阿拉善荒漠典型植物叶片碳、氮、磷化学计量特征

Foliar carbon,nitrogen and phosphorus stoichiometry of typical desert plants across the Alashan Desert

荒漠植物在水分限制、营养元素相对匮缺的条件下,经过长期的进化适应形成了自身独特的生理生态和生态化学计量特征。在阿拉善荒漠选择52个典型群落类型,分析和研究了54种荒漠植物叶片的碳、氮和磷的化学计量特征。结果表明:荒漠植物叶片的碳(C mg/g)、氮(N mg/g)和磷(P mg/g)含量变幅较大,分别为(379.01±55.42)mg/g、(10.65±7.91)mg/g和(1.04±0.81)mg/g,变异系数分别为0.15、0.74和0.78;C/N、C/P、和N/P分别为66.70±60.81、683.16±561.94、11.53±5.06。元素间相关性分析表明,叶片的C和N不相关(P>0.05),C与P显著正相关(P<0.05),N和P极显著正相关(P<0.01)。从植物功能型的角度分析发现,灌木和1年生草本植物对C的存储能力较低;占整体67%的灌木叶片的N、P含量最低,导致总体N、P含量较低;多年生草本和1年生草本植物叶N含量与灌木植物叶片和整体N含量无差别,而P含量明显高于灌木植物叶片和整体P含量且N/P明显低于灌木植物叶片和总体N/P,导致总体N/P较低。该研究结果与全球和中国尺度的研究相比发现,荒漠植物叶片C、N、P含量和N/P明显偏低,N/P<14说明阿拉善荒漠植物在受N、P共同作用的同时更易受N限制。

Carbon （C）, nitrogen （N） and phosphorus （P） play an important role in plant growth and regulate various physiological functions. Leaf C, N and P stoichiometry varies with many aspects of plant biology. The ratios of C/N and C/P may reflect the balance between the plant demand and N and P availability and constrain various processes. Previous data from soils in China pointed to a shortage of P. Shortage of N was also reported from the Alashan Desert. We therefore assumed that plant stoichiometry may reflect the low levels of N and P in the Alashan Desert soils. To find the ecological stoichiometry characteristics of C, N and P of the plants of the Alashan desert, we examined 54 typical desert species, which included three groups of plants： perennial shrubs （PS）, perennial herbs （PH） and annual herbs （AH）. A total of 25, 15 and 14 plants were sampled from PS, PH and AH, respectively. Our findings indicate that C, N, P in the plant leaves ranged from 236.48 to 513.54 （with an average of 379.01±55.42） mg/g for C, 1.2 mg/g to 37.37 （with an average of 10.65±7.91） mg/g for N, and 0.11 mg/g to 4.5 （with an average of 1.04±0.81） mg/g for P. Whereas C and P, and N and P were positively correlated in agreement with previous publications, no significant relation was found between C and N, in disagreement with previous publications. As for N and P, these values were substantially lower for PS. The average values for PH and AH were 11.55 （± 7.34） and 10.88 （± 7.17）, mg/g for N, and 1.47 （± 0.94）, and 1.41 （± 0.94） mg/g for P. As for PS, they were 10.38 （± 8.24） and 0.84 （± 0.65） mg/g for N and P, respectively. The average values found for N and P in the Alashan Desert were substantially lower than the typical values reported from other desert regions in China having on average 24.4 （± 8.10） and 1.74 （± 0.88） mg/g of N and P, respectively. Furthermore, out of all plants examined, 71% of the plants had a ratio of N/P 〈 14 which implies that plant growth is primary limited by N. Interestingly, the lowest values were found in leaves at the new shoots and we presume that nutrients are transferred from leaves at the older branches to leaves at the younger shoots. Our data thus imply that the Alashan desert plants are adapted to substantially low values of N, and also, following the low ratio of N/P, to low amounts of P.