新疆天山中段巴音布鲁克高山草地碳含量及其垂直分布

CARBON CONTENTS AND ITS VERTICAL DISTRIBUTION IN ALPINE GRASSLANDS IN BAYINBULAK, MIDDLE STRETCH OF THE TIANSHAN MOUTAINS OF XINJIANG

对新疆天山中段巴音布鲁克高山草地(高山草原和高山草甸)的生物量和土壤有机碳进行了测定。结果表明积分和分层两种估算方法得到的土壤有机碳含量没有显著差异,但积分算法的优势在于能推算不同深度的土壤有机碳含量,便于与以往的研究进行比较;高山草甸的生物量和土壤有机碳含量均大于高山草原;其地上生物量分别为71.4和94.9gC·m-2,地下生物量分别为1033.5和1285.2gC·m-2;1m深度的土壤有机碳含量分别为25.7和38.8kg·m-2;地上生物量呈现较为明显的垂直分布格局,即随着海拔的增加,地上生物量先呈增加趋势,但当海拔超过一定界限后生物量突然下降;土壤含水率是导致南坡(阳坡)土壤有机碳含量空间分异的重要因素,但北坡(阴坡)土壤有机碳含量还可能与地形、土壤质地等其它因素有关;两种高山草地(高山草原和高山草甸)的根系集中分布在40cm以内,0～20cm根系分别占其总量的76%和80%;土壤有机碳集中分布在60cm以内,0～20cm土壤有机碳分别占其总量的55%和49%;高山草原根系分布比高山草甸深,但较低的地下/地上比使得其有机碳分布比高山草甸浅。

Background and Aims Accurate estimates on the size of terrestrial orgamc carbon stocks are necessary for understanding their importance in regulating atmospheric CO2 concentrations. In this paper, hiomass and SOC contents in alpine grasslands （alpine steppe and alpine meadow） in Bayinbulak were estimated. In addition, the vertical distribution of belowground carbon was discussed. Our objectives were to （a） estimate biomass and SOC contents of two different alpine grasslands, （b） investigate the root distribution of two alpine grasslands, and （c） explore the vertical distribution of SOC of two alpine grasslands. Methods SOC content was estimated by an improved method （integral arithmetic method）. Based on continuous decrease of SOC density with soil depth, integral arithmetic method could estimate SOC content to a given soil depth. Key Results There were significant differences in the biomass between the alpine steppe and alpine meadow; aboveground biomass of the alpine steppe was 71.4 g C· m^-2, whereas aboveground biomass of the alpine meadow was 94.9 g C·m^-2; belowground biomass of the two alpine grasslands was 1 033.5 and 1 285.2 g C ·m^-2, respectively. No significant differences were found between integral arithmetic and traditional methods of estimating SOC contents. SOC contents of the alpine meadow was higher than in the alpine steppe ; SOC contents in the two alpine grasslands was 25.7 and 38.8 kg· m^-2, respectively. Most of the root biomass of the two alpine grasslands was in the upper 40 cm of the soil profile, while SOC was concentrated in the top 60 cm. The two alpine grasslands had different root distributions ; the percentage of root biomass in the top 20 cm averaged 76 % - 80 % for the alpine steppe and alpine meadow. Alpine meadows had a deeper root profile with only 49 % of the SOC in the upper 20 cm, whereas the alpine steppe had 55 % of the total SOC in the top 20 cm. Conclusions This study suggests that vegetation determines the vertical distribution of SOC through root： shoot ratio and its vertical root distribution.