酸性土壤中的碳氮耦合作用与N2O流失研究

Carbon and Nitrogen Coupling and N2O Emission in Acidic Soils among Different Vegetation Types

以贵阳不同植被类型酸性土壤(果园、草地、茶园、阔叶林、针叶林)0~30 cm表层土壤为研究对象,比较了5种植被类型土壤养分含量、微生物量碳、微生物量氮、微生物量C/N、土壤呼吸作用、反硝化作用差异。结果表明:(1)研究区域土壤有机碳含量在7.11~37.00 g/kg之间,全氮含量在0.95~3.64 g/kg之间,低于贵州石灰土上的次生林;土壤有机碳/全氮均值介于5.98∶1~16.93∶1之间,表现为针叶林>茶园>草地>阔叶林>果园;(2)土壤NH4^+-N含量在0.79~49.49 mg/kg之间,阔叶林最高,针叶林和茶园最低;NO3^--N含量均值在0.04~1.18 mg/kg之间,针叶林最高,茶园和阔叶林最低,可能与针叶林、茶树等植物优先利用NH4^+-N作为养分来源有关;(3)SMBC、SMBN分别介于818.01~3 192.86 mg/kg和141.36~531.42 mg/kg之间,SMBC/SMBN与pH值、铵态氮含量分别呈显著、极显著负相关,表现为针叶林>草地>茶园>果园>阔叶林;(4)土壤反硝化速率介于122.21~1 229.09 mg/(kg·h)之间,高于贵州石灰土上的次生林,果园和针叶林N2O流失率较高,反硝化作用产生的CO2不断被消耗。总的来说,区域土壤趋于有机碳积累,酸性环境、低NH4^+-N含量下微生物倾向于生物体碳的积累;土壤氮矿化速率较快,N2O流失率较高,初始NO3^--N水平是决定酸性土壤N2O释放率的主要因素。

The surface soil of 0~30 cm in acid soils of different vegetation types(orchards,grasslands,tea gardens,broadleaved forests,and coniferous forests)in Guiyang was studied and the nutrient contents,microbial biomass carbon,microbial biomass nitrogen,microbial biomass and microbes in soil of the five types were compared.The differences in microbial biomass carbon/nitrogen,soil respiration,denitrification,and diversity and abundance of ammonia oxidation microbial communities were studied to investigate the role of microbial-mediated soil carbon and nitrogen coupling in acidic soils.The results showed that the content of soil organic carbon in the study area was between 7.11 and 37.00 g/kg,and the total nitrogen content was between 0.95 and 3.64 g/kg,which was lower than the secondary forest on Guizhou lime soil.The mean value of soil organic carbon/total nitrogen was between 5.98:1 and 16.93:1,which was characterized by higher in coniferous forest,tea plantation,grassland and broad-leaved forest followed,lower in orchard.The content of NH4^+-N in study area soil was between 0.79~49.49 mg/kg which performed that the broad-leaved forest was the highest,while the coniferous forest and the tea garden were the lowest.The average NO3^--N content was between 0.04 and 1.18 mg/kg.Contrary to the content of NH4^+-N,the coniferous forest and the tea garden were the highest while the broad-leaved forests lowest,may be some plants(such as coniferous forest,tea,etc.)priority use of NH4^+-N as a source of nutrients.Soil microbial biomass carbon and microbial biomass nitrogen ranged from 818.01 to 3 192.86 mg/kg and 141.36 to 531.42 mg/kg,respectively.The ratio of soil microbial biomass carbon and microbial biomass nitrogen which was highest in the coniferous forests,followed by grassland,tea plantation and orchard,and lowest in the broad-leaved forests,was significantly negatively correlated with the pH value and ammonium nitrogen content.The rate of soil denitrification was between 122.21 and 1 229.09 mg/(kg·h),which was higher than the secondary forest on Guizhou lime soil.The greenhouse gas N2 O emission in orchard and coniferous forest was higher,which indicated that the CO2 produced by denitrification was constant.In general,the results suggested that the acidic soils in the area tend to accumulate organic carbon and the microorganisms also tend to accumulate microbial carbon under acidic and low NH4^+-N content environment.Nitrogen mineralization rate was faster among regional and the N2 O emission was higher and the initial NO3^--N level was the main factor that determined the release rate of N2 O in acidic soils.