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TREE MORTALITY AND GROWTH IN 11 SYMPATRIC MACARANGA SPECIES IN BORNEO
Author(s) -
Davies Stuart James
Publication year - 2001
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1890/0012-9658(2001)082[0920:tmagis]2.0.co;2
Subject(s) - biology , interspecific competition , shade tolerance , ecology , forest dynamics , sympatric speciation , ecological succession , juvenile , canopy
Interspecific differences in tree performance due to variation in resource availability are expected to influence the structure and dynamics of tropical forest communities. Patterns of mortality and growth over 32 mo in 11 species of Macaranga were analyzed to investigate factors influencing tree spatial distributions and the dynamics of early successional communities. Tree performance was assessed in relation to variation in light levels, soil texture, and tree ontogeny. Rates of mortality and growth varied by over an order of magnitude among species. Species common in high‐light microsites had higher mortality and growth rates. Higher low‐light mortality for these species reflected lower shade tolerances, supporting the view that shade tolerance involves a trade‐off between high‐light growth and low‐light mortality. Logistic and multiple regressions were used to test for independent effects of tree size and microenvironment on performance in the 11 species. Mortality and growth were significantly related to tree size in nine and eight species, respectively. Higher mortality and lower growth rates for juvenile trees were common. Despite positive correlations between light availability and tree size, mortality rates increased in three species, and growth rates decreased in four species at larger tree sizes. This pattern was particularly strong in smaller statured shade‐intolerant species and may reflect changes in biomass allocation following reproductive onset. Declines in growth at larger tree sizes for only some species resulted in changes in species' performance rankings through succession. Low‐light mortality rates were strongly correlated with species' distributions in the forest with respect to light levels, whereas biases in distributions with respect to soil texture were not supported by differential mortality. For all trees pooled and in several species, growth showed a threshold response to light levels, being light‐limited in low light but not in high light. Across all light levels, soil texture significantly influenced growth in six species. Five species and all trees pooled had significantly lower growth on the more nutrient‐poor and potentially drought‐prone sandy soils. The dynamics of Macaranga ‐dominated early successional communities are strongly influenced by soil resource and light availability, coupled with species‐specific ontogenetic trajectories of performance.