沿海滩涂垦殖对土壤氮总转化速率的影响分析

滩涂湿地在吸收、转化和滞留氮、磷等营养元素方面具有重要功能。选取江苏东部沿海典型滩涂区,分别对垦殖时间为0、3、6、17、30、60 a的沿海滩涂进行采样,对相应的土壤氮总转化速率指标进行实验测定。结果表明,滩涂垦殖后,表征氮素活化过程的指标,如总矿化率、总硝化率、净矿化率和净硝化率等有所增加,而有利于氮固持的铵态氮同化率指标无显著变化,硝态氮同化率指标变慢;围垦期限超过30 a后,各氮总转化速率指标渐趋稳定。相关性分析表明,净矿化率、总矿化率、铵态氮同化率、净硝化率、总硝化率与围垦年限呈显著正相关(p<0.01),相关性系数分别为0.966、0.929、0.819、0.800、0.798;硝态氮同化率与围垦年限呈显著负相关(p<0.01),相关性系数为-0.685;除铵态氮外,全氮、硝态氮、pH值、有机碳均与各氮总转化速率指标呈显著相关关系(p<0.01)。滩涂垦殖后土壤理化性质指标的改变带来土壤氮总转化速率的变化,一定程度上破坏了土壤氮生态系统平衡。

STUDY ON NITROGEN TRANSFORMATION RATES AFTER COASTAL BEACH RECLAMATION

Nitrogen cycle system is an important part of the material recycling of ecosystem and plays an important role in the ecological balance and the sustainable development of the human environment. Beach wetland is the transitional zone between land and marine ecosystems and is the buffer responding to the environmental change. It not only has an important function in absorption of nitrogen, phosphorus and other nutrients, but also plays a significant role in transformation and retention of those nutrients. However, with the recent rapid development of industry and agriculture, and the expanding coastal beach reclamation and heavy use of nitrogen fertilizer, the tidal wetland ecosystem has been destroyed to some extent. It's a serious threat to the nitrogen cycle system and to the ecological balance. Therefore, it's necessary to do some research in nitrogen transformation and transformation law after beach reclamation. In this paper we sampled over the beach wetlands of different reclamation ages. The selected reclamation ages are 0 a, 3 a, 6 a, 17 a, 30 a and 60 a. After samplings, we had experiments over these soils and then obtained corresponding gross nitrogen transformation rates. The results showed that the indicators representing nitrogen activations such as gross mineralization, nitrification, net mineralization and net nitrification rates accelerated after reclamation, while the ammonium assimilation rate that was beneficial to nitrogen retention had no significant change and the nitrate assimilation rate slowed down. All the nitrogen transformation rates became stabilized after the reclamation year 30 a. The correlation analysis showed that, the degree of correlation between soil gross nitrogen transformation rates and reclamation age was net mineralization> gross mineralization> ammonium assimilation > net nitrification> gross nitrification> nitrate assimilation (p<0.01). Among them, the soil gross mineralization rate, gross nitrification rate, ammonium assimilation rate, net mineralization, and net nitrification rate had significantly positive correlations with reclamation age. The correlation coefficients were 0.929, 0.798, 0.819, 0.966 and 0.800, respectively. However, the nitrate assimilation rate had a significantly negative correlation with reclamation age, and the correlation coefficient was -0.685. We also find that the total nitrogen, nitrate, pH and organic carbon had significantly correlation with gross nitrogen transformation rates (p<0.01), while the ammonium's correlation with gross nitrogen transformation rates was not so obvious (p<0.01).The beach reclamation brings changes over soil properties such as total nitrogen, nitrate, pH, organic carbon factors and so on. Then, these changes bring diversifications over various gross nitrogen transformation rates such as gross mineralization, nitrification, ammonium assimilation rate, nitrate assimilation rate and so on. However, all the changes will cause the nitrogen loss and simultaneously destruct the soil nitrogen ecosystem balance. Beach reclamation process is one of the factors leading eutrophication of coastal water. Therefore, it's necessary to respect and comply with soil nitrogen cycling and transformation law when we try to utilize them.