石羊河中下游不同退耕年限次生草地土壤无机氮、酶及微生物量冬季动态研究

为研究石羊河中下游退耕区次生草地冬季土壤肥力状况和微生物机制,测定并分析了石羊河中下游不同退耕年限和不同土层深度土壤无机氮(硝态氮、铵态氮)、酶活性(过氧化氢酶、脲酶、磷酸酶及蔗糖酶)及微生物生物量冬季动态变化。结果表明,研究区各土层(0~10,10~20,20~30,30~40 cm)土壤铵态氮与硝态氮随退耕年限不同逐年递增;除30~40 cm土层外,各土层土壤微生物量碳在退耕较短年限内(1~5 a)总体逐年递减,而在退耕较长年限内(8~31 a)逐年递增;土壤微生物量氮随恢复年限呈先下降(1~4 a)、后稳定(4~15 a)再上升(15~31 a)的趋势;各土层土壤微生物量磷则呈先上升,后下降,再上升的趋势;不同退耕年限间土壤过氧化氢酶活性差异不显著,脲酶、磷酸酶及蔗糖酶活性差异显著(P < 0.05),土壤酶活性总体随土层加深而降低。本试验为石羊河流域的植被恢复、土壤改良和科学管理提供了科学依据。

Study on the Winter Dynamics of Soil Inorganic Nitrogen,Enzyme Activity and Microbial Biomass of Secondary Grassland in Abandoned Farmland with Different Restoration Years in Shiyang River Area

To study the soil fertility and microbiological mechanisms of secondary grassland in abandoned farmland of Shiyang River in winter, soil inorganic nitrogen (nitrate nitrogen and ammonium nitrogen), enzyme activity (Catalase, Urease, Phosphatase and Invertase) and microbial biomass of secondary grassland in abandoned farmland with different restoration years and different soil depths in Shiyang River were measured and analyzed. The results indicated that both soil ammonium nitrogen and nitrate nitrogen increased in each layer (0~10 cm, 10~20 cm, 20~30 cm, 30~40 cm) with increasing the restoration ages. Except for the 30~40 cm soil layer, soil microbial biomass carbon in other layers had a downward trend within shorter abandoned ages (1 to 5 a) and an upward trend within longer ages (8 to 31 a); soil microbial biomass nitrogen reduced initially (1 to 4 a), then reached a steady level (4 to 15 a) and finally increased (15 to 31 a); soil microbial biomass phosphorus increased at first, then declined and increased afterwards. The activity of Catalase altered insignificantly while that of other three soil enzymes varied significantly in the same layer among different restoration years. Soil enzyme activity declined as the increase of soil depth in the same restoration year. This results can provide a theoretical base for the vegetation recovery, soil improvement and scientific arrangement in Shiyang river area.