An investigation of uncertainty in field habitat mapping and the implications for detecting land cover change

Land cover data for landscape ecological studies are frequently obtained by field survey. In the United Kingdom, temporally separated field surveys have been used to identify the locations and magnitudes of recent changes in land cover. However, such map data contain errors which may seriously hinder the identification of land cover change and the extent and locations of rare landscape features. This paper investigates the extent of the differences between two sets of maps derived from field surveys within the Northumberland National Park in 1991 and 1992. The method used in each survey was the Phase 1 approach of the Nature Conservancy Council of Great Britain. Differences between maps were greatest for the land cover types with the smallest areas. Overall spatial correspondence between maps was found to be only 44.4%. A maximum of 14.4% of the total area surveyed was found to have undergone genuine land cover change. The remaining discrepancies, equivalent to 41.2% of the total survey area, were attributed primarily to differences of land cover interpretation between surveyors (classification error). Differences in boundary locations (positional error) were also noted, but were found to be a relatively minor source of error. The implications for the detection of land cover change and habitat mapping are discussed.     

Predicting the distributions of plant species at the regional scale: a hierarchical matrix model

This paper describes a model which links four levels in an ecological hierarchy using a series of matrices. The four levels are landscape, land cover type, community and species. Each matrix quantifies the probabilistic associations between entities in two adjacent levels in the hierarchy. A landscape classification (1 km resolution) provides a spatial element to the model enabling the distributions of species to be predicted and presented as maps within a geographical information system (GIS). Implementation of the model in Northern England is described. The distributions of 579 species of plants were predicted and compared with data from independent field surveys. The predicted distributions were found to be accurate for 59 % of species. The distributions of rare and non-native (introduced) species of plant were relatively poorly predicted. The potential of this approach to model plant species distributions is discussed.     

The impact of landscape and adjacent land cover upon linear boundary features

The condition of over 200 km of traditional drystone walls wassurveyed within 115 km² in lowland, marginal upland and uplandlandscapes in northern England. The land covers adjacent to wallswere also recorded. Of the total length of walls surveyed, 12.6%were in disrepair. The condition of the walls differed betweenlandscapes and was also related to the type of vegetation in theadjacent enclosure. Walls enclosing conifer plantations andunimproved rough grazing were in poor condition reflectinghistorical and recent changes in their roles as livestock barriersand markers of ownership. The effect of other land covers on thecondition of walls was not consistent between landscapes. Usingdrystone walls as a simple model system suggests that the conditionof linear features in general may often be determined by both theadjacent land cover and the landscape in which the features occur.