黄土丘陵区小流域土壤碳氮磷生态化学计量特征的空间变异性

土壤碳、氮、磷是植物重要的营养来源和保障生态系统健康的重要生态因子,其含量及化学计量比的动态平衡对生态系统的生产力具有重要影响,分析土壤碳、氮、磷养分含量及化学计量比的空间变异性和影响机制,对区域土壤养分管理以及土地可持续利用具有重要意义。本研究选取位于黄土高原东缘的三眼井小流域,利用经典统计与地统计相结合的方法,分析了研究区表层土壤(0~20 cm)有机碳(SOC)、全氮(TN)和全磷(TP)以及土壤碳氮磷的化学计量比的空间变异性和影响机制。结果表明:(1)研究区表层土壤SOC、TN和TP的平均值分别为3.97、0.83和0.6 g·kg-1,C∶N、C∶P、N∶P的平均值分别为4.73、6.02、1.26,均属于中等变异水平。(2)土地利用类型和地貌类型对研究区土壤SOC、TN具有显著影响,林地和荒草地高于梯田和退耕地,梁上高于沟谷;TP主要受土地利用类型的显著影响,梯田显著高于其他三种土地利用类型;土地利用类型对土壤C∶N、C∶P和N∶P的影响较为一致,表现为梯田显著低于其他土地利用类型;C∶N还受到坡度和地貌类型的显著影响,C∶P和N∶P还分别受到坡度和海拔的显著影响。(3)采用回归克里格法得到的预测图更能体现环境要素的作用,空间预测精度较高,土壤碳、氮、磷生态计量特征的空间分布格局具有明显差异。因此,针对土壤碳、氮、磷生态计量特征的空间分布格局,采取不同的有机旱作、平衡施肥及水土保持措施等,并进行合理的空间配置,有助于改善研究区土壤碳、氮、磷的平衡状况。

Spatial variation of ecological stoichiometry of soil C,N and P in a small catchment of loess hilly area

As the important sources of nutrients for plants and the ecological factors guaranteeing ecosystem health,the contents and stoichiometry of soil carbon,nitrogen and phosphorus have important impacts on primary productivity.Understanding the spatial variability and driving forces of soil C,N and P content and stoichiometry is significant to soil nutrient management and sustainable land use.We analyzed the spatial variability and driving factors of soil organic carbon(SOC),total nitrogen(TN),total phosphorus(TP)contents and stoichiometric characteristics in Sanyanjing catchment on the eastern Loess Plateau,using classical statistics with geostatistics methods.Results showed that:(1)The mean contents of SOC,TN and TP were 3.97,0.83 and0.6 g·kg-1,and the mean value of C∶N,C∶P and N∶P was 4.73,6.02 and 1.26,respectively.There were moderate spatial variation of soil C,N and P contents and stoichiometry.(2)Land use types and landform types had significant effects on SOC and TN,with higher values in forest and grassland than in terrace and abandoned farmland,and higher at the ridge than at theravine.TP was mainly affected by land use type,with higher value in terrace than the other three land use types.Land use type had a consistent effect on soil C∶N,C∶P and N∶P,with lowest value in the terrace.Moreover,C∶N was significantly affected by slope gradient and landform type,and C∶P by slope gradient and N∶P by elevation.(3)Predicted maps by regression kriging method demonstrated the effects of environmental factors on ecological stoichiometry of soil C,N and P with better prediction accuracy.There were differences for the spatial patterns of ecological stoichiometry across the catchment.Different approaches of organic dry farming,balanced fertilization,soil and water conservation,and reasonable spatial allocation are beneficial to improving the balance of soil C,N and P in the study area.