水盐梯度对滨海湿地土壤养分指标和酶活性的影响

目的]研究海水入侵对滨海湿地土壤性质的影响,为分析水盐梯度对土壤养分指标和酶活性的影响机制提供依据。方法]采集胶州湾滨海湿地表层土壤并设计室内模拟试验,测定不同水盐梯度上的土壤养分指标和酶活性。结果]盐分和水分对土壤pH值和容重(BD)的影响显著;土壤有机质(TOM)、氨氮(NH_4~+-N)、速效磷(AP)、速效钾(AK)、蔗糖酶(SA)、脲酶(UA)、碱性磷酸酶(APA)均随水梯度的增加表现为先升高后降低的趋势,在30%水梯度时达到最高值;土壤TOM,AP,AK,SA,UA,APA均随盐梯度的增加而降低,NH_4~+-N随盐梯度的增加而增加。土壤SA与TOM,AP,AK存在显著正相关关系;APA与TOM,AP,AK,BD显著正相关;UA与pH值,BD显著正相关,与NH_4~+-N具有一定的相关性。结论]在一定范围内,土壤中水分过高或过低、盐分增加均会对土壤养分含量和酶活性产生抑制作用;土壤养分和酶活性之间存在密切的相关关系。

Effects of Water and Salt Gradients on Soil Nutrient Indices and Enzyme Activities in Coastal Wetlands

Objective] To analyze the influence mechanism of water and salt contents on soil nutrient and enzymatic activity, in order to provide scientific basis for exploring the effect of seawater intrusion on coastal wetland soil. Methods] The surface soil of the coastal wetland in Jiaozhou Bay was collected and the simulation experiments were conducted in laboratory to determine the soil nutrient index and enzymatic activity under different water salt gradients. Results] Soil pH value and bulk density (BD) were significantly affected by salinity and moisture, respectively. With the increase of soil water gradient, the total organic matter (TOM), ammonium nitrogen (NH₄⁺-N), available phosphorus (AP), available potassium (AK), sucrase activity (SA), urease activity (UA) and alkaline phosphatase activity (APA) increased initially and then decreased, reaching the maximum value at 30% water gradient. TOM, AP, AK, SA, UA and APA decreased with the increase of soil salinity gradient, while NH₄⁺-N showed an opposite variation trend. The correlation analysis showed that SA was positively correlated with TOM, AP and AK, and APA was positively correlated with TOM, AP, AK and BD. In addition, UA was positively correlated with soil pH value and BD, and had a certain correlation with NH₄⁺-N. Conclusion] In a certain range, excessive or low water content and increased salt content can inhibit the soil nutrient contents and enzymatic activities, and there is a close relationship between soil nutrients and enzyme activities.