[Effects of canopy on the redistribution of potassium and sodium ions in rainfall in Quercus acutissima and Camptotheca acuminata mixed plantation of the rainy area of western China]

The role of canopy in redistributing rainwater K⁺ and Na⁺ at different phenological stages (leafless stage, leaf expanding stage, frondent leaf stage and senesced leaf stage) was investigated in Quercus acutissima and Camptotheca acuminata mixed plantation in Mt. Lingyan of Dujiangyan city from December 2016 to November 2017. The concentrations of K⁺ and Na⁺ were 1.87 and 1.46 mg·L^-1 in the rainfall, respectively, and 5.78 and 1.39 mg·L^-1 in the throughfall, respectively. The highest and lowest K⁺ concentrations in the rainwater were found at leaf expanding stage and frondent leaf stage, respectively. Meanwhile, higher Na⁺ concentration in rainwater was found at leafless stage and leaf expanding stage, and lower concentration at frondent leaf stage and senesced leaf stage. The inputs of K⁺ and Na⁺ through rainfall were 25.47 and 21.60 kg·hm^-2·a^-1, respectively. The leaching flux of K⁺ was 13.64 kg·hm^-2·a^-1 from canopy by rainfall, with the flux of 1.67, 6.23, 2.28 and 3.46 kg·hm^-2 at the leafless stage, leaf expanding stage, frondent leaf stage and senesced leaf stage, respectively. On the contrary, the canopy intercepted 11.26 kg Na⁺·hm^-2·a^-1, with the interception rate being 32.6%, 18.0%, 44.9% and 31.5% at leafless stage, leaf expanding stage, frondent leaf stage, and senesced leaf stage, respectively. In conclusion, the redistribution of K⁺ and Na⁺ in the rainfall affected by Q. acutissima and C. acuminata mixed plantation canopy varied greatly with phenological stages. The results could provide basic data for further understanding of the cycles of K⁺ and Na⁺ in the forest ecosystem in the rainy area of western China.