Background and aim

Differences in root system architecture of species grown in mixtures may contribute to overyielding through spatial niche complementarity, depending on soil conditions. We investigated if differences in root system architecture in a grass-forb combination under drying soil conditions contributed to complementarity in root distribution.

Methods

Bristle oat (Avena strigosa Schreb.) and fodder radish (Raphanus sativus L.) were grown in containers (35 cm soil depth) in a greenhouse as sole stands and alternate row mixtures with continuous rewetting or in drying soil profiles. Drying soils reached 7.5 and 9.5% cm³/cm³ moisture at 0–10 and 10–20 cm depth respectively. Aboveground biomass and root system traits were quantified.

Results

Mixtures produced 60 and 34% more root length and 11 and 24% higher biomass than sole stands in moist and drying soil respectively. In drying soil bristle oat and fodder radish had respectively 58% and 13% higher root length density in mixtures than in sole stands, whereas fodder radish dominated the aboveground biomass. In drying soil, sole-growing bristle oat produced more root length in the bottom layer than in other layers, while sole-growing fodder radish produced more root length in the upper layer. In mixtures both species produced more root length in the upper layer.

Conclusions

Both species over-yielded when grown as a mixture either in moist or drying topsoil; however, they did not exhibit complementary root distribution. Contrary to the expected niche complementarity, plants of both species enhanced root placement in the top layer, whether dry or moist.

中文翻译：

---

在干燥的土壤中种植草和杂草混合物 – 根系不表现出空间生态位互补性

 背景和目的

根据土壤条件，混合物中生长的物种的根系结构差异可能通过空间生态位互补性导致产量过高。我们研究了在干燥土壤条件下，草-杂草组合中根系结构的差异是否有助于根系分布的互补性。

 方法

鬃毛燕麦 （Avena strigosa Schreb.） 和饲料萝卜 （Raphanus sativus L.） 在温室的容器（土壤深度 35 厘米）中种植，作为唯一支架和交替行混合物，连续再润湿或在干燥土壤剖面中种植。干燥土壤在 0-10 和 10-20 cm 深度分别达到 7.5% cm³/cm³ 水分。对地上生物量和根系性状进行了量化。

 结果

在潮湿和干燥的土壤中，混合物产生的根长分别比鳎目鱼高 60% 和 34%，生物量分别高 11% 和 24%。在干燥土壤中，鬃毛燕麦和饲料萝卜在混合物中的根长密度分别比鞋底林高 58% 和 13%，而饲料萝卜在地上生物量中占主导地位。在干燥土壤中，单生鬃燕麦在底层产生的根长比其他层长，而单生饲料萝卜在上层产生的根长更多。在混合物中，这两个物种在上层产生更多的根长。

 结论

当在潮湿或干燥的表层土壤中作为混合物生长时，这两个物种都产量过高;然而，它们没有表现出互补的根分布。与预期的生态位互补性相反，这两个物种的植物都增强了根系在顶层的位置，无论是干燥的还是潮湿的。