Identify the opportunities provided by developments in earth observation and remote sensing for national scale monitoring of soil quality

Defra wish to establish to what extent national-scale soil monitoring (both state and change) of a series of soil indicators might be undertaken by the application of remote sensing methods. Current soil monitoring activities rely on the field-based collection and laboratory analysis of soil samples from across the landscape according to different sampling designs. The use of remote sensing offers the potential to encompass a larger proportion of the landscape, but the signal detected by the remote sensor has to be converted into a meaningful soil measurement which may have considerable uncertainty associated with it. The eleven soil indicators which were considered in this report are pH, organic carbon, bulk density, phosphorus (Olsen P), nitrogen (total N), magnesium (extractable), potassium (extractable), copper (aqua regia extractable), cadmium (aqua regia extractable), zinc (aqua regia extractable) and nickel (aqua regia extractable). However, we also comment on the potential use of remote sensing for monitoring of soil depth and (in particular) peat depth, plus soil erosion and compaction. In assessing the potential of remote sensing methods for soil monitoring of state and change, we addressed the following questions: 1. When will these be ready for use and what level of further development is required? 2. Could remote sensing of any of these indicators replace and/or complement traditional field based national scale soil monitoring? 3. Can meaningful measures of change be derived? 4. How could remote soil monitoring of individual indicators be incorporated into national scale soil monitoring schemes? To address these questions, we undertook a comprehensive literature and internet search and also wrote to a range of international experts in remote sensing. It is important to note that the monitoring of the status of soil indicators, and the monitoring of their change, are two quite different challenges; they are different variables and their variability is likely to differ. There are particular challenges to the application of remote sensing of soil in northern temperate regions (such as England and Wales), including the presence of year-round vegetation cover which means that soil spectral reflectance cannot be captured by airborne or satellite observations, and long-periods of cloud cover which limits the application of satellite-based spectroscopy. We summarise the potential for each of the indicators, grouped where appropriate. Unless otherwise stated, the remote sensing methods would need to be combined with ground-based sampling and analysis to make a contribution to detection of state or change in soil indicators. Soil metals (copper (Cu), cadmium (Cd), zinc (Zn), nickel (Ni)): there is no technical basis for applying current remote sensing approaches to monitor either state or change of these indicators and there are no published studies which have shown how this might be achieved. Soil nutrients: the most promising remote sensing technique to improve estimates of the status of extractable potassium (K) is the collection and application of airborne radiometric survey (detection of gamma radiation by low-flying aircraft) but this should be investigated further. This is unlikely to assist in monitoring change. Based on published literature, it may be possible to enhance mapping the state of extractable magnesium (Mg), but not to monitor change, using hyperspectral (satellite or airborne) remote sensing in cultivated areas. This needs to be investigated further. There are no current remote sensing methods for detecting state or change of Olsen (extractable) phosphorus (P). Organic carbon and total nitrogen: Based on published literature, it may be possible to enhance mapping the state of organic carbon and total nitrogen (but not to monitor change), using hyperspectral (satellite or airborne) remote sensing in cultivated areas only. In applying this approach the satellite data are applied using a statistical model which is trained using ground-based sampling and analysis of soil

Lasst Gras darüber wachsen : Zur Überweidung der Grassteppe in der Inneren Mongolei

Die Lebensbedingungen der Nomaden in Zentralasien haben sich im letzten Jahrhundert grundlegend verändert. So wurden z.B. in der Inneren Mongolei, einer Autonomen Region im Nordosten von China, die Nomaden in der zweiten Hälfte des 20. Jahrhunderts sesshaft gemacht. In einem engen Zusammenhang mit diesen Veränderungen stehen die Überweidung der Grassteppe, Bodenerosion und Sandstürme in diesen Gebieten. Im Rahmen eines interdisziplinären Forschungsprojektes, das in Zusammenarbeit mit der Chinese Academy of Science durchgeführt und von der Deutschen Forschungsgemeinschaft gefördert wird, befasst sich eine Arbeitsgruppe des Instituts für Landschaftsökologie und Ressourcenmanagement der Universität Gießen mit Fragen zum Wasserhaushalt, mit der Wassererosion und mit dem Austrag von Kohlenstoff und Stickstoff über die Gewässer in der Inneren Mongolei

Coupling of groundwater, river level and rainfall in an upland floodplain

Upland floodplains provide an important function in regulating river flows and controlling the coupling of hillslope runoff with rivers. To investigate the responses of floodplain groundwater to river flows and rainfall events, a small floodplain in an upland area of the River Tweed catchment, Scotland, was characterised using geophysics, 3D geological mapping and hydrogeological testing; and monitoring undertaken from September 2011 to February 2013 of: groundwater levels in five pairs of piezometers; river stage and flow at the upstream and downstream limits of the study site; soil moisture on the adjacent hillslope; and meteorological parameters. Periodical groundwater chemistry and residence data were also collected. The floodplain aquifer is permeable throughout but partially stratified, comprising dominantly alluvial and glaciofluvial sandy gravels between 8 and 15m interspersed with thin, intermittent layers of low permeability silts, clays and peats. Overlying the gravel aquifer is a partial thin cover of low permeability alluvial silts, and it is underlain dominantly by low permeability glaciolacustrine silts and clays. High permeability solifluction deposits mantle much of the adjacent hillslope and provide a rapid connection to the floodplain aquifer. The unusually wet year of 2012 provides a good example of how a temperate upland floodplain responds to consistently high rainfall. Statistical analysis and graphical interpretation of groundwater level, rainfall, soil moisture and river stage demonstrates that: 1) dominant groundwater flow within the floodplain is in the same direction as the river, from up-valley to down-valley; 2) soil moisture in the hillslope is strongly correlated with local rainfall, but groundwater across much of the floodplain is more strongly influenced by river stage; except 3) groundwater near the edge of floodplain, which responds more slowly to local rainfall and river stage changes ; and 4) subsurface flow from the hillslope to the floodplain occurs during high rainfall events. A detailed investigation of three flood events, when the river rose above bank level and flooded adjacent fields and groundwater became artesian in parts of the floodplain, suggests that antecedent moisture conditions can partly explain the differences in groundwater response during different flood events, where high intensity or long duration rainfall can cause saturated soil conditions, reducing soil water storage capacity and hence promoting flood conditions. A conceptual model based on field data of groundwater flow after storm events during antecedent unsaturated and saturated soil conditions is presented

