岷江上游干旱河谷区灌丛植被土壤有机碳稳定性特征

Stability Characteristics of Soil Organic Carbon Under Brushwood Vegetation in Dry Valley of the Upper Reaches of Minjiang River

灌丛在岷江上游分布广泛,是干旱河谷区重要的物种,砍伐、开垦和过度放牧是导致其退化的根本驱动力。通过选取灌丛植被下土壤剖面,并以其被开垦后的农地(50a)及退耕荒坡(10a)为参照,对其土壤有机碳、重组有机碳及易氧化碳含量进行分析比较。结果表明:灌丛植被各层土壤总有机碳及重组有机碳均极显著大于对照的,对照间差异不显著,在0-100cm土壤剖面,对照1退耕荒坡及对照2农地土壤有机碳较灌丛植被的最高降幅分别达60.42%,70.92%,重组有机碳最高降幅则分别达76.54%,68.92%,并且灌丛及对照2农地土壤重组碳在0-100cm土层剖面上表现出先升高,然后再降低的分布特征,对照1退耕荒坡则在整个土壤剖面呈递减趋势;灌丛植被土壤易氧化碳均值高于对照的,与退耕荒坡的差异显著,但与农地的差异不显著,在0-100cm土层中,灌丛及对照土壤易氧化碳含量表现出先降低、升高、再降低的分布特征;相关分析表明,总有机碳与重组有机碳和易氧化碳达到极显著相关水平。综上表明灌丛植被保护土壤有机碳稳定能力极显著高于退耕荒坡和农地的,并且农地退耕也有利于土壤有机碳稳定性的提高。

As an important species in arid valley,brushwood is widespread in the upper reaches of Minjiang river,human deforestation,reclamation and overgrazing are the fundamental driving forces for its degradation.By selecting soil profiles under brushwood vegetation,meanwhile,taking farmland（50 a） and abandoned land（10 a） as references,soil organic carbon（SOC）,heavy-fraction organic matter（HF-OM） and readily oxidizable carbon（ROC） for these soil profiles were analyzed and compared.The results indicated that：The SOC and HF-OM contents under brushwood vegetation were significantly higher than references＇ in the whole soil layers,while no significant differences between references,in 0-100 cm soil depth,compared with brushwood vegetation,the maximum decrease of SOC of abandoned land and farmland respectively was 60.42%,70.92%,and 76.54%,68.92% for their HF-OM.Brushwood and farmland＇s HF-OM showed firstly increased,and then decreased distributions in the whole soil profiles,while abandoned land displayed decreasing trend;The mean of ROC in brushwood vegetation was also higher than that of the references,and was significant difference with abandoned land,but no significant differences with farmland,in 0-100 cm soil depth,the ROC content for both brushwood vegetation and references showed firstly decreased,and then increased,and finally decreased distributions;Correlation analysis showed that,the correlation levels between the total SOC and HF-OM or ROC were highly significant.The comprehensive analysis showed that the ability of brushwood vegetation to protect the stability of SOC was significantly higher than that of abandoned land and farmland,and abandoned farmland was also conducive to improve the stability of SOC.