Water quality and planktonic microbial assemblages of isolated wetlands in an agricultural landscape

Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Wetlands 31 (2011): 885-894, doi:10.1007/s13157-011-0203-6.Wetlands provide ecosystem services including flood protection, water quality enhancement, food chain support, carbon sequestration, and support regional biodiversity. Wetlands occur in human-altered landscapes, and the ongoing ability of these wetlands to provide ecosystem services is lacking. Additionally, the apparent lack of connection of some wetlands, termed geographically isolated, to permanent waters has resulted in little regulatory recognition. We examined the influence of intensive agriculture on water quality and planktonic microbial assemblages of intermittently inundated wetlands. We sampled 10 reference and 10 agriculturally altered wetlands in the Gulf Coastal Plain of Georgia. Water quality measures included pH, alkalinity, dissolved organic carbon, nutrients (nitrate, ammonium, and phosphate), and filterable solids (dry mass and ash-free dry mass). We measured abundance and relative size distribution of the planktonic microbial assemblage (< 45 μm) using flow cytometry. Water quality in agricultural wetlands was characterized by elevated nutrients, pH, and suspended solids. Autotrophic microbial cells were largely absent from both wetland types. Heterotrophic microbial abundance was influenced by nutrients and suspended matter concentration. Agriculture caused changes in microbial assemblages forming the base of wetland food webs. Yet, these wetlands potentially support important ecological services in a highly altered landscape.Funding was provided by the Joseph W. Jones Ecological Research Center.2012-07-2

Mécanismes et maitrise de la pollution diffuse agricole : le cas du phosphore et sa portée générale

Mechanisms and control of agricultural diffuse pollution: the case of phosphorus. The movement of phosphorus is primarily a surface phenomenon closely related to surface runoff and erosion. It is a discontinuous process, set in motion during surface runoff events. The potential for surface runoff begins with any process reducing the infiltration rate of the soil surface. The contribution of cultivated fields to surface runoff varies spatially and temporally in relation to their permeability, soil type, land use, and soil cover. The contribution of these fields to P transfer and export varies in the same way but depends also on the P content of the soils, especially at the soil surface. Subsurface flows general carry in much less phosphorus due to its fixation in the subsoil, except in some conditions such as sandy soils, long-term over-fertilization, and agricultural drainage. Some elements of the landscape are considered as buffers because they can filter and thus attenuate the P fluxes transferred in the hydrologic network (grass filter strips which are purposely constructed but also hedgerows and riparian vegetation). Within the network, particulate forms of P may settle may and dissolved forms of P may sorb onto sediment particles or precipitate or be taken up by biota. In addition, major obstacles such as wetlands can store and/or transform some of the phosphorus emitted from upstream fields. Thus a set of interacting processes moves P through the landscape within a "transfer system", which includes emission from sources (mainly soils or sediments) and transport (including transformation and attenuation). This transfer system comprises a highly diverse and complex set of landscape structures arranged in a complex and diverse hydrologic hierarchy and interacting with agricultural practices and management of the hydrologic network. This paper attempts to characterize the key phenomena and structures of the transfer system that determine the flux, storage, transfer and mass balance of phosphorus in agricultural watersheds. Strategies for controlling diffuse phosphorus pollution are also indicated

Approche agro-pédologique des zones pastorales sur calcschistes sédimentaires (Beaufortain-Alpes du Nord). I. Caractères de l'altération, propriétés hydriques et porales associées

