水位对湖滨带池杉(Taxodium ascendens)-落羽杉(Taxodium distichum)防护林土壤反硝化酶活性的影响

Responses of soil denitrifying enzyme activity from a lakeshore shelter forest of Taxodium ascendens and Taxodium distichum to water levels

针对青山湖流域水体氮(N)污染问题,采用乙炔抑制法研究青山湖湖滨带全年不淹水区域(NFZ)和淹水区域(平均水位为0、5、15和25cm,分别记为WL0、WL5、WL15和WL25)池杉(Taxodium ascendens)-落羽杉(Taxodium distichum)防护林0~40 cm土壤反硝化酶活性(DEA)特征及其影响因素,本研究可为明确湖滨带池杉-落羽杉防护林对水体N污染的控制及其生态功能提供数据支持和理论支撑.结果表明:研究区土壤DEA均值(范围)为130.89(7.83~716.7)μg·kg^(-1)·h^(-1),且具有较为明显的空间分异特征.WL0~WL25区域在水位增加情形下土壤NO_(3)^(-)-N、DOC、SOC和TN含量的增加共同驱动土壤DEA的增加,而土壤反硝化微生物功能基因丰度不是DEA变化的主要影响因素.NFZ区域较低的土壤含水量是该区域土壤DEA显著低于WL0~WL25区域的主要原因.WL0~WL25区域土壤NO_(3)^(-)-N、DOC、SOC和TN含量共同影响土壤DEA垂直分布,使WL0、WL15和WL25区域土壤DEA随深度增加而减小;而NFZ区域土壤DEA垂直变化主要受nir K基因丰度影响.

Due to the nitrogen(N)pollution,the acetylene inhibition method was used to study the characteristics of denitrifying enzyme activity(DEA)and its influencing factors of soil at the depth of 0~40 cm from a lakeshore shelterbelt forest of Taxodium ascendens and Taxodium distichum in the Qingshan Lake Basin.This study would improve the understanding of water N pollution control and ecological functions of the lakeshore shelterbelt forest.The lakeside zone was divided into year-round non-flooded zone(denoted as NFZ)and long-term flooded zone,with average water level of 0,5,15,25 cm(denoted as WL0,WL5,WL15 and WL25,respectively).results showed that the mean soil DEA was 130.89μg·kg-1·h-1,with a range of 7.83~716.7μg·kg^(-1)·h^(-1),and the soil DEA had obvious spatial variation in the study region.The increases in soil NO_(3)^(-)-N,DOC,SOC and TN concentrations in WL0~WL25 zones resulted in the increase in the soil DEA with increasing water levels,rather than the changes in abundance of functional genes of soil denitrifying microorganisms.The significantly lower soil DEA in the NFZ zone compared to the zones,mainly due to lower soil water content.vertical distribution patterns of soil DEA in WL0~WL25 zones mainly depended on the variations of soil NO3--N,DOC,SOC and TN,resulting in the decreased soil DEA with increasing soil depths in WL0,WL15 and WL25 zones.However,the vertical variations of soil DEA in NFZ zone were mainly driven by nirK geneabundance.