The steppe grasslands and larch forests in the Lake Hovsgol region of northern Mongolia are currently experiencing two strong ecological pressures: (1) increases in mean surface temperature as a result of climate change effects in high latitude regions, and (2) increases in grazing as the traditional nomadic culture becomes progressively more sedentary. Over the last 40 years, northern Mongolia has warmed almost 2^°C, there has been an increase in ecosystem water loss with no increase in precipitation, and the growing season now begins almost one month earlier than it did 10 years ago. We examined water-use efficiency (WUE) using stable isotopes of carbon (δ¹³C), to better understand the distribution of three perennial plant species (Festuca lenensis, Potentilla acaulis, and Potentilla sericea) across a natural moisture gradient in the steppe, a south-facing slope. Information about their WUE should help us predict changes in their distribution with respect to future decreases in soil moisture. Currently, the plant community is more diverse at drier locations higher on the slope, but productivity is greater lower on the slope. 

Results/Conclusions

Results indicate both inter- and intra-specific variation in δ¹³C values (and hence WUE). Intraspecific variation is significantly correlated with soil moisture in F. lenensis and P. acaulis, which are widely distributed throughout the gradient, but is not correlated with soil moisture in P. sericea, which is most common at the drier end of the gradient. On average, P. sericea exhibits higher water-use efficiency than the other two species. Based on these results, we would expect P. sericea to increase in abundance if soil moisture declines in the future. While we would expect F. lenensis and P. acaulis to tolerate a decrease in soil moisture, their ability to do so and their distributional responses will depend on the full extent of their physiological plasticity.