MCM scientists are contributing to the recognition that ecosystem responses to climate change are not necessarily gradual or directional, especially in low diversity ecosystems where harsh environmental conditions dominate (Fig. 1). For example, in soil ecosystems in the McMurdo Dry Valleys in Antarctica there are only a few soil nematode species, compared to the hundreds in a temperate soil sample, and the dominant nematode in the dry valley soils contributes disproportionably to soil carbon turnover. As a result, episodic increases or decreases in soil moisture may be amplified, causing a large change in ecosystem function because of the sensitivity of the dominant nematode species, rather than driving a shift in the community composition with other nematode species becoming more active.
Overall, the anticipated climate transitions in the Dry Valleys provide an excellent opportunity to examine contemporary patterns in ecological connectivity and predict how these patterns may change in the future. The reasons that measurements of rates of change and connectivity across the landscape are facilitated in the MDV are several:
- Landscapes are old (>106 years) with little direct anthropogenic impact
- Food webs are simple with low diversity of metazoan taxa (there are no vascular plants or vertebrates)
- Although considered a desert, the MDV contains a massive amount of water as ice
- Summer temperatures hover near 0°C and moderate summer warming can greatly increase hydrologic connectivity (through pulsed flood events and gradual increase in glacier melt)
Our past studies have shown the influences of a decadal cooling trend and intense seasonal warming events (Doran et al. 2002b; Foreman et al. 2004). Based on these observations we predict that the ecological impacts of sustained warming will be mediated by changes in hydrologic and wind-driven connectivity. Our conceptual model of changes in connectivity (Fig. 2) provides a basis for developing new models of MDV dynamics under a warming climate that will be relevant to many low diversity ecosystems worldwide.