CHARACTERISTICS OF NITROGEN CHANGES IN HYDROLOGICAL PROCESSES OF PINUS DENSATA FOREST IN SEJILA MOUNTAIN

摘要

Observations and sampling of atmospheric rainfall, through fall, and trunk stem-flow in the Pinus densata forests of Sejila Mountain were conducted. Samples of different forms of N and their contents and inputs were measured and analyzed. The results showed that from April to October, the total amount of atmospheric rainfall was 725.8 mm, the total through fall was 533 mm, and the total trunk stem-flow was 34.8 mm. The variation with the month showed a single-peak type. The relationship between trunk stem-flow and atmospheric rainfall was y=1.7103x~(0.7869 )(R~2=0.9674), and the relationship between through fall and atmospheric rainfall was: y=0.413x~(1.121) (R~2=0.9901). Monthly average concentrations of atmospheric rainfall were 0.4023 mg/L (NO_3~--N), 1.8779 mg/L (TN), 1.2141 mg/L (TON), and 0.2615 mg/L (NH_4~+-N), respectively. The monthly mean concentrations in the through fall were 0.2367 mg/L (NH_4~+-N), 0.4185 mg/L (NO_3~--N), 1.1891 mg/L (TON), and 1.8443 mg/L (TN), respectively. The mean monthly concentrations in trunk stem-flow were 0.2724 mg/L (NH_4~+-N), 0.4173 mg/L (NO_3~--N), 1.2617 mg/L (TON), and 1.9514 mg/L (TN), respectively. Fitting analysis found that atmospheric rainfall had good correlation with the four N component concentrations, and the correlation between through fall and NH_4~+-N was not obvious, and correlated well with the other three, trunk stem flow and concentration of four components the relationship between them was not obvious. In various forms of rain, the correlation between pH value and TN concentration was significant. From April to October, the TN input amount of atmospheric rainfall was 12.3098 kg/hm~2, among which the input amount was more TON, which was 7.9710 kg/hm~2, which accounted for 64.75. The input amounts of NO_3~--N and NH_4~+-N were 2.5475 kg/hm~2, 1.7914 kg/hm~2, respectively. Accounting for 20.69 and 14.55, respectively. The input amount of nutrient through fall was 9.5050 kg/hm~2, and the input amount of TON, NO_3~--N and NH_4~+-N accounted for 64.57, 21.99 and 13.46, respectively. Trunk stem flow input amount was relatively low, 0.5966 kg/hm~2, and the three inputs accounted for 64.83, 20.14, and 15.03, respectively. After the atmospheric rainfall passing through the canopy and trunk of the P. densata forest, the net TN leaching amount was - 2.2082 kg/hm~2.