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Aim of study: To understand throughfall (TF) sensitivity to variability in rainfall amount (P-g) for typical forest sites across the main climate types of Iran.

Area of study: Nine forest stands of several common native and introduced tree species situated in all common Iranian climate types, but located primarily in northern Iran.

Material and methods: A nondimensional relative sensitivity coefficient was employed to predict responses of TF to P-g changes. Projected P-g changes over the measurement sites for the period 2020-50 were estimated using one of the Coupled Model Intercomparison Project phase 5 (CMIP5) known as HadGEM2-ES under low and high emission scenarios (RCP 2.6 and 8.5).

Main results: TF displayed strong positive linear relationships with P-g at all sites [TF=0.66 P-g -0.16; R-2 =0.91]. The sensitivity coefficient ranged from 0.96-2.35 across the nine forest sites and large sensitivity coefficient differences were found between small (< mean annual P-g) and large (> mean annual P-g) storms for arid and Mediterranean plantations. Shifts in P-g and increased small storm frequency are preaicted for these regions (2020-50) under low and high emission scenarios.

Research highlights: TF sensitivity may be a useful variable when selecting tree species for afforestation to buffer expected shifts in P due to climate change.