退耕土壤的碳、氮固存及其对CO_2、N_2O通量的影响  

Soil carbon and nitrogen sequestration following cropland to forage grassland conversion and its effect to CO_2 and N_2O fluxes

作　　者：高亚琴[1] 黄高宝[2] 王晓娟[1] 马剑[1] 刘博[3] 黄涛[3] 李卿沛[3] 

机构地区：[1]甘肃农业大学资源与环境学院,兰州730070 [2]甘肃农业大学农业生态工程研究所,兰州730070 [3]甘肃农业大学农学院,兰州730070

出　　处：《生态环境学报》2009年第3期1071-1076,共6页Ecology and Environmental Sciences

基　　金：国家科技支撑计划基金项目(2006BAD15B06);国家自然基金项目(40771132)

摘　　要：采样分析陇中黄土高原地区农田退耕种植苜蓿3a、5a、8a后0～5、5～10、10～20cm土层土壤有机碳(SOC)、全氮(TN)、活性有机碳(SAOC)及矿质氮(NO3-N、NH4-N)含/储量的变化,并用静态箱—气质联用法对样地的CO2、N2O排放通量进行了测定,研究碳氮变化对土壤CO2、N2O排放通量的影响。结果表明:(1)SOC、TN基础含量很低的贫瘠土壤退耕后表现出明显的碳、氮固存效应,有很强碳、氮固存潜力。与未退耕休闲农田相比,退耕3a、5a、8a后0～20cmSOC储量分别提高了9.12%、20.18%、34.39%,SOC平均固存率分别为0.17、0.23、0.25mg/(hm2·a)。TN储量在5～10、10～20cm增加不明显,在0～5cm退耕3a、5a、8a后储量分别提高14.29%,35.71%和64.29%,各退耕年限0～20cmTN平均固存率均为0.2mg/(hm2·a);(2)退耕后各年限草地土壤活性有机碳(SAOC)含量有所增加,但各层含量变化不明显,其增加量远小于SOC的增加,说明退耕初期阶段积累了较多的土壤惰性碳;NO3-N含量增加明显,0～5、5～10cm土壤各退耕年限含量达5%的显著性差异,但退耕前后NH4-N含量无明显变化。(3)土壤CO2通量与SOC含量、SAOC含量、TN含量及N2O通量显著正相关;N2O通量与SOC含量、矿质氮含量及CO2通量显著正相关。说明在环境因素稳定的条件下,退耕后土壤碳、氮含量的增加会导致CO2、N2O排放的加剧,表现出大气CO2、N2O的"源"效应。By taking samples from forage grasslands （alfalfa） whicb had been converted from croplands for 3,5 and 8years in Loess Plateau area in middle of Gansu, changes of soil organic carbon（SOC）, total nitrogen （TN） concentrations/storage at the three depths of 0-5, 5-10, 10-20 cm were surveyed. And the fluxes of CO2 and N20 at the sampled lands were measured by using static chamber - GC technique. Based upon these measurements, the effects of converting cropland to grassland on SOC and TN contents and CO2 and N20 fluxes were investigated and discussed. The results showed as following： （1） The infertile sampled lands which had very low SOC and TN concentrations showed significant C,N sequestration and had a great potential of it. After conversion of annually crop to perennial alfalfa for 3, 5, 8 years ,SOC stock at 0-20 cm increased by 9.12%, 20.18%, 34.39% comparing to cropland, and SOC sequestration rates were estimated to be on average of 0.17, 0.23, 0.25 mg/（hm2·a） respectively. No significant change of TN stock were found at the 5-10, 10-20 cm depths, however, it increased at the 0-5 cm layer by 14.29%, 35.71% and 64.29% after converting for 3, 5, 8 years respectively. TN sequestration rates at 0-20 cm of different conversion years were all estimated to be on average of 0.2 mg/（hm2·a）. （2） The concentrations of SAOC increased after conversion, but the increments of SAOC were far less than that of SOC, which meant the conversion of cropland to alfalfa grassland accumulated more inertia soil carbon. The concentra- tions of NO3-N greatly increased after conversion, and the concentrations at 0-5, 5-10 cm of the three conversion years were up to 5% significant level, but the concentrations of NH4-N showed no significant change after converting. （3） The fluxes of CO2 were significantly positively correlated with the concentrations of SOC, SAOC, TN and N20 fluxes. Also, the fluxes of N20 were signifi- cantly positively correlated with the concentrations of SOC, TN, NO3-N, NH4-N and CO2

关 键 词：退耕 碳、氮固存 CO2、N2O 通量 

分 类 号：X14[环境科学与工程—环境科学]