gives the highest friction factor values for vegetation having branches with leaves. The theoretical flow resistance law, coupled with the relationship for estimating the Γ function having a scaling coefficient different for each investigated vegetation type, allowed an accurate estimate of the Darcy-Weisbach friction factor (errors less than or equal to 20% for 82.6% of the investigated cases). Finally, for the investigated vegetation species that are characterized by a condition with few leaves or leafless, the scaling coefficient a resulted strongly related to the bending stiffness. This analysis demonstrated that the highest Darcy-Weisbach friction factors correspond to vegetation species characterized by the highest values of bending stiffness. The friction factor values calculated for this last condition are characterized by errors that were less than or equal to ±20% for 90.6% of cases.

Although drought is an increasing problem in agriculture, the contribution of the root-associated bacterial microbiome to plant adaptation to water stress is poorly studied. We investigated if the culturable bacterial microbiome associated with five grapevine rootstocks and the grapevine cultivar Barbera may enhance plant growth under drought stress. Eight isolates, over 510 strains, were tested in vivo for their capacity to support grapevine growth under water stress. The selected strains exhibited a vast array of plant growth promoting (PGP) traits, and confocal microscopy observation of gfp-labelled Acinetobacter and Pseudomonas isolates showed their ability to adhere and colonize both the Arabidopsis and grapevine rhizoplane. Tests on pepper plants fertilized with the selected strains, under both optimal irrigation and drought conditions, showed that PGP activity was a stress-dependent and not a per se feature of the strains. The isolates were capable of increasing shoot and leaf biomass, shoot length, and photosynthetic activity of drought-challenged grapevines, with an enhanced effect in drought-sensitive rootstock. Three isolates were further assayed for PGP capacity under outdoor conditions, exhibiting the ability to increase grapevine root biomass. Overall, the results indicate that PGP bacteria contribute to improve plant adaptation to drought through a water stress-induced promotion ability.

This paper presents the new procedure MAC-D for the automated detection of undocumented Multiple Abrupt Changes in the mean value of Daily temperature series, recorded in a network of meteorological stations. MAC-D can be applied to series containing seasonality, multiple change points, outliers, and with a noise component that can be autocorrelated and non-normally distributed. The main novelties of the procedure are (1) the pretreatment of the observed series, to derive a series of daily values that complies with the theoretical requirements of the change point detection tests and in (2) the combined use of the reference series and pairwise comparison approaches. MAC-D consists of three phases in sequence. In phase 1, the seasonal and climatic fluctuations are estimated and removed, using the reference series approach. Phase 2 combines a linear filtering with a change point detection test in an iterative algorithm, which runs until full compliance between the characteristics of the filtered series and the test requirements is achieved. Phase 3 is aimed at removing the false change points, due to error propagation in the reference series analysis, by double checking the detected change points with the pairwise comparison approach. Monte Carlo estimations of the actual significance and overall performance of the procedure for different series features and test resolutions are provided. Results demonstrate that MAC-D performs very well with daily series having a wide range of different characteristics. Copyright © 2012 Royal Meteorological Society

N-Heterocyclic carbene (NHC) ruthenium complexes consisting of different donor substituents attached to the NHC ligand efficiently catalyse the transfer hydrogenation of ketones and of activated olefins in α,β-unsaturated ketones to give saturated alcohols. The most active catalyst precursor contains a tethered olefin as a hemilabile donor site. This complex also converts nitriles and, depending on the reaction conditions, either benzylamines are produced by means of transfer hydrogenation, or amides from formal addition of H2O. Kinetic analysis of the double hydrogenation of α,β-unsaturated ketones indicates fast isomerisation of the enol intermediate to its saturated ketone tautomer prior to the second hydrogenation. European Research Council Swiss National Science Foundation

