植被修复对重度盐碱地土壤酶活性和酶反应热力学特征的影响

由于环境变化和人为干扰,松嫩平原盐碱化土地面积不断增加,盐碱化程度也在不断加剧。本试验以松嫩平原西部盐碱化土壤为对象,研究了自然植被、羊草、燕麦和苜蓿修复对重度盐碱化土壤2种氧化还原酶(过氧化氢酶、多酚氧化酶)和3种水解酶(碱性磷酸酶、蔗糖酶、脲酶)活性和酶反应热力学特征的影响。结果表明: 随着温度的升高,5种土壤酶活性、活化自由能(ΔG)都逐渐升高,在40 ℃(或45 ℃)时达到最高,而土壤酶的活化焓(ΔH)和活化熵(ΔS)无显著变化;温度每增加10 ℃时的温度系数(Q₁₀)变化较小,范围为1.05～1.36。与裸地相比,过氧化氢酶活性在自然植被和羊草修复地升高,而在燕麦和苜蓿修复地降低,ΔG和酶活性的变化规律则相反,而ΔH、ΔS在羊草、燕麦修复地升高,在自然植被和苜蓿修复地降低;多酚氧化酶活性在各修复地都降低或不变,ΔH、ΔS在自然植被和羊草修复地降低,而在燕麦和苜蓿修复地不变,ΔG在各修复样地都表现为在40 ℃时升高,在其他温度下均降低或不变。在各修复地,3种水解酶活性均升高,酶的ΔG降低或不变,而ΔH和ΔS则差异较大。土壤酶活性及其热力学特征对温度变化和植被修复的响应存在较大差异。研究结果可为重度盐碱化土壤的修复提供理论依据。

Effects of phytoremediation on soil enzyme activity and thermodynamic characteristics of enzymatic reaction in severe saline-alkali land.

With the environmental changes and the increases of anthropogenic disturbance, the area and degree of salinization in saline-alkaline lands of Songnen Plain have been increasing with an unprecedented rate. In this study, the effects of restoration of natural vegetation, Leymus chinensis, Avena sativa and Medicago sativa, on the enzymatic activities and thermomechanical characteristics of enzyme catalyzed reaction of two oxidoreductases (catalase, polyphenol oxidase) and three hydrolases (alkaline phosphatase, sucrase, urease) were investigated in heavily saline-alkaline soils from western Songnen Plain. The results showed that the activities of those five soil enzyme as well as the activation free energy (ΔG) increased with increasing temperature, reaching respective maximum at 40 and 45 ℃. The activation enthalpy (ΔH) and entropy (ΔS) of soil enzyme did not change with increasing temperature. The temperature coefficient (Q₁₀) slightly changed and ranged from 1.05 to 1.36 by every 10 ℃ enhancement of temperature. Compared with the bare land, catalase activity increased in natural vegetation and L. chinensis rehabilitated land, but decreased in A. sativa and M. sativa remediation land. The change of ΔG of catalase showed a contrary trend with that of enzyme activities, while ΔH and ΔS increased in the restoration areas of L. chinensis and A. sativa, and decreased in the restoration of natural vegetation and M. Sativa. The activity of polyphenol oxidase decreased or remained unchanged in all restoration sites, and ΔH and ΔS decreased in natural vegetation and L. chinensis restoration sites, while remained unchanged in A. sativa and M. sativa restoration sites. ΔG of polyphenol oxidase reached the maximum at 40 ℃ in each restoration site and decreased or remained unchanged at other temperatures. The activities of three hydrolytic enzymes increased in each restoration site compared with the bare land, and the ΔG of the enzymes decreased or remained unchanged in each repaired area, while ΔH and ΔS varied greatly among the restoration sites. Taken together, significant responses of soil enzyme activity and their thermodynamic characteristics to temperature change and vegetation restoration were detected, which would provide better understanding for the restoration of heavily salinized soil.