Data from: Towards smarter harvesting from natural palm populations by sparing the individuals that contribute most to population growth or productivity

1. 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 sustaining yields over time. 2. 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. 3. We studied a population of 830 individuals, half of which was subjected to a 67 % defoliation treatment for three 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. 4. Individuals varying in size or past growth rate responded similarly to leaf harvesting in terms of growth and reproduction. By contrast, defoliation-induced reduction in survival chance was smaller in large individuals than in small ones. Simulations showed that harvest-induced population decline was much reduced when individuals from size and past growth classes that contributed most to population growth were spared. Under this scenario cumulative leaf harvest over 20 years was somewhat reduced, but long-term leaf production was sustained. A three-fold increase in leaf yield was generated when individuals with small leaves are spared. 5. 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.

1. 自然种群可产出多种产品，为数以百万计的人群提供收入来源，其开发利用必须遵循可持续原则。在这些被开发的种群中，个体表现存在极大异质性，这有望提升种群在开发后的恢复能力，进而助力长期维持产量水平。
2. 本研究以林下棕榈物种袖珍椰子（Chamaedorea elegans）为模式系统，探讨了利用个体异质性设计更智能收获方案的可行性，具体策略为保留对未来生产力和种群增长贡献最大的个体。该棕榈的叶片是重要的非木材林产品，且可通过节间长度评估个体间长期生长变异情况。
3. 我们对包含830个个体的种群展开研究，其中一半个体接受了为期三年的67%去叶处理。我们测定了去叶处理对生命率以及决定叶片市场适销性的叶片大小性状的影响。构建了以茎长、过往生长速率和去叶状态为影响因子的积分投影模型（Integral Projection Models），并通过评估瞬时种群动态来量化种群发展与叶片产量。随后我们模拟了两种保留策略场景：保留对种群增长贡献最大的个体，或是保留叶片尺寸低于市场适销标准的个体。
4. 不同体型或过往生长速率存在差异的个体，在叶片收获后的生长与繁殖响应模式相似。与之相反，大型个体的去叶诱导存活概率下降幅度小于小型个体。模拟结果显示，当保留对种群增长贡献最大的体型与过往生长类别的个体时，收获导致的种群衰退程度大幅降低。在此场景下，20年内的累计叶片收获量略有下降，但长期叶片产量得以维持。若保留叶片尺寸较小的个体，叶片产量可提升三倍。
5. 综合与应用 本研究证明，通过考虑被开发种群内的个体异质性，可以构建更智能的棕榈叶片收获系统。保留对种群增长贡献最大的个体，能够确保长期稳定的叶片产量。本文提出的概念与方法，可推广应用于存在显著个体异质性的被开发动、植物物种。