黄土丘陵区踩踏干扰对生物土壤结皮有机碳组分及碳矿化潜力的影响

Effects of trampling disturbance on soil organic carbon fractions and mineralization potential of biological soil crusts in the Loess Plateau Region,China

以黄土丘陵区近20年的封禁地为研究对象,采用野外调查结合室内分析,研究了不同强度的踩踏干扰对半干旱生态系统下生物结皮盖度、有机碳、易氧化碳和有机碳矿化量、矿化速率的影响,并应用一级动力学方程模拟了踩踏干扰下各层次生物土壤结皮有机碳矿化潜力的变化特征.结果表明:干扰后藻结皮和藓结皮盖度呈现逐渐降低的趋势,干扰度间差异显著;与不干扰处理相比,藻结皮盖度降幅在264%~339%,藓结皮盖度降幅在46%~127%.与不干扰处理相比,干扰显著降低了生物结皮层有机碳含量,降幅在211%~300%,干扰度间差异不显著;干扰增加了生物结皮层易氧化碳含量,增加量在1.5~3.4 g·kg-1,30%、40%和50%干扰度处理与不干扰处理间差异显著.干扰显著增加了生物结皮层的有机碳累积矿化量,但未改变其日均矿化速率;40%干扰度下的累积矿化量较不干扰处理显著增加77%.干扰显著增加了生物结皮层的有机碳矿化潜力,对0~2和2~5 cm土层无显著影响;40%干扰度下有机碳矿化潜力较不干扰处理显著增加4.7 g·kg^(-1);主成分分析结果显示,有机碳、易氧化碳、累积矿化量、矿化速率可以解释生物结皮层土壤有机碳矿化潜力变化的76.7%.干扰可能是诱发研究区生物结皮层有机碳矿化潜力增加的因素之一.

The experiment was conducted in the plots that had been enclosed for nearly 20 years in the hilly Loess Plateau region. The effects of trampling disturbance on the biological soil crust （biocrust） coverage, soil organic carbon （SOC）, soil easily oxidizable carbon （SEOC）, SOC mineralization amount and mineralization rate were investigated. The biocrust SOC mineralization potential after disturbance in different soil layers were simulated by a first-order kinetic equation. The results showed that the coverage of cyanobacteria biocrust and moss biocrust significantly decreased with the increases of disturbance intensity. Compared to no disturbance, the cyanobacteria coverage declined by 264%-339% and moss coverage declined by 46%-127%. Compared to no disturbance, SOC content in biocrust layer significantly decreased by 211%-300%. No significant difference was found among the five disturbance intensities. Disturbance increased SEOC content in biocrust layer, and the variation amounted to 1.5-3.4 g·kg-1 , with 30%, 40% and 50% disturbance differed significantly to no disturbance. Disturbance significantly increased biocrust SOC mineralization cumulative amount. However, SOC mineralization rate did not show any significant change. The SOC mineralization cumulative amount under 40% disturbance intensity increased by 77% compared to that under no disturbance. Disturbance significantly increased SOC mineralization potential in biocrust layer, but with no influence in 0-2 cm and 2- 5 cm soil layers. The 40% disturbance intensity significantly increased SOC mineralization potential by 4.7 g ·kg-1. The results of principal component analysis showed that SOC, SEOC, SMC and mineralization rate explained 76.7% of the variation of SOC mineralization potential in biocrust layer. Disturbance might be a main factor driving the increases of biocrust SOC mineralization potential in this area.