Why is it in news?

Contrary to previous claims and assumptions, a study now finds that droughts killed tree species that access deeper water much more.

Details

• Tree deaths due to droughts are a major threat in both temperate and tropical ecosystems. This could further aggravate with climate change, with droughts predicted to increase in many parts of the world.
• An inter-disciplinary team from institutes including Bengaluru’s Indian Institute of Science (IISc) studied how different species partition underground water resources up to a depth of 30 metres (just above the groundwater table) in Tamil Nadu’s Mudumalai National Park
• In a 50-hectare forest plot, the scientists measured how much 7,677 trees belonging to 12 common tree species grew and how many others died between 1992 and 2012, which also saw an intense drought (2000 to 2003). The team collected local hydrological data including daily rainfall and water-holding capacities of local soils to estimate how much water is available across varying soil depths.
• Devising a novel eco-hydrological model to quantify the depths from which trees took up water, the scientists find that while species like teak that absorbed water from near the surface may be adapted to droughts by surviving on scanty rainfall across the year, others like axlewood (Anogeissus) and laurel (Terminalia) took water from the deeper depths composed of weathered rocks. Their study, published in the Journal of Ecology, shows that though species that access deep water experience fewer droughts, they are more vulnerable to protracted droughts.

Conclusion

This novel hydrological modelling approach can help scientists model the impacts of increasing droughts on forests and their feedbacks on climate change.