Data from: Tree genetics strongly affect forest productivity, but intraspecific diversity-productivity relationships do not

Numerous studies have demonstrated biodiversity–productivity relationships in plant communities, and analogous genetic diversity–productivity studies using genotype mixtures of single species may show similar patterns. Alternatively, competing individuals among genotypes within a species are less likely to exhibit resource-use complementarity, even when they exhibit large differences in their effects on ecosystem function.
In this study, we test the impact of genotype diversity and genetic identity on ecosystem function using an ecosystem-scale common garden experiment. Distinct tree genotypes were collected across the entire natural range of the riparian tree Populus fremontii in the USA, and grown in 1–16 genotype combination forest stands. Due to the warm climate and irrigation of the planting location along the Colorado River (AZ, USA), mature forest physiognomy with trees up to 19 m tall was achieved in just five years.
Several key patterns emerged: (i) genotype richness did not predict forest productivity, suggesting a lack of net biodiversity effects; (ii) we found differences among genotype monoculture stands comparable to differences in average productivity across all forest biomes on Earth; (iii) productivity was predicted based on genetic marker similarity in trees; (iv) genetic-based differences in leaf phenology (early leaf-on and late leaf-fall timing) were correlated with >80% of the variation in tree and forest productivity irrespective of home-site conditions.
Large differences in productivity among genotypes can result in dramatic differences in forest productivity without resulting in diversity–productivity relationships that are present in species-scale biodiversity studies.

诸多研究已证实植物群落中存在生物多样性-生产力关系（biodiversity–productivity relationships），而基于单物种种内基因型混合种植的同类遗传多样性-生产力关系研究，或可呈现相似规律。不过，同一物种种内不同基因型的竞争个体，即便其对生态系统功能的影响差异显著，也更难表现出资源利用互补性（resource-use complementarity）。

本研究依托一项生态尺度同质园试验（ecosystem-scale common garden experiment），探究基因型多样性与遗传同一性对生态系统功能的影响。研究采集了美国境内河岸树种弗里蒙特杨（Populus fremontii）全部自然分布范围内的不同树基因型，并将其以1至16种基因型组合的方式构建人工林分。由于试验点位于美国科罗拉多河沿岸（亚利桑那州，AZ），气候温暖且具备灌溉条件，仅用五年时间便培育出树高可达19米的成熟林分。

研究得到四项核心发现：（1）基因型丰富度无法预测林分生产力，表明净生物多样性效应缺失；（2）纯基因型林分间的生产力差异，与全球所有森林生物群系的平均生产力差异量级相当；（3）树木的遗传标记（genetic marker）相似性可用于预测林分生产力；（4）基于遗传差异形成的叶片物候（leaf phenology）（展叶早、落叶晚的物候特征）与树木及林分生产力80%以上的变异显著相关，且不受原生境条件的影响。

不同基因型间的生产力差异显著，可导致林分生产力出现大幅变化，但并不会产生物种尺度生物多样性研究中观测到的那种多样性-生产力关系。