Jörgen Wissman

Butterflies in semi‐natural pastures and power‐line corridors – effects of flower richness, management, and structural vegetation characteristics

The aim of this study was to compare the butterfly assemblages in semi‐natural pastures and power‐line corridors and to analyse the effects of vegetation height, occurrence of trees and shrubs and different flowering vascular plant groups on butterfly diversity and abundance. Twelve of 26 analysed butterfly species were more abundant in power‐line corridors than in semi‐natural pastures. Only one species preferred semi‐natural pastures. In semi‐natural pastures butterflies were most common in segments with tall vegetation, whereas butterflies in power‐line corridors were most common in segments with vegetation of short or intermediate height. Short vegetation was sparser in power‐line corridors (mean cover 4%) than in semi‐natural pastures (33%), whereas tall vegetation was more common in power‐line corridors (59%) than in semi‐natural pastures (35%). The amount of flowers was the factor that affected the abundance of most species. Twenty‐one of the 26 species showed positive associations with numbers of flowers of different families. Flowers of the plant families Apiaceae, Caryophyllaceae, Primulaceae, Rubiaceae, Scrophulariaceae, and Violaceae showed positive associations with the abundance of several butterfly species. Vegetation height seems to be a limiting factor in semi‐natural pastures, and less intensive management (division of pastures into grazing pens, late season grazing, grazing every second year, or reduced grazing pressure) would benefit butterflies. In power‐line corridors (dominated by tall vegetation) the opposite would be beneficial for butterflies, for example more frequent clearing of vegetation along the power‐line trails combined with mowing of selected areas.

Biodiversity and Traditional Land Use in South-Central Sweden: The Significance of Management Timing

During the last 50–100 years, large numbers of species associated with seminatural grassland have declined. One reason for this is the considerable reduction of grassland area. Another possible explanation is the loss of historical management practices. This study addresses changes in the timing of management and its implications for biodiversity, and combines historical data on management timing (eighteenth century) with data on reproductive phenology of vascular plants and butterflies. All data are from south-east and south-central Sweden and demonstrate a considerable loss of grassland area, but an even greater loss of historical management practices. Historically, 21–32 per cent of the seminatural grassland area was subject to late season management (from early July A. DAHLSTROM, T. LENNARTSSON, J. WISSMAN AND I. FRYCKLUND 386 BIODIVERSITY AND TRADITIONAL LAND USE 387 Environment and History 14.1 Environment and History 14.1 onwards) by mowing or late-season grazing. In 2005, management had ceased in 97–99 per cent of the historically managed grassland, and current management was dominated by all-season grazing. 0.2 per cent of the grassland area was managed by mowing in 2005. Historically, at the time of mowing, 50–80 per cent of the butterfly species and 20–95 per cent of vascular plant species had completed their reproductive cycles, the proportions increasing with the later onset of management. The results suggest that the reduced use of late management is a major cause of the observed decline of grassland organisms.

The Effect of Timing of Grassland Management on Plant Reproduction

Seminatural grasslands are maintained by regular anthropogenic disturbance, usually grazing or mowing. Management action late in the growing season was historically more common than today. Two experimental grazing regimes, continuous stocking from May to September and late-onset grazing from mid-July, were compared in two Swedish grasslands. Effects on flowering and fruit production were studied and related to plant functional traits. Change in vegetation composition over six years was analysed in one grassland. Delayed onset of grazing enhanced fruit production up to four times. Phenology of reproduction was the most important plant trait explaining differences in reproduction among species. Diversity of vascular plant species was higher after six years of late-onset grazing. No differences in vegetation height or proportion of grazed shoots were found by the end of the season. The results suggest that early reproduction may function as an escape from damage and that late onset of grazing may be used as a substitute for labour-intense traditional mowing.

Mowing for biodiversity: grass trimmer and knife mower perform equally well

Mowing of semi-natural grasslands is an important management method to maintain the conservation value and species-richness of this habitat. Mowing using cutting instruments, e.g. sickle bar mowers, is thought to be superior by practitioners compared with other mechanical instruments that tears off the plant material, e.g. grass trimmers. However, almost no studies exist that supports this assumption. We analysed a 12-year field trial in a semi-natural grassland in south-eastern Sweden, with the aim of determining which mowing technique best maintains the conservation value of semi-natural grasslands. Two mowing techniques were compared: mowing using a hand-pushed sickle bar mower (a type of knife mower), or mowing using a grass trimmer at a 5-cm or 0-cm cutting height. The odds that a recorded species belongs to a group of indicator species were calculated for sample plots, and odds ratios were calculated contrasting treatments. Three types of indicator species classification systems were used: (i) indicators of management for species richness, (ii) indicators of excess nitrogen and (iii) indicators of lack of management. The odds ratios were calculated for years 1–5, 7 and 12 of the trial. In addition, Principal Response Curve analysis was performed to analyse the change in vegetation composition over time and ANOVA for plant species richness in plots. The results showed that over time there were no differences in the odds of finding indicators of any of the three types, for any of the mowing techniques. Furthermore, there were no apparent change in vegetation composition and only a small effect on richness. These results suggest that mowing using a sickle bar mower or a grass trimmer had the same effect on the floristic composition of grasslands, and both techniques can be recommended for use in semi-natural grasslands.

Grasslands of Gotland and Öland, Sweden

The traditionally grassland based landscape of southern Sweden has, during the last century, changed into a landscape with a focus on arable cultivation and forest production. Much of the species-rich grasslands are found in the south eastern parts of Sweden and on the alvar of the islands Oland and Gotland. The landscapes of the islands contain a mixture of different types of forest scattered with wetlands, alvar, and dry and mesic grasslands. In general the distribution of vegetation and farming follows the conditions of soil productivity and moisture. The areas that are dry and poor in nutrients are used as pastures or grazed forest. On soils that allow higher productivity, the land is used as open pastures, meadows and arable fields. The species composition of the islands is unique to the rest of Sweden. Near the water, salt tolerant species as Glaux maritima, Juncus gerardii and Agrostis stolonifera are found.Keywords: Oland grasslands; Agrostis stolonifera; Glaux maritima; Gotland grasslands; Juncus gerardii; Sweden landscape