甘南尕海湿地不同植被退化阶段土壤有机碳含量及动态

Temporal Dynamics of Soil Organic Carbon Content of Gahai Wetland in South Gansu at Different Stages of Vegetation Degradation

以尕海湿地区内的典型泥炭地和沼泽草甸为研究对象,采用野外样地定位观测和室内分析相结合的方法,研究植被退化过程中湿地土壤有机碳含量及动态。结果表明:随着植被退化演替,两类湿地的土壤有机碳含量显著降低(P<0.05)。未退化泥炭地土壤有机碳平均含量247.58g/kg,比退化地高出41.90%;未退化沼泽草甸有机碳含量为61.23g/kg,比轻度、中度、重度退化沼泽草甸土壤有机碳分别高出51.24%,51.75%和81.39%。泥炭地的SOC含量随土层的加深无显著变化,而沼泽草甸的SOC含量随土层加深逐渐降低,但随着植被退化程度的加剧,土壤有机碳含量降低的趋势明显减弱。泥炭地未退化阶段各土层土壤有机碳含量从5月到9月随时间变化均呈现"降—升—降"的变化趋势,即7月最低,8月最高,但这种变化趋势在退化阶段0—10cm和20—40cm土层表现恰好相反;而沼泽草甸4种退化阶段各土层土壤有机碳含量变化趋势差异较大,在0—10cm土层,未退化呈单峰型曲线,中度退化与其恰好相反;而在10—20cm和20—40cm土层,各退化阶段均表现为单峰型曲线。植物地上生物量与不同退化阶段土壤有机碳含量存在一定的线性相关关系,但与泥炭地的退化阶段显著相关,R2达到0.99,与沼泽草甸的各退化阶段相关不显著,R2均小于0.80。

The present study explored temporal dynamics of soil organic carbon content during the vegetation degradation process in typical peatlands and swamp meadows in Gahai wetland area,based on field observation and laboratory analysis.The results showed that soil organic carbon（SOC）content significantly decreased in 2types of wetlands with the vegetation degradation succession（P0.05）.The content of SOC averaged 247.58g/kg in undegraded peatlands,which was 41.90% higher than that in degraded peatlands.The content of SOC averaged 61.23g/kg in undegraded swamp meadows,which was 51.24%,51.75%,and81.39% higher than those in slightly,moderately,and heavily degraded swamp meadows,respectively.In peatlands,SOC did not significantly change with the increase of soil depth.However,SOC content in swamp meadows gradually decreased with the increase of soil depth,and the decrease of SOC content reduced with the increase of vegetation degradation degree.The content of SOC in all soil layers of undegraded peatlands exhibited a ＂decreasing-increasing-decreasing＂trend from May to September,reaching the highest level in July and the lowest level in August.However,SOC content in 0—10cm and 20—40cm soil layers of degraded peatlands exhibited the opposite trends.At 4degradation stages of swamp meadow,SOC content showed different change trends in different soil layers.In 0—10cm soil layer,the change trend of SOC content showed a single-peak-curve at undegraded stage,but exhibited the opposite trend at moderately degraded stage.But in 10—20cm and 20—40cm soil layers,the change trend of SOC content showed single-peak-curve at all stages of degradation.In addition,there was a linear correlation between aboveground plant biomass and SOC content in 0—40cm soil layer across different degradation stages.However,the correlation was significant at degradation stage of peatland（R2=0.99）,while was not significant at all degradation stages of swamp meadow（R20.80）.