Tolerance of the arctic graminoid Luzula arcuata ssp. confusa to simulated grazing in two nitrogen environments

Abstract

We investigated the response of the important forage plant Luzula arcuata Swartz ssp. confusa (Lindeb.) Blytt to simulated grazing during two growing seasons in a phytotron. Plants were clipped at five levels of intensity and fertilized at two levels of nitrogen. There was no reduction in net primary production of clipped compared with unclipped plants after either of the two growing seasons. Such results indicate that L. arcuata ssp. confusa can compensate for defoliation. Plants overcompensated in net aboveground primary production (NAPP) in the first season and compensated in NAPP in the second season. Plant traits contributing to the compensation in NAPP were stimulation of tillering in clipped plants, increase in specific leaf area of the most heavily clipped plants, and a higher proportion of NAPP occurring below clipping height in frequently clipped plants. Sexual reproduction (number of flowering shoots) was enhanced in the second season in plants clipped at 6 cm above the soil and reduced in plants clipped 3 cm above the soil. The response to clipping was independent of nitrogen treatment, suggesting that nitrogen did not limit regrowth even in the low nitrogen environment. Luzula arcuata ssp. confusa is tolerant of dry, cold and windswept, low-nutrient habitats in the Arctic. This study shows that it also is tolerant of defoliation.Key words: forage, herbivory, compensation, grazing responses, Svalbard.