Symbiotic Fungi: Principles and Practice (Soil Biology)

18 Analyses of Ecophysiological Traits of Tropical Rain Forest Seedlings 299
RGRbiomass fluctuated between 0.0093 and 0.0129 g g 1 day 1 for light-demanding
species, while for shade-tolerant species t fluctuated from 0.0014 to 0.0059
gg 1 day 1 (Fig. 18.3). Significant differences for all factors were registered: soil
(p < 0.002), AMF (p < 0.027), species (p < 0.001). In this case, Heliocarpus
donnellsmithii was the one with the highest growth rate, and all interactions were
significant: soil AMF (p < 0.001) being the soil from pastureland without AMF
the interaction with the lowest values of RGR based on biomass, soil species
(p < 0.001), species AMF (p < 0.001), soil AMF species (p < 0.001). The
interaction Ficus yoponensis TRF soil M + presented the highest growth rate,
and it was significantly different from all shade-tolerant species growing in
pastureland soil without AMF.
18.3.3.2 Survivorship
Survival percentage rates were between 19 and 51% for light-demanding species;
survivorship curve comparisons are showed in Table 18.2. For shade-tolerant
species survival percentages were between 20 and 33%, and survivorship curve
comparisons are showed in Table 18.3.
18.3.4 Remarks
In general, RGR based on height or biomass, and survivorship values were higher
for pioneer species than for shade-tolerant ones. All species suffered a high
mortality, mainly because of the dry season and the transplanting.
It is very interesting that in most species, the treatment with the highest RGR
response was not highest for survivorship. This probably has to do with the idea of
resource allocation: one individual can not allocate all resources to just one of its
functions, and certain functions always receive more resources. When resources are
allocated to height or biomass, survival is disadvantaged and vice versa.
Most species, independently of their life history traits, clearly improved their
growth or survivorship in tropical rain forest soil compared with pastureland,
which can probably be explained by soil quality. Quality implies a better structure
and a higher AMF diversity, etc. The former result is supported by the hypothesis
that AMF determine aboveground diversity (van der Heijden et al. 1998;
Klironomos et al. 2000; HartandKlironomos2002; van der Heijden 2002) and
every forest plant species depends on certain fungi species that are only found in
forest soil.
Grouping species by life history traits was insufficient because some of the
plant species broke with these classifications. We expected low growth rates and
higher response to AMF for shade-tolerant species, but we found that Ficus
yoponensis and F. insipida did not respond in that way; whereas we supposed
that pioneer species would have high growth rates and low response to AMF, but