贺兰山东麓不同植被类型叶片化学计量特征研究

Leaf Stoichiometric Characteristics of Different Vegetation Types on the Eastern Slope of Helan Mountains

为了探究贺兰山东麓地区不同植被类型植物叶片碳氮磷含量及其计量比特征与环境因子的关系。该研究于研究区沿海拔梯度设置了高山草甸、云杉纯林、山杨纯林、浅山灌丛和荒漠草原5个典型植被样地,测定了63种植物叶片碳、氮、磷含量和样地土壤养分特征,分析了植物叶片碳氮磷含量及其计量比特征与环境因子的关系。结果表明:(1)贺兰山东麓地区63种植物叶片平均C含量为520.46±62.08 mg·g-1,平均N含量为24.03±3.37 mg·g-1,平均P含量为1.69±0.51 mg·g-1;植物叶片N、P、C/N、C/P、N/P服从正态分布,而叶片C不符合正态分布,且叶片C/P和N/P较之C/N变异更大。(2)不同生活型植被叶片化学计量差异显著;叶片C、P含量乔木最高,叶片N含量草本最高;乔木植物叶片C/N最高,而N/P最低;叶片的C/P灌木最高。(3)植物叶片N含量、N/P和C/P均随海拔上升而增高,在海拔2073 m(山杨纯林处)显著降低,之后又呈显著增高趋势;而植物叶片P含量和C/N在山杨纯林处达到最高值随后呈显著下降趋势。(4)荒漠草原和浅山灌丛受到P限制,云杉纯林受到N限制,高山草甸可能受N、P的共同限制。虽然山杨纯林植物N/P<14,但因其具有较高的N、P吸收能力,且N转换率显著高于P,故不认为山杨纯林植物受到N限制。

In order to investigate the relationship between leaves carbon(C),nitrogen(N)and phosphorus(P)contents and environmental factors in different vegetation types on the eastern slop of Helan Mountains,we selected five typical vegetations including alpine meadow(Ⅰ),pure forest of Picea crassifolia(Ⅱ),pure forest of Populus davidiana(Ⅲ),shallow shrub(Ⅳ)and desert grassland(Ⅴ)along the elevation gradient.The contents of C,N and P in the leaves of 63 plant species and soil nutrient characteristics in sample plots were determined.The relationship between the C,N,and P contents and their stoichiometric characteristics of plant leaves and the environmental factors were investigated.The result showed that:(1)Based on the 63 plant species on the eastern slop of Helan Mountains,the average leaf C,N and P contents were 520.46±62.08 mg·g-1,24.03±3.37 mg·g-1 and 1.69±0.51 mg·g-1,respectively.Leaf N,P,C/N,C/P and N/P had a normal distribution(P>0.05),while leaf C did not conform to positive distribution(P<0.05).Leaf C/N and N/P were more variable than C/N.(2)Leaf stoichiometric characteristics in different life forms had significant difference.Trees had the highest leaf C and P contents,while the herbs had the highest leaf N content.The trees had the highest C/N and lowest N/P,while the shrubs had the highest C/P.(3)The leaf N,N/P,and C/P were increased with the altitude rising,only decreasing at 2073 m(pure forest of P.davidiana).Leaf P and C/N reached peak at 2073 m,then decreased with altitude rising.(4)Our results suggested that desert grassland,shallow shrub were subjected to P,while the pure forest of P.crassifolia was limited by N.The alpine meadow was limited by N and P,although N/P of pure forest of P.davidiana was under 14,the high absorptivity of N and P rejected the N limitation.