Inorganic Nutrient Inputs from Precipitation, Throughfall, and Stemflow in Pinus densiflora and Quercus mongolica Stands in an Urban Forest Ecosystem

Abstract

We measured the amount of precipitation, stemflow, and throughfall and concentrations of nine major inorganic nutrients (H+, NH4 +, Ca2+, Mg2+, K+, Na+, Cl-, NO3 -, and SO4 2-) to investigate the nutrient inputs into soil from precipitation in Pinus densiflora and Quercus mongolica stands from September 2015 to August 2016. The precipitation inputs of H+, NH4 +, Ca2+, Mg2+, K+, Na+, Cl-, NO3 -, and SO4 2- into soil were 0.170, 15.124, 42.227, 19.218, 14.050, 15.887, 22.391, 5.431, and 129.440 kg·ha-1·yr-1, respectively. The P. densiflora stemflow inputs were 0.008, 0.784, 1.652, 1.044, 0.476, 0.651, 1.509, 0.278, and 9.098 kg·ha-1·yr-1, and those for Q. mongolica were 0.008, 0.684, 2.429, 2.417, 2.941, 1.398, 2.407, 0.436, and 13.504 kg·ha-1·yr-1, respectively. The P. densiflora throughfall inputs were 0.042, 21.518, 52.207 27.694, 20.060, 24.049, 37.229, 10.241, and 153.790 kg·ha-1·yr-1, and those for Q. mongolica were 0.032, 15.068, 42.834, 21.219, 20.294, 20.237, 24.288, 5.647, and 119.134 kg·ha-1·yr-1, respectively. Of the total throughfall flux (i.e., stemflow + throughfall flux) of the nine ions for the two species, SO4 2- had the greatest total throughfall flux and H+ had the lowest. The net throughfall fluxes of the ions for the two species had various correlations with the precedent dry period, rainfall intensity, rainfall amount, and pH of precipitation. The soil pH under the Q. mongolica canopy (4.88) was higher than that under the P. densiflora canopy (4.34). The difference in the soil pH between the two stands was significant (P 0.01). This study shows the enrichments of inorganic nutrients by two representative urban forests in temperate regions and the roles of urban forests during rainfall events in a year.