陕南秦巴山地农田生态系统氮磷元素化学计量特征

Stoichiometric characteristics of nitrogen and phosphorusin agro-ecosystem of Qinba Mountainous area in southern Shaanxi,China

目的分析陕南秦巴山区农田生态系统中土壤与农作物的N,P元素化学计量特征,探讨土壤环境与植被间的N,P元素关系,为研究秦巴山区农田生态系统的养分循环规律提供参考。方法以白菜(Brassica campestris L.spp.Chinese cabbage)、油菜(Brassica campestris L.)、菠菜(Spinacia oleracea L.spinach)3种农田为研究对象,选取自然草地和人工马尾松林(Pinus massoniana Lamb.)为对照,分层采集土样和农作物(植物)叶器官,利用连续流动分析仪(FlowsysⅢ)测定N,P含量。结果 (1)农田生态系统土壤的总氮(total nitrogen简称TN)、总磷(total phosphorus简称TP)垂直分布总体上均表现出随土层深度增加而下降的趋势。3种农田生态系统的土壤TN、TP低于对照自然草地和人工马尾松林,农作物的平均含氮量明显高于对照的自然草和人工马尾松林。(2)农田生态系统的土壤N/P在垂直方向上的变化存在一定差异,3种农田生态系统的土壤N/P均高于对照的自然草地,3种农田作物的N/P均高于草本植物,但低于马尾松林。(3)不同生态系统的土壤和植被平均N/P差异显著(P<0.05),植被N/P和土壤N/P的相关性达到极显著水平(P<0.01),表现为随土壤N/P的增加植被N/P呈现出线性增加的趋势。结论农田生态系统的土壤N/P和农作物N/P显著相关。

Purposes--To explore the relationship between nitrogen and phosphorus in soil envi- ronment and vegetation by analysing the stoichiometric characteristics of leaf total nitrogen （TN） and total phosphorus （TP） of different plants and soil, and to provide reference for researching nutrient circulation of ecosystem in Qinba Mountainous area in southern Shaanxi, China. Methods-- With cab- bage （Brassica campestris L. spp. Chinese cabbage）, oilseed rape （Brassica campestris L. ）, andspinach （Spinacia oleracea L. spinach） as research objects and natural grasslands and Pinus massoniana Lamb as the control group, TN and TP contents are measured with continuous flow analy- zer （Flowsys HI） after the stratification sampling of soil and crops （plants） leaf organs. Results-- 1） The contents of TN and TP in the surface layer （0-10 cm） of farmland soil for cabbage, oilseed rape, and spinach are larger than that in non-surface layer （10-100 cm）, and they are much less than in the natural grasslands and woodland. However, the average content of nitrogen in crop treatments is larger than that in the natural grasslands; 2） The soil N/P ratio had significantly vertical difference, and the soil N/P ratio is larger than that in the natural grasslands, the N/P of the aforesaid three farmland crops is higher than that of herbs, but lower than that of Masson pine. 3） the average N/P ratio of soil and vege- tation in different ecosystems has significant difference （ P〈0.05）, the N/P of associated vegetation and soil reaches a significant level （P〈0.01）, which shows that the ratio of N to P （P〈0.01） of vegetation has a tendency to linear increase with the increase of the ratio of N to P of soil. Conclusion-- The N / P ratio of farmland soil and the N/P ratio of crop was significantly correlated.