Plant species diversity for soil health

Plant diversity loss impairs ecosystem functioning, including important effects on soil. Most studies that have explored plant diversity effects belowground, however, have largely focused on biological processes. As such, our understanding of how plant diversity impacts the soil physical environment remains limited, despite the fundamental role soil physical structure plays in ensuring soil function and ecosystem service provision.

As a result of changing land use to feed a growing population, climate change, and contamination of land with toxic chemicals, our soil resources are deteriorating, posing a serious threat to food security.

Plant roots play a key part in keeping soil together, making it resistant to erosion and helping water flow through the soil, which can help to prevent floods. But until now little was understood about how roots of different plant communities affect the physical condition of the soil. A team of researchers from the UK, Netherlands and Germany presented new evidence that an increase in plant species diversity can protect soil in grasslands by improving soil structure.

In a series of experiments in field sites in the UK (plant manipulation experiment conducted at the Lancaster University Field Station) and Germany (large scale plot experiment in Jena), the researchers tested the soil's structural stability when planted with a variety of different grasses, herbs and legumes. They found that soil structure improved with higher plant diversity and that the diverse properties of different plant roots were the key factor in keeping soil healthy.

For example legumes are better at getting water into the soil more quickly and maintaining root-soil strength. Grasses, however, have fine rooting systems that enhance the stability of soil making it more resistant to erosion. Combining these effects enhances the benefits for the soil. 

We only need to look at historical examples such the American Dust Bowl of the 1930s to see that globally, the physical degradation of our soil presents a serious threat to human well-being. This study offers clear evidence that by increasing species richness we can not only increase ecological value, but also provide a degree of protection to our soil which is good news for the future.

Soils are severely degraded in many parts of the world and these findings suggest that enhancing plant diversity could be an important way of speeding up their restoration to bring back fertility. It is almost like different combinations of roots can be used to engineer the soil, working to enhance its physical structure which is key to soil health.