三峡库区消落带4种适生植物根际与非根际土壤养分与酶活性特征研究

三峡库区消落带植被修复过程中，物种的更替对库区土壤的地球化学循环产生潜在影响。以三峡库区忠县石宝寨汝溪河消落带植被修复示范基地165-170 m海拔段人工种植狗牙根、牛鞭草、落羽杉以及立柳根际与非根际土为试验对象，探究其根际与非根际土壤的养分含量及酶活性差异，以阐明不同物种的生长适应性及其根际养分利用策略，比较不同物种对库区土壤的营养改良作用。结果表明：（1）三峡库区消落带4种适生植物根系活动导致根际与非根际土壤养分因子以及土壤酶活性产生差异，不同物种的栽植均在一定程度上使库区土壤营养条件得以改善；（2）碳、氮两种元素在4种适生植物根际土壤中发生不同程度的富集，但磷素与钾素在不同物种根际与非根际土壤之间的变化不一致；（3）蔗糖酶、脲酶以及酸性磷酸酶在4种适生植物根际土中均表现出一定程度的根际正效应（R/S>1），且狗牙根对3种土壤酶的根际活化效果最为明显，其根际效应分别高达2.39、1.89和2.7；（4）在植物根系的调控下，根际土中有机质与氮素、磷素以及钾素的相关性更为显著，而非根际土壤中，仅钾素与有效氮、有效磷呈显著负相关，其余各土壤养分因子之间均无显著相关性；（5）与落羽杉和立柳两木本植物相比，狗牙根与牛鞭草两草本植物根际具有更为合理的养分调节模式，对库区土壤的改良效果更好。

Characteristics of nutrient content and enzyme activity in the rhizosphere and bulk soils of four suitable plant species in the hydro-fluctuation zone of the Three Gorges Reservoir

Species replacement has a potential impact on the soil geochemical cycle in the process of vegetation restoration in the hydro-fluctuation zone of the Three Gorges Reservoir. In this study, the rhizosphere and bulk soils of Cynodon dactylon, Hemarthria altissima, Taxodium distichum, and Salix matsudana were collected between 165-170 m elevation in the vegetation restoration demonstration base of Ruxi River to clarify the growth adaptability and nutritional utilization strategies of these four suitable plant species within a more precise rhizosphere range. We would like to compare soil amelioration effect by exploring the differences of nutrient contents and enzyme activities between rhizosphere and bulk soils. The results showed that:(1) root activities of four suitable plant species in the hydro-fluctuation zone of the Three Gorges Reservoir resulted in differences in soil nutrient contents and soil enzyme activities between rhizosphere and bulk soils. The soil nutrient conditions were improved to a certain extent by planting. (2) Carbon and nitrogen were enriched in different degrees in rhizosphere soils, but the changes of phosphorus and potassium in rhizosphere and bulk soils of different species were not consistent. (3) Sucrase, urease and acid phosphatase showed different degrees of positive rhizosphere effect (R/S>1) in four suitable plants, and C. dactylon had the most obvious activation effects on three soil enzymes in the rhizosphere, with the values of rhizosphere effect were as high as 2.39, 1.89 and 2.7, respectively. (4) The correlation between organic matter, nitrogen, phosphorus and potassium was more significant with the regulation of plant roots in the rhizosphere, however, only potassium had negative correlation with available nitrogen and phosphorus significantly. There was no significant correlation among other soil nutrient factors in the bulk soil. (5) Compared with T. distichum and S. matsudana, C. dactylon and H. altissima had more reasonable nutrient regulation patterns in rhizosphere and had better effects on soil improvement in the reservoir.