Background
The authors write that "alpine shrub- and grasslands are shaped by extreme climatic conditions such as a long-lasting snow cover and a short vegetation period," and they say that "such ecosystems are expected to be highly sensitive to global environmental change."

What was done
In a unique experiment, which they describe as "the first quantitative and spatially explicit estimates of climate change impacts on future growing season length and the respective productivity of alpine plant communities in the Swiss Alps," Rammig et al. monitored climatic conditions and plant growth for nearly a decade at seventeen "snow meteorological stations" in different alpine regions throughout the mountainous parts of Switzerland.

What was learned
First of all, they determined there were "highly significant correlations between mean air temperature in May/June and snow melt out, onset of plant growth, and plant height." And using these correlations to project plant growth under future climatic conditions based on the gridded output of a set of regional climate models, they determined that (1) "melt out and onset of growth were projected to occur on average seventeen days earlier by the end of the century than in the control period from 1971-2000," and that in response to these changes (2) "plant height and biomass production were expected to increase by 77% and 45%, respectively," while in some cases, they found that (3) "projections of biomass production over a season resulted in changes of up to two-fold."

What it means
As might have been expected, warming is good -- no, it's really good -- for lands at the margins of where low temperatures, snow-cover and permafrost have typically limited the ability of earth's plants to grow to their full potential.