Responses of a Subarctic Dwarf Shrub Heath Community to Simulated Environmental Change

• Published in: The Journal of ecology 1998-04, Vol.86 (2), p.315-327
• Main Authors: M. C. Press, Potter, J. A., Burke, M. J. W., Callaghan, T. V., Lee, J. A.
• Format: Article
• Language: English
• Subjects: Aboveground biomass; Biomass; Human ecology; Lichens; Marine ecosystems; Nutrient nutrient interactions; nutrients; Plants; Species; species abundance; Subshrubs; temperature; water; Water temperature
• ISSN: 0022-0477; 1365-2745
• DOI: 10.1046/j.1365-2745.1998.00261.x

1 A dwarf shrub heath in subarctic Sweden was subjected to factorial manipulation of air temperature, water and nutrient supply for 5 years. The responses of the vegetation to the perturbations were then assessed by point intercept (quadrat) analysis followed by determination of above-ground biomass. 2 Nineteen vascular and 23 non-vascular species (or species groups) were recorded and the most dramatic response was that of the grass Calamagrostis lapponica to nutrient addition, with abundance being stimulated by a factor of more than 18 compared with plots not subjected to nutrient addition. Calamagrostis lapponica did not show any significant responses to temperature or water alone but there was a synergistic interaction between all three variables. 3 The abundance of the dominant dwarf shrubs (Empetrum hermaphroditum, Vaccinium vitis-idaea, V. myrtillus and V. uliginosum) was unaffected by the perturbations but elevated temperature stimulated the biomass of V. uliginosum by 125% and total shrub biomass by 16%. The low ratio of current year's growth to standing biomass may have concealed other responses of the dwarf shrub group to the perturbations. 4 The response of the non-vascular flora to the perturbations was either neutral or negative, with lichens showing the most dramatic responses. Lichen biomass on temperature- and nutrient-amended plots was 56% and 18%, respectively, of that on unperturbed plots. Nutrients also exerted a negative effect on the biomass of bryophytes, and the combined biomass of lichens and bryophytes on nutrient-treated plots was almost a third of that on plots which did not receive additional nutrients. 5 Total above-ground biomass was not affected by the perturbations but the total number of interceptions determined by point quadrat analysis was greater on the elevated temperature and nutrient-treated plots. Point quadrat analysis also revealed an accumulation of litter and standing dead material in response to the nutrient and temperature perturbations, both singly and in combination, suggesting a faster turnover of plant material. 6 Both temperature and nutrients increased canopy height and also interacted synergistically such that together they resulted in a mean canopy height of 14.9 cm compared with 8.0 cm in plots subjected to neither perturbation. 7 Nutrient addition lowered species richness by 17.7%, mainly through its impact on the mosses and lichens. 8 In general, nutrient addition elicited the greatest response, fol