荒漠草地土壤^(15)N同位素对水分变化的响应

Response of Soil ^(15)N Isotope to Water Changes in Desert Grassland

影响δ15N格局的因素主要有气候、时间、地形和土地利用等,而水分是干旱区植被分布的主要限制因子,对调节荒漠草地稳定性N同位素具有重要作用。利用15N标记法,通过不同的增水处理,研究了古尔班通古特沙漠南缘氮素标记样地和未标记样地土壤N同位素对水分变化的响应,得出以下结论:(1)增水处理增加了对土壤水分的补给,随着增水量的增加土壤水分含量不断增加;(2)研究区土壤δ15N值变化范围为12.19‰~13.33‰,增水处理对未标记样地土壤δ15N值并没有显著的影响;(3)添加氮素后,样地土壤δ15N值明显升高。随着增水量的增加,土壤总δ15N呈现出典型的倒"U"型曲线,不同土层深度的土壤δ15N值也发生了显著的变化;(4)标记样地50-100 cm土层土壤δ15N值要明显高于非标记样地,表明标记样地土壤中添加的稳定性15N同位素仍在向更深的土层移动。

Climate,time,topography and land use are the main factors which influence the distribution patter of δ15N.Water,the main limiting factors to the distribution of plants in arid and semi-arid areas,plays an important role in regulating the 15N isotope in the desert grassland.Using the 15N labeling method,the response of soil N isotope to water change for labeled sample plots and unlabeled sample plots in the southern fringe of Gurbantunggut desert were studied under the different water increasing level.The results showed that：（1）The treatment of increasing water increased the soil water.With the increasing of the water increasing level,the soil water was increasing.（2）The range of soil δ15N was from 12.19‰ to13.33‰ in the study area.The treatment of increasing water didn＇t have significant impact on the soil δ15N in the labeled sample plots.（3）The soil δ15N was increase significant after nitrogen addition.With the increasing of the water increasing level,the changes of total soil δ15N showed a typical inverted ＂U＂ curve and the δ15N in the different soil layer was also changed significant.（4）The δ15N of the 50-100 cm soil layer in the labeled sample plots was higher than that in the unlabeled sample plots,which indicated that the added 15N isotope in the labeled sample plots was still moving to the deeper soil.