Report on grassland ecosystem manipulation experiments

We report information and preliminary results on grassland ecosystem manipulation experiments located inside and outside Europe. Five sites of seven have manipulated rainfall in field conditions, one site has manipulated atmospheric CO2, and one site has manipulated atmospheric CO2 in combination with temperature and rainfall. The three sites located outside of Europe (Brazil, Senegal, South Africa) had set up new field experiments during the course of Animal Change project with a new design of shelters allowing partial interception of rainfall. This report synthetises information given by each principal investigator during a workshop organised before the 3rd annual meeting of Animal Change in Madrid. In Ireland and Switzerland, rainfall was totally intercepted during 10 weeks in Summer time on 15 mixtures (1, 2, 4 species) of four agriculturally relevant species. In Senegal, South Africa and Brazil, new experiments were setup with the same shelter design in order to intercept fraction of rain during the growing season. For these three sites, arid, semi-arid and tropical grasslands were studied, respectively. In Hungary and France, other climate change drivers, atmospheric CO2, air temperature and rainfall were also manipulated in more controlled conditions on perennial grassland vegetation. Preliminary results showed that in moderate drought conditions occurring in Switzerland, legumes and deep rooted species performed better than grasses and shallow rooted ones. Whereas in Ireland as more severe drought conditions occurred this pattern was not observed. For the three experiments located outside Europe, % of precipitations interception ranged between 15 to 75%. In semi-arid climatic conditions, interception of up to 50% of recipitations during 5 months had no effect on production. But when vegetation received only 25% of the rainfall, a decline of production was observed. In this ecosystem, changes of phytomass were explained by climatic stress index like precipitations – potential evapotranspiration (P – PET). In subtropical climatic conditions encountered in South Africa, reduction of precipitation had a strong negative (-49%) effect on herbage yield in January and February, however in November, only about 19% of rainfall intercepted induced the same effect. These results stressed vulnerability of the semi-arid grassland that has been detected from about 19% of rainfall interception in November. In Brazil, the experiment has been setup and the shelters tested in 2014. Rainfall are intercepted and added in order to simulate climate scenario for the southern Brazilian region, with some regional models predicting increase, others decrease in precipitation. Overall, preliminary results observed for the different sites emphasised potential changes of grassland production and forage quality induced by changes in precipitation for different climatic zone areas. However, sites comparison will be possible when climatic and grassland production data will be available for all sites