新垦沙地农田土壤有机碳时空变异特征

Field-scale Spatial and Temporal Variation of Soil Organic Carbon in a Reclaimed Sandy Farmland

针对河西走廊临泽绿洲边缘区域的新垦沙地农田,采用传统统计学和地统计学相结合的方法研究田块尺度的土壤有机碳时空变异特征。结果表明:(1)在本研究的空间尺度内,土壤有机碳含量在2.66～6.90g.kg-1范围之间变化,平均值为4.45g.kg-1,变异系数为24.5%;其空间分布呈明显的斑块状,最佳的变异函数理论模型为指数模型,其块金值和基台值分别为0.13和1.28,偏基台值和基台值的比值及变程分别为0.90及18.24m;土壤有机碳空间分布与全氮、碱解氮、速效磷、速效钾含量及电导率显著正相关(p<0.01),与pH值显著负相关(p<0.05)。(2)在本研究的监测时间尺度内(2004—2010年),土壤有机碳年平均值在3.81～4.71g.kg-1幅度内变化,变异系数为6.8%,无明显的变化趋势;土壤有机碳含量年际间变化与播种量显著正相关,与作物产量显著负相关,而与施氮量、灌溉量和地上部生物量相关不显著。综上所述,新垦沙地农田土壤有机碳含量较区域水平低,其田块尺度的空间异质性是由成土母质、地形等区域因素作用的结果,而对农田管理影响下的新垦沙地农田土壤有机碳含量演变规律的研究需建立在更长时间尺度的土壤监测数据基础上。

At the marginal regions of the Linze Oasis in Hexi corridor,a study was conducted to proclaim the field-scale spatial and temporal variation characteristic of soil organic carbon in a reclaimed sandy farmland.The results showed that according to the data collected from tests of spatial variation,the content of soil organic carbon ranged from 2.66 to 6.90 g·kg-1,and the average content and variation coefficient of soil organic carbon were 4.45 g·kg-1 and 24.5%,respectively.The exponential model was fitted to the semivariograms of soil organic carbon.The nugget（C0）,sill（C0＋C）,C/（C0＋C） and range were 0.13,1.28,0.90 and 18.24 m,respectively.Significant positive correlations were observed between soil organic carbon and total nitrogen,available nitrogen,available phosphorus,available potassium,electricity conductivity,and significant negative correlation were observed between soil organic carbon and pH.According to the data collected from tests of temporal variation,the annual average of soil organic carbon ranged from 3.81 to 4.71 g·kg-1,and its variation coefficient was 6.8%,indicating that the annual change of soil organic carbon in this reclaimed field was not obvious.The annual average content of soil organic carbon had significantly positive correlations with seeding rate,and negative correlation with crop yield.There were no significant correlations between soil organic carbon,nitrogen and irrigation application rate.It could be demonstrated that the soil organic carbon content of reclaimed farmland was lower than regional level.Spatial variability of soil organic in this reclaimed field was mainly affected by regional factors such as soil parent material and geography.However,to understand the effect of cropland management on evolution rule of soil organic carbon,soil monitoring needs to conduct more long in this reclaimed field.