芦芽山典型植被土壤有机碳剖面分布特征及碳储量

Soil organic carbon storage and profile inventory in the different vegetation types of Luya Mountain

基于芦芽山沿海拔梯度分布的灌丛草地、针阔混交林、寒温性针叶林和亚高山草甸四类典型植被下土壤剖面实测数据,分析了土壤有机碳的垂直分布特征及其与土壤理化因子的关系。结果表明,各植被类型下土壤剖面上层SOC含量最高,最大值往往出现在10—20 cm层,然后向下逐渐减小。土壤有机质含量由剖面上层最大值向下降低过程中,某深度土壤剖面层段有机质含量急剧减小。亚高山草甸剖面这一深度为20 cm,寒温性针叶林剖面为50 cm,针阔混交林剖面为20 cm,灌丛草地剖面为40 cm。0—10 cm层各植被类型间SOC含量差异不显著;10—20 cm层,亚高山草甸和寒温性针叶林SOC含量显著高于其他类型;20—50 cm层,亚高山草甸SOC含量与灌丛草地接近,显著高于针阔混交林,低于寒温性针叶林。植被类型对有机碳剖面分布影响较大。土壤剖面各层有机碳含量与容重呈显著负相关,与土壤含水量和全氮含量呈显著正相关,与土壤pH值呈弱的负相关,与深层黏粒和粉粒含量正相关,在30—50 cm正相关性显著。逐步回归分析结果表明,亚高山草甸SOC含量与土壤总氮含量、含水量和容重显著相关,寒温性针叶林SOC含量与全氮含量显著相关,针阔混交林SOC含量则与总氮含量和土壤容重显著相关,而灌丛草地SOC含量与容重显著相关。在20 cm深度,4种植被土壤有机碳密度差异不显著;50 cm深度亚高山草甸、寒温性针叶林土壤有机碳储量显著高于针阔叶混交林和灌丛草地,50 cm深度土壤有机碳储量与海拔高度呈显著线性正相关(R2=0.299,P=0.01)。

The patterns and controls of soil organic carbon （SOC） storage are critical for our understanding of the biosphere, given the importance of SOC for ecosystem process and feedback of this pool to atmospheric composition and the rate of climate change. Understanding the distribution of organic carbon inventories in soil profile is crucial for assessing regional, continental and global soil C storage and predicting and ameliorating the consequences of global change. This study was conducted to determine the soil organic carbon inventories of 0-1.0m depth at 21 plots in four vegetation types from 1703m to 2756m in Luya Mountain. The four vegetation types were subalpine meadow （SM）, cold-temperate needleleaf forest （CNF）, coniferous and broad-leaved mixed forest （CBF） and shrub-grassland （SG） （former cropland）. The results showed that the profile distribution of SOC was different under different vegetation types, indicating the effect of vegetation on SOC. The SOC storage in the profiles decreased generally with increasing depth under the four vegetation types, with sharp reduction at the depth of 20era for SM, 50cm for CNF, 20cm for CBF and 40cm for SG. The maximum SOC storage occurred at the depth of 10--20cm in most cases. The four vegetation types had no significant difference for SOC storage at the O--lOcm soil profile. The SOC content of the SM was closer to that of SG at all the soil profiles, but was significantly higher than that of CBF and lower than that of CNF at the 20--50cm soil depth. The SOC storage waspositively correlated with soil total nitrogen and water content, but negatively with bulk density. Soil organic carbon was significantly related with clay and silt content in deeper soil layers. The result of stepwise linear regression analysis showed that the SOC storage was correlated with total nitrogen, water content and bulk density for SM, with TN for CNF, TN and BD for CBF and BD for SG. Within 50 cm depth, the SOC storage was 13. 564, 11. 827, 9. 461, 9. 111 kg/m^2 for SM, CNF, CBF and SG respectively. The SOC storage in SM was significantly greater than in CBF and SG （P = 0. 031 and 0. 021 ） within 50 cm depth, while there was no significant difference among the four vegetation types within 20 cm depth. There was an apparent trend that the soil organic carbon storage increased with increasing altitude （R^2= O. 299 ,P = 0. O1 ）.