Interspecific variation of functional traits in a CAM-tree dominated sandy coastal plain

Abstract

Question: Although the restinga vegetation lies adjacent to the species-rich Atlantic Rainforest, fewer species thrive due to low available resources of the sandy substrate. We asked whether there is a specific set of functional traits related to the ability to attain high dominance in a restinga dominated by a CAM photosynthesis tree. Location: Restinga of Jurubatiba National Park, north of the state of Rio de Janeiro, Brazil. Methods: We chose traits that are commonly used in large screenings, leaf mass per area (LMA), leaf longevity (LL) and leaf nitrogen concentration (LNC). We also measured the functional traits, midday leaf water potential (C min ), pressure-volume curves, nitrogen isotope discrimination (d 15 N) and chlorophyll fluorescence. We compared species using ANOVA and ordination analysis. Results: The two most dominant species differed from subordinate species in terms of leaf succulence (SUC) and C min . However, they were also significantly different from each other in LMA, SUC, leaf thickness and LNC. C min and d 15 N had the strongest loadings on the third ordination axis, which, despite explaining only 18.2% of total variance, was the only axis reflecting variation in species dominance. Conclusions: Despite high interspecific variation, the most common traits of the leaf economic spectrum were not directly associated with variation in species dominance. In contrast, the bulk modulus of elasticity, C min and d 15 N were important not only to track the connection between plant traits and environmental factors, but also between plant traits and community structure.

Going Back to Basics: Importance of Ecophysiology when Choosing Functional Traits for Studying Communities and Ecosystems

“…Is the biological meaning of a given trait the same under different ecological contexts, spatial and temporal scales or in different regions of the globe? Apparently, the answer is "no" (Witkowski & Lamont 1991;Rosado & de Mattos 2010;Wright & Sutton-Grier 2012). Some global trade-offs between traits reflecting contrasting resource use strategies (Wright et al 2004) do not hold among environments subjected to varying conditions (Rosado & de Mattos 2010;Wright & Sutton-Grier 2012).…”

“…Apparently, the answer is "no" (Witkowski & Lamont 1991;Rosado & de Mattos 2010;Wright & Sutton-Grier 2012). Some global trade-offs between traits reflecting contrasting resource use strategies (Wright et al 2004) do not hold among environments subjected to varying conditions (Rosado & de Mattos 2010;Wright & Sutton-Grier 2012). Therefore, the choice of traits to up-scale responses of individuals to communities and ecosystems should be based on their adequacy under a specified ecological context.…”

“…Due to the successful explanation of global patterns of trait variation and the relatively easy measurements, some functional traits have become widely used. However, it is starting to be questioned whether the status of such "fashionable traits" is always justified (Díaz et al 2002;Rosado & de Mattos 2010;Wright & Sutton-Grier 2012). Is the biological meaning of a given trait the same under different ecological contexts, spatial and temporal scales or in different regions of the globe?…”

“…When the chosen trait is the product of other underlying traits it is necessary to investigate if the latter respond independently to the environmental driver of interest. If so, it is essential to use the underlying traits instead of the resultant trait (Witkowski & Lamont 1991;Rosado & de Mattos 2010).…”

Variações fenotípicas em Andira fraxinifolia Benth. (Fabaceae) em duas fitofisionomias de Restinga

“…Nos ambientes de Restinga, os resultados apontaram que as mais evidentes variações fenotípicas são as morfoanatômicas (massa foliar por área, espessura foliar, densidade foliar, suculência foliar e densidade da madeira), as fisiológicas (concentração de clorofilas a + b, potencial de água na folha, módulo de volume de elasticidade, pressão osmótica e isótopos estáveis de 15 N, 16 O e 1 H) e as fenológicas (taxas de rotatividade, longevidade e mortalidade de foliar) (Franco et al 1996, Scarano et al 2001, Berg et al 2004, Dias et al 2006, Cavalin & de Mattos 2007, Gessler et al 2008, Rosado & de Mattos 2010, Rosado et al 2013 Andira fraxinifolia Benth (Fabaceae) é uma planta lenhosa, perenifólia, heliófila, seletiva higrófita, endêmica no Brasil e característica da Mata Atlântica (Lorenzi 1992). Ocorre em abundância nas florestas tropicais da costa atlântica do país, incluindo as florestas de Restinga (Pennington 1996).…”