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Abstract: Natural populations deliver a wide range of products that provide income for millions of people and need to be exploited sustainably. Large heterogeneity in individual performance within these exploited populations has the potential to improve population recovery after exploitation and thus help sustain yields over time. We explored the potential of using individual heterogeneity to design smarter harvest schemes, by sparing individuals that contribute most to future productivity and population growth, using the understorey palm Chamaedorea elegans as a model system. Leaves of this palm are an important non‐timber forest product and long‐term inter‐individual growth variability can be evaluated from internode lengths. We studied a population of 830 individuals, half of which was subjected to a 67% defoliation treatment for 3 years. We measured effects of defoliation on vital rates and leaf size—a trait that determines marketability. We constructed integral projection models in which vital rates depended on stem length, past growth rate and defoliation and evaluated transient population dynamics to quantify population development and leaf yield. We then simulated scenarios in which we spared individuals that were either most important for population growth or had leaves smaller than marketable size. Individuals varying in size or past growth rate responded similar to leaf harvesting in terms of growth and reproduction. By contrast, a reduction in survival chance was smaller in large individuals than in small ones. Simulations showed that harvest‐induced population decline was greatly reduced when sparing individuals from size and past growth classes that contributed most to population growth. Under this scenario, cumulative leaf harvest over 20 years was somewhat reduced, but long‐term leaf production was sustained. A threefold increase in leaf yield was generated when individuals with small leaves were spared. Synthesis and applications. This study demonstrates the potential to create smarter systems of palm leaf harvest by accounting for individual heterogeneity within exploited populations. Sparing individuals that contribute most to population growth ensured sustained leaf production over time. The concepts and methods presented here are generally applicable to exploited plant and animal species which exhibit considerable individual heterogeneity. [ABSTRACT FROM AUTHOR]

Assessing the demographic effects of leaf area losses in perennial plants is important to determine population resilience to natural and anthropogenic disturbances. Yet, while impacts of defoliation on vital rates of adult plants have been well documented, consequences for seed dispersal and seedling recruitment have been barely explored., Here, we assessed the effects of defoliation on fruit production, fruit/seed size, seed dispersal and seedling recruitment in populations of Chamaedorea ernesti-augustii, a tropical rain forest, understorey palm from Mesoamerica, whose leaves are exploited as a highly valuable non-timber forest product ( NTFP)., Fruit size and seed production were quantified in mature palms that were subjected to 0% (control), 25%, 50%, 75% and 100% experimental removal of standing leaves, applied every 6 months over 2 years. Seed dispersal by birds and gravity, and seed predation by small vertebrates on the ground were also quantified. Rates of seedling recruitment were recorded in non-defoliated and 'sterile' populations (75% sustained defoliation and periodical removal of all produced fruits). Finally, a stochastic model was used to quantify the overall effect of defoliation on seedlings recruited from locally (i.e. dispersed by gravity) and immigrant produced seeds (i.e. dispersed by birds)., Increasing defoliation strongly reduced seed production. The probability of bird dispersal was positively correlated with fruit/seed size. Isolated (i.e. bird-dispersed) seeds endured lower predation rates than grouped (i.e. gravity-dispersed) ones. Modelling showed that seedling recruitment rate is severely reduced in highly defoliated populations due to a strong decline in the number of seedlings coming from local seed sources. Surrounding non-defoliated populations could partly compensate for this effect via seedlings coming from immigrant seeds., Synthesis. Chronic and intense defoliation negatively affects seed production and dispersal, which reduces the probability of seedling recruitment. Such effects may have a profound impact on the dynamics and genetic variability of populations, which should be taken into account when considering the effects of natural defoliation and sustainability of leaf-harvesting regimes. [ABSTRACT FROM AUTHOR]

1. Perennial plants often endure chronic loss of leaf area due to recurrent physical damage, herbivory and, for species used as non-timber forest products, due to leaf harvesting. However, little is known about functional and demographic resilience (extent and speed of recovery) of plants subjected to varying levels of chronic defoliation. 2. We used a dioecious, understorey palm ( Chamaedorea elegans) to evaluate temporal trajectories and rates of recovery of leaf functional traits and vital rates (survival, growth and reproduction) after being subjected to experimental chronic defoliation regimes. 3. Pristine populations of mature C. elegans, categorized by gender (male and female), were subjected to five defoliation levels (0%, 33%, 50%, 66% or 100% of newly produced leaves) every 6 months over a period of 3 years (1997-2000). To evaluate recovery from defoliation, surviving palms were monitored for 3 years after the cessation of the defoliation treatment (2000-2003). We recorded leaf functional traits (leaf persistence, leaf production rate, leaf size and leaf area) and annual rates of mortality, growth and reproduction. 4. Cumulative effects of chronic defoliation concomitantly reduced leaf traits, survival, growth and reproduction, and this effect was stronger in female than in male palms, independent of plant size. Recovery from defoliation was faster in males than in females, but proceeded gradually overall. Survival increased first, followed by growth, while reproductive traits showed the slowest recovery rate. Recovery was independent of plant size. Notably, 3 years after defoliation treatment, the standing leaf area and probability of reproduction had not recovered to pre-defoliation levels. Additionally, we found that the occurrence of a severe drought in the first year (2000) after defoliation ceased led to decreased survival, growth and reproduction and the ability of plants to recover from defoliation. 5. Synthesis. Chronic defoliation reduces fitness components of C. elegans palms differentially between genders. Recovery is gradual and is slower and less complete in females compared with males. The lower level of resilience to chronic defoliation shown by female plants may have profound consequences for the dynamics and genetic variability of populations of tropical understorey plants undergoing prolonged defoliation. Such effects may be aggravated by severe drought episodes that are expected to increase in frequency according to global climate change predictions. [ABSTRACT FROM AUTHOR]

1. Rain forest understorey plants suffer leaf area losses due to natural causes or when leaves are harvested as non-timber forest products. The negative effects of defoliation on plant fitness can be exacerbated during periods with strong water shortage and high temperatures, typical during ENSO (El Niño Southern Oscillation) years in Mexico and Central America. At present, the isolated and combined demographic effects of ENSO events and repeated defoliation on tropical rain forest plants are poorly understood. 2. We studied the consequences of repeated defoliation and an ENSO event on vital rates (mortality, growth, and reproduction) of the dioecious understorey palm Chamaedorea elegans. From March 1997 to March 2000 (including the 1998 ENSO year), we subjected 814 mature individuals to one of five defoliation treatments (0–100% of newly produced leaves were removed twice a year), recording mortality, growth (leaf production) and reproduction (inflorescence and seed production) every 6 months. 3. Increasing defoliation strongly reduced reproduction but had smaller effects on growth and mortality. Among non-defoliated palms, the probability of mortality increased with light availability, likely due to drought stress during the dry season, but this was not the case for the defoliated plants, probably because leaf area removal lowered transpiration and increased the root mass-to-leaf area ratio. During the ENSO year, growth and inflorescence production were stimulated, but survivorship and seed production diminished significantly, independent of defoliation level. 4. Synthesis. Variation in light availability and the occurrence of severe droughts can strongly affect demographic behaviour of understorey plants such as C. elegans, significantly influencing the effects of defoliation. Thus, strong episodic disturbance events (such as ENSO, insect outbreaks, strong storms, fires and landslides) should be taken into account to adequately understand the mechanisms that determine the population dynamics of forest plants and the potential for sustainable utilization of non-timber forest products. [ABSTRACT FROM AUTHOR]