Jane Wellens

Landscape metrics with ecotones: pattern under uncertainty

Landscape metrics are in widespread use, but previous research has highlighted problems over scale and error in the reliability of the metric values. This paper explores the variation of metric values when it is hard to distinguish exactly where one land cover type changes into another; when the ecotone is not an abrupt transition, but has a spatial extent in its own right. The values of metrics are explored in a landscape classified, using satellite imagery and the fuzzy c-means classifier, into fuzzy sets so that every location has a degree of belonging to all classes. The result is that any ecotone can be characterised by a variety of metric values depending on the degree to which a location is in any particular land cover class. The values recorded show some similarities, however, to those for an interpretation of the same landscape with abrupt changes, but the nature of that similarity varies unpredictably between metrics and classes. This analysis provides a limited degree of reassurance for those using metric analysis where the boundaries may have spatial extent, but much further work is required to establish an improved description of metrics under this condition.

Detecting change in vague interpretations of landscapes

Abstract For a number of years researchers have advocated the use of fuzzy classifications in the study of land cover mapping from satellite imagery. Some studies have looked at the change of fuzzy spatial object, but none have considered the direct corollary of the so-called change detection matrix. In this paper we discuss populating the fuzzy change matrix, using fuzzy logic statements. Intersection is the principal operation, but it is argued that the Bounded Difference is the intersection operation for which the results make sense for determining loss and gain of a cover type. While the minimum operator works in actually populating the matrix. An alternative matrix can be generated using just the Bounded Difference. The detection of ecotones and the analysis of ecotone change are also discussed. It is suggested that the mappings derived express subtle variations in land cover types and change in those types as well as in ecotones, which may be related more conclusively to an ecological process than are Boolean mappings with associated linear boundaries.

Monitoring the grazing resources of the Badia region, Jordan, using remote sensing

In this paper we discuss how low spatial resolution (1 km) ERS ATSR-2 and NOAA AVHRR satellite data were used to map and monitor changes in the grazing vegetation of the Badia region of Jordan. This area is typical of many arid zone grazing areas, comprising sparse vegetation and highly reflective soils. These two factors were found to severely limit the usefulness of satellite-derived vegetation indices that are frequently used to map and monitor vegetation in more temperate areas. Furthermore, the relationship between vegetation indices and percentage vegetation cover was found to be site-specific, thus reducing their application for large-scale vegetation monitoring. As an alternative, a hybrid geometric optical/empirically based model was developed for the area. This was based on the illumination geometry and reflectance values from the red and near-infrared scattergram of the satellite images. The output of the model was a series of maps indicating percentage vegetation cover for different dates and these were used to construct maps showing areas of vegetation change. Strong correlations (r(2) = 0.837) were found between estimates of percentage vegetation cover derived from the model, and measurements made at a series of 16 field sites in the area. The use of geometric optical models based on satellite imagery improves the ability to map areas of grazing vegetation in arid areas such as the Badia and provides a good alternative to the use of vegetation indices

What is Online Research?: Using the Internet for Social Science Research

Online research is perhaps the most obvious but also the most difficult of research methods. What is Online Research? is a straightforward, accessible introduction to social research online. The book covers the key issues and concerns for all social scientists, with sections on research design, ethics and good practice. Short, clear case studies are used throughout to allow students to see examples of the research in practice. Wide ranging and interdisciplinary, What is Online Research Methods? shows researchers how to engage in the online environment in innovative ways, and points the way forward for future research.

Teaching about bioethics through authoring of websites

There is growing awareness of the need to equip students to think through the ethical implications of developmentsin biology. We describe an exercise in which students work in teams to produce websites about current contro-versialissues within the subject. Participants report a significant improvement in their knowledge of bioethics and acquisition of new generic skills. Additionally, we note not only a broadening of their consciousness about suchissues, but also an increase in their use of appropriate scientific terminology. This web-authoring activity couldreadily be adapted for use with students in a broader range of disciplines at both tertiary and secondary level.