The time series of measurements of hydro-meteorological variables often suffer from imperfections such as missing data, outliers and discontinuities in the mean values. The discontinuity in the mean can be the effect of: instrumental offsets and of their corrections, of changes in the monitoring station or in the surrounding environment. If the discontinuities can be identified with a reasonable precision, a correction of the erroneous data can be made. Several authors have put their great effort into developing techniques to identify non-climatic inhomogeneities; the resulting statistical methods are especially effective when the series contains a single change point, while their performances decline when the series contains multiple change points or inhomogeneous segments (a portion of the series bounded by two complementary shifts). These limitations also affect the standard normal homogeneity test (SNHT), one of the most effective and widely applied tests. We present a composite method of homogeneity testing, standard normal homogenization composite method (SNHCM), including the SNHT as one component, which improves the SNHT performances with multiple change points and inhomogeneous segments. A number of comparisons among the new method, the SNHT and a powerful optimal segmentation method (OSM-CM), are illustrated in the paper. SNHCM demonstrates their performances in change-point detection similar to, or better than, the SNHT and very close to the OSM-CM. The SNHCM is effective in recognizing complex patterns of discontinuities, especially inhomogeneous segments, which represent a severe problem for SNHT; on the contrary, SNHT performs slightly better only when the series contains a single change point, but the difference between the two methods is negligible. Compared to the OSM-CM, SNHCM provides very similar performances, with some favourable features deriving from the fact that it is computationally lighter, simpler to implement, can easily handle very long series and is based on statistical hypothesis tests with a well-defined and adjustable significance level. Copyright © 2010 Royal Meteorological Society

The hydrological response of a catchment is the result of combined hillslope and channel network delays in the translation of rainfall to discharge at the catchment outlet. In this paper we examine three simple descriptions of the channel network response following an instantaneous hillslope runoff input within a general framework in which the role of network morphology is described using the probability density function (pdf) of network path lengths, and the role of hydrodynamic dispersion is described using a solution of the linear advection dispersion equation. We show that the pdf of path lengths, represented by the area function, can be adequately approximated by a triangular distribution with just two parameters (the mean and maximum network path lengths). The triangular pdf can be combined with a description of residence times in individual paths to derive an analytical expression for the hydrological response of the channel network. This expression provides a better approximation of the network response than both the original geomorphological instantaneous unit hydrograph (GIUH), based on Horton–Strahler ratios, and a single-channel representation, based on the concept of geomorphological dispersion. Using the same expression, we show that geomorphological factors generally prevail in controlling the mean and variance of network residence times. In contrast, hydrodynamic dispersion is shown to have a significant influence on the skewness of the network response over a wide range of catchment characteristics, strongly influencing the hydrograph peak and time to peak values in these cases. Copyright © 1999 John Wiley & Sons, Ltd.

The influence of the method of identification of the drainage network on its geomorphological characteristics and on its hydrological response is analysed. Blue lines, photo-interpreted networks and networks generated from digital elevation models (DEMs) by an automatic algorithm are compared with field observations for two small alpine catchments. The comparisons are carried out in quantitative terms by using several geomorphological indices and functions and by calculating the hydrological response of the networks as represented by their geomorphologic instantaneous unit hydrograph (GIUH). The results show that the effect of the identification method on the geomorphological indices and on the hydrological response is significant, and that the threshold area for channel initiation is not constant. Moreover, the available data show a poor correlation between local slope and threshold area. Finally, the influence of the threshold area on the shape of the GIUH is larger when the residence time on the hillslopes is of the same order as the residence time in the network. In the opposite case, the variability of the flow velocity along the network seems to play an important role. © 1997 John Wiley & Sons, Ltd.

The identification and analysis of natural channel networks from digital elevation models are discussed from the point of view of their environmental applications. An interactive, graphical software package that implements some of the most widely used techniques for the automatic recognition of channel networks and for the computation of some useful geomorphologic indices and functions is presented.

A simple model for estimating likely spatial patterns in landscape-scale denitrification rates is described. In the absence of limiting nitrate concentration, denitrification is assumed to be controlled principally by the soil water regime and the amount of available soil carbon. A formulation of TOPMODEL is used to estimate the spatial distribution of water table depths. Soil carbon concentration is assumed to decrease exponentially with depth. The spatial distribution of carbon concentrations at the soil surface is assumed to be imperfectly correlated with the topographic index used in TOPMODEL. Monte Carlo simulation techniques were used to introduce a stochastic element to the spatial distribution of soil carbon. This allowed estimates of the uncertainty in model outputs, resulting from uncertainties in the distribution and variability of soil carbon to be made. The model predicted spatial and temporal patterns of nitrate-non-limiting denitrification for a 15 year period in the Slapton Wood catchment in southwest England. Predicted denitrification followed a slight seasonal pattern with a winter maximum. Total annual denitrification losses tended to be positively correlated with total annual precipitation in the catchment. Highest rates tended to be predicted near to the stream. The modelling approach provides a means of assessing the proximity of local-scale field measurements to probable landscape-scale denitrification fluxes. Combining a deterministic model core with a stochastic generation of model parameters or state variables provides an attractive way of embracing variability and uncertainty whilst maintaining a conceptual description of the system dynamics. Copyright © 2002 John Wiley & Sons, Ltd.