En altitude, l'altération des calcschistes sédimentaires (calcshales) conduit à des sols contenant une teneur élevée en limon fin, de composition minéralogique essentiellement micacée. La pédogénèse se caractérise sur ce type de roche, par une argilisation importante due à une microdivision des micas, vers la surface du sol. Ce phénomène entraîne une profonde réorganisation de la phase solide, de l'espace poral et en fin de compte, conditionne les propriétés hydriques des sols. Dans ce premier texte, un ensemble de méthodes de mesure et d'observation est employé pour décrire l'évolution de la géométrie du système de porosité hérité de la roche, après sa décarbonatation. Cette approche permet de visualiser et de quantifier le volume poral total, la taille, la morphologie et la continuité des pores. La gamme de tailles prise en compte s'étend du nm jusqu'au mm. Grâce aux résultats obtenus, il est possible de comprendre les aspects du fonctionnement hydrique qui conditionnent les relations sol-végétation et qui constituent, par conséquent, un facteur clef pour l'exploitation pastorale. Les propriétés du matériau d'altération perdent de l'importance quand la pente s'accentue; la circulation de l'eau et la topographie deviennent alors prépondérantes pour expliquer la différenciation des sols et des végétations prairiales. Ces interactions seront traitées dans une deuxième partie.Landscape ecology of alpine pastures in a sedimentary calcschist area (Beaufortain, Northen Alps). I. Characteristics of weathering: consequences on hydric and poral behaviour of soils. The weathering of sedimentary calcschist (calcshales) in the Beaufortain mountain pasture region (fig 1), gives rise to soils containing very high amounts of fine (< 5 μm) micaceous silt particles (fig 2; tables II, III). Pedogenesis on this type of parent rock is characterized by a significant argilization (physical breakdown of mica particles) towards the soil surface (table II), causing a total reorganization of solid particle arrangement and corresponding pore geometry (fig 2.2, 2.4, 2.5). A series of physical methods (table I) is used here in order to describe the origin and evolution of the pore geometry during pedogenesis, starting from the pore system inherited from the parent rock after its decarbonization (fig 2.2 and 2.3). These methods enable the observation and the quantification of the porosity in terms of total pore volume, pore size and pore morphology as well as that aspect concerning continuity of the pores. The pore size ranges from the nm to the mm. Analysis of the pore system and the related soil water behaviour (figs 3, 4, 5; table II) performed in different horizons of a representative soil profile indicates the constraints for local agriculture. On hill slopes the superficial water circulation and topography are major factors explaining soil and vegetation differentiation. Such soil-vegetation-land use interactions will be discussed in a second paper considering typical geomorphological land units

Approche agro-pédologique des zones pastorales sur calcschistes sédimentaires (Beaufortain-Alpes du Nord). II. Répartition des sols et des valeurs d'usage pastoral

National audienceThe originality of pedogenesis on calcschist in the Beaufortain mountain pasture region lies in the homogeneity with respect to the size, form and mineralogical nature of the constituents of the decarbonation residue: mica platelets with fine silt particles. In in situ developed soils, the main evolution observed between the weathering horizon and the soil surface is of a physical nature. The physical breakdown of silt particles takes place concomitantly with the disappearance of the pore system inherited from the weathered rock. In the (B) horizon, a microscopy (pore size ≈ 0.6 μm) becomes visible, which is the result of the microdivided mica particle arrangement (particle size < 6 μm). A low water availability and low hydraulic conductivities in this soil horizon with regard to the C horizon therefore occurs. These data have been presented in the first paper. Such soil structure modification produces pertinent repercussions with respect to pasture vegetation. Significant agronomic constraints thus arise in all areas with a flat topography (plateau, fig 1, table II). The uptake of water and nutritious elements (bases) by the root systems of the pasture cover is impeded as the thickness of the (B) horizon with unfavorable physical properties increases (figs 2, 3). In such an environment with a strong tendency to acidification, soil evolution is highly dependent on agronomic farming intensity, both today and in the past (table II, fig 4). As soon as hill slopes get steeper (solifluxion slopes, fig 5, table III), the superficial water movements and topography become major factors explaining soils and vegetations differentiation, often organized in mosaic distribution patterns (table III, IV). Hence, within the same mountain pasture area, calcareous, acid and hydromorphic soils can be observed, each soil type imposing its own specific farming constraints (table IV).L’originalité de la pédogénèse sur calschistes sédimentaires, en altitude (étage subalpin), réside dans l’homgénéité du résidu de décarbonatation (plaquettes de micas de taille limons fins). Au sein des sols développés en place, la principale évolution qui se manifeste entre l’altérite et la surface du sol, est une microdivision de ces particules limoneuses. Celle-ci s’accompagne d’une disparition du système de macroporosité hérité de la décarbonatation de la roche et de l’apparition, dans l’horizon (B), d’un système de micropores. Il s’ensuit une faible disponibilité de l’eau et une vitesse d’écoulement très faible dans cet horizon par rapport à l’horizon C (1 er partie). Cette organisation du sol liée à la pédogénèse, a des répercussions très significatives sur la végétation prairiale et sa dynamique. Elle représente une contrainte agronomique qui s’exprime surtout en situation de plateau. L’approvisionnement en eau et en éléments nutritifs (bases) par le système racinaire du tapis végétal, est alors limité par l’épaisseur de l’horizon (B) et les risques de dégradation de la valeur fourragère sont maximaux. L’évolution pédogénétique et les potentialités dépendent alors étroitement de l’intensité et des modalités de l’exploitation pastorale actuelle et (ou) passée, seuls facteurs susceptibles d’atténuer et de compenser les effets des propriétés physiques défavorables de la couverture pédologique. Au total, sur les plateaux le paysage pastoral porte d’abord la marque des pratiques agricoles. Inversement, dès que la pente s’accentue (situation de versant de solifluxion), la circulation de l’eau et la topographie deviennent les facteurs prépondérants pour expliquer la différenciation en mosaïque des sols et des végétations et révéler les contraintes spécifiques d’entretien des diverses zones

