【目的】在长期林分经营中,为了保证目的树种正常生长,通常选择去除人工林的林下植被。研究不同林下植被管理措施对尾巨桉(Eucalyptus urophylla × grandis)人工林土壤理化、生物性质的影响,同时评价土壤质量的变化,为桉树人工林林下植被的科学管理提供理论依据。【方法】以广西壮族自治区南宁市的第4代尾巨桉人工林(林分株行距2 m×3 m)为对象,分别使用人工抚育、除草剂抚育和人工+除草剂抚育等3种处理方法去除尾巨桉人工林的林下植被,于2023年8月采集不同处理林地中[0,10)、[10,20)、[20,40) cm这3个土层的土壤样品,分析不同林下植被管理措施下尾巨桉人工林地的土壤理化及生物性质差异。随后采用全量数据集(TDS)和最小数据集(MDS)对不同林下植被管理措施林地的土壤质量进行综合评价,并通过线性回归分析验证本研究所建立最小数据集的准确性。【结果】不同林下植被管理措施林地的土壤理化、生物性质以及土壤综合质量存在明显差异。人工抚育林地土壤物理性质良好,[0,10)cm土层的土壤密度显著低于人工+除草剂抚育林地,总孔隙度和最大持水量显著高于人工+除草剂抚育林地,而不同林下植被管理措施林地土壤的毛管孔隙度、毛管持水量和田间持水量差异不显著;在[0,40)cm土层,不同林下植被管理措施林地土壤的有机质、全氮、碱解氮、速效钾、微生物生物量碳(MBC)、微生物生物量氮(MBN)和微生物生物量磷(MBP)含量优劣依次为人工抚育>人工+除草剂抚育>除草剂抚育;土壤有效磷含量在不同林下植被管理措施林地的优劣依次为除草剂抚育>人工+除草剂抚育>人工抚育。在同一林下植被管理措施林地中,随着土层深度增加,土壤总孔隙度、非毛管孔隙度、最大持水量和有机质、全氮、全磷、速效养分、微生物生物量养分含量明显降低,土壤密度明显增加。将MBC、MBN、MBP含量作为生物活性指标,结合土壤物理、化学指标构建出由MBP、MBC、毛管持水量、非毛管孔隙度和pH组成的最小数据集,基于最小数据集得到的不同林下植被管理措施林地土壤质量评价结果与基于全量数据集得到的结果一致,土壤质量指数大小排序为人工抚育>人工+除草剂抚育>除草剂抚育。【结论】人工去除林下植被使林地土壤综合质量较好,通过除草剂去除林下植被导致林地土壤质量进一步衰退,在桉树人工林经营中应以人工抚育为主,尽量减少除草剂的使用频率,从而达到维护土壤质量,保证桉树人工林持续高质量经营的目的。

【Objective】Understory vegetation is frequently removed during long-term stand management to promote the growth of target tree species. This study aims to investigate the effects of different understory vegetation management measures on soil physicochemical and biological properties in Eucalyptus urophylla×grandis and to assess associated changes in soil quality, while thereby providing a theoretical basis for the scientific management of Eucalyptus plantation understory vegetation.【Method】The research was conducted in a fourth-generation E. urophylla×grandis plantation (plant spacing: 2 m × 3 m) in Nanning, Guangxi Zhuang Autonomous Region, China. Three understory vegetation removal methods were applied: artificial tending, herbicide tending, and a combination of artificial and herbicide tending. Soil samples were collected in August 2023 from three depth layers [0,10), [10,20), [20,40) cm in plots subjected to each treatment. The samples were analyzed to determine differences in soil physicochemical and biological properties. Soil quality was comprehensively evaluated using the total dataset (TDS) and a minimum dataset (MDS) approach. The accuracy of the newly established MDS was validated through linear regression analysis.【Result】Different understory vegetation management measures led to distinct differences in soil properties and overall soil quality. The forest land soil receiving artificial tending maintained superior physical properties, in the 0-10 cm soil layer, bulk density was significantly lower, while total porosity and maximum water-holding capacity were significantly higher compared to artificial and herbicide tending forest land. However, capillary porosity, capillary water-holding capacity, and field water-holding capacity were not significantly affected by the different understory vegetation management measures. Within the 0-40 cm soil layer, the contents of soil organic matter, total nitrogen, alkaline hydrolyzed nitrogen, available potassium, microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and microbial biomass phosphorus (MBP) generally followed the order: artificial tending> artificial and herbicide tending > herbicide tending. In contrast, the available phosphorus content showed the opposite trend: herbicide tending> artificial and herbicide tending> artificial tending. With increasing soil depth under the same management practice, total porosity, non-capillary porosity, maximum water-holding capacity, and the contents of organic matter, total nitrogen, total phosphorus, available nutrients, and microbial biomass decreased significantly, whereas bulk density increased significantly. Using soil MBC, MBN, and MBP as key biological indicators, a minimum dataset was constructed, comprising MBP, MBC, capillary water-holding capacity, non-capillary porosity, and pH. Soil quality evaluation based on this MDS yielded results consistent with those from the TDS. The soil quality index under different treatments followed the order: artificial tending> artificial and herbicide tending > herbicide tending.【Conclusion】Artificial removal of understory vegetation maintained better soil quality, whereas herbicide application led to further decline in the soil quality of plantation forests. The management of Eucalyptus plantations should prioritize artificial tending, and herbicide use should be minimized to maintain soil quality and ensure the long-term, high-quality management of these Eucalyptus plantations.