Growth responses of Calamagrostis lapponica to simulated environmental change in the sub-arctic

Abstract

A sub-arctic heath community dominated by dwarf shrubs has been subjected to three components of environmental change (temperature, water and fertilizer) in a factorial experiment over three growing seasons. Above-ground biomass of the most abundant grass in the ecosystem, Calamagrostis lapponica, was measured after one, two and three seasons, shoot height and flowering frequency were recorded after two and three seasons. There was up to 50 times more above-ground biomass at the end of the second season compared with the end of the first season. Fertiliser had the greatest effect on all parameters, resulting in greater biomass, increased flowering and a greater shoot height. The mean biomass of C. lapponica was greatest in the third season, but still contributed less than 8% of the above-ground biomass in the fertilised plots; the dominant species being ericaceous dwarf shrubs. The response of the grass to temperature and water was not as marked as the response to fertiliser. Temperature increase led to greater shoot height in both seasons whilst in the first season both warmer temperature and water additions resulted in greater biomass. All treatment effects were less in the third season than in the second, perhaps because of competition from the dominant dwarf shrubs which respond more slowly to the perturbations than the grass. The responses of the C. lapponica and the dwarf shrubs to the treatments are compared. If climate change results in greater solute availability in this ecosystem, there may be a marked change in species composition with C. lapponica becoming more prevalent.