Richard V. Birnie

Erosion rates on bare peat surfaces in Shetland

Abstract Measurements of erosion rates were made on bare peat surfaces at two hill‐top sites between 1982–1987. The aim was to provide estimates of the time taken to achieve full‐depth erosion of the blanket‐peat cover. Annual erosion rates were between 1–4 cm yr1 indicating that, for an average 1.5 m deep blanket peat, bare surfaces will persist for 30–150 years if geomorphological and management factors remain constant. These figures are of the same order of magnitude as those reported from higher altitudes in the Pennines.

Detection of surface soil variation using high-resolution satellite data: results from the U.K. SPOT-simulation investigation

Abstract A problem in using multispectral scanner(MSS) data for soil and landsystem analysis in north-west Europe is the poor spatial resolution which is insufficient to provide adequate within-field data. The SPOT satellite system will provide MSS data at 20m resolution and panchromatic data at 10m resolution. For any given ground feature the SPOT MSS mode will provide considerably more sample areas than LANDSAT 80m data. The object of this study is to determine how far variation in surface soil parameters can be detected and quantified on the basis of SPOT data.

A method of land evaluation including year to year weather variability.

Abstract Land evaluation is sensitive to the effects of annual variability in weather. A method to incorporate this variability into land evaluation systems is proposed, using the land capability system for Scotland as a case study. Land capability classes were found to be sensitive to the climate reference period from which data are taken. Individual stations rarely occupy their long-term land capability class. In addition, the relative position of stations in the land classification alters from year to year, indicating variations with time in spatial correlation structures. Markov chain analysis was used in a risk assessment approach to estimate the mean return time to a land capability category for individual stations and for areas of land. The main conclusions were: that land evaluation systems should not be applied using data from a different period to the baseline weather period used to establish the classification; there is a need to establish whether groups of stations tend to behave in similar ways over space and through time; mapping zones of risk could provide a means of formally incorporating weather variability into land evaluation.

A review of the current status of wind energy developments in Scotland

Abstract Despite the UK governments commitment to increasing renewable energy‐generating capacity, there has been limited adoption of wind‐energy technologies in Scotland. The Public Electricity Suppliers have taken a conservative view due to existing contractual obligations and generating over‐capacity. Local planning authorities have encountered a lack of linkage between national energy policy and other rural policy objectives. It is argued that these issues and wider community concerns must be dealt with before wind energy is likely to make a significant contribution to the energy economy of Scotland.

Spatio-temporal modelling of broad scale heterogeneity in soil moisture content: a basis for an ecologically meaningful classification of soil landscapes

We describe the classification of landscapes characterised bymineral soil using a model that calculates soil moisture availability on amonthly basis. Scotland is used as a case study area. The model uses potentialsoil moisture deficit, estimated using broad scale (40 × 40 km)climate patterns, in conjunction with meteorological station measurements toobtain finer scale values of climatic soil moisture deficit. Point estimates ofsoil available water are obtained for soil characteristics using appropriatepedotransfer functions, and geostatistical techniques are used to upscale theresults and interpolate to a 1-km grid. Known heterogeneityin soil physical characteristics is used to provide local corrections to thepotential soil moisture deficit, estimated using the climatic variables above.Temporal profiles of monthly water content are modelled for each1-km location and classified into six classes usingunsupervised cluster analysis. The spatial distribution of these classesreflects regional variations in the availability of moisture and energy, onwhich finer-grained topographic patterns are superimposed. In the case study,the broad scale spatial heterogeneity of heathlands and grasslands on mineralsoils in Scotland is shown to be strongly related to the soil moistureclassification. The results can be used in studies investigating the patternsofdistribution of communities at the landscape and regional scale.

A portable two-band radiometer

Abstract A lightweight and portable two-band radiometer is described which is suitable for estimating standing-crop biomass values using the infrared/ red reflectance ratio, or some linear combination of these characteristics. The instrument is simple to use and employs a single viewing element to eliminate any problems of non-coincidence of the target recorded by the detecting elements.

Thermal infrared survey of Aberdeen City: data processing, analysis and interpretation

Abstract The survey procedure and subsequent development of a microcomputer processing and analysis system adopted for a thermal survey of Aberdeen City is described. Thermal shadows on the imagery are shown to reflect air-mixing patterns at ground level and the sheltering effects of natural windbreaks, whereas canopy temperatures are related to vertical air-temperature profiles, thus enabling identification of frost hollows. Determination of heal loss from buildings was found to be problematical. The technique allows pollution sources and water-mixing patterns in river estuaries and nearshore zones to be identified.

Estimation of light interception and biomass of the potato (Solanum tuberosum L.) from reflection in the red and near-infrared spectral bands

Radiance measurements of the potato crop at near-infrared (NIR) and red (R) wavelengths were related to ground cover, light interception and destructive growth measurements in 1986. The relationship between the ratio NIR/R and crop ground cover was dependent upon crop nitrogen (N) status, as a result of fertilizer applications increasing the chlorophyll concentration in leaves. Calculation of cumulative light interception, assuming a 1:1 relationship between light interception and ground cover, showed a curvilinear relationship with cumulative NIR/R (Σ-NIR/R ), with N application increasing the slope of the line. Values of Σ-NIR/R were related to total crop dry weight, giving a separate quadratic equation for crops grown with or without N fertilizers. These relationships were tested by predicting, retrospectively, the biomass of crops grown in 1985 with several different levels of fertilizer nitrogen. During the period of canopy expansion, radiometric data overestimated crop growth. After canopy closure, the mean differences between measured and estimated values of crop dry weight were not significantly (P>0.1) different from zero, as long as the quadratic equation derived from the N-fertilized crops was used. The implications of using radiometric data for modelling crop growth are discussed.

Pixel-mixing effects and their significance to identifying snow condition from LANDSAT MSS data

Abstract Radiometric measurements on snow in LANDSAT MSS wavebands have shown a correlation between snow condition and the ratio of green/infrared (band 4/band 7) wavebands. Systematic changes from wet dense snow at tow altitudes to dry less dense snow at higher altitudes should be revealed by a decrease in the intensity ratio band 4/band 7 with altitude. However, analysis of spring LANDSAT MSS images for the Cairngorm Mountains shows that the intensity ratio band 4/band 7 actually increases with altitude. A mixed-pixel hypothesis is invoked to account for this pattern. The results suggest that only in areas where the snow cover is continuous can information on snow condition be reliably obtained from LANDSAT MSS data.