科尔沁沙地主要植物细根和叶片碳、氮、磷化学计量特征

Carbon,nitrogen and phosphorus stoichiometry in leaves and fine roots of dominant plants in Horqin Sandy Land

弄清半干旱区植物叶片和细根的碳(C)、氮(N)、磷(P)元素的化学计量特征及其关联性对于认识植物C、N、P元素之间的交互作用及平衡制约关系、植物的养分利用策略,以及对全球变化的响应具有重要的意义。该研究对科尔沁沙地60种主要植物叶片和细根的C含量、N含量、P含量、C:N、C:P、N:P的差异性及其相关性进行了研究。结果表明:1)科尔沁沙地60种主要植物叶片平均C含量、N含量、P含量和C:N:P分别为424.20 mg·g^(-1)、25.60 mg·g^(-1)、2.10 mg·g^(-1)和202:12:1。细根平均C含量、N含量、P含量和C:N:P分别为434.03 mg·g^(-1)、13.54 mg·g^(-1)、1.13 mg·g^(-1)和384:12:1。细根N、P含量近似等于叶片平均N、P含量的1/2;叶片与细根的N:P并无显著差异,具有明显的保守性,反映了植物地上和地下养分吸收与分配比例的一致性;2)不同生活型植物间叶片和细根的C、N、P含量及其化学计量比存在显著差异,杂类草植物具有较高的叶片N、P含量,禾草类植物具有较高的叶片C:N和C:P,一年生杂类草和禾草类植物叶片的N:P较低。与非豆科植物相比,豆科植物具有较高的C、N含量和较低的C:N,表明不同生活型植物对养分的适应策略不同;3)相关分析表明,叶片和细根的N、P含量间显著正相关,细根C含量与N含量之间以及C含量与P含量之间显著负相关,表明植物体内这3种元素之间存在相互作用;4)科尔沁沙地植物叶片和细根间的C、N、P含量及化学计量比均有显著的正相关关系,说明植物光合产物和养分在地上和地下部分之间分配具有平行的比例关系,但不同生活型植物叶片和细根之间元素含量的相关性存在一定差异,这可能与不同生活型植物的养分利用效率有关。

Aims The stoichiometric characteristics of carbon （C）, nitrogen （N） and phosphorus （P） in plant organism is vital to understand plant adaptation to environment. In particular, the correlations of elemental stoichiometric characteristics between leaf and fme root could provide insights into the interaction and balance among the plant elements, nutrient use strategies and plant response to global change. Methods We measured C, N, P contents and C：N, C：P, N：P in leaves and fine roots of 60 dominant plants in Horqin sandy land. The 60 plant species were classified into five life forms and two categories such as perennial forb, annual forb, perennial grass, annual grass, shrub, legume, and non-legume. We statistically analyzed the diff- erences and correlations of C, N and P stoichiometry either between fine root and leaf or among five life forms. Important findings The average C, N and P concentrations in leaves of 60 plant species in Horqin sandy land are 424.20 mg-g-1, 25.60 mg·g^-1 and 2.10 mg-g-1, respectively. In fine roots, the corresponding element concen- trations are 434.03 mg·g^-1, 13.54 mg·g^-1, 1.13 mg·g^-1. N and P concentrations in leaf are approximately twice as high as averages in fine root. Furthermore, similar N：P between leaf and fine root indicates conservative charac- teristic of elemental stoichiometry in plant organism, suggesting that nutrients distribution is proportional between aboveground and underground of plants. There are significant difference of C, N, P, C：N, C：P and N：P in leaf and root among five life forms. N and P in forb and C：N and C：P in grass are averagely higher than those in other life forms. N：P in annual forb and grass, however, are lower than those in other life forms. C, N in legume are higher than those in non-legume, while C：N in legume is lower than in non-legume. These results imply that nutrient use strategies are significantly different among plant life forms. Correlations analysis showed that N and P in leaf or fine root positively correlated, but C and N, C and P in fine root negatively correlated, suggesting coupling rela- tionship among C, N and P in leaf and fine root. Subsequently, we detected positively significant correlations in C, N, P and their ratios between leaf and fine root, suggesting proportional distribution of photosynthate and nutrient between aboveground and underground during plant growth. Generally, these results supplied fundamental data to understand mass turnover and nutrients cycling of leaves and roots in sand land.