To celebrate British Science Week we held an open morning at one of our field sites in the River Frome catchment, near Bristol. Participants met at the University of the West of England on Frenchay Campus on a day that could not decide whether it was going to be cold, sunny or both.
We walked to Simms Hill, where we met Josh Roberts, Chairman of the Simms Hill Community Woodland group. He explained the history of the wood; much of it was planted in the 1970s to try and reduce the impact of the M32 construction on the environment but there are also veteran trees that are relics of former hedgerows and farm boundaries. The community group carry out a wide range of activities to enhance the biodiversity of the woodland and maintain the health of the trees. We discussed how hot dry summers and warm wet winters might affect trees. Prolonged hot dry spells can reduce the growth of trees not just in the year of drought but for several following years. The hot dry summer of 2003 reduced tree growth for up to 4 years (Anderegg et al. 2015 Science 349, 528-531). The effects need not necessarily be bad; milder winters give a longer growing season which might benefit some species. Josh told the group about advice available from the Forestry Commission on the impacts of climate change in England’s Woodlands (www.forestry.gov.uk/publications). This was followed by a demonstration of how to measure height, girth and canopy dimensions of trees before the group worked in pairs to measure trees along the woodland path.
The group then went to see the grassland experiments where we are studying the effects of reduced rainfall on the growth and species composition of grasslands. We have established experiments on six sites spread over three river catchments (the Frome near Bristol, the Don near Sheffield and the Eden in Fife). On each site we have set up metal frames with perspex roofs which reduce the incident rainfall by about 50% .
See our earlier posts for more information about setting up the experiments
Grassland is the UK’s most important crop by area, covering just over half of the entire UK landmass, more than 12 million hectatres. In 2012 11 million hectares were classified as agricultural grassland; supporting around 10 million cattle and calves and 23 million sheep and lambs (Defra, 2012). Not all grasses are equally palatable to animals; Timothy (Phleum pratense) is one of the most palatable grasses while Cocks Foot (Dactylis glomerata) is eaten when it is young but the older leaves are tough and tend to be avoided. We know that drought has dramatic effects on the rate of growth of grass, in dry summers you may not need to mow the lawn so often. In pot experiments reducing the water supply by about 50 % for a month reduced the weight of herbage in Cocks Foot and Timothy by about 60%. Cocks Foot quickly resumed growth when water was resupplied; but the effect of drought on Timothy was persistent and even increased, reducing the weight of hebage to about 32% of that in well watered pots (Okamoto et al. 2011Grassland Science 57, 192-197).
The group helped us to collect data on the number of plant species in flower and visited by pollinators. They also learnt how we monitor changes in the number of species present and assess the growth response of the grassland to the drought treatment through measurements of plant height and the amount of herbage produced.
By Dr Sarah Ayling, Research Associate