围湖造田不同土地利用方式土壤有机碳和易氧化碳

围湖造田是我国20世纪50年代后期开始大量出现的与水争地的人类干扰活动。以太湖流域肖甸湖区为试验地,测定分析了该围湖造田区香樟（Cinnamomum camphora）林、水杉（Metasequoia glyptostroboides）林、毛竹（Phyllostachys heterocycla）林和农田4种不同典型土地利用方式35年后0～10 cm、10～20 cm、20～40 cm土壤有机碳和易氧化碳含量的差异,以及土壤易氧化碳的季节动态。结果表明：表层（0～10 cm）土壤有机碳含量林地显著高于农田,阔叶林高于针叶林。土壤易氧化碳含量随季节与土层深度的变化而变化,香樟林与毛竹林春夏季节大于冬季,水杉林与农田季节波动较平缓。4种土地利用方式下土壤有机碳和易氧化碳均随土层增加含量递减。与围湖地区内的溪流底泥相比,林地与农田表层土壤有机碳含量均有明显增加;与旱地发育的植被土壤相比,围湖后的土壤有机碳含量较低,易氧化碳含量较高,土壤有机碳稳定性较差。围湖造田作为人类对自然生态系统的一种干扰方式,显著改变了原有生态系统的碳循环特征,因此在研究全球碳循环中,围湖造田对生态系统碳循环的影响应该给予充分考虑。

Soil organic carbon and readily oxidizable carbon of reclaiming land from lake under different land uses

Reclaiming land from a lake area is a kind of human disturbance that has emerged in large numbers since the late 1950s in China.In order to understand the characteristics of soil organic carbon（SOC） and readily oxidizable carbon（ROC） in the reclaiming land from lake under different land uses in the Xiaodian lake area,the concentrations of SOC and ROC,and the seasonal change of ROC concentration in the 0～40 cm soil layer were analyzed.The results showed that at 0～10 cm depth of soil,the concentrations of SOC at cropland site were significantly lower than those in the three kinds of forest sites,and there were significant lower concentra-tions of SOC at the coniferous forest compared to the broadleaf forest.Taking into account the four land uses,the seasons and the three soil depths,the ROC concentrations at Cinnamomum camphora and Phyllostachys heterocycla forests in spring and summer were higher than those in winter,while at Metasequoia glyptostroboides and cropland sites the seasonal changes were relatively slight.The concentrations of SOC and ROC declined with increasing depths.Compared with the remnant bed sediment of lake in the research area,SOC at the forests and the cropland significantly increased.SOC concentrations were lower and ROC concentrations were higher in the impoldering land relative to the upland of the same climate zone.The stability of SOC in the impoldering land was lower than that in the upland.Thus it is important to note the effect of reclaiming land from a lake on the carbon cycle in terms of global climate change.