尕海湿地植被退化过程中土壤有机碳矿化特征

为了揭示植被退化对湿地土壤碳矿化过程的影响,以甘南尕海4种不同植被退化梯度的湿地(未退化(UD)、轻度退化(LD)、中度退化(MD)及重度退化(HD))为研究对象,采用室内恒温培养和碱液吸收法研究不同土层土壤有机碳(SOC)矿化速率和累积矿化量,结合一级动力学方程,分析土壤半矿化分解时间(T1/2)、有机碳矿化潜势(C0)等参数对植被退化的响应。结果表明:(1)不同植被退化梯度湿地SOC矿化速率在培养期内呈现出基本一致的变化趋势,表现为,培养初期(0~4天)矿化速率快速下降,且数值较高,培养中后期缓慢下降(4~41天)并趋于平稳;各培养温度下,不同植被退化梯度湿地土壤在各土层有机碳矿化速率大小均为UD>LD>MD>HD。(2)在整个培养期间,各植被退化梯度湿地土壤有机碳矿化速率均随土层加深而降低,表层0-10 cm的矿化速率(1.14~16.23 mg/(g·d))均显著高于10-20 cm(1.05~2.85mg/(g·d))和20-40 cm土层(0.94~1.26 mg/(g·d))。(3)4种植被退化梯度湿地在不同温度下的土壤有机碳累积矿化量均值排序为5°C(34.54 mg/g)<15°C(46.67 mg/g)<25°C(58.28 mg/g)<35°C(86.46 mg/g)。(4)一级动力学方程的C0值随植被退化程度增加呈递减趋势,而C0/SOC随着温度的升高而降低。因此,植被退化能显著降低高寒湿地土壤有机碳矿化速率,而气候变暖能够显著增加湿地土壤有机碳矿化量。

Characteristics of Soil Organic Carbon Mineralization During Vegetation Degradation in the Gahai Wetland, China

In order to reveal the effect of vegetation degradation on soil carbon(SOC)mineralization in wetland,four intensities of vegetation degradation of Gahai wetland(non-degraded(UD),slightly degraded(LD),moderately degraded(MD),and heavily degraded(HD))were selected for the research objects on the eastern Qinghai-Tibet Plateau.Soil samples(0-40 cm)were collected from three depths(0-10,10-20 and 20-40 cm).SOC mineralization was determined by the laboratory incubation method.The first-order kinetic equation were applied to analyze the response of soil semi-mineralization decomposition time(T1/2)and organic carbon mineralization potential(C0)to vegetation degradation.The result showed that:(1)SOC mineralization rate displayed similar trends during the four vegetation degradation stages:during the early incubation period(0~4 day),SOC mineralization rate was high and decreased fast,and then the rate decreased slowly and tend to stabilize during the middle and late periods(4~41 day).The order of SOC mineralization rate in different vegetation degradation stages was UD>LD>MD>HD at all temperatures.(2)During the whole incubation period,the SOC mineralization rate in different vegetation degradation stages decreased with increasing soil depth.The SOC mineralization rate in different vegetation degradation stages were 1.14~16.23 mg/(g·d),significantly higher than those in 10-20 cm layer(1.05~2.85 mg/(g·d))and 20-40 cm layer(0.94~1.26 mg/(g·d)).(3)The order of average cumulative amount of SOC mineralization with four vegetation stages at different temperatures was 5°C(34.54 mg/g)>15°C(46.67 mg/g)>25°C(58.28 mg/g)>35°C(86.46 mg/g).(4)The C0 value of first-order kinetic equation decreased with increasing degradation degree,while the C0/SOC decreased with increasing temperature.Therefore,vegetation degradation in the alpine wetland significantly decreased the SOC mineralization rate and climate warming significantly increased the cumulative amount of SOC mineralization.