Abstract: Reducing the threats of sulfate ion (SO42-) deposition to terrestrial ecosystems is a great challenge. The canopy interception effect on SO42- deposition has been well documented, but the interception efficiency of the gap edge remains unknown. Therefore, a subalpine dragon spruce (Picea asperata) plantation was evaluated in the upper reaches of the Yangtze River. The dynamics of the SO42- concentration in the throughfall were investigated from the gap edge to the closed canopy during the rainfall and snowfall periods from August 2015 to July 2016. The annual input ofSO42- totaled 2.56 kg/ha through rainfall and 0.69 kg/ha through snowfall. The total annual net interception fluxes (NIFs) of SO42- at the gap edge and in the closed canopy were 1.48 kg/ha and 0.66 kg/ha, respectively, and the net interception ratios (NIRs) accounted for 45.40% and 20.25%, respectively. The NIF and the NIR of SO42- at the gap edge were higher than those in the closed canopy. Therefore, the results suggested that a significant amount of SO42- deposition was intercepted by the tree canopy in the subalpine plantation, with more SO42- deposition at the gap edge than in the closed canopy, which is beneficial for improving the water quality in the upper reaches of the Yangtze River via forest management.
Keywords: Canopy interception; Sulfate ion;Throughfall; Gap edge; Closed canopy; Picea asperata
