不同水位时期东洞庭湖湿地土壤微生物生物量碳氮和酶活性变化

为从土壤微生物的角度分析东洞庭湖不同植被类型湿地土壤质量状况,本研究选取了苔草、芦苇和柳树3种典型植被类型为对象,在平水期、丰水期和枯水期对其土壤微生物生物量碳(MBC)、氮(MBN)和酶活性进行监测,并分析其主要影响因子。结果表明: 1)3个水位时期,各植被类型湿地土壤MBC、MBN、蔗糖酶和纤维素酶活性(枯水期纤维素酶除外)均表现为0～10 cm高于10～20 cm,而土壤过氧化氢酶活性则相反。2)各植被类型湿地0～20 cm土层土壤MBC、MBN和MBC/TOC(总有机碳)、MBN/TN(总氮)皆以丰水期最低。3)各植被类型湿地0～20 cm土层土壤蔗糖酶活性峰值均出现在枯水期,而纤维素酶活性峰值出现在平水期,过氧化氢酶活性季节性波动较小,以丰水期稍高。4)不同植被类型间比较:平水期和丰水期,芦苇湿地土壤蔗糖酶活性显著高于其他植被类型,而其土壤纤维素酶活性最低,枯水期不同湿地间两种酶活性差异不显著。土壤过氧化氢酶活性在平水期以苔草湿地最高,枯水期以柳树湿地最高,丰水期以芦苇湿地最低。5)相关性分析表明,土壤MBC、MBN和蔗糖酶与TOC、TN、总磷(TP)呈显著正相关,而与pH值呈显著负相关。土壤纤维素酶和过氧化氢酶与TOC、TN、TP呈显著负相关,与pH值呈显著正相关。表明季节性水位波动影响土壤C、N、P和pH值,并对土壤微生物生物量碳、氮和酶活性产生显著影响,使其呈现明显的季节性变化特征。

Changes of soil microbial biomass carbon,nitrogen, and enzyme activities in East Dongting Lake wetlands at different water levels

We analyzed soil quality based on soil microbial characteristics of three different vegetation types in the wetlands of East Dongting Lake, including Carex tristachya wetland (CTW), Phragmites australis wetland (PAW), and Salix babylonica wetland (SBW). The soil microbial biomass carbon (MBC), nitrogen (MBN) and enzyme activities were measured and the key influen-cing factors were analyzed during the normal, flood, and dry periods. The results showed that: 1) The amounts of MBC, MBN, and the activities of invertase and cellulase (except cellulase of dry season) in 0-10 cm were higher than those in 10-20 cm for all wetlands, while the catalase activity showed an opposite pattern. 2) The amounts of MBC and MBN and the values of MBC/TOC and MBN/TN for the 0-20 cm soil layer of each vegetation type wetland were the lowest in flood period. 3) Soil invertase activity for each vegetation type wetland in the 0-20 cm soil layer peaked in the dry period, while soil cellulase activity peaked in the normal period. The seasonal fluctuation of soil catalase activities in all wetlands were small, with activities being slightly higher in flood period than the other two periods. 4) Among different vegetation types, soil invertase activity of PAW was significantly higher than that of other vegetation types, and cellulase activity of which was the lowest in both normal and flood periods. There was no difference in these two enzymes activities among wetlands during the dry period. The highest soil catalase activity was found in CTW during normal period and in SBW during dry period, respectively, while its lowest value was in PAW during flood period. 5) Soil MBC, MBN and invertase activity were correlated positively with soil TOC, TN and TP, and negatively correlated with soil pH. The activities of soil cellulase and catalase were significantly negatively correlated with TOC, TN, TP and positively correlated with pH. It suggested that the seasonal fluctuation of water level affected soil C, N, P contents and pH values, with consequences on soil MBC, MBN and enzyme activities.