贺兰山不同林型植物碳氮磷与土壤养分及坡向关系

The relationships between carbon,nitrogen,phosphorus in plants,soil nutrients and slope in different forest types in the Helan Mountains

以贺兰山阴坡和阳坡同海拔范围分布的青海云杉林(Picea crassifolia)、蒙古扁桃灌木林(Prunus mongolica)和灰榆灌木林(Ulmus pumila)为研究对象,分析各坡向不同植物根茎叶碳氮磷与土壤养分特征,辨识影响其养分含量变化的关键因子,揭示不同林型植物碳氮磷与土壤养分及坡向关系。结果表明:灰榆灌木林、蒙古扁桃灌木林土壤有机碳(C)、全氮(N)、全磷(P)含量均具有显著差异,阴坡青海云杉林土壤有机碳(37.69 g·kg^(-1))、全磷(0.65 g·kg^(-1))含量最高。在相同坡向,青海云杉林土壤有机C、全N以及碱解氮(AN)均高于其他林型;土壤C/N、C/P在不同林型及坡向间无显著性差异,N/P低于中国陆地土壤平均水平,说明土壤存在严重的N供应不足;植物叶片C含量在不同林型间均差异显著,其中阴坡青海云杉林叶片C含量最高,为483.92 g·kg^(-1)。植物根系C、N、P含量与叶片变化趋势一致;植物叶片C含量与土壤C含量无显著相关关系,但植物叶N与土壤N呈显著负相关,而植物叶片P与土壤有效P呈显著正相关;植物叶、根对坡向敏感,但植物在C同化以及N、P固定过程中与土壤不完全处于同步状态,土壤N/P、AN是引起植物根茎叶养分含量变化的关键因子。

We analyzed C,N,and P concentrations in roots,stems and leaves of different plant species,as well as soil nutrients in different slope aspects in Picea crassifolia forest,Prunus mongolica shrublands,and Ulmus pumila shrublands distributed in same altitude on the shady and sunny slopes of Helan Mountains.The key factors affecting plant nutrient contents were identified,and the relationships between C,N,and P of plants and soil nutrients as well as the slope aspects of different forest types were examined.There were significant differences in soil organic C,total N,and total P contents in Ulmus pumila shrublands and Prunus mongolica shrublands,and soil organic C(37.69 g·kg^(-1))and total P(0.65 g·kg^(-1))contents were the highest in Picea crassifolia forest on the shady slope.On the same slope aspects,soil organic C,total N,and alkaline hydrolyzable N(AN)of Picea crassifolia forest were higher than those of other two forest types.There were no significant differences in soil C/N and C/P among different forest types and slope aspects,and the N/P was lower than the average level of soils in China,indicating that there was a serious shortage of soil N supply.Leaf C content varied significantly among different for-est types,with the highest value of 483.92 g·kg^(-1) in Picea crassifolia forest on a shady slope.The pattern of C,N,and P contents in roots were consistent with those in leaves.There was no significant correlation between leaf C con-tent and soil C content,a significant negative correlation between leaf N and soil N,and a significant positive correlation between leaf P and soil available P.Nutrients in leaves and roots are sensitive to slope aspects,but the processes of C assimilation and N and P fixation were not entirely synchronized with soils.Soil N/P and AN are the key factors driving the changes of nutrient contents of roots,stems,and leaves.