Seedling interactions in a tropical forest in Panama

Abstract

Competition is believed to be a central force limiting local diversity and controlling the structure of plant communities. However, it has been proposed that the stressed understory environment limits total understory plant density to such low levels that competitive exclusion cannot be an important factor limiting the local diversity of understory plants. To evaluate the importance of inter-seedling competition, we performed a seedling competition experiment with five shade-tolerant species in a tropical moist forest in Panama. Three-month-old seedlings were transplanted into the forest singly or with their roots intertwined with a single conspecific or heterospecific seedling in all pairwise species combinations. If competition is important, performance (survival, stem height, and number of leaves after one and six years) would be expected to be lowest with a conspecific neighbor and greatest without a neighbor. The experiment was replicated in five 0.24-m(2) plots at each of 20 sites in tall secondary forest. To test whether seedling performance differed among treatments we fitted linear mixed models (LMM) and generalized linear mixed models (GLMM), treating species identity and microsite (site and plot) as random effects. The five shade-tolerant study species all experienced good establishment with relatively high survival and growth rates. The neighbor treatment consistently affected seedling performance, but the effect was always very small, both in absolute terms and relative to the much stronger species and microsite effects. Seedlings with a conspecific neighbor consistently performed worse than seedlings with a heterospecific neighbor, but having no neighbor generally did not cause superior performance relative to the other treatments. We conclude that direct competitive interactions are relatively unimportant among understory plants in humid tropical forests.

Dispersal and microsite limitation of a rare alpine plant

“…Such microsites created by disturbance may include increased light availability and higher soil temperatures, which were measured in plots free from vegetation in another sowing experiment (Chambers et al 1990). Interspecific competition Plant Ecol (2012) 213:395-406 403 was also reduced by our disturbance regime, but intraspecific competition could still be present in disturbed plots, which is assumed to be higher than competition between seedlings of different plant species (Svenning et al 2008). Intraspecific competition for nutrients might at least partially explain the low survival rate in the second year, which was nearly half of that observed in the first year (Table 4), when seedlings were smaller and their roots were less intermingled.…”

“…At the local scale, distribution is theoretically limited by the availability of either microsites or seeds E. S. Frei (&) Á J. F. Scheepens Á J. Stöcklin Section of Plant Ecology, Institute of Botany, University of Basel, Schönbeinstrasse 6, 4056 Basel, Switzerland e-mail: eva.frei@unibas.ch (Münzbergova and Herben 2005). However, in nature, local distribution seems to be influenced by a complex interaction of microsite availability, seed limitation, and inter-or intraspecific competition between seedlings (Svenning et al 2008;García-Camacho et al 2010;Egawa and Tsuyuzaki 2011).…”

Local neighborhood and species' shade tolerance influence survival in a diverse seedling bank

“…Negative effects of conspecific neighbors may also result from intense competition between conspecifics. However, recent studies have shown seedling-seedling competition in tropical forests to be weak (Paine et al 2008, Svenning et al 2008.…”

Seasonal and spatial variation in water availability drive habitat associations in a tropical forest

“…We propose that this tolerance allows plateau specialists to persist in the seedling layer of the drier habitat, while less drought-tolerant species drop out over time due to seasonal water limitation. While competition between seedlings is generally weak in tropical forests (Paine et al 2008, Svenning et al 2008, it is likely to intensify when the seedling layer responds to canopy openings. In the drier plateau habitat, advanced regeneration will largely be composed of drought-tolerant species (i.e., they will be present in greater numbers than less tolerant ones) and will therefore be more likely to win open sites.…”