1.College of Forestry, Guangxi University;2.Key laboratory of Environment Change and Resources Use in Beibu Gulf, (Nanning Normal University), Ministry of Education;3.State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmosphere Physics, Chinese Academy of Sciences
National Natural Science Foundation of China (31760201); Guangxi Science and Technology Plan Project (AD19245194, AD20238040).
深刻认识桉树人工幼龄林根区和非根区土壤属性特征对优化桉树营林措施具有重要意义。本研究以桉树人工幼龄林为研究对象，分析冬季和夏季桉树人工幼龄林根区和非根区0~20 cm和20~40 cm深度土壤理化性质、C:N:P化学计量比和细菌数量，探讨桉树人工幼龄林根区和非根区土壤理化属性和细菌丰度特征。结果表明，非根区土壤可溶性有机碳（DOC）、有机碳（SOC）、全氮（TN）含量显著大于根区土壤，非根区0~20 cm土壤可溶性有机氮（DON）和全磷（TP）含量显著大于根区土壤。夏季根区、非根区土壤含水量、DON、SOC和非根区DOC含量显著大于冬季；夏季桉树根区和非根区0~20 cm土壤TN、TP、土壤全钾含量显著低于冬季。参照全国土壤分级标准，冬季根区土壤SOC和夏季根区土壤TN含量为四级较缺乏水平。与全球森林土壤C:N:P平均值相比，桉树幼龄林根区土壤C:N夏季高、冬季低，且根区土壤N:P和C:P均低于平均水平，推断桉树人工幼龄林冬季根区土壤存在C限制，夏季根区土壤存在N限制。桉树非根区0~20 cm土壤细菌丰度显著大于根区0~20 cm和非根区20~40 cm土壤。夏季土壤细菌丰度较冬季显著增加。研究表明，桉树人工幼龄林非根区土壤C、N含量和细菌丰度较根区高，根区土壤可能处于C、N元素缺乏状态，根区、土壤深度和季节是影响桉树幼龄林土壤理化性质和细菌丰度的重要因素。
Deeply understanding soil properties in root and non-root zones of the young Eucalyptus plantation is very important for optimizing Eucalyptus plantation management. In order to investigate soil physicochemical properties and bacterial abundance characteristics of root and non-root zones in the young E. urophylla × E. grandis plantation, we selected the young Eucalyptus plantation as the research object in this study, collected the root and non-root zone soils at the depths of 0-20 cm and 20-40 cm during winter and summer of 2020, and analyzed soil the physicochemical properties, the C:N:P stoichiometric ratios and the bacterial abundance characteristics. Results showed that the contents of dissolved organic carbon (DOC), soil organic carbon (SOC), and total nitrogen (TN) in the non-root zone were significantly higher than those in the root zone, while the contents of soluble organic nitrogen (DON) and total phosphorus (TP) at the 0-20 cm depth of the non-root zone soil were significantly higher than those in the root zone. The contents of soil water content, DON, SOC of the root and non-root zones, and DOC of the non-root zone in summer were significantly higher than those in winter. Soil TN, TP, and total potassium contents at the 0-20 cm depth of the root and non-root zone in summer were significantly lower than those in winter. According to the national soil nutrient classification standard, SOC content of the root zone in winter and soil TN content of the root zone in summer were classified as the fourth grade and were on the relatively deficient levels. Compared with the average C:N:P of global forest soil, the soil C:N in the root zone was high in summer and low in winter, and both N:P and C:P in the root zone were lower than the average. Therefore, it is inferred that there was C limitation in winter and N limitation in summer of the root zone soil. Bacteria abundance at the 0-20 cm depth of the non-root zone soil from Eucalyptus plantation was significantly higher than that in the 0-20 cm root and 20-40 cm non-root zones. Bacteria abundance in summer was significantly higher than that in winter. In conclusion, the soil nutrients of C, N and bacteria abundance in the non-root zone were higher than those in the root zone. The root zone soil may be in a relative C and N-limitation status. Furthermore, the root zone, the soil depth and the seasonality were found as the important factors affecting soil physicochemical properties and bacterial abundance in the young Eucalyptus plantation.