Regulating water disturbance for mitigating drought stress to conserve and restore a desert riparian forest ecosystem

Intermediate water disturbance (in the form of overflow of surface water and changes in the depth of groundwater) may help to accelerate restoration of degraded riparian forest ecosystems in extremely arid areas and enhance the resistance of those ecosystems to drought. To test this possibility, we selected the lower reaches of the Tarim River in China to analyse monitoring data on vegetation and hydrology spanning a 16-year period, and a 100-year data record of tree rings in Populus euphratica. The results suggested that ecological water conveyance can restore degraded desert riparian forest ecosystems. In the early stages of restoration, the interval between two overflows should not be longer than 3 years. Intermediate disturbance (1-2 overflows a year, each lasting 21-30 days) proved conducive to the formation of a plant community that is both diverse and stable, thereby supporting the intermediate disturbance hypothesis. Both P. euphratica and Tamarix chinensis adopt suitable strategies for using groundwater from different depths to adapt to drought. Based on these results, appropriate disturbance modes related to both surface water and groundwater are proposed for the restoration and conservation of desert riparian forest ecosystems under varying intensities of drought. These modes offer scientific guidance on more efficient use of water and on ecosystem management in similar areas around the world.