铵态氮沉降对内蒙古呼伦贝尔草地CO_2通量的影响（英文）

大气氮沉降可能会影响陆地生态系统的碳通量。本文主要目的是探讨在氮素缺乏的草地生态系统中,氮素添加是否会增加CO2通量。本研究于2008和2009生长季进行,采用静态箱-气相色谱法研究CO2通量对氮沉降增加的响应。结果表明,2年的氮素添加并没有显著影响土壤NH4+含量,NO3-含量只是在2009年生长季后期有所增加。高氮处理增加了CO2通量,而低氮处理在2008年抑制了CO2通量,2009年后期增加了CO2通量。而且氮素添加显著增加了地上生物量和根系的生物量。CO2通量与土壤水分、土壤温度的关系并没有因为氮素的添加而改变,但是氮素添加增加了CO2通量对土壤水分和土壤温度的敏感性。这些结果表明,在未来大气氮沉降增加的背景下,呼伦贝尔草甸草原CO2通量有可能会增加。

Effects of Simulated NH4+ Deposition on CO2 Fluxes in the Hulun Buir Meadow Steppe of Inner Mongolia,China

Atmospheric nitrogen (N) deposition may affect carbon (C) sequestration in terrestrial ecosystem. The main objective of this paper was to test the hypothesis that N addition would increase CO₂ emission in the N limited meadow steppe in Inner Mongolia, China. Response of CO₂ fluxes to simulated N deposition was studied in the growing season of 2008 and 2009 by static chamber and gas chromatograph techniques. Parallel to the flux measurements, soil temperature, soil moisture, TOC, DOC, soil NH₄⁺ and NO₃^- were measured at the same time. The results indicated that two-year N additions had no significant effect on NH₄⁺, but slightly increased NO₃^- in the later period. The HN treatment tended to increase CO₂ fluxes in the two years, and LN treatment tended to decrease CO₂ fluxes in 2008, and shifted to increase CO₂ fluxes in later growing season of 2009. N addition significantly increased the aboveground biomass and root biomass. The correlation between CO₂ fluxes and moisture or temperature factors did not significantly change due to N addition, but N addition enhanced the moisture sensitivity of CO₂ fluxes as well as the temperature sensitivity of CO₂ fluxes. These results suggest that the increasing ammonium N deposition would be likely to stimulate CO₂ fluxes in the meadow steppe of Inner Mongolia, China.