Influence of young poplar stands on floristic diversity in agricultural landscapes (Sweden)

Floristic diversity in 21 small short-rotation poplar plantations, 0.1 to 13 ha in size and aged 6 to 14 yr, was compared with adjacent agricultural fields of various crop types. The poplars were grown on former agricultural land and most of the study sites were located in southern and central Sweden. Surveys of ground vegetation were carried out by using nested quadrats (plots of 0.25 and 0.016 m(2) size) located along normally five transects running perpendicular to the habitat boundaries. Mean cumulative species number across all sites (all transects and plots included) was around 20 and similar in poplar stands and arable fields. However, the two habitat types shared only 3 to 12 species (mean: 8 species). Mean species number per survey plot was 4.5 in poplar stands compared to 5.3 in arable fields. Classification (TWINSPAN) and Detrended Correspondence Analysis (DCA) showed some floristic separation of the two habitat types. The results were interpreted in a landscape context. Mainly based on the low quantity of species shared by poplar stands and adjacent arable fields, the results support the hypothesis that small-scale poplar plantations increase floristic diversity in landscapes dominated by agriculture. Compared to old-growth mixed deciduous forests in different regions of Sweden, species richness of poplar plantations was similar or lower.