封育年限对伊犁绢蒿荒漠土壤有机氮组分的影响

为探究荒漠土壤有机氮组分对封育年限的响应规律,研究了不同封育年限(封育时间为0、1、4和11a)对中度退化伊犁绢蒿(Seriphidium transiliense)荒漠草地土壤全氮(total nitrogen,TN)、轻组氮(light fraction organic nitrogen,LFON)、颗粒氮(particulate organic nitrogen,PON)、微生物量氮(soil microbial biomass nitrogen,SMBN)及其分配比例的影响。结果表明,与封育0a相比,其它封育年限5-10、10-20、30-50cm土层的TN含量均显著降低(P0.05),且0-50cm土层TN含量随封育年限延长呈"降-升"趋势;封育11a,0-5cm土层PON含量达到最高,而封育4a,5-10和20-30cm土层PON分配比例显著增加;0-20cm土层LFON含量增加显著,且0-5cm土层含量最高。0-50cm土层SMBN随封育年限增加呈"降-升"趋势,而封育4a,5-10和20-30cm土层SMBN分配比例显著高于封育0a和封育1a(P0.05);0-10cm土层LFON和0-50cm土层LFONR与封育年限呈显著正相关。总之,短期封育(1~11a)下,中度退化伊犁绢蒿荒漠土壤全氮含量仍未得到恢复,但促进了LFON、PON、SMBN及其分配比例的增加。

Effects of grazing exclusion length on soil organic nitrogen in Seriphidium transiliense desert

To explore the effects of different grazing exclusion lengths on soil organic nitrogen,we studied total soil nitrogen,particulate organic nitrogen,light fraction organic nitrogen,soil microbial biomass nitrogen and their distribution ratios in a moderately degraded Seriphidium transiliense desert.The influence of different grazing exclusionlengths on the percentage of soil organic nitrogen was researched using a control,one grazingexclusion year,four grazing-exclusion years and eleven grazing-exclusion years.Compared with the control,the content of total soil nitrogen significantly decreased in 5-10,10-20 and 30-50 cm of soil depth and the content of total nitrogen in 0-50 cm of soil depth appeared first to decrease then increased with the increase in grazing-exclusion years.The particulate organic nitrogen was highest in 0-5 cm of soil depth after eleven grazing-exclusion years,with a significant increase in the accumulation of particulate organic nitrogen distribution ratios in soil depths of 5-10 and 20-30 cm.Light fraction organic nitrogen significantly increased in 0-20 and 0-5 cm of soil depth,while it reached the highest after four grazing-exclusion years.The soil microbial biomass nitrogen appeared first to decrease then increased in 0-50 cm of soil depth.Comparing four grazing-exclusion years with the control and one grazing-exclusion year,soil microbial biomass nitrogen distribution ratio significantly increased in 5-10 cm and 20-30 cm of soil depth.Correlation among grazing-exclusion years with light fraction organic nitrogen in 0-10 cm of soil depth and light fraction organic nitrogen distribution ratio in 0-50 cm of soil depth was significantly positive.In conclusion,the content of total soil nitrogen was not recovered,but light fraction organic nitrogen,particulate organic nitrogen,soil microbial biomass nitrogen and their distribution ratios increased after short-term grazing exclusion (1 ～ 11 a) in moderately degraded S.transiliense desert.