喀斯特湿地转变为农用地对土壤有机硫形态及芳基硫酸酯酶活性的影响

Effects of natural wetland conversion to farmland on soil organic sulfur forms and arylsulphatase activities in karst areas

【目的】土壤有机硫形态及芳基硫酸酯酶活性能敏感地反映土壤硫库的变化,厘清喀斯特湿地转变为农用地后不同土地利用方式下土壤有机硫形态和芳基硫酸酯酶活性的变化特征及其影响因素,对喀斯特湿地土地合理利用和土壤质量管理具有重要意义。【方法】以典型桂林会仙喀斯特天然沼泽湿地为对照(沼泽湿地),以由其转变而来的5种土地利用方式,即水稻田、旱地、果园、养殖地和弃耕地为研究对象,采集0—10、10—20、20—30和30—40 cm共4个土层的样品,分析各形态有机硫含量及芳基硫酸酯酶活性。【结果】1)与沼泽湿地相比,5种土地利用方式的土壤全硫储量、酯键硫、碳键硫以及残渣态硫含量均呈降低趋势。5种土地利用方式土壤碳键硫、酯键硫和残渣态硫占有机硫的比例分别为39.08%~63.54%、22.91%~34.28%、13.55%~28.46%,与沼泽湿地相比,酯键硫和残渣态硫占比降低,碳键硫占比升高(P<0.05)。2)沼泽湿地土壤有机硫含量范围在158.41~442.18 mg/kg,全硫含量范围在180.22~510.83 mg/kg,全硫平均值为345.53 mg/kg,低于世界土壤全硫含量均值(700 mg/kg)。不同土地利用方式下,0—40 cm土层土壤全硫和有机硫含量均值大小整体表现为:湿地>水稻田>旱地>养殖地>果园>弃耕地,湿地与其他土地利用方式间存在显著差异(P<0.05)。3)在0—40 cm土层中,不同土地利用方式下土壤芳基硫酸酯酶活性均随土层深度的增加而降低。相较于沼泽湿地,5种土地利用方式的土壤芳基硫酸酯酶活性均降低,水稻田、旱地、果园、养殖地和弃耕地降幅分别为18.19%、27.48%、39.72%、33.81%和51.77%(P<0.05)。【结论】会仙喀斯特天然湿地转变为其他土地利用方式后,土壤全硫和有机硫含量显著下降(P<0.05),全硫含量(98.06~222.87 mg/kg)小于我国南方10省耕作层土壤全硫平均值(299 mg/kg)。土壤有机碳、全氮、含水量和芳基硫酸酯酶是土壤有机硫形态含量的主要影响因素。因此,减少湿地人为垦殖,有利于维持会仙喀斯特湿地土壤养分的平衡与生态系统的健康。

【Objectives】Soil organic sulfur forms and arylsulphatase activities are sensitive to the changes of soil sulfur pool.We compared the soil organic sulfur forms and arylsulphatase activity characteristics of the main land use types derived from the natural karst wetland,to assess the sustainability of land use types.【Methods】The study was carried out in a typical karst wetland area in Guilin City,Guangxi Zhuang Autonomous Region of China.Soil samples were taken in the natural marsh wetland(CK),and the derived paddy field,upland,orchard,breeding land and abandoned land,at depths of 0−10,10−20,20−30 and 30−40 cm for the analysis of organic sulfur forms and arylsulphatase activities,respectively.【Results】1)Compared with CK,soil total S stocks,the contents of ester bonded sulfur,carbon bonded sulfur and residual sulfur showed decreasing in the other five land use types.The carbon bonded sulfur,ester bonded sulfur,and residual sulfur accounted for 39.08%−63.54%,22.91%−34.28%,and 13.55%−28.46%of the organic sulfur,respectively.The ester bonded sulfur and residual sulfur proportions in the soils under five land use types were lower than CK,and the carbon bonded sulfur proportion was higher than CK(P<0.05).2)The soil organic and total S content in CK ranged 158.4−442.2 mg/kg and 180.2−510.8 mg/kg.The average total S in CK was 345.5 mg/kg,lower than that of the world(700 mg/kg).The average organic and total S contents in the 0−40 cm soil layers under the five land use types were all significnatly different from those of CK,and declined in the order of CK>paddy field>upland>breeding land>orchard>abandoned land.3)The arylsulphatase activities decreased with the increasing of soil depth under all the land use types.Compared with CK,the soil arylsulphatase activities of the five land types decreased by 18.19%(paddy field),27.48%(upland),39.72%(orchard),33.81%(breeding land),and 51.77%(abandoned land),respectively.【Conclusions】The reclamation of natural marsh wetlands leads to the decrease of soil total and organic sulfur contents significantly(P<0.05).The average soil total sulfur content under the five land use types(98.06−222.9 mg/kg)is lower than that of soils at tilling layer in 10 provinces(299 mg/kg)in southern China.Soil organic carbon,total nitrogen,soil water content and arylsulphatase are the main factors causing the proportion change of soil organic sulfur forms.Therefore,controlling the reclamation scale of karst wetland is important for maintaining the balance of soil nutrients and ecosystem health of the Huixian karst wetland in the long run.