Scale-dependent importance of environment, land use and landscape structure for species richness and composition of SE Norwegian modern agricultural landscapes |
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| Authors: | Rune H Økland Harald Bratli Wenche E Dramstad Anette Edvardsen Gunnar Engan Wendy Fjellstad Einar Heegaard Oddvar Pedersen Heidi Solstad |
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| Institution: | (1) Department of botany, Natural history museum, University of Oslo, P.O. Box 1172, Blindern, Oslo, 0318, Norway |
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| Abstract: | 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. |
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| Keywords: | Land use intensity Landscape structure Patch Spatial scale Spatial variation Variation partitioning Vascular plants |
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