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Effects of drought threaten reproduction of subalpine species in a warmer climate

The change in phenological processes are one of the most obvious features of the changing climate. An example of this is the earlier greening up or onset of flowering. These earlier-in-the-year processes, caused by the interaction of warmer temperatures and less snow cover, can have both positive and negative effects on the stability of sub-alpine grasslands. This aspect of climate change in grasslands has been studied by a team from the University of Bayreuth. Their findings were recently published in the journal Ecosphere.

Some species in the grassland communities studied exhibit sufficient plasticity, meaning they can adapt to changes and "keep up with climate change" (climate tracking). Other species that lack such adaptive capacity are sorted out in a very short time (already within ~5 years) and replaced by others. To study such processes, the flowers of all species in transplanted communities (along an altitudinal gradient from 1260m to 350m) were counted weekly and studied as an indicator of investment in their sexual reproduction (important for genetic exchange). The majority of species could withstand a +1°C climate warming with more flowers and more biomass (positive effect), while a +3°C warming already led to a significant change in species composition and reproduction. However, the main reason for this is not the higher average annual temperature, but the distribution of precipitation in vegetatively important months. If communities suffered from water shortages, they invested less in both biomass and reproductive organs (flowers).

Increasingly frequent drought events will therefore threaten the sexual reproduction of sub-alpine species communities, even if at first glance they might benefit from climate warming due to longer vegetation periods.