浦东东滩湿地围垦对土壤碳氮储量及酶活性影响

Effects of Reclamation on Soil Carbon, Nitrogen Storage and Enzyme Activity in Dongtan Wetland of Pudong

沿海滩涂湿地围垦为区域发展提供了潜在的土地资源,同时也深刻影响土壤质量演变及碳氮循环过程。以上海浦东东滩湿地光滩、2000年围垦后自然演替草地、2000年围垦林地和1994年围垦林地为研究对象,通过样地调查和室内分析研究了土壤总氮、总有机碳、水解性氮、易氧化有机碳含量及土壤酶活性变化。结果表明:随围垦时间延长,土壤碳氮储量显著增加(P<0.05),1994年围垦后的林地土壤碳氮储量分别比光滩增加了58t·hm^(-2)和3.64t·hm^(-2),2000年围垦后的林地和草地碳氮储量分别比光滩增加了31.79t·hm^(-2)、2.85t·hm^(-2)和29.75t·hm^(-2)、1.77t·hm^(-2)。土壤易氧化有机碳和水解氮含量也随围垦年限增加而显著增大(P<0.05)。围垦后随植被恢复的进行,土壤酶活性显著增强(P<0.05),但过氧化氢酶和纤维素酶在不同围垦期不同土地利用方式之间均没有显著差异(P>0.05),土壤尿酶和蔗糖酶活性随围垦年限增加而显著增大(P<0.05),相同围垦期林地和草地之间4种土壤酶活性没有显著差异(P>0.05)。土壤碳氮含量与土壤酶活性呈显著正相关,但与土壤含盐量呈显著负相关。土壤含盐量的降低是提高土壤酶活性,促进土壤碳氮积累的重要环境因素之一。该研究证实围垦有利于土壤碳氮储量的增加,围垦地造林提高了土壤固碳能力,加速了土壤肥力改善,但林分不同生长阶段对沿海围垦地土壤固碳增肥的效果具有较大差异。

Coastal wetland reclamation provides potential land resources for regional development,and it has a great impact on soil quality evolution and carbon and nitrogen cycle process.Total soil nitrogen,total organic carbon,hydrolysable nitrogen,readily oxidized organic carbon and soil enzyme activity of intertidal zone and reclaimed land in 1994 and 2000 were studied in Dongtan wetland of Pudong,Shanghai.The results showed that soil carbon and nitrogen storage significantly increased in the reclaimed woodland and grassland with increasing of reclamation time(P<0.05).Compared with the intertidal zone,soil carbon and nitrogen storage of woodland which was reclaimed in 1994 increased by 58 t·hm-2 and 3.64 t·hm-2,respectively;soil carbon and nitrogen storage in the grassland and woodland which were reclaimed in 2000 increased by 31.79 t·hm-2,2.85 t·hm-2 and 29.75 t·hm-2,1.77 t·hm-2,respectively.The contents of soil readily oxidize organic carbon and hydrolyzed nitrogen also increased significantly with the increase of reclamation time(P<0.05).Soil enzymes activity increased significantly along with vegetation restoration after reclamation(P<0.05),but activities of the catalase and cellulase had no significant differences between different land use types in different reclamation period(P>0.05),urease and invertase’s activities increased significantly with the increase of reclamation time(P<0.05).The activities of the four soil enzymes had no significant difference between woodland and grassland at the same reclaimed land(P>0.05).There was a significant positive correlation between soil carbon,soil nitrogen and soil enzyme activity,and negatively correlated with soil salt content.The decrease of soil salt content was one of the important environmental factors to increase soil enzyme activity and promote the accumulation of soil carbon and nitrogen.This study indicates that reclamation is beneficial to the increase of soil carbon and nitrogen storage.Afforestation in reclaimed land improves soil carbon sequestration and accelerates improvement of soil fertility.However,different tree growth stages greatly influence soil carbon sequestration and fertilization.