| The rainfall redistribution of Betula platyphlla secondary forest in north of greater Xing’an Mountains were observed and sampled in the forest growing season and then measured the hydro-chemical characteristics, in order to study the rainfall redistribution and precipitation nutrient import characteristics. The results showed that:(1) During the observation period, there were 28 rainfall and the total rainfall was 439.2 mm, the single rainfall was between 2.8-66.8 mm. Most of the rainfalls were light rain and moderate rain, and there was only one storm. July rainfall is the largest, accounting for 45.15% of the total rainfall. Total penetration of rain was 370.60 mm, accounting for 84.80%of the total rainfall, the stemflow was 2.78% of the total rainfall, canopy interception was 12.42%, total shrub interception and litters interception was 0.37%,26.67% respectively.(2) About the seasonal dynamics of the water chemistry characteristics, the change of pH and TDS were little, but the change of trace elements in metallic elements were large.In the rainfall, Mg2+ content was the most stable, fluctuated between 0.316-1.003 mg/L, the change of NO3- was biggest, the maximum was 35.77 times more than the minimum; In the penetrating rain, the NO3- changed the largest, PO43- changed the smallest. In the metallic elements, Mg2+ also changed the smallest, and the maximum was 161.41 times more than the minimum of Mn. In the stemflow, Cl- changed the smallest, the value fluctuated 0.148-2.115 mg/L.SO42-changed the largest, the maximum was 133.94 times more than the minimum. In the metallic element, Ca2+ was the most stable, its value fluctuated 3.977-38.104 mg/L.Cu2+ changed the biggest; In the shrub penetrating rain, K+ was the largest change element, and in the anions, Cl" changed the smallest; In the liier water, Mg2+ changed very large, Cu2+ changed the largest, and in the anions, NO3- changed very great, the maximum was 1107.02 times more than the minimum.(3) The pH and TDS showed an increasing trend after reducing, the minimum values both were in the stem flow, the values respectively were 5.30,15 mg/L. The highest values of pH and TDS were in the rainfall and litter water. In anions, the highest values of F- and SO42-were in the stem flow, and others were in the litter water. NO3- changed the most greatly, the maximum was 101.4 times more than the minimum. In the metallic elements, the highest values of Na+、Zn2+ and Mn were in the stem flow, others were in the litter water. And the lowest concentrations were almost in rainfall(except Ca2+、Cu2+).(4) The whole nutrient input of precipitation was 95.414 kg/hm2. After the rain through the forest canopy, the content of F-、Cl-、NO3-、Ca2+、Fe and Cu2+ decreased in different degree, the others increased, and the total nutrient content of throughfall was reduced to 93.557 kg/hm2. After passing through the litter layer, in addition to the Na+, the other elements increased. The total amount of nutrient input increased by 72.149 kg/hm2. Compared with the rainfall input, litter water input was increased by 70.296 kg/hm2, in which Cl-、Na+ and Cu2+ content were lower than the rainfall, other elements were different degrees of increase. Eventually the total amount of nutrient that rainfall through secondary forest input the soil was 165.711 kg/hm2, and the anion input amount was 37.823 kg/hm2, the metallic element was 127.888 kg/hm2. To the nutrient input, the litter layer was stronger than the canopy layer. |
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