Spatial scaling of CO2 efflux in a temperate grazed grassland

Understanding CO2 efflux from soil at different scales is important when up-scaling CO2 measurements from plot to larger scales, but there have been few studies investigating spatial CO2 efflux in temperate environments. We conducted a nested analysis of variation to explore how the CO2 efflux variation occurs between different spatial scales. Ninety-six manual dynamic chamber flux measurements of CO2 were undertaken during three, four hour surveys within seven grouped sites, each containing an optimised nested design with lag distances of 0.3m, 1m, 3m and 9m across six hectares of grazed hillslope grassland. This design also included continuous logging soil moisture sensors (plus conductivity and temperature) at 10cm soil depth. A previous study showed at this site that the variation of soil moisture is divided relatively equally between the four spatial scales 9m. The proportion of large-scale (>9m) variation increased after rainfall. In contrast in the three surveys analysed to date, the vast majority of the variation in CO2 flux occurred over the two smallest scales. No significant correlation between CO2 and soil moisture was observed over any of the spatial scales. All of these three surveys were conducted on relatively dry soils. We also investigated whether there were significant temporal variations in CO2 efflux over a period of three weeks using an automated soil flux system. These data showed there was no significant temporal variability between 10:00 to 16:00 hrs during late summer. There has recently been substantial rainfall at the field site and we are now conducting additional surveys to examine how the total CO2 fluxes and their spatial variation is effected by these wetter conditions

Investigating the role of groundwater in catchment functioning in the Eddleston Catchment, Scotland

BGS have been investigating the role of groundwater in catchment functioning for the past 10 years in the Eddleston Research Catchment – a tributary of the River Tweed, located in the Scottish Borders. The research is part of a wider initiative funded by the Scottish Government examining the evidence for the efficacy of natural flood management and river restoration measures. Here we give a brief summary of several of the experiments undertaken: (1) exploring the coupling of an upland floodplain aquifer with the river and hillslope; (2) examining soil permeability and infiltration in different land uses and superficial geology; (3) monitoring groundwater flow and soil moisture changes underneath a forest strip; and (4) using tracers to measure the partitioning between groundwater flow, soil water and event runoff during storm events. The research experiments reinforce the importance of subsurface conditions, and in particular geology in shaping the response of catchments to rainfall. Groundwater plays an important, but often unrecognised role in mediating catchment flows, and variability in superficial geology often exerts a larger control on flooding than land use

Forest management and flood alleviation: understanding water storage capacity of organic soil-subsoil below ancient forest, planted forest, and grassland

A number of serious flood events in recent years have focused attention on flood prevention and mitigation and modelling work suggests that climate change will lead to an increase in the intensity and frequency of flood events in many areas. To understand how soil hydraulic characteristics develops in relation to facilitating the infiltration and storage of storm rainfall, a hypothetical pedogensis sequence was first developed and then tested by investigating a grassland site and four Scots pine (Pinus sylvestris) forests of different ages in the Scottish Highlands. These sites are: grassland, six and 45 year-old Scots pine plantations, remnant 300 year old individual Scots pines and a 4000 year old Caledonian Forest. The soil characteristics measured were: field saturated hydraulic conductivity (Kfs) using a constant head well permeameter, root numbers and proportion were estimated from soil pits and soil cores were taken for three different soil depths (0.06 – 0.10, 0.16 – 0.20 and 0.26 to 0.40m) for laboratory measurements to estimate organic matter, soil water release curves, macro-pores, and X – ray tomography measured pore connectivity and soil pore structure. It was observed that cutting down of the plantation increased organic matter because of the increase of dead biomass and decreased pore connectivity, which resulted in reduced hydraulic conductivity during the early years of re-afforestation. Where older trees were left, after cutting and removing younger trees; the range of OM, hydraulic conductivity, pore connectivity, and macropores remained similar to and older Scots pine plantation (45 years old). The undisturbed Ancient Caledonian remnant forest (approximately 4000 years old) was observed to have remarkably heterogeneous soil characteristics, providing extreme values of Kfs (12 to 4992 mm hr-1), OM, and macropores. Such ranges of soil characteristics were considered to be the optimum to reduce local flooding, because the soil matrix could transport high intensity storm rainfall and re-direct storm rainfall to deeper layers and the presence of micropores and larger quantity of OM provides a greater area to store. This combination of soil characteristics would slow down the flow of rainfall to ground water reservoirs and rivers and reduce flood peaks