J Plant Ecol ›› 2015, Vol. 8 ›› Issue (4): 359-367 .DOI: 10.1093/jpe/rtu028

• Research Articles • Previous Articles     Next Articles

In the lack of extreme pioneers: trait relationships and ecological strategies of 66 subtropical tree species

Cristiane Forgiarini1,4, Alexandre F. Souza2,*, Solon J. Longhi3 and Juliano M. Oliveira1   

  1. 1 Programa de Pós-Graduação em Biologia, Diversidade e Manejo da Vida Silvestre, Universidade do Vale do Rio dos Sinos, Av. UNISINOS 950, C.P. 275, São Leopoldo 93022-000, RS, Brazil; 2 Departamento de Ecologia, CB, Universidade Federal do Rio Grande do Norte, Campus Universitário, Lagoa Nova, Natal 59072-970, RN, Brazil; 3 PPG-Engenharia Florestal, Dep. de Ciências Florestais, Universidade Federal de Santa Maria, Av. Roraima, s/n, Bairro Camobi, Santa Maria 97105-900, RS, Brazil; 4Present address: Departamento de Botânica, Instituto Biociências, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 9500, Prédio 43433, Campus Agronomia, Porto Alegre 91501-970, RS, Brazil
  • Received:2014-04-29 Accepted:2014-10-12 Published:2015-07-24
  • Contact: Souza, Alexandre

In the lack of extreme pioneers: trait relationships and ecological strategies of 66 subtropical tree species

Abstract: Aims Despite the growing interest in the topic of functional ecology, there are still forest regions that have not been examined, as most work has been done in the tropics. Unresolved issues include the strength of a growth-mortality trade-off in trees (originally identified for seedlings) and the nature of the association between plant traits and vital rates, if any. Our objectives were to examine whether (i) ecological strategies in South American mixed forests are organized along the fast competitor × slow stress-tolerator and height gradients as the main strategy axes depicted in the overall trait and vital rate correlation structure, and (ii) a tentative path model we proposed can explain the patterns of covariation among traits and vital rates.
Methods We studied a different habitat (subtropical mixed conifer-hardwood forests) and region (Brazilian Atlantic Forest) from the majority of related studies in forests, carried out in the Neotropical region. Data on total height, stem slenderness, crown depth, wood density, specific leaf area, leaf and seed length, seed dispersal mode, annual mortality, diameter relative growth rate and relative growth rate under favorable conditions were measured in southern Brazil for 66 tree species. Data were subjected to principal components analysis and path analysis. Restricted data on saplings and treelets were analyzed through correlation.
Important findings Studied traits were reduced to four principal components. Principal components analysis produced axes that fit the resource acquisition versus resource-conservation and the height-mortality trade-offs, although the former was split into two distinct axes. Seed size and seed dispersal mode appeared independently of these axes. A path model showed that leaf length and specific leaf area caused direct changes in trunk slenderness and, indirectly through growth, affected mortality. Expected trade-offs between growth and survivorship and between wood density and stem slenderness trade-offs were not found. This may result from the lack of extreme pioneers and over-representation of slow-growing hardwood species found in Atlantic subtropical forests of South America. This suggests that the fastest growing species in the region do not grow so fast as to compromise wood density and survivorship, but grow fast enough to benefit from increased size. Relationships between traits and vital rates seem to be mediated by the assembly process of regional floras, and the relative importance of traits like SLA and wood density may vary between floristic regions.

Key words: Araucaria angustifolia, Atlantic forest, ecological strategies, life-history trade-offs, mixed forests

摘要:
Aims Despite the growing interest in the topic of functional ecology, there are still forest regions that have not been examined, as most work has been done in the tropics. Unresolved issues include the strength of a growth-mortality trade-off in trees (originally identified for seedlings) and the nature of the association between plant traits and vital rates, if any. Our objectives were to examine whether (i) ecological strategies in South American mixed forests are organized along the fast competitor × slow stress-tolerator and height gradients as the main strategy axes depicted in the overall trait and vital rate correlation structure, and (ii) a tentative path model we proposed can explain the patterns of covariation among traits and vital rates.
Methods We studied a different habitat (subtropical mixed conifer-hardwood forests) and region (Brazilian Atlantic Forest) from the majority of related studies in forests, carried out in the Neotropical region. Data on total height, stem slenderness, crown depth, wood density, specific leaf area, leaf and seed length, seed dispersal mode, annual mortality, diameter relative growth rate and relative growth rate under favorable conditions were measured in southern Brazil for 66 tree species. Data were subjected to principal components analysis and path analysis. Restricted data on saplings and treelets were analyzed through correlation.
Important findings Studied traits were reduced to four principal components. Principal components analysis produced axes that fit the resource acquisition versus resource-conservation and the height-mortality trade-offs, although the former was split into two distinct axes. Seed size and seed dispersal mode appeared independently of these axes. A path model showed that leaf length and specific leaf area caused direct changes in trunk slenderness and, indirectly through growth, affected mortality. Expected trade-offs between growth and survivorship and between wood density and stem slenderness trade-offs were not found. This may result from the lack of extreme pioneers and over-representation of slow-growing hardwood species found in Atlantic subtropical forests of South America. This suggests that the fastest growing species in the region do not grow so fast as to compromise wood density and survivorship, but grow fast enough to benefit from increased size. Relationships between traits and vital rates seem to be mediated by the assembly process of regional floras, and the relative importance of traits like SLA and wood density may vary between floristic regions.