高原湖泊湿地草海沉积物胞外酶与有机碳的时空动态

摘要

The present study focused on the investigation on the contents of organic carbon and the activities of extracellular enzymes as well as the related environmental factors in the sediments of different water level gradients in Caohai County,Guizhou Provincewere,from March to Decemberin 2015 with an interval of one month.The results showed that the organic carbon content in the sediments of the grassland ranged between 243.03～37.35g/kg.Along with the declining of water level,the wetland was degraded,organic carbon was largely reduced and the soil carbon pool was lost.Polyphenol oxidase (PPO) exhibited a low activity in the Yanzicai wetland of profundal zone,and this enzyme activity increased with the decline of water level.However,the activities of hydrolases,such as invertase,urease and phosphatase,were not elevated,which is not totally consistant with the "enzyme lock" mechanism hypothesis.Moreover,a strongly negative correlation was observed between the PPO activity and organic carbon content in sediments,and a certain negative correlation between PPO activity and phosphatase activity.No significant correlation existed between PPO activity and invertase or urease.The temporal and spatial dynamics of enzyme activity could be well explained by phytomass and soil physio-chemical indicators (TN,TP,pH,SMC).Based on the above results,it is suggested that the increase of PPO activity caused by the water level declining could be an important mechanism underlying carbon pool loss in sediments of grassland wetland.%于2015年3、5～12月每月进行一次采样,对贵州草海不同水位梯度湿地沉积物有机碳含量与胞外酶活性及其环境因子进行了研究.结果表明,草海湿地沉积物有机碳碳含量在243.03～37.35g/kg之间,水位降低湿地退化有机碳含量大幅降低,土壤碳库损失;深水区眼子菜湿地多酚氧化酶(PPO)活性较低,水位降低湿地退化过程中多酚氧化酶活性增加,但是水解酶(蔗糖酶、脲酶和磷酸酶)并未沿着水位的降低而增大;沉积物中PPO活性与有机碳含量极显著负相关,与磷酸酶活性显著负相关,与蔗糖酶、尿酶相关性不显著;植物生物量和土壤理化因子(TN、TP、pH值、SMC)能够很好解释酶活性时空动态.水位降低PPO活性升高是草海湿地沉积物碳库损失的重要机制,但水解酶活性并未随着PPO活性升高而增大,这表明我们的结果与“酶锁”机制假说不完全相符.