Effects of forest on precipitation chemistry and total suspended particles of stem-flow in Jiufeng National Forest Park, Beijing

Abstract

Precipitation chemistry was monitored in two different types of forests (mixed Pinus tabulaeformis and Quercus variabilis forest and pure Q. variabilis forest) in Jiufeng National Forest Park, in western Beijing. Results showed that the pH value of precipitation ranged between 6.13 and 6.97 and no acid rain appeared; the mean electrical conductivity (EC) was 0.18 mS/cm and mean total suspended particles (TSP) was 44.02 mg/L, but these values changed significantly with different amounts of stem-flow. Acidification occurred in the stem-flow to different extents: that of P. tabulaeformis > Q. variabilis. The mean EC value of stem-flow in P. tabulaeformis in the mixed forest was 1.00 mS/cm, which was 5.88 times as high as that of precipitation outside the forest. EC values of Q. variabilis in pure and mixed forests show little difference, 0.34 and 0.30 mS/cm, respectively and were 2.00 and 1.76 times higher than that of precipitation. During the summer, EC values of stem-flow of P. tabulaeformis decreased over time and with an increase in the amount of precipitation. The mean TSP of stem-flow in mixed forest was 116.95 mg/L, but 87.14 mg/L in the pure forest, which were 72.93 and 43.12 mg/L higher than that of precipitation.