Root responses of grassland species to spatial heterogeneity of plant–soil feedback

Plants live in environments in which local conditions differ, for example the amount and type of available nutrients. If the availability of nutrients is patchy, plants can direct their roots towards patches that have highest availability. Similar patchy distributions can be found for soil biota (e.g. fungi or bacteria), but the response of plants to this type of spatial variation is not known.

This study investigated if rooting patterns of plants can respond to the patchiness of soil biota. The authors expected that plants might avoid patches with pathogenic soil biota. To test that expectation, the authors used four grassland species and soils on which they had been growing before, to obtain ‘own’ and ‘foreign’ soils. The study created four compartments in a pot and assigned soil of each of the four species to one of the compartments (heterogeneous soil treatment). As a control situation the authors mixed the four soil types (homogeneous soil treatment) and in another control we removed soil biota. In order to study effects of soil biota on nutrient uptake by roots we added labelled nitrogen (15N) to the soil.

It was found that most species performed better when their own and foreign soils were distributed heterogeneously, rather than when they were homogeneously mixed. The amount of roots and the nitrogen uptake rate of these roots were higher in ‘foreign’ than ‘own’ soils. When the soil was sterilized to remove soil biota, these differences disappeared, showing that indeed the soil biota caused the difference between heterogeneous and homogeneous soils.

The authors conclude that plants perform better if they grow in soils with patchy distribution of pathogenic soil biota, compared to when the same amount of pathogens are homogeneously mixed, because plants can selectively avoid the patches with pathogens. Plants can be disproportionately efficient in nutrient acquisition in patches without soil biota. The results imply that diverse plant communities may be more productive than species poor vegetation, because in species rich vegetation plant species can find more patches without soil pathogens where they could maximize nutrient acquisition.


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