Following abandonment of traditional mowing of mat-grass Nardus stricta sub-alpine grasslands in the Giant Mountains (Krkonoše), northern Czech Republic, over the last 50 years purple moor-grass Molinia caerulea has expanded considerably. This study investigated whether reinstatement of the traditional mowing regime would reverse Molinia encroachment and help to restore the original Nardus grassland.
The traditional mowing regime of one cut per year in late July was introduced to study plots over a period of six years, and plant response compared with adjacent unmown areas (control). Vegetation parameters (including percent cover, canopy height, panicle density and biomass production) were recorded. Species richness was determined and soil nutrient availability analysed.
After 6 years of mowing management, Molinia cover decreased significantly (from 79% to 7%), canopy height declined from an average of 45 to 14 cm, biomass production declined from 313 to 54 g/m² and panicle density from 129 to 18/m². As mowing progressed and Molinia declined, patches of bare ground were created and partly colonized by wavy hair-grass Deschampsia (Avenella) flexuosa. No Nardus seedlings appeared in the mown plots, despite it being common in adjacent areas.
Cutting significantly decreased potassium (K) availability in the soil (8 g/m² removed over 6 years). Compared to the control, N:P, N:K and K:P ratios in the plant biomass were not significantly affected by mowing.
No significant effect of cutting on species richness was apparent, thus although reinstatement of cutting reduced Molinia, it did not increase species richness and restoration to original Nardus grassland was not achieved over the 6-year study period.