Revealing the changes of labile nitrogen(LN)fractions in soil aggregates of eucalypt plantations at different ages is of great significance for better understanding of soil nitrogen cycles in such plantations.In this study,the state-owned Daguishan forest farm in Guangxi was selected as the research area,and the soil of eucalypt plantations with different ages(1,2,4 years)along with some adjacent abandoned land(control)during traditional rotation period were selected as the research objects.The undisturbed soil samples of the 0～20 cm soil layer were collected and divided into 4 granular aggregates by the wet sieving method,including＞2 mm,1～2 mm,0.25～1 mm and＜0.25 mm.The contents of LN fractions in soil aggregates of different sizes were determined.The LN components include Particulate Organic Nitrogen(PON),Microbial Biomass Nitrogen(MBN),Ammonium Nitrogen(Ammonium Nitrogen),Nitrate Nitrogen(NH4+-N),Nitrate Nitrogen(NO3--N)and Alkali-hydrolyzable Nitrogen(AN).The results showed that the content of LN in soil aggregates increased significantly as aggregate size decreased in the soil of eucalypt plantations of different ages,resulting in more soil LN distributed in＜0.25 mm aggregates.Overall,the content of LN in soil increased at first and then decreased after the planting of eucalypts,and the highest content was found when the plantation was 2-year-old,indicating that the soil nitrogen availability of eucalypt plantations was the highest at this age.Therefore,after eucalypt plantations reach age 2 years,attention should be paid to supplementing soil LN so as to maintain the nitrogen supply levels of eucalypt plantation soils.
NETL
NSTL
维普
万方数据
