中文摘要：

以福建省三明市砂岩发育的土壤为材料,应用干、湿筛法比较研究了格氏栲天然林、木荷林和锥栗林土壤团聚体粒径分布、稳定性及有机碳分布的差异,分析了团聚体稳定性与土壤有机碳的关系。结果表明：（1）干筛处理下,各林分土壤团聚体均以〉5mm粒径为主,且随粒径的减小而减少;湿筛处理下,各林分虽以〉0.25 mm大团聚体为主,但林分间差异显著,格氏栲天然林、木荷林和锥栗林0-10cm土层〉0.25mm大团聚体所占比例分别为78.4%,70.53%和55.62%;10-20cm土层趋势与之相似,所占比例分别为71.93%,67.05%和52.72%。（2）各林分0-10cm和10-20cm土层干筛MWD值、分形维数D值均无显著差异;湿筛处理后,两土层MWD值格氏栲天然林均为最高（3.22mm和3.12mm）,木荷林次之（2.86mm和2.81mm）,锥栗林最低（2.46mm和2.21mm）,林分间差异显著,分形维数D值及PAD值变化趋势则与之相反,均以格氏栲天然林最低,其中锥栗林PAD值显著高于其他林分。（3）天然林转换成人工林后,0-10cm土层各粒径水稳性团聚体有机碳含量均显著下降,但都随着粒径的减小呈先增加再减少再增加,以0.25～2mm和〈0.053mm粒径团聚体有机碳含量最高。（4）0-10cm土层〉0.25mm水稳性大团聚体数量与土壤有机碳含量呈极显著正相关,10-20cm土层两者关系不显著。研究表明,天然林转换成人工林对土壤结构产生了较大影响,导致大团聚体数量减少,团聚体稳定性下降以及表层土壤团聚体有机碳含量降低,人为扰动的增加、地表覆盖度的下降及有机质输入的减少可能是产生这一现象的主要原因,而10-20cm土层虽然呈现出随土壤有机碳含量下降大团聚体数量减少的趋势,但相关性并不显著,表明在有机质含量较低时,团聚体稳定性可能受到其他因素的影响。

英文摘要：

By using dry-sieving and wet-sieving methods,the effects of forest conversion from a native Castanopsis kawakamii（CK）forest to two pure plantations of Schima superba（SS）and Castanea henryi（CH）on soil aggregate size distribution and stability,such as mean weight diameter（MWD）,fractal dimension（D）and percentage of aggregate disruption（PAD）,and analyzed the relationship between aggregate stability and soil organic carbon in Sanming City of Fujian province.The results showed that：（1）Under the condition of dry sieve,soil aggregates were dominated by 〉5 mm particle size in each forest,and reduced with size decreased.Under the condition of wet sieve,soil aggregates in each forest was dominated by 〉0.25 mm particle size and there were significant difference between forests.The proportion of〉0.25 mm macroaggregates of the CK,SS and CH were 78.40%,70.53% and 55.62% in 0-10 cm depth,71.93%,67.05% and52.72%in 10-20 cm depth,respectively.（2）The difference in MWD and Dvalues of dry-sieved aggregates among forests were not significant.But after wet-sieved,the MWD was highest in CK in both 0-10 cm and10-20 cm depth,followed by the plantations of SS and CH.Values were 3.22 and 3.12,2.86 and 2.81,2.46 and 2.21 mm,respectively.On the contrary,the Dand PAD were lowest in CK and highest in the CHplantation,especially the PAD of the CH was significantly higher than other forests.（3）The organic carbon content of water-stable aggregates decreased significantly after native forest conversion,and 0.25～2mm and〈0.053 mm size aggregates had the highest contents of organic carbon.（4）The relationship between〉0.25 mm macroaggregates content and soil carbon organic content was significant in 0-10 cm depth,but not in 10-20 cm depth.The findings indicated that native forest converted to plantations had significant effects on soil structure,which may be related to the increasing of human disturbance,the reduction of vegetation coverage,and the decrease of organic matter inputs.Although the amoun