湖北后河保护区珙桐的叶功能性状研究

该研究分析了珙桐群落主要叶功能性状之间的关系,比较了珙桐与林分其它优势树种以及珙桐Ⅰ级(胸径dbh<2.5 cm)、Ⅱ级(dbh2.5～22.5 cm)和Ⅲ级(dbh>22.5 cm)3个龄级间叶功能性状上的差异。结果表明,珙桐的比叶面积(SLA)与单位质量的叶建成成本(CCm)、单位面积的叶建成成本(CCa)呈显著负相关(p<0.01)。通过与林分其它优势树种相比较,珙桐具有较高的SLA、单位的质量的叶氮含量(Nmass);而CCm、CCa、单位面积的叶氮含量(Narea)却相对较低,这表明珙桐能较有效地利用有限资源。珙桐不同龄级的最大光合速率(Amax)、暗呼吸速率(Rd)、光补偿点(LCP)和光饱和点(LSP)均表现为珙桐Ⅲ级>Ⅱ级>Ⅰ级,而SLA则表现为Ⅰ级>Ⅱ级>Ⅲ级(p<0.05)。尽管珙桐Ⅰ级在林下表现出较强的弱光适应能力,但在后期建成为Ⅱ级的过程中,叶片形态与光合生理特性均表现出对遮荫环境的不适应,光资源不足可能是珙桐种群更新受限的主要限制因子之一。

Leaf functional traits of Davidia involucrate at Houhe Nature Reserve in Hubei

This paper studied the correlations among the main leaf functional traits in tree species in Davidia involucrate communities at the Houhe Nature Reserve in Hubei.The main leaf functional traits were compared between D.involucrata and other dominant trees by age classes first class(dbh<2.5 cm),second class(dbh=2.5 22.5 cm)and third class(dbh>22.5 cm)].Results showed that specific leaf area(SLA) had significantly negative correlations with both the mass-based(CCm) and area-based(CCa) leaf construction cost(p<0.01).A higher SLA and mass-based leaf nitrogen concentration(Nmass) but lower CCm,CCa,and area-based leaf nitrogen concentration(Narea) were found in D.involucrate as compared with other tree species,suggesting a more efficient capture of limiting resources in D.involucrate than in other species.Maximum rate of photosynthesis(Amax),dark respiration rate(Rd),light compensation point(LCP),and light saturation point(LSP) were all ranked in the order of third class > second class > first class,but SLA showed a reverse sequence(p<0.05).Results in this study suggest that D.involucrata has a flexible light-adaptation strategy in its early growth phase as first class under the shade,but becomes shade-intolerant when growing into second class.Light limitation is likely one of the major constraints in population growth of D.involucrate.