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Summary: Vegetation demographic models (VDMs) endeavor to predict how global forests will respond to climate change. This requires simulating which trees, if any, are able to recruit under changing environmental conditions. We present a new recruitment scheme for VDMs in which functional‐type‐specific recruitment rates are sensitive to light, soil moisture and the productivity of reproductive trees.We evaluate the scheme by predicting tree recruitment for four tropical tree functional types under varying meteorology and canopy structure at Barro Colorado Island, Panama. We compare predictions to those of a current VDM, quantitative observations and ecological expectations.We find that the scheme improves the magnitude and rank order of recruitment rates among functional types and captures recruitment limitations in response to variable understory light, soil moisture and precipitation regimes.Our results indicate that adopting this framework will improve VDM capacity to predict functional‐type‐specific tree recruitment in response to climate change, thereby improving predictions of future forest distribution, composition and function. [ABSTRACT FROM AUTHOR]

Long-term studies have revealed that the structure and dynamics of many tropical forests are changing, but the causes and consequences of these changes remain debated. To learn more about the forces driving changes within tropical forests, we investigated shifts in tree species composition over the past 25 years within the 50-ha Forest Dynamics Plot on Barro Colorado Island (BCI), Panama, and examined how observed patterns relate to predictions of (1) random population fluctuations, (2) carbon fertilization, (3) succession from past disturbance, (4) recovery from an extreme El Niño drought at the start of the study period, and (5) long-term climate change. We found that there have been consistent and directional changes in the tree species composition. These shifts have led to increased relative representations of drought-tolerant species as determined by the species' occurrence both across a gradient of soil moisture within BCI and across a wider precipitation gradient from a dry forest near the Pacific coast of Panama to a wet forest near its Caribbean coast. These nonrandom changes cannot be explained by stochastic fluctuations or carbon fertilization. They may be the legacy of the El Niño drought, or alternatively, potentially reflect increased aridity due to long-term climate change. By investigating compositional changes, we increased not only our understanding of the ecology of tropical forests and their responses to large-scale disturbances, but also our ability to predict how future global change will impact some of the critical services provided by these important ecosystems. [ABSTRACT FROM AUTHOR]

Major shifts in many ecosystem-level properties of tropical forests have been observed, but the processes driving these changes are poorly understood. The forest on Barro Colorado Island (BCI) exhibited a 20% decrease in the number of trees and a 10% increase in average diameter. Using a metabolism-based zero-sum framework, we show that increases in per capita resource use at BCI, caused by increased tree size and increased temperature, compensated for the observed declines in abundance. This trade-off between abundance and average resource use resulted in no net change in the rate resources are fluxed by the forest. Observed changes in the forest are not consistent with other hypotheses, including changes in overall resource availability and existing self-thinning models. The framework successfully predicts interrelated changes in size, abundance and temperature, indicating its utility for understanding changes in the structure and dynamics of ecosystems. [ABSTRACT FROM AUTHOR]

Participatory research documented the hunting yields of 59 households in five neighboring indigenous villages in western Panama. These households captured 2,580 kg of game over 8 months, with 47% of the harvest coming from agricultural areas. The quantity of game captured in anthropogenic habitats is influenced by the hunting strategies employed. Only 25% of game captured during hunting trips was captured in agricultural areas, as opposed to 93% while “awaiting” and 65% using traps. Reliance on different strategies is in turn dependent on age, gender, and access to firearms. I argue that garden hunting is not a response to game depletion, but rather a productive activity that is complementary to broader cultural and economic patterns, and that simultaneously protects crops from animal predation. The creation of heterogeneous habitat mosaics through shifting cultivation has played a key role in the relationship between people and wildlife in the humid neotropics, leading to adjustments in both animal foraging patterns and indigenous hunting practices. [ABSTRACT FROM AUTHOR]

The responses of tropical forests to global anthropogenic disturbances remain poorly understood. Above-ground woody biomass in some tropical forest plots has increased over the past several decades, potentially reflecting a widespread response to increased resource availability, for example, due to elevated atmospheric CO2 and/or nutrient deposition. However, previous studies of biomass dynamics have not accounted for natural patterns of disturbance and gap phase regeneration, making it difficult to quantify the importance of environmental changes. Using spatially explicit census data from large (50 ha) inventory plots, we investigated the influence of gap phase processes on the biomass dynamics of four 'old-growth' tropical forests (Barro Colorado Island (BCI), Panama; Pasoh and Lambir, Malaysia; and Huai Kha Khaeng (HKK), Thailand). We show that biomass increases were gradual and concentrated in earlier-phase forest patches, while biomass losses were generally of greater magnitude but concentrated in rarer later-phase patches. We then estimate the rate of biomass change at each site independent of gap phase dynamics using reduced major axis regressions and ANCOVA tests. Above-ground woody biomass increased significantly at Pasoh (+0.72% yr(-1)) and decreased at HKK (-0.56% yr(-1)) independent of changes in gap phase but remained stable at both BCI and Lambir. We conclude that gap phase processes play an important role in the biomass dynamics of tropical forests, and that quantifying the role of gap phase processes will help improve our understanding of the factors driving changes in forest biomass as well as their place in the global carbon budget.