中文摘要：

对低效人工林进行改造，是提高林分质量和生态效能的重要措施。本文对广东省东莞市林业科学园内尾叶桉（Eucalyptusurophylla）人工林2种不同改造模式和未改造尾叶桉人工林土壤和凋落物持水能力进行了研究。2种改造模式分别为均匀伐除70％和40％原有桉树后间种乡土阔叶树（分别记为模式I和模式II），未改造桉树林作为对照（CK）。结果表明：与CK相比，改造3年后，模式I和Ⅱ的表层（0—20cm）土壤毛管孔隙度、自然含水量、田间持水量和有效蓄水量显著提高，0—40cm土壤非毛管孔隙度显著下降（P〈0．05）；模式I和Ⅱ凋落物吸水速率和最大持水率显著增加，凋落物储量和最大持水量显著减小；各林分凋落物吸水速率与浸泡时间呈幂函数关系，凋落物持水率、持水量与浸泡时间均呈对数函数关系；林分改造提高了林地0～60cm土壤水源涵养功能，且两种改造模式之间无显著差异（P〉0．05）；各林分土壤持水能力均远大于凋落物，凋落物最大持水量仅为0—20cm土层有效持水量的0．59％～2．06％。

英文摘要：

Transformation of low-quality forest stand is an important measure to improve forest stand quality and its ecological functions. In this paper, two transformed stands and one control stand of Eucalyptus urophylla plantations in the Dongguan Forest Research Park, Guangdong Province of South China were taken as the objects to study the water-holding capacities of soil and litter. The two transformation modes were 1 ） evenly removing 70% of E. urophylla trees followed by planting native broadleaved trees in canopy gaps （Mode I ） and 2） evenly removing 40% of E. urophyUa trees followed by planting native broadleaved trees in the gaps （ Mode Ⅱ）, and the un-treated E. urophylla plantation was served as the control （CK）. After 3-year transformation, as compared with CK, the surface （0-20 cm） soil capillary porosity, natural water content, field water-holding capacity, and effective water retaining capacity in Mode I and Mode 11 had a sig- nificant increase, while the non-capillary porosity in 0-40 cm soil layer was in adverse. The wa- ter-absorption rate and the maximum water-holding rate of the litters under Modes I and Ⅱ were significantly higher, but the litter biomass and its maximum water-holding capacity were signifi- cantly lower than those under CK. The water-absorption rate of the litters in the three plantations had a power function relationship with the litter＇ s immersion time, while the water-holding rate and water-holding capacity of the litters were exponentially correlated with the immersion time. Overall, stand transformation increased the water-holding capacity of 0-60 cm soil layer signifi-cantly, and no significant difference was observed between Modes Ⅰ and Ⅱ. For all the planta- tions, the water-holding capacity of soil was far higher than that of litter, and the maximum wa- ter-holding capacity of litter was only 0. 59% -2.06% of the effective water-holding capacity of surface soil layer.