Effects of foraging tunnels created by plateau zokors on plant above-ground biomass and species richness of graminoids and forbs in alpine grasslands

Question

Foraging-tunnel disturbances created by herbivorous mammals can influence the above-ground plant biomass of grassland communities. The plateau zokor (Eospalax baileyi) was considered a focal animal for investigating the effect of foraging-tunnel disturbances created by herbivorous mammals on the above-ground biomass and species richness of graminoids and forbs. Here, we ask how foraging-tunnel disturbances created by plateau zokors influences above-ground plant biomass and species richness of graminoids and forbs in alpine grasslands.

Location

The study was conducted at three sites of alpine grasslands in the Qinghai-Tibetan Plateau, China.

Methods

In this study, all vascular plants were divided into graminoids and forbs, and 30 paired quadrats were randomly selected from each site. In total, 90 tunnel quadrats and 90 non-tunnel quadrats were surveyed and sampled.

Results

This study showed that foraging-tunnel disturbances decreased the plant species richness of the grassland community and forbs by 16.5% and 17.7% respectively, whereas the response of graminoid species richness to foraging-tunnel disturbance was different among the three sites, in which foraging-tunnel disturbance decreased the graminoid species richness at Maqu and Xiahe sites and had no impact on the graminoid species richness at Tianzhu site. Regarding forbs, some legumes identified in the non-tunnel quadrats were not observed in the tunnel quadrats. The foraging-tunnel disturbances resulted in an above-ground plant biomass decrease of 21.9% in the grassland community, 27.3% in forbs, and 17.2% in graminoids respectively. The percentage of graminoids in the above-ground plant biomass increased from 50.4% in non-tunnel quadrats to 55.5% in tunnel quadrats, a relative increase of 10.1% from the initial percentage.

Conclusions

These results indicate that the foraging-tunnel disturbances seemed to improve the forage availability for livestock in tunnel quadrats due to a higher relative proportion of graminoids in the grassland plant community, despite a decrease in graminoid biomass. However, the tunnels not only decreased the above-ground plant biomass and species richness of forbs, but also might have a negative impact on soil nitrogen input because of the absence of some legumes. The findings of this study suggest that reseeding some legumes is an effective approach to maintaining plant diversity and soil fertility, which can compensate for the negative effect of foraging-tunnel disturbance on alpine grasslands.