Neighbours shape plant life more than expected, Leiden scientists find
Scientists at Leiden University have discovered that plants are strongly influenced by their neighbours, not just above ground but also through hidden networks in the soil. Their findings challenge long-held ideas about how plants shape their environment and could help improve sustainable farming.
Neighbours matter, for people, but definitely also for plants. While plants are often studied in isolation, new research by Leiden researchers Mireadili Kuerban, Sofia Gomes and Martijn Bezemer shows that nearby plants can dramatically change what happens underground.
Until now, plants have mainly been treated as if they act alone. Instead, this research shows that plants, soil and microbes form a shared system, shaped by who grows next to whom.
This research shows that plants, soil and microbes form a shared system
A missing link in research
Scientists already knew that plants interact with microbes in the soil. But these interactions are usually studied for individually grown plants, explains Bezemer. ‘Another field looks at plant–soil or plant–plant interactions, but they don’t look at interactions with microbes. These fields are barely integrated.’
Because of this split, researchers often missed the role of neighbouring plants. ‘It’s easier to study one interaction, so most studies stop there,’ Kuerban explains.
One simple idea, thousands of pots
To test their ideas, the team designed large-scale experiments. The concept was simple: grow plants in soil, measure their microbes, and then add a neighbour to see what changes.
‘We grew plants with and without microbes, and then introduced a second plant,’ Kuerban explains. ‘The design is simple, but the scale is enormous: thousands of pots.’
This is far larger than most experiments. Every plant had to be grown, measured by hand, and its microbiome analysed, resulting in years of work.
A dramatic effect underground
The results were striking. Plants growing alone strongly shape the microbial community around their roots, something that we knew already. But that influence drops sharply when a neighbour is present.
‘For bacteria, the plant is responsible for about 70% of the variation,’ says Kuerban. ‘With a neighbour, that drops to about 20%.’ In other words, neighbouring plants can change the composition of microbes by around 50%. ‘We used to think the plant determines everything in its roots and the surrounding soil,’ says Kuerban. ‘But that’s not true.’
Neighbouring plants can change the composition of microbes by around 50%
Soil with a ‘memory’
The research also studied so-called soil “legacies”, the lasting effects plants leave behind after they are removed. ‘A plant changes the microbiome in its roots and surrounding soil,’ says Kuerban. ‘Even when the plant is gone, that change remains. It’s like a memory.’
Interestingly, bacteria and fungi behave differently. Bacteria respond quickly and change fast, while fungi grow slowly and persist longer. This means fungi play a bigger role in these long-term effects, while bacteria are more influenced by the direct presence of neighbours.
Not just competition
The findings also challenge the idea that plants mainly compete with each other. In some cases, neighbours may actually help each other.
Plants release sugars and chemicals into the soil that feed microbes. Different species release different substances, which together can create a better environment. ‘One plant provides certain chemicals, another provides certain microbes,’ says Bezemer. ‘Together, they can form an optimal combination.’
‘It highlights the importance of what happens below ground.’
From lab to field
The research also links to farming, as field studies show that mixed grasslands without fertilisation can perform as well as heavily fertilised monocultures. Scaling up these findings and predict plant interactions in real fields could help farmers choose better crop combinations, improve yields, and reduce fertiliser use ‘Our work shows why mixtures can work,’ says Kuerban. ‘It highlights the importance of what happens below ground.’
The research is published in Microbiome and Nature Plants.