Heathlands more susceptible to climate change due to landscape management
Dutch heathlands are a typical ‘cultural landscape’ that cannot exist without landscape management. A new study by a European science team, which included Dr Albert Tietema of the University of Amsterdam, shows how active landscape management makes heathlands more susceptible to the effects of climate change. The study’s results were published in the top-journal ‘Nature Communications’ on 24 March.
Studying climate change in a cultural landscape
Heathlands benefit from regular mowing, sod cutting and grazing to reduce the amount of nutrient. Nutrient-poor conditions are a profitable habitat for heath; without it the vegetation would be gradually replaced by grasses such as Deschampsia flexuosa or Festuca arundinacea, and eventually the vegitation would change into forest. Heathlands therefore exist at the grace of active nature management by man.
Tietema works as an ecologist at the Institute for Biodiversity and Ecosystem Dynamics (IBED) and studied the effects of climate change on Dutch heathlands with his international colleagues. At unused heathlands at the artillery range ‘ASK Oldebroek’, Tietema has been studying the long-term effects of climate change since 1999, mostly in response to temperature increases and yearly droughts. Comparable experiments were performed simultaneously at six other European research locations. In the European study, the sites we compares on the basis of elapsed time since their last major disturbance by e.g. mowing, fires or plagues of insects.
Effects of climate change
The newly publishes study now demonstrates the connection between the stability and the response of heathland to climate change. For example, the drought treatment slows the growth of Dutch heathlands, while comparable but undisturbed heathlands in Denmark experienced no impeding effects of the drought treatment. The researchers also found that the amount of plant species depends on the stability of the ecosystem. At the Spanish field site of the team, still recovering from a fire, researchers found that the drought treatment reduced the amount of plants over time. In contrast, a comparable (unburned) field site in Italy showed no reduction in plant diversity. Albert Tietema: ‘Effects of climate change can only be properly understood and predicted if we account for prior disturbances of the landscape, such as those caused by fires or recent landscape management. The lacking attention for the effects of such disturbances may have caused serious underestimations of the true effects of climate change.’
Curtains for artificial climate change
In order to experimentally simulate the effects of climate change in plats of land, researchers used an innovative approach involving automated curtains. Their approach is based on the concept that clear nights, with no clouds, are generally colder than nights with a cloud cover. This process is simulated in the heathlands by a system that automatically draws a horizontal curtain across the studied plots at night. The curtain reflects the radiant heat back to the surface. This procedure has been going on every single night since 1999 and has caused an average temperature increase in the order of 1°C. Using the same curtain, other plots have been subjected since 1999 to drought by closing the curtain during rain fall for a period of 2-3 months. On average this reduces the annual precipitation by 20%. The temperature increase of 1°C and the reduction of precipitation are comparable to expected scenarios of climate change.
Video of the automated curtain system at the Oldenbroek site:
Kröel-Dulay Gyorgy, Johannes Ransijn, Inger Kappel Schmidt, Claus Beier, Paolo De Angelis, Giovanbattista de Dato, Jeffrey S. Dukes, Bridget Emmett, Marc Estiarte, János Garadnai, Jane Kongstad, Edit Kovács-Láng, Klaus Steenberg Larsen, Dario Liberati, Romà Ogaya, Torben Riis-Nielsen, Andrew Smith, Alwyn Sowerby, Albert Tietema, Josep Penuelas. Increased sensitivity to climate change in disturbed ecosystems. Nature Communications 6:6682 doi: 10.1038/ncomms7682 (2015).