A new German study recreated the local 100-year weather extremes of both drought and heavy rainfall. The researchers assessed the impacts of these extreme weather events on plots containing mixtures of grasses, herbs, shrubs and legumes, which represent naturally occurring grassland or heath communities.
For all plant communities, productivity remained broadly stable in the face of drought or heavy rainfall, despite the fact that the rate of plant tissue die-back (percentage of dead plant fibre above ground) significantly increased in response to both weather extremes. Interestingly, more diverse grassland communities (plots with more species) were less prone to die-back, a stress response, than plots that had fewer plant species.
The results show that if legumes were in the plots, overall plant productivity increased, regardless of the weather conditions. Also, in plots that contained a mixture of grasses and dwarf shrubs, productivity increased in response to heavy rainfall. This was attributed to the presence of a grass species that performs better under conditions of increased soil moisture. Other plant species performed better in drought conditions. Overall the contrasting results suggest that the complementary effects of different species in mixed plant communities should be considered in more detail….Haymaking, photo by Les Chatfield from Brighton, England, Wikimedia Commons via Flickr, under Creative Commons Attribution 2.0 License