Plant roots and fungi underground interact in important ways, but we don't fully understand how. In a forest in China, researchers found that the network of these interactions is not very connected, with equal interactions and moderate specialization. The abundance and spatial overlap of plants and fungi help predict how they interact, but not how specific they are. Spatial overlap is better at predicting interactions than abundance. The type of fungi and plants involved also play a role in how they interact. Overall, both random chance and specific factors shape how plants and fungi interact underground.