The last couple of months have been very busy in the grassland mesocosm experiments.
The DRY project has set up an experiment using rainfall manipulation to study the effects of drought at six sites spread over three river catchments (the Eden in Fife, the Don in Yorkshire and the Frome in S. Gloucestershire).
Each week we have been measuring the height of the vegetation at random points and the height of selected plant species, we have also been recording the number of flowers and pollinators in the plots. These measurements will help us to understand the short term effects of drought on vegetation growth and timing of flowering. Each year in June we identify the plants in our experimental areas and estimate (if one was looking down from above) how much of the area each species covers – this is called percentage cover. This information will allow us to see if the drought treatment changes the type (species) of plant present and which plants are the most dominant.
We need to make sure that our plots are managed in the same way as the rest of the field, so that we can be confident that any differences we observe between the droughted and non-droughted areas are due to drought not to changes in how the vegetation has been managed. In the Frome catchment, at our site near Yate, hay is normally cut in late June to mid-July. This means we have to cut our plots at this time. We have instruments with wires in the plots so this has to be done by hand, no small job with fifteen 3 m x 3 m plots. Before cutting the plots we cut a 10 cm x 50 cm strip of vegetation; this was taken back to the lab and sorted into the different plant types: grasses and grass- like plants, dead material, broad leaved plants, mosses and liverworts, ferns and horsetails, and woody material; before being dried and weighed.
These weights can be compared with the percentage cover results to see if the plant type that covers the largest area has the highest weight, and to see how the drought treatment has affected the weight of vegetation (equivalent to the yield of hay).
Mesocosm plot after cutting, the wooden T-piece holds an ‘i-button’ that records temperature and relative humidity (S.Ayling)
Thanks to all the people who have volunteered to help us with the experiments especially to Tony Smith from the Bristol Naturalists Society for help with plant identification and to Anna who came into UWE in the evening, after work , to help sort and weigh the vegetation. We will be measuring the vegetation height and counting flowers and pollinators each week until after the first frosts and collecting more plant samples in the autumn so if you are interested in getting involved please contact us.
DRY@uwe.ac.uk or +44(0)117 3287024