模拟氮沉降对典型阔叶红松林土壤微生物生物量碳氮的影响

Effects of simulated nitrogen deposition on soil microbial biomass carbon and nitrogen in a mixed broadleaf Korean pine forest

【目的】探究氮沉降增加对阔叶红松(Pinus koraiensis)混交林土壤微生物生物量碳氮的影响。【方法】对阔叶红松林进行模拟氮沉降实验,设置对照(N0,0 kg/(hm^2·a))、低氮(N1,30 kg/(hm^2·a))、中氮(N2,60kg/(hm^2·a))和高氮(N3,120 kg/(hm^2·a))共4组处理,在实验样地内采集0～10 cm、≥10～20 cm土层中的土壤,测定土壤微生物生物量碳(SMBC)及土壤微生物生物量氮(SMBN)含量及变化。【结果】(1)模拟氮沉降未改变SMBC、SMBN及SMBC/SMBN的垂直分布;SMBC、SMBN在生长季月动态曲线均为以8月中旬为峰值的单峰型曲线,SMBC/SMBN的曲线波动较大,0～10 cm土层以N0处理的结果波动范围最小(2.83～6.97)。(2)模拟氮沉降仅对0～10 cm土层6、8月中旬的SMBC以及5、6、8月中旬的SMBC/SMBN有显著影响(P<0.05),而对SMBC、SMBN及SMBC/SMBN的生长季平均值无显著影响。【结论】模拟氮沉降对阔叶红松林土壤微生物生物量的影响仅在个别月份中表现明显,而对于整个生长季而言,更长时间的模拟氮沉降实验才可能对土壤微生物生物量产生明显的影响。

[ Objective ] This study explored the effects of increasing nitrogen deposition on soil microorganisms in a mixed broadleaf Korean pine （Pinus koraiensis ） forest. [ Method ] A simulated nitrogen deposition experiment was performed in a mixed broadleaf Korean pine forest. Nitrogen deposition levels were contacted as control （NO, 0 kg/（ hm^2· a） ）, low N （N1, 30 kg/（hm^2·a））, medium N （N2, 60 kg/（hm^2·a））, and high N （N3, 120 kg/（hm^2·a））. Soil samples were collected from 0-10 cm and ≥ 10-20 cm soil layers monthly from mid-May to mid-September in 2014, and soil microbi- al biomass carbon （SMBC） and soil microbial biomass nitrogen （SMBN） were measured. [ Result] First, the simulated nitrogen deposition did not influence the vertical changes of SMBC, SMBN, or SMBC/SMBN; seasonal changes of SMBC and SMBN between the four treatments plots during the growing season showed a unimodal curve ; and the season- al dynamics of SMBC/SMBN were obvious and their ranges were different. The 0-10 cm soil layer in the NO treatment plot had the smallest range （2. 83-6. 97）. Second, the simulated nitrogen deposition significantly affected the SMBC in June and August in the 0-10 cm layer and the SMBC/SMBN of May, June, and August in the 0-10 cm layer （P〈 0.05 ）. However, the simulated nitrogen deposition did not significantly affected seasonal averages of SMBC, SMBN and SMBC/SMBN.[ Conclusion]There was a obvious effect of simulated nitrogen deposition on soil microbial biomass in the mixed broadleaf Korean pine forest in some specific months. However, to find a distinct effect throughout the whole grow- ing season would require longer simulated nitrogen deposition.