Forbs in Viking lands: The effect of disturbing dominant graminoids on forb recruitment in tundra grasslands.

Abstract

Certain graminoids can be successful in grasslands to the extent it is a phenomenon called "the Viking Syndrome". Nevertheless, forbs also make up a substantial part of vascular plant diversity in grasslands and are important resources of mammalian herbivores. Here we assess the hypothesis that forb recruitment is constrained by dominant graminoids, limiting access to safe sites for germination. We report on a disturbance experiment of plots with four different graminoid species in tundra grasslands of the Varanger Peninsula, Norway. Plots were selected to sample both rodent-disturbed and undisturbed areas. The dominant graminoids in each plot were removed, reducing their shading capabilities and belowground rhizome and root systems. Results show that forb recruitment one year following disturbance was significantly enhanced by manual graminoid removal. Dominant graminoid type, small rodent disturbance, initial forb abundance, and abiotic conditions had no effect on forb recruitment, whereas initial species richness had a positive relationship. Furthermore we found that manual disturbance had low impact on the species exchange ratio based on richness (SERr), suggesting that disturbance did not reduce the capacity of species to reside and move within the grassland. Our findings support the hypothesis that forb recruitment is limited by dominant graminoids.