围垦年限及施氮对滨海湿地CH4好氧氧化过程的影响

Effects of Reclamation Year and Nitrogen Application on Aerobic Methane Oxidation Potential in Coastal Wetlands

本试验选取崇明东滩的光滩湿地和芦苇湿地为对照,比较研究不同围垦年限(19、27、51、86 a)的围垦区稻田耕层土壤CH_(4)好氧氧化的速率和固碳量以及对氮肥的响应特征。结果表明,围垦稻田土壤有机碳(SOC)含量随围垦年限增长而显著增加,而湿地土壤的酸碱度(pH)、硫酸根离子(SO42–)浓度和电导率(EC值)则均随围垦年限增长而呈逐渐下降趋势。围垦稻田的CH_(4)好氧氧化速率存在显著差异,其中围垦27 a稻田最高,为32μg/(g·d),但远低于芦苇湿地(82μg/(g·d))。CH_(4)好氧氧化驱动的固碳净增量(^(13)C-SOC)介于10.3~19.6μmol/g,与CH_(4)氧化速率显著正相关。围垦86 a稻田CH_(4)好氧氧化的固碳效率(^(13)C-SOC净增量/^(13)CH_(4)转化量)为61%,显著高于围垦19 a和27 a稻田。添加3种氮肥(NH_(4)^(+)-N,NO_(3)^(-)-N,Urea)均显著提高了围垦稻田土壤的CH_(4)好氧氧化速率,尤其以NH_(4)^(+)-N最为明显。相反,3种氮肥对围垦稻田土壤的^(13)C-SOC净增量没有明显影响,导致其CH_(4)氧化的固碳效率减小。综上,滨海稻田的CH_(4)好氧氧化速率与围垦年限并无显著正相关,但围垦年限长的稻田中CH_(4)氧化的固碳效率较高;施加氮肥可显著提高围垦稻田土壤的CH_(4)好氧氧化速率。

In this study,the Chongming Dongtan Natural Wetland in the Yangtze River estuary was selected as the control,and aerobic CH_(4)oxidation rate and related carbon sequestration characteristics were investigated in paddy field soils under different reclaimed years(19,27,51 and 86 a).The results show that soil organic carbon(SOC)content in reclaimed paddy fields is increased significantly with the increase of reclaimed year,whereas pH,EC,and SO42-concentration of soils are gradually decreased.There is significant difference in aerobic CH_(4)oxidation rates of soils under different reclaimed years,and the highest value is found in the 27 a reclaimed paddy field(32μg/(g·d)).However,all of aerobic CH_(4)oxidation rates are much lower in the reclaimed rice fields than that in the reed wetland(82μg/(g·d)).The net increment of carbon sequestration(^(13)C-SOC)driven by aerobic CH_(4)oxidation is 10.3-19.6μmol/g,significantly positively correlated with CH_(4)oxidation rate.Carbon sequestration efficiency(net increment of^(13)C-SOC/^(13)CH_(4)conversion)of aerobic CH_(4)oxidation is 61%in the reclaimed 86 a paddy fields,significantly higher than that in the 19 a and 27 a reclaimed paddy fields.The addition of N fertilizers(NH_(4)^(+)-N,NO_(3)^(-)-N,Urea)can significantly increase aerobic CH_(4)oxidation rates in the reclaimed paddy soils,especially for NH_(4)^(+)-N.On the contrary,N additions have no significant effect on the net increment of^(13)C-SOC in the reclaimed paddy soils,resulting in the reduction of carbon sequestration efficiency of aerobic CH_(4)oxidation.In conclusion,reclaimed year does not significantly influence aerobic CH_(4)oxidation rate in coastal wetlands but increases carbon sequestration efficiency of aerobic CH_(4)oxidation,N fertilizer can significantly improve aerobic CH_(4)oxidation rate in reclaimed paddy fields.