杨树人工林土壤微生物生物量碳对模拟氮沉降的响应

Effect of nitrogen deposition simulation on soil microbialbiomass carbon in poplar plantations at different stand ages

在杨树人工林生长季的6,8,10月,对3种不同龄(幼龄、中龄、成熟)林开展野外模拟氮沉降试验。每种龄林设置20个样方,设定4个梯度,即N1,N2,N3,N4[N沉降依次分别为5,10,15,30 g/(m^(2)·a)]和对照N0(无N沉降),样地内采集3个深度(0—15,15—25,25—40 cm)的土样测定土壤微生物生物量碳含量,以研究苏北沿海杨树人工林土壤微生物生物量碳对氮沉降的响应。结果表明:幼龄杨树人工林的土壤微生物生物量碳含量随着施氮量的增加而增加,最大值为607.75 mg/kg;一定量的氮处理可以增加中龄林和成熟林土壤微生物生物量碳的含量,过高则会抑制土壤微生物生物量碳的含量;幼龄杨树人工林中土壤微生物生物量碳含量随土层的加深而降低;3个龄级杨树人工林中土壤微生物生物量碳含量都具有显著的时间动态,幼龄林土壤微生物生物量碳含量的最大值出现在10月(607.75 mg/kg),中龄林出现在8月(1 444.43 mg/kg),成熟林则出现在6月(974.33 mg/kg)。研究结果显示,氮沉降对表层土壤微生物的影响最大;高含量氮的沉降抑制杨树人工林的生长。

Field trials by nitrogen deposition simulation at three ages of poplar plantation(young,middle-aged and mature)were conducted during the growth season(in June,August and October).Each stand age was set with 20 plots and 4 nitrogen deposition gradients,including N1,N2,N3 and N4[5,10,15 and 30 g/(m^(2)·a)respectively]and N0(Control).Soil at three depths(0—15,15—25 and 25—40 cm)in plot to measure soil microbial biomass carbon(SMBC)content,in order to study the response to nitrogen deposition in poplar plantations along the coast of northern Jiangsu.The results showed that the SMBC content of young poplar stand increased with the increase of nitrogen application,the maximum reaching 607.75 mg/kg;A certain nitrogen treatment could increase the content of SMBC in mid-aged and mature stands while excessive nitrogen treatment could inhibit the content of SMBC;The SMBC in young poplar stand decreased with the deepening of soil layers;The SMBC content in the three-aged poplar stands showed significant temporal dynamics.The maximum SMBC content in young stand appeared in October(607.75 mg/kg),mid-aged stand appeared in August(1444.43 mg/kg),and mature stand appeared in June(974.33 mg/kg).It was concluded that nitrogen deposition had the greatest effect on the surface soil microorganisms,and high nitrogen deposition inhibited the growth of poplar plantations.