Soil available nitrogen, dissolved organic carbon and microbial biomass content along altitudinal gradient of the eastern slope of Gongga Mountain

Gongga Mountain is a unique mountain in western China which has not only modern low-latitude glaciers,but also an integrated vertical vegetation distribution from subtropical forests to tundra. Our study aimed to understand the soil fertility status of subalpine and alpine ecosystems in this region through measuring the soil available nitrogen (SAN), dissolved organic carbon (DOC) and soil microbial biomass (SMB) along the eastern slope of Gongga Mountain. We found that the SAN, DOC and SMB varied along the altitudinal gradient, and decreased from the soil surface to subsurface, probably due to the different return plant residue, decomposition rate, as well as temperature and moisture in different elevations. The range of NH4+-N content was from 1.7 mg kg-1 to 134.2 mg kg-1; NO3 + NO2-N was from 2.6 mg kg-1 to 202.0 mg kg 1; DOC was from 30.6 mg kg-1 to 610.2 mg kg-1; soil microbial biomass carbon (SMBC) was from 41.4 mg kg-1 to 2538.5 mg kg-1; and soil microbial biomass nitrogen (SMBN) was from 0.6 mg kg-1 to 410.7 mg kg-1. SAN, DOC and SMB were all significantly related to each other, indicating that all these three indexes are dependent on soil organic matter. At last, the ratio of SMBC to SMBN ranged from 2.4 to 65.3, mostly less than 6.0, which meant the bacteria dominated the soil microbial community in our study sites

Comparison with other studies about methane flux from wetlands on the Qinghai-Tibetan Plateau reported with the static chamber method.

<p>Comparison with other studies about methane flux from wetlands on the Qinghai-Tibetan Plateau reported with the static chamber method.</p

Standing water depths of the hollow stands during the growing seasons from 2005 to 2007.

<p>Different letters indicate significant difference (<i>P</i><0.05).</p

Significance of impacts of year, stand types and their combined effect on CH₄ emission and environmental factors in growing season.

*<p>Significant impact P<0.05;</p>**<p>highly significant impact, P<0.01; ns, no significant impact.</p

Spatiotemporal variation of CH₄ fluxes.

<p>a. Mean CH₄ fluxes in different stands during the growing seasons; b. Inter-annual variation of CH₄ emission from the open fen of 2005 to 2007. Different letters indicate significant difference for each panel (<i>P</i><0.05).</p

Seasonal variation of CH₄ emission from the three plant stands from 2005 to 2007.

<p>Different letters indicate significant difference (<i>P</i><0.05).</p

Weather conditions of Zoige.

<p>a. Annual air temperature and precipitation from 1957 to 2007 of Zoige County; b. Daily air temperature and precipitation from 2005 to 2007 in the study area.</p