黄土丘陵半干旱区人工柠条林土壤固碳特征及其影响因素

为了探讨黄土丘陵区不同生长年限的人工柠条林地土壤有机碳含量的变化特征及其影响因素,更好地阐明黄土丘陵区柠条林土壤的固碳机理,本文采用时空替代法,以撂荒2 a的坡耕地为对照,对黄土丘陵半干旱区不同林龄(10 a、17 a、26 a、34 a、40 a、50 a)人工柠条林地土壤有机碳(SOC)、全氮(STN)、全磷(STP)及柠条林的根系生物量和枯落物现存量进行了分析。结果表明:1)在0~60 cm的土层剖面上,0~20 cm土层SOC含量明显高于其他土层,并随土层深度的增加逐层递减,其中柠条林地0~20 cm土层SOC含量变化幅度为2.68~11.44 g·kg-1,而40~60 cm土层SOC含量仅在1.64~2.73 g·kg-1波动;与对照相比,随林龄增加柠条林地0~60 cm土层平均SOC含量先减小后增加最后趋于平稳:10 a和17 a柠条林SOC含量比对照显著降低了34.5%和26.9%,26 a柠条林的SOC含量显著升高,其值是对照的1.43倍,40 a和50 a柠条林SOC含量处于积累与消耗相对稳定的状态。2)对SOC含量与STN、STP含量及根系生物量和枯落物现存量进行相关性分析表明,SOC含量与STN含量、根系生物量及枯落物现存量之间存在极显著线性相关,但与STP含量相关性不明显,说明土壤中氮含量的增加能明显提高土壤的固碳能力,而根系生物量和枯落物现存量的多少能够决定土壤的固碳水平。

Soil carbon sequestration characteristics of plantations and influencing factors in Loess Hilly Semiarid Region

Using spatio-temporal substitution method, this study analyzed soil organic carbon (SOC), soil total nitrogen (STN), soil total phosphor (STP), root biomass and litter biomass of Caragana microphylla plantations of different ages. Soil carbon content change characteristics under C. microphylla plantations and the influencing factors in the Loess Hilly Semiarid Region were discussed. It threw further light on soil carbon mechanisms under C. microphylla plantations. The results suggested that at 0~60 cm soil profile, SOC content steadily decreased with soil depth increasing. Also SOC content in the 0~20 cm soil layer was higher than that in the other soil layers. At 0~20 cm soil layer, SOC content was 2.68~11.44 g·kg^-1. At 40~60 cm soil depth, however, SOC content fluctuated only minimally and was 1.64~2.73 g·kg^-1. Compared with two-year abandoned sloping farmland (CK), variations in average SOC content under C. microphylla at 0~60 cm soil depth initially decreased and then increased before finally stabilizing with time. At C. microphylla ages 10 and 17, SOC content significantly decreased by 34.5% and 26.9%, respectively, compared with that in CK. At C. microphylla age 26, SOC content significantly increased, which was 1.43 times as that in CK. At C. microphylla ages 40 and 50, however, SOC content was in the state that accumulation and consumption of SOC was relatively stable. Correlation analysis showed that SOC was significantly correlated with STN, root biomass and litter biomass. However, there was no correlation between SOC and STP contents. The results indicated that soil carbon sequestration capacity increased by increasing soil total nitrogen content. Both the amounts of root biomass and litter biomass dictated soil carbon sequestration degree.