These studies emphasize the need to investigate the effects of herbivores across environmental gradients.
These studies emphasize the need to investigate the effects of herbivores across environmental gradients.We conducted our study in a reindeer-grazed tundra system in northern Fennoscandia.We randomly selected 1 m × 1 m plots on both sides of the fence (32 plots in total) within those sites that were paired as topographically and edaphically uniform as we could.
Herbivores impact nutrient availability and cycling, and the net effect of herbivory on soil nutrients is generally assumed to be positive in nutrient-rich environments and negative in nutrient-poor ones.
This is, however, far from a uniform pattern, and there is a recognized need to investigate any interactive effects of herbivory and habitat fertility (i.e., plant C/N ratios) on soil nutrient availabilities.
Traditionally it has been assumed that herbivores have mainly positive effects on N availability and primary production in nutrient-rich environments dominated by plants of high quality (i.e., low carbon (C) to N ratios), and mainly negative ones in nutrient-poor environments dominated by plants of low quality (i.e., high C/N ratios) (Hobbs ).
However, this is far from a uniform pattern and at least one study has actually supported the opposite pattern, that is, a negative relationship between habitat/plant quality and the effect of herbivores on N availability (Bakker and others ).
Mean annual temperature at the site was −3.3°C based on local loggers, and the average precipitation at the nearest climatic station (Kautokeino) is 389 mm/year.
We conducted the study across a reindeer fence, established in the 1960s to prevent reindeer from entering their winter ranges during summer.The increase in N availability was linked to a decrease in plant and litter C/N ratios, suggesting that a shift in vegetation composition toward more graminoids favors higher N cycling.Soil P availability was not as closely linked to the vegetation and is likely regulated more by herbivore-induced changes in soil physical and chemical properties.JS contributed to design of the study, performed research, analysed data, and wrote the paper.MB contributed to design of the study, research and writing of the paper.We want to emphasize that grazing in this study includes trampling on the vegetation in its definition.for a description of topographic gradients in the arctic).The study area is located in Reisadalen, Troms Fylke, northern Norway (69°30′N, 27°30′E) between 500 and 700 m a.s.l., which is about 100 m above the local tree line.The area experiences a sub-oceanic climate (Oksanen and Virtanen ).Mean elevation ±SE between depressions and exposed ridges is shown.We chose four replicates sites for each vegetation type.