Apport d'un modèle simplifié de simulation du bilan hydrique pour l'analyse de la satisfaction du besoin en eau de prairies irriguées des Alpes internes

Le recours à l'irrigation des prairies permanentes du val d'Aoste (Alpes italiennes) s'explique par la faible pluviosité estivale et la forte demande d'évapotranspiration. Pour étudier la satisfaction des besoins en eau de divers types de prairies irriguées, nous avons utilisé un modèle simplifié de calcul des variations de la teneur en eau du sol. Il s'agit du module bilan hydrique de CREAMS (chemical, runoff, and erosion from agricultural management systems). Dans un premier temps, nous caractérisons la variabilité des différentes variables entrées dans le modèle : propriétés hydriques des sols, fréquences, dates et doses d'irrigation. Nous évaluons par ailleurs la valeur d'un paramètre de calage décrivant la répartition du système racinaire avec la profondeur. Dans un deuxième temps, nous simulons les variations de la teneur en eau du sol sur un réseau de 8 parcelles dont nous suivons l'humidité volumique et la production de matière sèche. Les calculs donnent des résultats comparables aux humidités observées et le rendement en matière sèche est corrélé significativement aux déficits hydriques moyens calculés. Le modèle ainsi validé nous permet de simuler le comportement hydrique de différentes parcelles représentatives de la variabilité régionale des sols et des pratiques d'irrigation.A simplified water-balance model for the analysis of the satisfaction of water requirements in irrigated inner Alps meadows. Irrigation of permanent meadows in Val d'Aosta (inner Italian Alps) is rendered necessary by low summer precipitations and by a high evapotranspiration demand. To study the satisfaction of the water requirement of vegetation, a simple model of water balance calculation was used. This is the 'hydrology' module of CREAMS (chemical, runoff, and erosion from agricultural management systems). We first characterized the variability of the different input variables: hydric properties of the soils, dates and frequencies of irrigation, and doses of water supplied. We also assessed the value of a parameter that relates root distribution with depth. We noticed a great variability of soil properties and irrigation practices. We then ran a simulation of water balance on 8 plots where soil moisture and dry-matter yield were monitored. The results of the calculations were comparable to the observed soil moisture values. Moreover, the dry-matter yields were correlated with the calculated mean water deficit. Simulations run with the model provide a framework adapted to the regional variability of soil properties and agricultural practices, which can be used to analyse interaction of the factors involved in the water balance

Mitigation Measures for Water Pollution and Flooding

This chapter discusses the range of measures that can be used to mitigate the impacts of water pollution and flooding. It makes a distinction between source measures which aim to reduce the amount of water or pollutant initially mobilised, pathway interventions which seek to slow the flow of pollutant enriched water once it has become mobilised and methods to protect receptor water bodies which are intended to reduce peak flows or prevent pollutants moving further through a catchment. In many European countries the policies and programmes used to increase the adoption of such measures are heavily influenced by EU obligations stemming from the Floods, Nitrates and Water Framework Directives. Typical approaches used involve a combination of regulation, financial incentives and advice provision. There are also a range of tools that can be used to model the potential effects of mitigation measures and a number of research programmes generating findings that may be of value to the landscape planner