Nutrient limitation in boreal plant communities and species influenced by scything

Abstract

Abstract. The nutrient status was studied in permanent plots of four plant communities, two rich‐fen communities and two wooded grassland communities, all formerly used for haymaking. The concentrations of N, P and K in plant material of dominant and subdominant species (above‐ and below‐ground) were measured in plots experimentally scythed annually or biennially for two decades, and in plots unscythed for four decades. Three of the communities had an N:P ratio of 14 or less, indicating N‐limitation; the most fertile grassland community had particularly low values for the N:P ratio (6–12), as did a majority of the species, including all tall‐herb species. A species‐rich community of fen‐margin vegetation in the lowest productive rich fen, had an N: P ratio of 17–19 in the above‐ground biomass, which indicates P‐limitation of nutrients. Molinia caerulea and Thalictrum alpinum were found to be the vascular plants with the highest N:P ratio, indicating P‐limitation of nutrients. Calculations of N:K and K:P ratios indicated possible K‐limitation in the rich‐fen communities, especially for Thalictrum alpinum , the species with the highest N:K value. No expected change from N‐ to P‐limited growth was found; in contrast, a reduction in the N:P ratio was found in the annually scythed plots of the rich fens, suggesting that reduced biomass production is mainly a result of disturbance by scything. As expected, a reduction in the concentration of K was detected in the scythed plots.