Drought is leaving lasting changes in Austrian soils

Austria’s current drought already matches scenarios researchers had expected only in coming decades, ORF reported. Innsbruck ecologist Michael Bahn warned of long term consequences for soils, plants and the water balance, saying a so called soil memory could intensify future droughts.

For almost two decades, Bahn and his research team have conducted experiments in which plants and soils are subjected to artificial water stress. “It is a little bit of a shock for us that the scenarios we tested for the coming decades are already happening with this clarity,” Bahn told the Austria Press Agency. Much remains to be learned about the long term effects of such episodes, he said.

Very low rainfall combined with extreme heat has affected Austria for months. Bahn, who heads the Functional Ecology research group at the University of Innsbruck’s Institute of Ecology, said the occurrence of the drought was not surprising in the context of climate change. However, he described the speed at which negative forecasts were becoming reality as alarming.

As temperatures rise, extreme events such as droughts are becoming more frequent. Ecologists study these conditions in experiments using covered areas, including on alpine pastures in Tyrol’s Stubai Valley and at the Raumberg-Gumpenstein research institute in Styria.

Many parts of Austria now resemble the areas used in the drought experiments, following heat records, record evaporation and very little rain. The visible effects include significant losses in crop production, early departures from alpine pastures and shortages of animal feed. The Austrian hail insurance association reported total agricultural losses of about one billion euros on Monday.

Drought leaves a memory in the soil

Studies have shown that repeated droughts can permanently reduce the ability of soils to retain water. They can also change plant and soil communities. Immediately after such episodes, heat and drought resistant plant species become more dominant.

There are also longer term consequences, Bahn said, referring to the “soil memory”. He and his colleagues found that droughts of different severity changed the composition and networks of microorganisms in the soil in different ways. These microorganisms subsequently affected how well plants could withstand a new drought or recover from one.

Researchers still need to determine under which conditions and in which regions critical thresholds are reached, leaving plants and soils with little or no ability to recover from extreme droughts.

The timing, duration and intensity of droughts are important factors for ecosystems. Heatwaves accelerate the onset of droughts, which reduce the cooling release of water vapour from ecosystems and can further intensify the heat. Soil conditions, species composition and biodiversity also play important roles.

Protecting soil can help protect the climate

Changes in soil management could help reduce some of the effects. Measures that promote the development and protection of organic matter, or humus, are also important for climate protection, Bahn said.

Humus binds carbon in the soil and prevents it from entering the atmosphere as part of greenhouse gases. “Soils are the largest carbon store we have. Protecting soil is climate protection,” Bahn said.

Humus is also essential for supplying nutrients and storing water in soils. Research has further shown that repeated extreme droughts can change the distribution of pores in soil, making it harder for plants to access soil water.