亚热带常绿林不同冠层小枝叶面积-叶生物量关系研究

Relationship between leaf area and leaf biomass of different canopies in subtropical evergreen forest

叶面积与叶生物量的关系对于理解植物叶片的碳收益和投资权衡策略具有重要意义。收益递减假说认为植物的叶面积与叶生物量成显著异速生长关系,其异速生长指数<1.0,但该假说是否适用于不同生活型(常绿与落叶)亚热带木本植物不同冠层高度(上下冠层)当年生小枝的叶片仍不清楚。以江西亚热带常绿阔叶林的69种常绿与落叶木本植物当年生小枝上的叶为研究对象,采用标准化主轴回归估计(standardized major axis estimation,SMA)方法检验不同冠层高度和生活型叶面积与叶生物量的异速生长关系。结果显示:(1)当年生小枝叶生物量在不同冠层高度和生活型的植物中无显著差异(P>0.05),叶面积在常绿和落叶植物中有显著差异(P<0.05),常绿和落叶植物的比叶重存在显著差异(P<0.05),而落叶植物的比叶重在不同冠层高度存在显著差异(P<0.05),同一冠层,常绿植物比叶重显著高于落叶植物(P<0.05);(2)69种植物的叶面积与叶生物量异速生长指数具有物种特异性,60.9%的物种叶面积与叶生物量呈等速生长关系;(3)不同冠层和生活型植物的叶面积与叶生物量呈等速生长关系,但其异速生长常数在不同冠层高度与生活型间存在差异。这些结果表明冠层高度和生活型未改变叶面积-生物量之间的等速生长关系,不支持"收益递减"假说。

The relationship between leaf area and leaf biomass is important for understanding the trade-off between leaf carbon investment and return.According to the"diminishing returns hypothesis",the leaf area should scale allometrically with leaf biomass,with the allometric scaling exponent<1.0.However,it is not clear whether such hypothesis holds true for the leaves belonging to the different canopy height(upper and lower canopy)and different life types(evergreen and deciduous)of subtropical woody plants.The standardized major axis regression method was used to test the scaling relationship between leaf area and leaf biomass of 69 woody plants in Yangjifeng Nature Reserve,Jiangxi.The results showed that the leaf area differed significantly between evergreen and deciduous plants(P<0.05),whereas,no significant difference in the biomass of small branches and leaves were detected in the current year twigs in different life types and in different canopy heights(P>0.05).The leaf mass per area(LMA)of evergreen and deciduous plants was significantly different(P<0.05).At the same canopy height,the LMA of evergreen plants was significantly higher than that of deciduous plants(P<0.05).Furthermore,LMA of deciduous plants differed significantly in different canopy heights(P<0.05).The scaling exponents between leaf area and leaf biomass plants varied significantly among 69 subtropical woody species.60.9%of species showed isometric relationship between leaf area and leaf biomass.Furthermore,the scaling relationship between leaf area and leaf biomass of different canopy heights and life types all shared the sometric exponent,but with different scaling constants.These results indicated that canopy heights and life types did not change the isometric scaling relationship between leaf area and biomass for such in 69 subtropical woody species,and did not support the"diminishing returns"hypothesis.