Growth, biomass allocation and plant nitrogen concentration in Chilean temperate rainforest tree seedlings: effects of nutrient availability

Abstract

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.

Relative growth rate in phylogenetically related deciduous and evergreen woody species

“…Considering all the species without taking into account phylogeny, variation in RGR was explained by the variation in LAR and mostly in SLA. Similar results have been found in many studies of both herbaceous plants (Garnier 1992;Lambers and Poorter 1992;Poorter and Van der Werf 1998) and woody species (Reich and Walters 1992;Huante et al 1995;Cornelissen et al 1996Cornelissen et al , 1998Lusk et al 1997).…”

“…In these resource-rich habitats, the possession of a high SLA (more area per unit dry weight) and the associated high protein concentrations would allow greater efficiency in acquiring light and in photosynthesis, leading to better competitive ability. In fact, species with high SLA are usually found in nutrient-rich and productive habitats (Nielsen et al 1996;Lusk et al 1997). In addition, other important factors such as higher tolerance to both shade and/or frost can also be important for explaining the distribution of deciduous species.…”

Biomass allocation, growth, and photosynthesis of genotypes from native and introduced ranges of the tropical shrub Clidemia hirta

“…Evidence of greater shade tolerance of plants grown in low light would be seen in traits that maximize carbon gain and minimize carbon costs, such as higher SLA, LAR, LMR, and Amax as well as lower dark respiration rates and light compensation points. In particular, SLA should be greater for introduced genotypes because this trait has a strong positive relationship with RGR for many woody taxa, especially in low light conditions (Lusk et al 1997;Huante and Rincon 1998;Wright and Westoby 1999;Shipley 2002). Allocation patterns were also expected to differ because insect herbivores and fungal pathogens are abundant in Costa Rica, part of the native range, and almost absent in Hawaii, part of the introduced range (DeWalt et al 2004): introduced genotypes should allocate less to roots and more to above-ground growth and reproduction than native genotypes in the absence of natural enemies (Blossey and Nötzold 1995).…”

The impact of global climate change on tropical forest biodiversity in Amazonia

“…Laurelia philippiana, Lusk et al 1997). Under fertile conditions, these plants have characteristic high shoot:root ratios and high surface-area:volume ratios, as they are limited by light availability rather than nutrients.…”