作物多样性实验:理解一年生作物系统物种多样性效应的机理

Crop Diversity Experiment:towards a mechanistic understanding of the benefits of species diversity in annual crop systems

受到草地生物多样性实验研究植物多样性对初级生产力影响的启发,2018年建立的“作物多样性实验”旨在测试自然生态系统生物多样性的效应是否也适用于一年生作物系统,以及作物混合种植(简称作物混作)是否也能实现超产,即作物混作的产量超过作物单作的最高产量。实验的前3年结果表明,作物混作不仅增加了产量,而且通常也比最高产的作物单作产量高。作物多样性效应在环境胁迫下更显著,且通常是在与豆科作物混作时实现超产。然而,我们也观察到在有利条件下和没有豆科植物的混作中,也有超产现象。对产量效应的潜在机制研究发现,作物物种之间存在直接的互补关系和通过其他生物的间接效应。前者包括氮吸收中的化学、空间和时间互补性,水分吸收的根分布互补性,以及光利用的空间和时间互补性。在间接机制中,除了“作物多样性实验”中未研究但在其他研究得到证明的对害虫和疾病的互补抑制之外,我们还证明作物混作中对杂草的互补抑制和植物生长促进微生物的丰度更高。因此,“作物多样性实验”不仅支持了生物多样性实验所证明的生态过程,也支持了作物系统中的生物多样性的生态系统功能假设,而且作物物种多样化的作物系统为可持续生产食物提供了有价值工具。

Inspired by grassland biodiversity experiments studying the impact of plant diversity on primary productivity,the Crop Diversity Experiment setup in 2018 aimed at testing whether these biodiversity benefits also hold for annual crop systems and whether crop mixtures also achieved transgressive overyielding,i.e.yield in mixture that was higher than the most productive monoculture.The first 3 years of the experiment demonstrated that crop mixtures do not only increase yield compared with an average monoculture but often also compared with the highest yielding monoculture.The crop diversity effects were stronger under more stressful environmental conditions and were often achieved in mixtures with legume crops.However,we observed transgressive overyielding also under favorable conditions and in mixtures without legumes.With our investigation of the underlying mechanisms of the yield benefits we found both direct complementarities between crop species and indirect effects via other organisms.The former included chemical,spatial and temporal complementarity in N uptake,complementary root distribution leading to complementary water uptake,as well as spatial and temporal complementarity in light use.Among the indirect mechanisms we identified complementary suppression of weeds and more abundant plant growth-promoting microbes in crop mixtures,apart from complementarity in pest and disease suppression not yet studied in the Crop Diversity Experiment but demonstrated elsewhere.In consequence,the Crop Diversity Experiment supports not only the assumption that the ecological processes identified in biodiversity experiments also hold in crop systems,but that diversification of arable crop systems provides a valuable tool to sustainably produce food.