No evidence of long-term warming and reindeer grazing influencing the quality of plant species on reindeer summer pastures in Finnmark

Sandfjorddalen on the Varanger peninsula is a summer pasture for semi-domesticated reindeer in Finnmark. Photo: Fanny Berthelot.

To our knowledge - this is the first study that uses a large spatial sampling design to assess long-term impacts of herbivory and climate on plant nutritional quality (i.e., both defense and nutrient concentrations). 

We found substantial variations in plant chemical composition between species, and part of this between-species variation was associated with plant functional groups. We also documented strong seasonal decreases in the concentrations of nutrients (N and P) and weaker seasonal increases in the concentrations of defense compounds (Si and Ph) over the summer. 

Boxplots: Chemical composition per plant functional group in % dry weight (%DW).

Stacked plot: Variance in chemical compound concentrations explained by the main predictor variables in %. 

The seasonal decline in nutrient concentrations was steeper in warmer sites than in cooler sites, while defense compounds seemed not to be affected by the temperature. 

We found no evidence for long-term effects of reindeer grazing intensity on the average chemical composition of the plants. 

Graphic model outputs: Outputs from Generalized mixed effects models about the effects of our predictors of interest on the chemical composition of plants. The overlap of the confidence interval with 0 indicates no effect.

Our results indicate that what is likely to matter to reindeer in terms of plant quality is mainly determined by seasonal changes in plant chemical composition as well as the species composition of the pastures. 

Full paper

• 4 December 2025
• Author: Leif Einar Støvern
• Number of views: 6