Calibration of a rangeland biomass model using NOAA-AVHRR 1.1-km data

The Normalized Difference Vegetation Index (NDVI) has been generated from data from the advanced very high resolution radiometer (AVHRR) for nine rangeland sites in Tunisia. Over one hundred images have been utilized to provide information about the vegetation at approximately monthly intervals for the period September 1983 to August 1992. These data were used to validate a rangeland biomass production model which has been developed for the nine rangeland sites. The model used daily rainfall data, estimates of potential evapotranspiration, and a series of site-specific vegetation parameters in order to estimate actual daily transpiration and an index of growing season yield. Although these outputs are not directly related to NDVI they are functions of the same plant tissues which indices such as the NDVI measure. A significant relationship (p > 0.05) was found between the NDVI and estimates of transpiration for all but one of the sites. The relationship between NDVI, integrated over a growing season, and the model derived yield index were not, however, found to be so strong.

Initial assessment of ATRS-2 data for retrieval of forest characteristics

Initial assessment of the utility of ATSR-2 1 km data for retrieval of forest characteristics was made. Principal component analysis was applied to an image of a tropical forest site in order to assess the dimensionality of the 14 ATSR-2 features, which include 4 spectral and 3 thermal bands, obtained at 2 view angles. The combined dataset had a 5-dimensional structure. The optimal combination of spectral features for discriminating forest characteristics in this site were the four ATSR-2 nadir channels, plus either the forward red or green channel, which gave a 4-dimensional data structure. Sensitivity analysis of a forest BRDF model was employed to investigate the relationships between nadir and forward samples of the ATSR-2. Simulated relationships between nadir and forward samples, for stands of varying fractional ground cover and crown LAI, indicate weak non-linear relations for all spectral bands. BRDF simulation results indicate that some additional information, not contained in the nadir data, is contained in the forward data. A stochastic scene simulation, coupled with the BRDF model, was used to approximate the data structure of an ATSR-2 image. Results are interpreted in terms of a number of important factors operating in an ATSR-2 scene that may either reduce or enhance BRDF effects in the measured radiance, and thus affect the success of inverse BRDF algorithms. These factors include sensor spatial resolution, scales of variation of surface cover features, and differences in the sampling characteristics between nadir and forward scans. Further testing of ATSR-2 data, including the utility of its spectral bandwidths and its multi-temporal capability, is required for a variety of different forested sites.

Mapping tropical forests: a bottom-up approach

Attempts to map different tropical forest types on a continental scale had varying success. Remotely sensed reflectance from forest canopies responds not only, or even primarily, to the species composition, but to a large number of factors, including soil type, forest structure, shadows and penology. This paper describes how detailed field data from sites in Bolivia are being used to develop and improve methods of tropical forest mapping from small scale satellite imagery. The paper presents preliminary work towards a novel procedure which characterizes canopy roughness from observations of forest structure and classifies imagery into canopy roughness classes by establishing a link between the shadow pattern information in the imagery and the canopy roughness of the forests. The inversion of the procedure will subsequently provide a means to extract forest structure information from satellite imagery and to generate improved maps of the tropical forest zone.

Potential of ATSR-2 satellite imagery for identifying and mapping different humid tropical forest ecosystems

Maps of the spatial distribution of different forest types of humid tropical forests are urgently needed for studies of biodiversity, ecology, deforestation and to provide inputs to global circulation models. Recent attempts to map the tropical forests of South America have relied on NOAA-AVHRR data which, with a 1.1 km spatial resolution, is suitable for mapping vegetation at regional and continental scales. Such attempts have, however, generally focused on identifying the forest/non-forest boundary and on determining rates of deforestation and have failed to differentiate different humid tropical forest types. A new sensor -- the ATSR-2 - - launched in 1994 has advantages over the AVHRR. The ATSR-2 has a similar spatial resolution to the AVHRR but its improved radiometric resolution in the visible and near- infrared regions mean that subtle differences in the spectral response of different forest canopies may be detected. In addition, the ATSR-2 has the ability to near-simultaneously view the target area from two different angles providing the scope for reducing atmospheric effects in the data. This capacity may also afford valuable information about the structure of the forest canopy. This paper describes the work currently being undertaken to utilize these characteristics of the ATSR-2 instrument to identify and map humid tropical forests in South America. The project is, in particular, examining how the differences in the (1) phenology, (2) structure, and (3) size, shape and frequency of gaps in the canopy influence the spectral response of different forest types. To date the project has concentrated on determining these parameters for tropical forests in Bolivia and extensive ground observations have been made for different forest plots.