基于地理种源的刨花楠苗木比叶面积与叶片化学计量学关系

探讨植物比叶面积(SLA)与叶片碳(C)、氮(N)、磷(P)化学计量学关系,能够反映植物为获取最大光合生产所采取的内部调控机制,共同体现植物的适应策略。利用生长于同一土壤与气候环境中培育的刨花楠(Machilus pauhoi)1年生苗木,对其SLA与叶片C、N、P含量进行测定,并对SLA与叶片C、N、P化学计量学特征及其与种源地环境因子的关系进行分析。结果表明:(1)叶片养分含量的变异系数大小排序为CNP;SLA与叶片N、P含量呈显著的正相关,与叶片C∶N及C∶P呈极显著的负相关。(2)SLA与经度、年均温、年降水量呈显著负相关;叶片C、N、P含量也受种源地环境因子影响,其中以海拔最为重要。研究结果有助于理解刨花楠苗木的生存适应对策,对探究刨花楠对养分的资源利用效率等具有重要意义。

Variation in relationships between SLA and Leaf C, N, P stoichiometry in Machilus pauhoi among locations

Machilus pauhoi is a native subtropical forest hardwood species. Due to its ecological and economic importance and its growing market demand, it is necessary to explore the survival strategies of M. pauhoi. Specific leaf area (SLA), leaf nitrogen, and phosphorus concentration are closely associated with plant performance. For example, SLA is closely related to plant growth and survival strategies. The elements C, N, and P are mainly biogenic elements in plants and relatively stable leaf C, N, and P stoichiometry is fundamental to plant growth and physiological processes. C is a structural material, while N and P are the limiting elements for the plant growth. Therefore, the relationships between leaf nutrients (i.e., C, N, P concentration) and SLA are of considerable interest to researchers attempting to understand nutrient resource use efficiency, as well as to those interested in plant ecological adaption and survival strategies. To understand the mechanisms underlying variation in leaf nutrients and SLA among geographic locations, one-year old seedlings of M. pauhoi were collected from five counties in Jiangxi Province. Leaf C, N, P stoichiometry, and SLA were compared and the relationships between these traits and associated environmental factors analyzed. The results indicated that across the five M. pauhoi populations, mean leaf C, N, and P concentrations were 45.94%, 1.983% and 0.244% respectively. Leaf C concentration had the lowest coefficient of variation (0.0123), whereas leaf P concentration had the highest coefficient of variation (0.2233). Mean values of C/N, C/P, and N/P were 23.7, 224.81, and 9.482, respectively, across the five M. pauhoi populations. SLA was positively correlated with leaf N and P and negatively related to leaf C:N and C:P ratios. However, SLA showed no significant relationship with leaf C concentration, which might result from the relatively constant leaf C concentration among the five populations. Furthermore, SLA showed negative relationships with longitude, mean annual temperature and mean annual precipitation, indicating that SLA was sensitive to environmental factors. Likewise, leaf C, N, and P concentrations were also influenced by spatial variation in environmental factors. Altitude was the most important environmental factor influencing leaf nutrient variation among the five M. pauhoi populations. Our study suggests that it is useful to explore the efficiency of nutrient utilization in plants, and will aid understanding of the survival strategies of M. pauhoi seedlings. However, further studies are needed to understand the relationships between SLA and stoichiometry of leaf C, N, P which may change in later growth stages.