森林对鹫峰国家森林公园降水化学及树干茎流悬浮物的影响

通过对北京鹫峰国家森林公园两种不同林分（油松栓皮栎混交林和栓皮栎纯林）的降水化学特征的定位监测与分析，结果表明:大气降水的pH值变化范围为6.13～6.97，没有出现酸雨；电导率(EC)平均为0.18 mS/cm，悬浮物含量平均为44.02 mg/L.但降水通过林木树干后，其pH值、EC值及悬浮物含量均发生了显著变化.树干茎流出现不同程度的酸化现象:油松的酸化栓皮栎的酸化.混交林中油松树干茎流的EC值平均为1.00 mS/cm，是林外降水的5.88倍，纯林和混交林中栓皮栎的EC值差别不大，分别为0.34、0.30 mS/cm，分别是林外降水的2.00倍和1.76倍；油松树干茎流的EC值随夏季降水量、降水次数的增加而降低.混交林树干茎流的悬浮物平均含量为116.95 mg/L，纯林的为87.14 mg/L，分别比林外降水的高出72.93、43.12 mg/L. 

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

The chemistry of forest precipitation was monitored in two different types of forests(Pinus tabulaeformis & Quercus variabilis mixed forest and Quercus variabilis pure forest)in Jiufeng National Forest Park, Western Beijing. Results show that the pH value of precipitation ranges between 6.13 and 6.97 and no acid rain appeared; mean electrical conductivity(EC) was 0.18 mS/cm and the mean total suspended particles(TSP) is 44.02 mg/L, but these values changed significantly with stem-flow. Stem-flow shows acidification to different degrees(Pinus tabulaeformis> Quercus variabilis).The mean EC value of the stem-flow of Pinus tabulaeformis in the mixed forest is 1.00 mS/cm, 5.88 times larger than that of precipitation outside the forest. EC values of Quercus variabilis in pure and mixed forest show little difference, 0.34 mS/cm and 0.30 mS/cm respectively,2.00 and 1.76 times larger than that of outside precipitation. In summer, EC values of stem-flow of Pinus tabulaeformis decreases with the increase of times and with an increased amount of precipitation. The mean TSP of stem-flow in mixed forests is 116.95 mg/L, but 87.14 mg/L in a pure forest, 72.93 mg/L and 43.12 mg/L higher than that of precipitation.