不同植被覆盖对养分在土壤水稳性团聚体中分布特征的影响

研究了重庆缙云山不同植被覆盖下土壤结构的稳定性,以及土壤有机碳和养分在水稳性团聚体中的分布特征.结果表明:不同植被覆盖对土壤水稳性团聚体的分布和土壤结构稳定性有显著影响.竹林土壤>0.25 mm水稳性团聚体含量以及土壤结构的稳定性显著低于马尾松林和草地土壤.植被覆盖对养分在土壤水稳性团聚体中的分布模式没有显著影响,在>2mm水稳性团聚体和<0.053 mm粒级的粉砂与粘粒组分中,有机碳、全氮、全磷以及交换性K~+、Na~+、Ca~(2+)、Mg~(2+)的浓度最高;地表植被覆盖的变化对有机碳、全氮、全磷和交换性盐基离子在各粒级水稳性团聚体中的含量产生显著影响,草地和竹林土壤有机碳和全氮显著高于马尾松林土壤,主要表现在0.25-0.053 mm粒级水稳性团聚体中有机碳和全氮含量,草地和竹林土壤显著高于马尾松林土壤;而草地土壤>2 mm水稳性团聚体和<0.053 mm粒级的粉砂与粘粒组分中的磷显著高于马尾松林和草地土壤.不同植被覆盖下土壤水稳性团聚体中交换性盐基离子均以Ca~(2+)、Mg~(2+)为主,占交换性盐基总量(Total exchangeable bases TEB)的91.8%～92.9%.草地土壤各个粒级的TEB都要大于其他两种植被覆盖下的土壤.

Distribution of Nutrient Elements within Water-stable Aggregates under Different Vegetation

Soil organic carbon and nutrient distribution within water-stable aggregates(WSA)and the stability of soil aggregates were studied under different vegetation in Jingyun mountain,Chongqing.It was found that vegetation significantly influenced soil WSA distribution pattern and soil structure stability.The soil covered with bamboo had a lower fraction of>0.25 mm-WSA,and thus had a lower stability of soil structure than soils covered with pine and meadow.Similar distribution patterns of SOC and nutrients within WSA under different vegetations were observed.Generally,concentations of SOC,total nitrogen,total phosphorus and exchangeable K~+,Na~+,Ca~(2+),Mg~(2+)within the aggregates>0.25 mm and<0.053 mm fractions were higher than the others.While the effects of vegetation on the distribution patterns of SOC and nutrients in WSA were not significant,its effects on amounts of organic matter,total nitrogen,total phosphorus and exchangeable cations were significant.Soils covered with pine and meadow had a higher SOC pools and total nitrogen amounts because of the higher SOC pools and total nitrogen amounts in 0.25～0.053 mm-WSA.The amount of phosphorus,however,soil covered with meadow was higher than soils covered with pine and bamboo because of the contribution of the>2mm and<0.053 mm aggregate fractions.The concentrations of divalent cations{Ca~(2+)and Mg~(2+)}were higher than monovalent cations(Na~+and K~+)in soils,the sum of Ca~(2+)and Mg~(2+)concentrations represented 91.8%～92.9%of the TEB.Soils covered by meadow had a higher amount of TEB than soils covered with pine and bamboo in every particle sizes.