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A complex set of interactions among neighbors influences plant performance and community structure. Understanding their joint operation requires extensive information on species characteristics and individual performance. We evaluated first-year survival of 35 719 tropical forest seedlings of 222 species and 15 annual cohorts relative to the density of conspecific and heterospecific neighbors and the phylogenetic similarity of heterospecific neighbors. Neighbors were from two size classes, and size asymmetric interactions provided insight into likely mechanisms. Large heterospecific and conspecific neighbors reduced seedling survival equally, suggesting resource competition rather than host-specific enemies as a mechanism. In contrast, much stronger negative conspecific effects were associated with seedling neighbors capable of limited resource uptake, suggesting shared pests rather than competition as the mechanism. Survival improved, however, near phylogenetically similar heterospecific neighbors, suggesting habitat associations shared among closely related species affect spatial patterns of performance. Improved performance near phylogenetically similar neighbors is an emerging pattern in the handful of similar studies. [ABSTRACT FROM AUTHOR]

It has been hypothesized that tropical trees partition forest light environments through a life history trade-off between juvenile growth and survival; however, the generality of this trade-off across life stages and functional groups has been questioned. We quantified trade-offs between growth and survival for trees and lianas on Barro Colorado Island (BCI), Panama using first-year seedlings of 22 liana and 31 tree species and saplings (10mm < dbh < 39 mm) of 30 tree species. Lianas showed trade-offs similar to those of trees, with both groups exhibiting broadly overlapping ranges in survival and relative growth rates as seedlings. Life history strategies at the seedling stage were highly correlated with those at the sapling stage among tree species, with all species showing an increase in survival with size. Only one of 30 tree species demonstrated a statistically significant ontogenetic shift, having a relatively lower survival rate at the sapling stage than expected. Our results indicate that similar life history trade-offs apply across two functional groups (lianas and trees), and that life history strategies are largely conserved across seedling and sapling life-stages for most tropical tree species. [ABSTRACT FROM AUTHOR]

1 The role of seed limitation in tropical forests remains uncertain owing to the scarcity of experimental evidence. We performed seed addition experiments to assess seed limitation for 32 shade-tolerant tropical forest species and monitored the natural seed rain of 25 of these species for 17 years. 2 One, two or five seeds were sown into 0.0079-m2 plots for large- ( n = 5 species), medium- ( n = 5) and small-seeded species ( n = 22), respectively. The experiment was replicated at 69 sites, placed in groups of three at 23 locations. Seedling establishment was evaluated after 1 and 2 years in paired seed addition and control plots. Natural seedling emergence and understorey plant density were also measured. 3 Median natural seed rain was 0.31 seeds m−2 year−1 per focal species. 4 Seed addition enhanced seedling establishment in 31 and 26 of the 32 species after 1 and 2 years, respectively. Mean number of focal species’ seedlings after 2 years was 0.002 seedlings in control plots and 0.12, 0.37 and 0.60 seedlings in seed addition plots for large-, medium- and small-seeded species, respectively. 5 A 25 seeds added treatment increased seedling establishment by ≥ 2.0-fold over the five seeds added treatment after 2 years. 6 Community-wide recruitment and understorey plant density were strongly seed-limited. The natural density of understorey plants averaged 12 plants m−2 and was significantly less than for seedlings of the single focal species in plots with ≥ 2 seeds added 2 years earlier. 7 The number of established seedlings per seed added was independent of seed size. 8 Treatment (adding zero or five seeds), species identity and location all affected seedling establishment for the 11 small-seeded species represented at all sites, with treatment and its interactions accounting for 86% of the explained variation. 9 Our results suggest that seed limitation plays a dominant role in seedling recruitment and understorey plant community assembly in tropical forests. Although strong seed limitation may set the stage for species-neutral community assembly, the species differences in seedling establishment rate and its spatial variation demonstrate an important role for species-specific processes. [ABSTRACT FROM AUTHOR]

