川西亚高山针叶林不同恢复阶段土壤的硝化和反硝化作用

NITRIFICATION AND DENITRIFICATION IN SUBALPINE CONIFEROUSFORESTS OF DIFFERENT RESTORATION STAGESIN WESTERN SICHUAN, CHINA

采用气压过程分离(Barometric process separation,BaPS)技术对川西亚高山针叶林不同恢复阶段土壤的总硝化和反硝化作用速率进行了测定,结果表明川西亚高山针叶林不同恢复阶段土壤的总硝化和反硝化速率差异不显著(p<0.05),不同恢复阶段土壤总硝化作用的Q10值差异不显著(p<0.05);总硝化作用速率与土壤含水量呈显著正相关(p<0.05),与土壤pH值、土壤有机质、全氮及C/N相关不显著;不同恢复阶段土壤反硝化速率均维持在一个较低的水平,反硝化速率与土壤中的C/N显著正相关(p<0.05),与土壤含水量、pH值、有机质及全氮相关不显著。与反硝化作用相比,硝化作用对亚高山针叶林土壤氮损失的影响可能更大。

Nitrification is biological conversion of organic or inorganic nitrogen compounds from a reduced a more oxidized state. Denitrification is generally referred as the microbial reduction of nitrate to nitrite and further gaseous forms of nitric oxide, nitrous oxide and molecular nitrogen. They are functionally interconnected processes in the soil nitrogen cycle that are involved in the control of long-term nitrogen losses in ecosystems through nitrate leaching and gaseous N losses. In order to better understand how nitrification and denitrification change during the process of ecosystem restoration and how they are affected by various controlling factors, gross nitrification rates and denitrification rates were determined using the barometric process separation （BaPS） technique in subalpine coniferous forests of different restoration stages. The results showed that the forest restoration stage had no significant effect on gross nitrification and denitrification rates （One-way ANOVA, p 〈 0.05）. There were no significant differences in the temperature coefficient （Q10） for gross nitrification rate among all forest types （One-way ANOVA, p 〈 0.05）. Gross nitrification rates were positively related to water content （p 〈 0.05） but not to soil pH, organic matter, total nitrogen, or C/N ratios. Denitrification rates in all forest soils were low and not closely related to the water content, the pH value, organic matter, or total nitrogen. Nevertheless, we found that C/N ratios obviously affected denitrification rates （p 〈 0.05）. Resuits from this research suggest that gross nitrification is more responsible for the nitrogen loss from soils as compared with denitrification.