毛竹向阔叶林扩展过程中的叶功能性状研究

为探明毛竹在异质生境下的适应特性和生存对策,开展毛竹向阔叶林扩展过程(1号样方为毛竹纯林,2号样方为毛竹占优势的竹阔混交林,3号样方为阔叶林占优势的混交林,4号样方为阔叶纯林)叶功能性状特性研究,并探讨不同年龄(Ⅰ~Ⅳ度)毛竹的叶功能性状在扩展方向的变化特征。结果表明:1)不同扩展样方间的叶干物质含量(LDMC)、叶C含量(C)、叶N:P比(N:P)差异显著,其中2号样方内LDMC显著高于4号样方,1号样方内C含量显著低于3号和4号样方,1号和2号样方内N∶P显著高于3号和4号样方。比叶面积(SLA)、叶N含量(N)、叶磷含量(P)及叶C∶N比(C∶N)在不同样方间差异不显著。说明毛竹对不同生境做出一定的适应性判断。2)不同年龄毛竹的SLA和LDMC在1号样方内出现显著差异,I度竹显著不同于III度和IV度竹;C含量和N含量在2号样方内不同年龄竹间产生显著性差异。C∶N仅在2号样方内不同年龄竹间差异达显著水平;N∶P在1~3号样方中差异显著,均表现为II度竹中最低,I度竹次之。说明不同年龄毛竹叶功能性状在1号样方内差异性较突出,2~4号样方内叶功能性状的特性可能是由于环境因素的作用消弱了毛竹自身发育间的差异。3)不同扩展样方内SLA与LDMC呈显著负相关关系、N与P呈显著正相关关系,SLA与C、N和P均呈正相关关系,而LDMC与C、N和P呈负相关关系。随SLA和LDMC变化,C变化最大,N次之,P变化最小,说明毛竹叶功能性状间的权衡关系沿扩展方向发生了适应性调整。 

Response of leaf functional traits of Moso bamboo during the invading process into the broad-leaved forest

As a clonal plant, Moso bamboo can invade surrounding forests; however, little information on the leaf functional traits of the species during the invading process is known. In this study, we examined dry matter content ( LDMC) , carbon content ( C) and stoichiometric ratios of leaves among four forest types ( type 1: pure bamboo forest, type 2:bamboo-dominated mixed forest, type 3: broad-leaved trees-dominated mixed forest, and type 4: nearly pure broad-leaved forest ) as well as at differentculm age classes (Ⅰ,Ⅱ,Ⅲ and Ⅳ) . The LDMC, C and N:P ratios were significantly different among the four forest types; the LDMC in type 2 was significantly higher than that in type 4 , the C in type 1 was significantly lower than that in types 3 and 4 , and N:P ratios in types 1 and 2 were higher than those in types 3 and 4. No significant differences were found for specific leaf area (SLA), leaf nitrogen content ( N) , leaf phosphours content ( P) and leaf N:P ratio among the four types. These results demonstrated that Moso bamboo has taken adaptive measuresto different habitats. With regard to the culm age, the SLA and LDMC were significantly different among the four culm age classes in type 1; for instance, both in class I differed remarkably from that in Ⅲ and Ⅳ, respectively. In type 2, the C, N and C:N ratio showed remarkable differences among the age classes, while N:P ratios were different in types 1 -3, having the lowest in classⅡ, followed by classⅠ. These findings indicated that the leaf functional traits caused by culm age was more distinct compared with other three forest types. The inconsistency of age effect was most likely caused by the stronger environmental influences,which counteracted the variation in growing culm with different ages in types 2-4 . Bivariate correlations indicated that SLA correlated significantly negatively with LDMC, but positively with C, N and P, while LDMC showed opposite relationships with C, N and P, respectively;N was positively correlated with P. When SLA and LDMC changed, the most notable variation occurred in C, followed by N, and least in P, suggesting that the stoichiometric ratios ( tradeoff) of leaf functional traits of Moso bamboo has presented adaptive adjustment during the invading process.