垦殖对黄河三角洲盐渍土碳氮分布特征的影响

以黄河三角洲新生盐碱地为例,采用空间替代时间的方法,选取未利用的盐碱地对照(CK)和平均开垦年限分别为小于5 a、10~15 a、20~25 a、30~35 a、50~60 a的小麦/玉米连作土地类型为研究对象,对1 m深土壤碳(有机碳、无机碳、全碳)、氮(全氮、碱解氮)含量进行了分析,研究不同垦殖年限下土壤碳氮水平和垂直分布特征。结果表明:垦殖后,土壤有机碳含量较未垦殖盐碱地均表现为显著提高(p0.05);盐碱地垦殖显著增加了0~40 cm土壤的碳储量,且随垦殖年限增加而增加;40~100 cm土层的有机碳含量无趋势性变化规律;土壤全氮、全碳、无机碳变化与有机碳变化表现出相似规律;垦殖30 a后土壤碳氮养分基本稳定,表层(0~40 cm)含量高于底层(40~100 cm)含量;垦殖年限主要影响0~30 cm土壤碱解氮含量;无机碳作为组成全碳的主要成分,极易受灌溉和地下水的影响。垦殖虽然显著增加土壤有机碳、全氮含量,但垦殖后碳氮比(C/N)呈降低趋势,约30 a后基本稳定,不同垦殖年限C/N平均为9.35,低于全国平均水平,反映出研究区土壤碳氮养分不均衡问题。

Effects of Reclamation on Distribution of Soil Carbon and Nitrogen in Saline Soil of the Yellow River Delta

Comparison was made of a tract of virgin saline-alkali soil land (CK) with farmlands different in cultivation history, that is, < 5, 10 ~ 15, 20 ~ 25, 30 ~ 35 and 50 ~ 60 years of wheat or corn mono-cropping, using the space- substituting-time method to explore effects of land cultivation on horizontal and vertical distributions of soil carbon and nitrogen content in the 0 ~ 100 cm topsoil layer of the saline-alkali land in the Yellow River Delta. Results show that land cultivation significantly increased the contents of soil organic carbon, inorganic carbon, total carbon, total nitrogen, and available nitrogen, especially in the topsoil layer, and the effects became more significant with the cultivation going on, but leveled off after 30 years of cultivation. Groundwater table is a factor affecting nutrient accumulation in deep soil layers, to a certain extent. Organic carbon was significantly and positively related to total N, but in farmlands, C/N exhibited a declining trend, which leveled off after 30 years of cultivation. However, the C/N in the farmlands of the region is lower than the average of the country, which indicates that in long-cultivated farmlands, it is still essential to further increase the level of soil organic carbon.