Gunnar Engan

Scale-dependent importance of environment, land use and landscape structure for species richness and composition of SE Norwegian modern agricultural landscapes

Knowledge of variation in vascular plant species richness and species composition in modern agricultural landscapes is important for appropriate biodiversity management. From species lists for 2201 land-type patches in 16 1-km2 plots five data sets differing in sampling-unit size from patch to plot were prepared. Variation in each data set was partitioned into seven sources: patch geometry, patch type, geographic location, plot affiliation, habitat diversity, ecological factors, and land-use intensity. Patch species richness was highly predictable (75% of variance explained) by patch area, within-patch heterogeneity and patch type. Plot species richness was, however, not predictable by any explanatory variable, most likely because all studied landscapes contained all main patch types – ploughed land, woodland, grassland and other open land – and hence had a large core of common species. Patch species composition was explained by variation along major environmental complex gradients but appeared nested to lower degrees in modern than in traditional agricultural landscapes because species-poor parts of the landscape do not contain well-defined subsets of the species pool of species-rich parts. Variation in species composition was scale dependent because the relative importance of specific complex gradients changed with increasing sampling-unit size, and because the amount of randomness in data sets decreased with increasing sampling-unit size. Our results indicate that broad landscape structural changes will have consequences for landscape-scale species richness that are hard or impossible to predict by simple surrogate variables.

The effect of field experience on the accuracy of identifying land cover types in aerial photographs

Abstract The purpose of this study was to examine the contribution of field experience to the attribute accuracy of land cover maps based on interpretation of aerial photographs. A senior photogrammetrist using true colour aerial photographs delineated land cover polygons in two areas with similar, but not identical, land cover features. Ten experts with long experience from interpretation of aerial photographs were then asked to label these land cover polygons. The experts fell into two broad categories: ‘field trotters’ and ‘photogrammetrists’ according to their professional background. After completing the labelling of the polygons in the first area, all experts spent 1 day in the field in order to compare their results to ground truth. The fieldwork was supervised by a vegetation ecologist. After the field session, the experts proceeded to label the polygons in the second area. The results did not reveal statistically significant differences between the two groups. Neither did any of the groups improve their performance as a result of the fieldwork.