Trade–off between growth and survival of juvenile trees species of cerrado savanna in central Brazil

Background/Question/Methods

In spatially heterogeneous environment a trade-off between growth in high light and survival in the shade has been indicated as a key mechanism promoting species coexistence by niche divergence. Although many studies were performed in the tropical and temperate forest, no study investigated this hypothesis in the savanna. For seven naturally established juvenile tree species in cerrado (Neotropical savanna) of central Brazil, I selected and fitted the best model between stem relative growth rates (RGR) with increasing tree cover among three alternative models with Akaike Information Criterion (AIC). The plant light compensation points (PLCP) were RGR is zero in the maximum tree cover was recorded for each species. The maximum RGR in the high light environment and the annual mortality was calculated in the shade for each species during the period of the census. The relationship between maximum RGR in high light environment and mortality in the shade was examined with Pearson (r) correlation and phylogenetic independent contrast (r_PIC).

Results/Conclusions

Among the three models, the power growth model showed the lowest AIC and performed best. Species differed in the growth response with increasing tree cover from linear to curve–linear. The PLCP differed significantly among species. Two species were shade intolerant with high RGR, and low PLCP and three were shade tolerant with low RGR and high PLCP. A strong and significant positive relationship between RGR in shade and RGR in high light was observed across species (r = 0.82, P = 0.011 and r_PIC = 0.80, P = 0.015). Species with the higher RGR in the shade also realized a higher RGR in high light environments. The mortality rate in shade was significantly positively correlated with RGR in high light environment (r = 0.86, P = 0.007 and r_PIC = 0.90, P = 0.003). The intolerant shade species showed a higher mortality rate than shade-tolerant species. These results indicate that species with higher growth in high light has a low survival in the shade under tree cover showing that this result is consistent with the hypothesis of a trade-off between growth in high light and survival in shade habitats in cerrado. This result also extends the occurrence of this trade-off further than previously recorded in temperate and tropical forest to include the cerrado savanna and indicate a more general pattern for this mechanism.