【摘要】 利用棉花长期连作定位试验田,探究秸秆还田下棉田土壤呼吸日变化和季节变化以及碳排放随着连作年限增加的变化特征,揭示长期连作棉田碳排放量与不同土层土壤有机碳和微生物量碳含量的关系,为衡量和评价长期连作及秸秆还田的生态效应提供理论依据。试验田设有连作5 a、10 a、15 a、20 a、25 a和30 a的棉花秸秆连年还田小区,采用LI-8100土壤碳通量测定仪测定棉田土壤呼吸速率的日变化和季节变化,根据棉花生育期的天数和土壤呼吸速率计算出棉花各个生育期的土壤碳排放量,并分析了土壤碳排放与有机碳和微生物量碳含量的关系。研究结果表明,秸秆还田不同连作年限棉田土壤呼吸速率日变化和季节变化差异表现为随着连作年限的增加整体上呈现增加的变化趋势,30 a最大,5 a最小;不同连作年限棉田土壤呼吸速率日变化均表现相同的规律,呈现单峰曲线,在15:00达到峰值,最小值均在凌晨05:00出现;不同连作年限棉田土壤呼吸速率随着季节的变化呈现先升高后下降的趋势,7月下旬土壤呼吸速率最高,30 a土壤呼吸速率比5、10、15、20、25 a增加4.96%、4.33%、1.98%、2.52%、1.31%。随着连作年限增加棉花各个生育期及全生育期土壤碳排放量整体上呈现逐渐增加的变化趋势,相同连作年限棉花不同生育期土壤碳排放量差异表现为铃期>苗期>花期>蕾期>絮期,铃期土壤碳排放量最高,不同连作年限棉田铃期碳排放量占全生育期总碳排放量的25.48%~25.60%。长期连作及秸秆还田棉田土壤碳排放量与0~20 cm土层土壤总有机碳含量及两个土层微生物量碳含量呈显著的线性相关关系(P<0.05),与20~40 cm土层土壤总有机碳含量呈极显著的线性相关关系(P<0.01),土壤碳排放与有机碳的线性相关性高于与微生物量碳的线性相关性,土壤碳排放与20~40 cm土层土壤有机碳及微生物量碳的线性相关性高于与0~20 cm土层的线性相关性。这表明秸秆还田下不同连作年限棉田土壤呼吸速率表现出明显的日变化和季节变化规律,并且随着秸秆还田年限的增加土壤碳排放量具有增加的趋势。更多还原

【Abstract】 In this paper, the use of long-term continuous cropping of cotton located experimental plot, exploring cotton soil respiration diurnal and seasonal changes as well as carbon emissions increased with continuous cropping of variation under straw returning, revealimg the long-term continuous cropping of cotton field relationship between the carbon emissions and different soil organic carbon and soil microbial biomass carbon content, providing a theoretical basis for measuring and evaluating the long-term ecological effects of continuous cropping and straw returning. Experimental field which cotton straw were returned into the soil had six continuous cropping plots, such as 5, 10, 15, 20, 25 and 30 years. Diurnal variations and seasonal variations of soil respiration rate in cotton field was measured by LI-8100 automated soil CO2 efflux system, according to the growth stages of days and soil respiration rate to calculate the carbon emissions of each growth stages, and analyzed the relationships between soil carbon emissions and organic carbon and microbial biomass carbon content. The results showed straw returning continuous cropping years cotton soil respiration diurnal and seasonal variation showed a trend, with the increase of the over all increase in continuous cropping years, 30 year is maximum, 5 year is minimum. Different Cotton Soil respiration diurnal variation showed the same rule, showing a single peak, peaked at 15:00 and minimum occurred at 05:00. Soil respiration rate of continuous cropping cotton field changes with the seasons firstly increased then downward trend, the highest soil respiration rate in late July, 30 a soil respiration rate higher than 5 a, 10 a, 15 a, 20 a, 25 a increase of 4.96%, 4.33%, 1.98%, 2.52%, 1.31%. With the continuous cropping of cotton increased presented each growth period and growth period soil carbon emissions increasing trend overall. The same continuous cropping Years cotton in different growth period differences in soil carbon emissions showed: bolling stage > seedling stage > flowering stage > budding stage > boll opening stage, the highest carbon emissions was at bell soil, cropping in cotton boll growth stage of the carbon emissions accounted for total carbon emissions 25.48%~25.60%. Long-term continuous cropping of cotton and straw returning soil carbon emissions and 0~20 cm soil organic carbon content of the soil and two soil microbial biomass carbon content showed a significant linear correlation(P<0.05), soil carbon emissions and 20~40 cm soil total organic carbon content of the soil showed very significant linear correlation(P<0.01), the linear correlation between soil carbon emissions and organic carbon was higher than that in soil carbon emissions and microbial biomass carbon, the linear correlation between soil carbon emissions and 20~40 cm soil organic carbon content of the soil and microbial biomass carbon were higher than those in 0~20 cm soil. This indicates different continuous cropping Years of cotton in straw returning soil respiration shows significant diurnal and seasonal variation, and soil carbon emissions increased with the increase of straw returning years.更多还原