Lusk C H, Contreras Olga, Figueroa Javier
Departamento de Ciencias Biológicas, Universidad de Talca, Casilla 747, Talca, Chile , , , , , , CL.
Departamento de Botánica, Universidad de Chile, Casilla 653, Santiago, Chile, , , , , , CL.
Oecologia. 1996 Dec;109(1):49-58. doi: 10.1007/s004420050057.
Seedlings of nine southern Chilean trees were grown at three nutrient supply rates, to examine the roles of growth rate, biomass distribution and nutrient use traits in determining species natural distributions on resource gradients. Relative growth rate (RGR) showed no overall relationship with species site requirements, although RGR of fertile-site species tended to be more responsive to nutrient supply. In the low-nutrient treatment, infertility-tolerant Fitzroya cupressoides showed a higher RGR rank than a fertility-demanding species (Laurelia philippiana) which outgrew it substantially at the highest supply rate. This reversal of RGR ranks was associated with divergent nutrient use responses: at high nutrient supply both spp. had similar plant nitrogen concentrations (PNC), whereas at the low supply rate Fitzroya's production of biomass per unit of assimilated N was twice that of Laurelia's. However, this pattern does not appear to serve as a general explanation of the respective distributions of the study species, as RGR ranks of most species were unaltered by nutrient supply. At low nutrient availability, no clear differences in shoot:root ratio (SRR) were apparent between poor-site and fertile-site species. However, at high nutrient availability, SRR was markedly higher in the latter, resulting from differences in biomass allocation to stems (not leaves). Leaf area ratios (LAR) were higher in fertile-site species than in those tolerant of low fertility, because of differences in specific leaf area rather than leaf weight ratio. Very high LAR at high nutrient supply was characteristic of most shade-tolerant angiosperms, but not of shade-tolerant conifers. Although PNC showed no overall differences between poor- and fertile-site species, sensitivity of PNC to external supply rate was greatest in two infertility-tolerant conifers. In contrast, the angiosperm Weinmannia trichosperma, although tolerant of low fertility, responded to increased nutrient supply with greatly increased RGR and little change in PNC. Results show little trait convergence between conifers and angiosperms in adaptation both to shade and to infertile soils; i.e. fitness of different taxa in a given environment may hinge on different trait combinations.
对智利南部9种树木的幼苗在3种养分供应水平下进行培育，以研究生长速率、生物量分配和养分利用特性在决定物种在资源梯度上的自然分布中的作用。相对生长速率（RGR）与物种的立地需求总体上没有关系，尽管生长在肥沃立地的物种的RGR往往对养分供应更敏感。在低养分处理中，耐贫瘠的智利柏的RGR排名高于对肥力要求较高的物种（菲律宾月桂树），而在最高养分供应水平下，菲律宾月桂树的生长量远超智利柏。RGR排名的这种逆转与不同的养分利用反应有关：在高养分供应下，两个物种的植物氮浓度（PNC）相似，而在低养分供应水平下，智利柏每单位同化氮的生物量产量是菲律宾月桂树的两倍。然而，这种模式似乎并不能普遍解释研究物种各自的分布情况，因为大多数物种的RGR排名并未因养分供应而改变。在低养分有效性条件下，生长在贫瘠立地和肥沃立地的物种之间的茎根比（SRR）没有明显差异。然而，在高养分有效性条件下，后者的SRR明显更高，这是由于生物量分配到茎（而非叶）上的差异所致。肥沃立地物种的叶面积比（LAR）高于耐低肥力物种，这是由于比叶面积的差异而非叶重比的差异。在高养分供应下，非常高的LAR是大多数耐荫被子植物的特征，但耐荫针叶树并非如此。尽管贫瘠立地和肥沃立地物种之间的PNC总体上没有差异，但两个耐贫瘠针叶树的PNC对外界供应速率的敏感性最大。相比之下，被子植物毛籽文冠果虽然耐低肥力，但随着养分供应增加，其RGR大幅增加，而PNC变化不大。结果表明，针叶树和被子植物在适应荫蔽和贫瘠土壤方面几乎没有性状趋同现象；也就是说，不同分类群在特定环境中的适合度可能取决于不同的性状组合。
