长期定位施肥下黑土呼吸的变化特征及其影响因素

Characteristic of black soil respiration and its influencing factors under long-term fertilization regimes

阐明长期不同施肥下的土壤呼吸特征及其影响机制对黑土区固碳减排研究至关重要。该研究基于1990年开始的国家土壤肥力与肥料效益监测网站-吉林省公主岭市黑土监测基地,选取不施肥(CK)、单施氮磷钾肥(NPK)、无机肥配施低量有机肥(NPKM1)、1.5倍的无机肥配施低量有机肥(1.5(NPKM1))、无机肥配施高量有机肥(NPKM2)和无机肥配施秸秆(NPKS)6个处理,明确了长期不同施肥下土壤总呼吸和异养呼吸的季节变化特征,并分析了土壤温度、水分、微生物量碳氮、铵态氮、硝态氮与土壤呼吸和异养呼吸的关系。结果表明:长期有机无机肥配施可以显著提高土壤有机碳、全氮、土壤速效磷、有效钾的含量和土壤活性有机碳库组分含量(P<0.05);与不施肥相比,长期有机无机肥配施和无机配施秸秆处理分别显著增加土壤呼吸及异养呼吸碳累积排放量56.32%~86.54%和70.01%~100.93%;根系呼吸对土壤呼吸的整体贡献为23.68%~34.30%;相关分析表明,土壤呼吸速率和异养呼吸速率与土壤温度极显著正相关(P<0.01),与土壤含水率呈显著负相关(P<0.01),土壤温度可以分别解释土壤呼吸和异养呼吸变化的42.79%和39.61%;土壤微生物量碳氮、土壤硝态氮均与土壤呼吸速率和异养呼吸速率极显著相关(P<0.01),土壤微生物量碳氮、土壤硝态氮可以分别解释土壤呼吸和异养呼吸变化的78.42%和77.18%,58.33%和56.79%,59.29%和59.14%;土壤铵态氮虽然显著影响土壤呼吸速率(P<0.05),可以解释土壤呼吸变化的5.56%,但其对异养呼吸速率的影响不显著。综合来看,微生物量碳对土壤呼吸及异养呼吸的影响最大,而土壤含水率(>15%)越高则土壤呼吸越弱;无机配施秸秆处理可以提高土壤碳库组分含量,且作物生育期内土壤呼吸及异养呼吸碳累积释放量均低于等氮量下施用有机肥(NPKM1)的处理,为最佳的农田管理措施。

Clarifying characteristic and its influence factors of soil respiration under long-term different fertilization is essential to the research on carbon sequestration as well as carbon emission reduction in black soil area. Our experiments were conducted in National Fertility Monitoring Station in Gongzhuling City since 1990, and 6 fertilization treatments were set up, including no fertilizer （CK）, only chemical fertilizer application （NPK）, inorganic fertilizer combined with low level of organic manure （NPKM1）, 1.5 times the amount of inorganic fertilizer combined with organic fertilizer of NPKM1 （1.5 （NPKM1））, inorganic fertilizer combined with high amount of organic manure （NPKM2）, and inorganic fertilizer combined with straw （NPKS）. The seasonal variation characteristics of total and heterotrophic soil respiration were analyzed, and the relationships between relevant factors （soil temperature, moisture content, microbial biomass carbon and nitrogen （MBC,MBN）, ammonium and nitrate nitrogen） and total or heterotrophic soil respiration were determined. The results showed that long-term combined application of organic manure and chemical fertilizer could significantly improve content of soil organic carbon, total nitrogen, soil available phosphorus and potassium and soil active organic carbon components （P〈0.05）. Compared with CK, long-term combined application of chemical fertilizer and organic manure, and chemical fertilizer and straw treatment could significantly increase soil carbon cumulative emissions by 56.32%-86.54% and 70.01%-100.93%, respectively. The total contribution of root respiration to soil respiration was 23.68%-34.30%. Correlation analysis indicated that soil respiration rate was significantly positively correlated with soil temperature （P〈0.01）, but significantly negatively correlated with soil moisture content （P〈0.01）. And soil temperature could explain 42.79% and 39.61% of changes in soil respiration and heterotrophic respiration, respectively. Soil respiration rate and heterotrophic respiration rate were significantly correlated with MBC, MBN and nitrate nitrogen （P〈0.01）, which could explain 78.42% and 77.18%, 58.33% and 56.79%, 59.29% and 59.14% of changes in soil respiration and heterotrophic respiration, respectively. The soil ammonium nitrogen significantly affecting the soil respiration rate （P〈0.05）, could account for 5.56% of the changes in soil respiration, but it had no significant effect on the rate of heterotrophic respiration. Therefore, MBC had the greatest influence on total and heterotrophic soil respiration rate, and higher soil moisture content resulted in weaker soil respiration and heterotrophic respiration rates. NPKS could maintain soil carbon pool component content and microbial activity, and in addition, the carbon cumulative emissions during crop growth period were lower than that of NPKM1 under equal quantity of nitrogen of chemical fertilizer and organic manures, which was the best farmland management measure.