Knowledge from agriculture and ecological field studies suggests that plant monocultures lose productivity over time, but the drivers underlying the long‐term performance of monocultures of grassland species are not completely understood. We examined the performance of 60 grassland species growing in monoculture for 12 years in a biodiversity experiment (Jena Experiment) and studied three groups of biotic drivers potentially affecting plant performance in monocultures over time: 1) soil biota (nematode communities, arbuscular mycorrhizal fungi), 2) leaf traits related to leaf economics spectrum, and 3) plant life‐cycle characteristics related to buffered population growth (viable seeds in topsoil, seedling density, seed survival). Monocultures of 15 out of 60 species increased productivity, while monocultures of the remaining 45 species showed slight to strong losses of productivity over time, resulting in zero biomass in 15 species. All three biotic drivers were related to the varying long‐term performance of monocultures. Their combined influence on monoculture performance could be interpreted as a tradeoff between ‘fast’ versus ‘slow’ life strategies. ‘Fast’ species showed rapid resource use and little buffering of population growth through a viable seed bank, which led to high biomass production in young monocultures but a consecutive loss of biomass production over time. ‘Slow’ species were characterized by positive nematode effects (high abundance of predatory nematodes), conservative use of resources, and a viable seed bank with high recruitment success resulting in gradually increasing productivity over time. In summary, our study highlights the importance of studying long‐term field monocultures to investigate the complex role of different biotic drivers responsible for productivity changes over time. These insights provide an essential baseline for estimating biodiversity effects on productivity as well as to understand and predict long‐term performance of plant populations.

中文翻译：

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线虫群落，植物营养经济性和生命周期特征共同决定了12年内植物的单培养性能

来自农业和生态田间研究的知识表明，植物单一栽培会随着时间的流逝而丧失生产力，但是对草原物种单一栽培的长期表现背后的驱动力尚未完全了解。我们在生物多样性实验（耶拿实验）中研究了60种在单一培养中生长12年的草地物种的性能，并研究了三组可能随时间推移影响单一种植中植物性能的生物驱动因子：1）土壤生物区系（线虫群落，丛枝菌根真菌） ，2）与叶片经济谱相关的叶片性状，以及3）与缓冲种群的生长相关的植物生命周期特征（表土中的活种子，幼苗密度，种子存活期）。60种物种中有15种的单种养殖提高了生产力，而其余45种的单种养殖随着时间的推移显示出轻微至强烈的生产力损失，导致15种生物量为零。所有这三种生物驱动因素都与单一栽培的长期表现有关。他们对单一文化表现的综合影响可以解释为“快速”与“慢速”生活策略之间的权衡。“快速”物种显示出资源的快速利用，并且通过一个可行的种子库几乎没有缓冲种群的增长，这导致了年轻的单一养殖生物量的高产，但随着时间的流逝生物量的连续损失。“慢”物种的特征是具有积极的线虫效应（捕食性线虫数量很多），资源的保守使用以及可行的种子库，且募集成功率很高，从而随着时间的推移逐渐提高了生产力。综上所述，我们的研究强调了研究长期田间单种养殖的重要性，以调查不同生物驱动因素对生产力随时间变化的复杂作用。这些见解为估算生物多样性对生产力的影响以及了解和预测植物种群的长期表现提供了重要的基线。