北京山地不同针叶林型下土壤脲酶动力学和热力学特征研究

Kinetic and thermodynamic properties of urease in different coniferous forest soils in Beijing Mountainous Area

该研究选取了北京山地人工油松林、人工白皮松林、天然油松林和人工落叶松林4种针叶林型下0-0.2 m和0.2-0.4 m土层的土壤,通过测定不同的底物浓度、培养时间及培养温度下的放氨量,计算出脲酶的各项动力学和热力学参数,探讨了北京山地4种针叶林型下土壤脲酶酶促反应特征。结果表明,4种林型下土壤酶促反应的Vmax值随土层深度的增加而减小,随温度的升高而增大;Km值能在一定程度上反映土壤脲酶酶促反应的变化规律;土壤酶促反应K值和Ea值均表现出随温度和土壤深度变化而变化的规律,但变化特点因林型而异;酶促反应ΔH和ΔG值随温度和土壤深度的变化而呈规律性变化;ΔS为负值,说明土壤脲酶酶促反应体系中有序性增大。

The soils from layer 0-0.2 m and 0.2-0.4 m under four coniferous tree species （ Pinus tabulaeformis Carr. plantation, P. bungeana Zucc. ex Endl. plantation, Larix principis-rupprechtii Mayr. plantation, P. tabulaeformis Carr. natural secondary forest） were sampled to study the kinetic and thermodynamic properties of urease by measuring NH3 - N released in reactions when the substrate concentration, reactive time and temperature changed, so as to figure out the kinetic and thermodynamic parameters. The results showed that the maximal velocity （ Vmax） in urease-catalyzed reactions in different coniferous forest soils decreased with the increase of soil depth and reactive temperature, and Michaelis constant （Km） could reflect some rules existing in the urease-catalyzed reactions to a certain extent. The reaction velocity constant （K） and activation energy of soils （Ea） varied with soil depth and reactive temperature, but the characteristics of the changes were different among the different tree species. The urease-catalyzed reaction AH and A G varied the tested soils, AS was negative and these indicated that the order in the system of soil increased.