Herbivore diversity in tundra is changing. Large-scale biogeographical studies report diversity of vertebrate herbivores in tundra to be positively related to plant productivity and climate. Similar positive associations of herbivore diversity with plant productivity have been reported at large spatial scales also for invertebrates, while at local scale invertebrate diversity is more strongly related to plant diversity. For vertebrate herbivores, drivers of diversity at local scales remain poorly known and finer-scale data is needed to assess these relationships. Since different herbivores have different nutritional requirements, we can expect that at local scale herbivore diversity would be more strongly linked to productivity and nutritional composition of plant communities than to climate.
With this one-time sampling observational protocol, we plan on collecting local-scale data on vertebrate herbivore diversity, plant biomass and plant nutrient content (C, N, P) to test the generality of these relationships both at local scale and across multiple sites in nutrient-limited and low-productive tundra.
In addition, we will collect faecal samples of different species of herbivores to explore species-specific nutritional stoichiometry (both related to nutrient requirements and output to ecosystem) and diet overlap as possible drivers of diversity in local herbivore assemblages. We will use chemical analyses for assessing C:N:P stoichiometry of different herbivore species, and DNA metabarcoding for identifying diets and diet overlap between different herbivores.
The protocol was tested during summer 2022 by five independent research teams at Karupelv (E Greenland), Narsarsuaq (S Greenland), Vesturöræfi (Iceland), Dovrefjell (Norway) and Niilanpää (Finland). Further, in summer 2023 8 additional sites collected data using the protocol. Implementing the protocol takes about 2 working days for 2 people.
Study questions
- Question 1: What is the relative importance of aboveground biomass, nutrient content of vegetation and climate as drivers of herbivore diversity at local site scale and across the tundra biome?
- Question 2: Is herbivore diet overlap related to aboveground biomass, nutrient content of vegetation or plant community composition?
- Question 3: Is nutrient content of herbivore faeces related to nutrient content of vegetation (C:N and C:P)?
Figure 1. Sampling design for the TExNet observational protocol. At each study site, two habitat types used by herbivores are targeted. Within each habitat, three homogenous habitat patches, roughly 10 x 10 m in size, are selected. In each patch we assess herbivore diversity, aboveground biomass and plant community composition.