Functional explanations for variation in bark thickness in tropical rain forest trees

Abstract

Summary1. The complex structure of tree bark reflects its many functions, which include structural support as well as defence against fire, pests and pathogens. Thick bark, however, might limit respiration by the living tissues of the trunk. Nevertheless, little research has addressed community-level variation in bark thickness, and to the best of our knowledge, no one has tested multiple hypotheses to explain variation in bark thickness. 2. We conducted an extensive survey of bark thickness within and among species of trees in the tropical rain forests of French Guiana. Trunk bark thickness increased by 1AE2 mm per 10 cm increase in stem diameter, and varied widely at all taxonomic levels. Mean trunk bark thickness was 4AE5 mm (range: 0AE5-29 mm), which was less that found in two Amazonian rain forests in previous studies. This survey of bark thickness should be of use for forest management since tree survival through fire is strongly predicted by bark thickness. 3. We combined the survey data with multiple datasets to test several functional hypotheses proposed to explain variation in bark thickness. We found bark to provide an average of 10% of the flexural rigidity of tree stems, which was substantially less than that found in the only other study of bark stiffness. Bark thickness was uncorrelated with species' association with fire-prone habitats, suggesting that the influence of fire on bark thickness does not extend into moist Forests. There was also little evidence that bark thickness is affected by its function as a defence against herbivory. Nor was there evidence that thick bark limits trunk respiration. 4. A re-analysis of previously collected anatomical data indicated that variation in rhytidome (non-conducting outer bark) thickness explains much of the variation in overall bark thickness. As rhytidome is primarily involved in protecting the living tissues of the trunk, we suggest that bark thickness is driven mostly by its defensive function. 5. Functional explanations for the variation in bark thickness were not clear-cut. Nevertheless, this study provides a foundation for further investigation of the functional bases of bark in tropical trees.

Hydrological properties of bark of selected forest tree species. Part 2: Interspecific variability of bark water storage capacity

“…The long time of experiments indicates the complexity of the processes of filling the bark retention container. Paine et al (2010) showed that total bark thickness is dependent on rhytidome thickness. Given the strong dependence of bark thickness H on the breast height diameter of trees for particular species (Fig.…”

Environmental factors predict community functional composition in Amazonian forests

“…A longer dry season thus simultaneously filters for wood traits related to resource conservation, and conversely for leaf traits related to resource acquisition (Table S4), suggesting that tropical trees can invest differentially in wood and leaf tissues to optimize their performance across environmental gradients. The functional significance of bark thickness in tropical forests is still unclear (Paine et al 2010), but our results suggest that bark thickness could be related to climatic parameters. Additionally, changes in leaf area could also be affected by climate, because smaller leaves could better avoid overheating by limiting the surface irradiated by the sun.…”

Rebrota de indivíduos lenhosos em área de cerrado sentido restrito como resposta ao fogo

“…Cerrado apresentam características que lhes conferem resistência ou que favorecem sua rápida recuperação quando há ocorrência de fogo (COUTINHO, 1990;PAINE et al, 2010;SATO et al, 2010). Entre estas características podemos destacar ritidomas espessos e corticosos (HOFFMANN et al, 2009), órgãos de reserva subterrâneos MIRANDA et al, 2002) e elevado investimento em biomassa de raiz (HOFFMANN; FRANCO, 2003a;OLIVEIRA et al, 2005).…”

“…presença de ritidomas espessos e corticosos HOFFMANN et al, 2009;MIRANDA et al, 2002;PAINE et al, 2010;PAUSAS, 2014), presença de órgãos de reserva subterrâneos (CLARKE et al, 2013;MIRANDA et al, 2002), nível de investimento em biomassa de raiz (HOFFMANN; FRANCO, 2003a;OLIVEIRA et al, 2005) e capacidade de rebrota (CLARKE et al, 2010;HOFFMANN;MOREIRA et al, 2008;RIBEIRO et al, 2012).…”

“…Entre as estratégias adaptativas associadas ao fogo está a forte suberização do tronco e dos galhos, o que contribui para o isolamento térmico dos tecidos internos, mesmo em altas temperaturas (COUTINHO, 1990;MIRANDA et al, 2002;MOREIRA et al, 2007;PAINE et al, 2010;PAUSAS, 2014); elevado investimento em biomassa radicular (HOFFMANN ;FRANCO, 2003b); grande capacidade de armazenamento de água e carboidratos no caule (BUCCI et al, 2004) e em órgãos subterrâneos (CLARKE et al, 2013;OLIVEIRA et al, 2005). Também é evidenciada a alta capacidade de rebrota (COUTINHO, 1990;HOFFMANN, 1998;MOREIRA et al, 2008;PAUSAS;KEELEY, 2014).…”