火烧对古尔班通古特沙漠土壤养分和土壤酶活性的影响

以古尔班通古特沙漠2016年6月意外火烧事件为背景,对比分析火烧和未火烧样地区不同土壤深度化学性质、土壤酶活性的变化特征,为全面评估火烧对温带荒漠生态系统的影响提供土壤学依据。结果表明:火烧样地和对照样地土壤养分含量和酶活性总体上均表现为上层土壤(0—5 cm)大于下层土壤(5—10 cm),仅土壤氧化酶(过氧化氢酶)活性表现为下层土壤大于上层土壤。同时,火烧和土壤深度存在交互效应,火烧对土壤特性的影响受土壤深度的限制。土壤化学性质受火烧的影响主要表现在0—5 cm土壤层,尤其是速效养分在火烧之后有显著增加趋势。火烧对5—10 cm土壤层土壤化学性质无显著影响。火烧后,硝态氮(NO3-N)含量显著下降,铵态氮(NH4-N)含量上升。土壤水解酶、氧化酶活性在火烧之后降低,具体表现为,蔗糖酶、脲酶、β-葡萄糖苷酶活性在0—5 cm和5—10 cm土壤层均极显著下降,而碱性磷酸酶活性仅在0—5 cm土壤层显著下降。过氧化氢酶活性则在5—10 cm土壤层活性显著下降。表明上层土壤水解酶活性对火烧干扰较为敏感,氧化酶活性在火烧干扰下相对稳定。从各土层土壤酶活性的变化特征来看,火烧对水解酶活性的影响随土壤深度增加而降低,而氧化酶则呈现相反的趋势。总体而言,火烧显著提高了古尔班通古特沙漠土壤速效养分的含量,降低了土壤酶活性,不同土壤酶对火烧响应的敏感程度不同。为深入评估火烧干扰对温带荒漠生态系统的影响提供一定理论依据。

Effect of fire on soil nutrient content and enzyme activity in Gurbantunggut desert

Fire disturbance influences both above-ground and below-ground nutrient cycles by burning some of the vegetation, litter, and duff, which leads to nutrient losses. It can also cause important changes in soil chemical properties and enzyme activity. In desert ecosystems, large-scale fires, previously considered as rare events, are now a major threat to these areas. The present study was undertaken in Gurbantunggut desert, where wildfire incident occurred in July 2016, to examined the short-term effects of fire on soil nutrient content and enzyme activity in different soil layers (0-5 cm and 5-10 cm). The original vertical distribution patterns of soil nutrients and enzyme activity were not changed by fire disturbance. Soil nutrient content and soil enzyme activity, except for that of catalase, were higher in the 0-5 cm soil layer than in the 5-10 cm soil layer. An interaction was present between fire and soil depth, and the effect of fire on soil properties was limited by soil depth. Soil chemical properties were mainly affected by fire in the 0-5 cm soil layer. Soil hydrolase and oxidase activity decreased after the fire, and the activity of sucrase, urease and beta glucosidase decreased in the 0-5 and 5-10 cm layers. Alkaline phosphatase activity decreased only in the 0-5 cm soil layer,and catalase activity decreased only in the 5-10 cm layer. The activity of hydrolase in the upper soil layer was sensitive to fire disturbance, and that of oxidase was relatively stable under the interference of fire. Analysis of the characteristics of soil enzyme activity in the different soil layers indicated that effect of fire on hydrolytic enzyme activity decreased with increase in soil depth, while that of oxidase showed the opposite trend. Overall, fire disturbance increased the content of soil available nutrients and significantly decreased soil enzyme activity in Gurbantunggut desert.