氮沉降对长白山白桦山杨天然次生林土壤微生物量碳氮和可溶性有机碳氮的影响

Effects of Nitrogen Deposition on Soil Microbial Biomass Carbon/Nitrogen and Dissolved Organic Carbon/Nitrogen in Natural Secondary Forests of Betula Platyphylla and Populus Davidiana in Changbai Mountains

土壤理化性质易受氮沉降、温度变化、二氧化碳浓度等外界环境因子的影响,其中土壤微生物量碳、氮(MBC、MBN)和可溶性有机碳、氮(DOC、DON)作为土壤中高活性物质,更易受到诸如氮沉降等环境变化的影响,尤其是不同月份的温度和水分变化会对其产生显著影响。长白山白桦山、杨天然次生林对人工模拟氮沉降响应的控制试验始于2006年,共设计3个氮添加处理,即对照CK(N 0 kg·hm^?2·a^?1)、低氮LN(N 25 kg·hm^?2·a^?1)和高氮HN(N 50 kg·hm^?2·a^?1),每个处理重复3次。于2017年植物生长季(5-10月),按照不同土壤深度(上层0-10 cm和下层10-20 cm)分别对土壤pH、DOC、DON和MBC、MBN进行了分析。结果表明,(1)氮添加导致土壤pH显著降低(P<0.05),变异系数随氮添加量逐步降低,且上、下层土壤表现一致。(2)氮沉降对上层土壤DOC表现为促进作用,对下层土壤DOC影响不显著(P>0.05)。HN处理抑制上层土壤DON,而LN处理对5月和9月的上层土壤DON有促进作用,对6月和8月有抑制作用;LN处理促进下层土壤DON,而HN处理有抑制作用。(3)氮沉降在春季月份对MBC和MBN有抑制作用,秋季月份有促进作用;LN处理降低了夏季月份MBC和MBN,HN处理则差异不显著。(4)氮添加、月份、土壤深度以及三者之间的交互作用对土壤各指标都有显著影响,由此可见,单个月份的研究结果并不能代表整个生长季的总体变化趋势。故建议在开展土壤易发变化组分研究时,应同时关注时空变化对其的影响,并进行综合分析,才能确保研究结果的准确性和完整性。

Soil pH,dissolved organic carbon(DOC)and nitrogen(DON),microbial biomass carbon(MBC)and nitrogen(MBN)are susceptible to changes in the ambient environment.Nitrogen deposition can affect soil pH,DOC,DON,MBC,MBN,except nitrogen deposition,the soil physiochemical properties could be influenced by soil depth,temperature and moisture in different months of the year.The field experiment of simulated nitrogen deposition was started in Betula platyphylla-Populus davidiana natural secondary mixed forest in Changbai Mountains from 2006 to now,and the research was carried out in 2017.The experiment was divided into three nitrogen addition treatments:CK(N 0 kg·hm^-2·a^-1),LN(N 25 kg·hm^-2·a^-1)and high nitrogen(HN,N 50 kg·hm^-2·a^-1).Soil pH,DOC,DON and MBC,MBN were analyzed in different soil depth(upper layer:0-10 cm,lower layer:10-20 cm)during growth season(from May to October,2017).The results show that,(1)Soil pH decreased significantly under nitrogen addition,the coefficient of variation decreased with nitrogen addition,and the upper and lower layers of soil showed the same performance.(2)Nitrogen deposition promoted DOC in the upper soil layer,and it had an inhibitory effect in individual month and had no significant effect on DOC in the lower soil layer.HN treatment inhibited upper soil DON,LN treatment in May and September promoted DON,and inhibited in June and August.LN treatment promoted DON in the lower soil layer,HN treatment inhibited the DON,and there were differences in individual month.(3)Nitrogen deposition inhibited MBC and MBN in the spring months and promoted the autumn months.LN treatment reduced the amount of MBC and MBN in the summer months,and the effect of HN treatment was not significant.And(4)nitrogen addition treatment,monthly changes,soil depth and the interaction among the three have a significant impact on above soil parameters.So,the result of a single month does not represent the trend of the entire growing season.In later research,we should make a comprehensive analysis of the effects of spatiotemporal variation on the easily changeable substances and organisms in the soil in order to ensure the integrity of the research results.