Plant species loss reduces rare soil microbes through diversity effect amplified by multitrophic interactions

Abstract
Evidence is mounting that plant diversity loss erodes ecosystem functioning by altering biochemical processes regulated by diverse organisms aboveground and belowground. However, we know little about how plant diversity loss influences soil biodiversity, especially whether loss of ecologically rare and/or functionally distinctive plants leads to a reduction in the rare soil microbes associated with soil multifunctionality. In plant species-rich alpine meadow communities on the Tibetan Plateau, we conducted a 12-year plant species removal experiment to reveal the effect of losing ecologically rare and functionally distinctive (many) forbs, versus the loss of (few) dominant sedges and (several) common forbs, on soil biodiversity. We found that the removal of rare forbs, rather than dominant species and common plants, significantly decreased the richness of soil bacteria and fungi by decreasing rare microbial taxa in later years. This decline in the richness of rare taxa was attributed not only to the decreased plant richness but also to increased soil nematodes, especially fungivores and omnivores-predators. The study revealed that the loss of rare plants induces the loss of rare soil microbes through the plant diversity effect amplified by belowground multitrophic interactions, triggering shifts in microbial community composition and soil food web structure.