杨树人工林复合经营模式对土壤N_(2)O与CO_(2)排放的影响

Effects of compound management patterns in poplar plantations on the emissions of N_(2)O and CO_(2) from the soil

为探讨杨树人工林复合经营模式对土壤温室气体排放的影响,基于11年生“南林-895杨”(Populus×euramericana‘Nanlin-895’)人工林,设置纯林、林下种植麦冬(Ophiopogon japonicas)和林下养鸡3种复合经营模式,采用静态箱-气相色谱法每月测定土壤N_(2)O和CO_(2)排放通量,同时测定土壤温湿度,分析复合经营模式对土壤N_(2)O和CO_(2)排放和产量的影响及与相关影响因子的关系。结果表明:不同复合经营模式林下土壤温、湿度存在显著差异;不同杨树复合经营模式间,土壤N_(2)O和CO_(2)排放速率动态变化与年累积排放量存在显著差异,杨树林下种植麦冬的土壤N_(2)O年累积排放量最高,为233.47 mg·m^(-2)·a^(-1),而林下养鸡的土壤CO_(2)年累积排放量最高,达2328.87 g·m^(-2)·a^(-1)。总体来看,不同复合经营模式林地土壤温室气体(N_(2)O和CO_(2))年累积排放量为林下养鸡>林下种植麦冬>杨树纯林;土壤温、湿度对土壤CO_(2)和N_(2)O排放速率有显著影响,其中,土壤CO_(2)排放速率与土壤温度之间呈显著线型相关,而与土壤湿度呈现抛物线型关系;土壤N_(2)O排放速率与土壤温、湿度的关系均可用抛物线型关系来描述。综上所述,不同杨树复合经营模式改变了林地土壤的温、湿度,进而对温室气体排放产生了显著的影响。从1年的研究结果看,种植麦冬和养鸡的杨树人工林林地土壤温室气体的年累积排放量高于纯林,表明林农复合经营增加了土壤温室气体的排放。

To evaluate the effects of different compound management patterns on soil greenhouse gas emissions in poplar plantations,a field experiment was performed at the"Nanlin-895 Poplar"(Populus×euramericana‘Nanlin-895’)plantations of 11-year old.Three compound management patterns were conducted in this experiment as follows:pure poplar plantation(P),planting Ophiopogon japonicas under the plantation(L),raising chicken under the plantation(C).The characteristics of soil N_(2)O and CO_(2) emission fluxes were monthly measured by static chamber technique,while the soil temperature and moisture were measured synchronously to analyze the impacts of compound management patterns on N_(2)O and CO_(2) emissions and crop yield,as well as the relationships between the related impact factors.The results indicated that there were significant differences in soil temperature and moisture among the different management patterns,while the significant differences in the monthly emission rates and annual cumulative emissions of soil N_(2)O and CO_(2) were also detected among different management patterns.The annual cumulative emission of soil N_(2)O was the highest in the pattern of planting O.japonicus under poplar plantation,reaching 233.47 mg·m^(−2)·a^(-1),whereas the annual cumulative emission of soil CO_(2) was the greatest in the pattern of raising chicken under poplar plantation,up to 2328.87 g·m^(−2)·a^(-1).In general,the annual cumulative emission of soil greenhouse gases(N_(2)O and CO_(2))in the different compound management patterns was as follows:raising chicken under the plantation>planting O.japonicas under the plantation>pure poplar plantation.Soil temperature and moisture had significant effects on soil CO_(2) and N_(2)O emission rates,and there was a significant linear correlation between soil CO_(2) emission rate and soil temperature,while a parabolic relationship between soil CO_(2) emission rate and soil moisture.However,the relationships of N_(2)O emission rate to soil temperature and moisture could be described by parabola.As mentioned above,different compound management patterns in poplar plantations modified the soil temperature and moisture,and then significantly affected the greenhouse gas emissions from the soils.Based on the results,the annual cumulative emissions of soil greenhouse gases in two agroforestry compound management patterns(planting O.japonicas in the plantation and raising chicken under the plantation)were higher than those in the pure plantation,indicating that poplar agroforestry patterns would increase the soil greenhouse gas emissions.