The 'functional traits' of species have been heralded as promising predictors for species' demographic rates and life history. Multiple studies have linked plant species' demographic rates to commonly measured traits. However, predictive power is usually low - raising questions about the practical usefulness of traits - and analyses have been limited to size-independent univariate approaches restricted to a particular life stage., Here we directly evaluated the predictive power of multiple traits simultaneously across the entire life cycle of 136 tropical tree species from central Panama. Using a model-averaging approach, we related wood density, seed mass, leaf mass per area and adult stature (maximum diameter) to onset of reproduction, seed production, seedling establishment, and growth and survival at seedling, sapling and adult stages., Three of the four traits analysed here (wood density, seed mass and adult stature) typically explained 20-60% of interspecific variation at a given vital rate and life stage. There were strong shifts in the importance of different traits throughout the life cycle of trees, with seed mass and adult stature being most important early in life, and wood density becoming most important after establishment. Every trait had opposing effects on different vital rates or at different life stages; for example, seed mass was associated with higher seedling establishment and lower initial survival, wood density with higher survival and lower growth, and adult stature with decreased juvenile but increased adult growth and survival., Forest dynamics are driven by the combined effects of all demographic processes across the full life cycle. Application of a multitrait and full-life cycle approach revealed the full role of key traits, and illuminated how trait effects on demography change through the life cycle. The effects of traits on one life stage or vital rate were sometimes offset by opposing effects at another stage, revealing the danger of drawing broad conclusions about functional trait-demography relationships from analysis of a single life stage or vital rate. Robust ecological and evolutionary conclusions about the roles of functional traits rely on an understanding of the relationships of traits to vital rates across all life stages. [ABSTRACT FROM AUTHOR]

Extreme events shape population and community trajectories. We report episodic mortality across common species of thousands of long-lived perennials individually tagged and monitored for 20 years in the Colorado Desert of California following severe regional drought. Demographic records from 1984 to 2004 show 15 years of virtual stasis in populations of adult shrubs and cacti, punctuated by a 55–100% die-off of six of the seven most common perennial species. In this episode, adults that experienced reduced growth in a lesser drought during 1984–1989 failed to survive the drought of 2002. The significance of this event is potentially profound because population dynamics of long-lived plants can be far more strongly affected by deaths of adults, which in deserts potentially live for centuries, than by seedling births or deaths. Differential mortality and rates of recovery during and after extreme climatic events quite likely determine the species composition of plant and associated animal communities for at least decades. The die-off recorded in this closely monitored community provides a unique window into the mechanics of this process of species decline and replacement. [ABSTRACT FROM AUTHOR]

Background Many tropical forest tree species delay greening their leaves until full expansion. This strategy is thought to provide newly flushing leaves with protection against damage by herbivores by keeping young leaves devoid of nutritive value. Because young leaves suffer the greatest predation from invertebrate herbivores, delayed greening could prevent costly tissue loss. Many species that delay greening also produce anthocyanin pigments in their new leaves, giving them a reddish tint. These anthocyanins may be fungicidal, protect leaves against UV damage or make leaves cryptic to herbivores blind to the red part of the spectrum. Methods A comprehensive survey was undertaken of seedlings, saplings and mature trees in two diverse tropical forests: a rain forest in western Amazonia (Yasuní National Park, Ecuador) and a deciduous forest in Central America (Barro Colorado Island, Panamá). A test was made of whether individuals and species with delayed greening or red-coloured young leaves showed lower mortality or higher relative growth rates than species that did not. Key results At both Yasuní and Barro Colorado Island, species with delayed greening or red young leaves comprised significant proportions of the seedling and tree communities. At both sites, significantly lower mortality was found in seedlings and trees with delayed greening and red-coloured young leaves. While there was little effect of leaf colour on the production of new leaves of seedlings, diameter relative growth rates of small trees were lower in species with delayed greening and red-coloured young leaves than in species with regular green leaves, and this effect remained when the trade-off between mortality and growth was accounted for. Conclusions Herbivores exert strong selection pressure on seedlings for the expression of defence traits. A delayed greening or red-coloured young leaf strategy in seedlings appears to be associated with higher survival for a given growth rate, and may thus influence the species composition of later life stages. [ABSTRACT FROM AUTHOR]