The common mycorrhizal network originated from Brachiaria brizantha suppresses the growth of seedlings from the grass itself and native trees in shouthern Brazil

Abstract

Abstract The common mycorrhizal network (CMN) is formed by arbuscular mycorrhizal fungi (AMF) that interconnect plant roots, and promote the exchange of nutrients, water, and signaling compounds, in addition to serving as a mechanism of competition among plants. It was evaluated the influence of CMN, originated from the adult invasive grass Brachiaria brizantha, on the development of seedlings of B. brizantha itself and of the native trees Heliocarpus popayanensis (early-successional) and Cariniana estrellensis (late-successional). The plants were grown in a substrate composed of fertile soil and sterilized sand in a 3:1 ratio, with 640 native AMF spores per gram of soil. The treatments were: 1) Seedlings of B. brizantha, H. popayanensis, and C. estrellensis grew under the influence of CMN originated from adult B. brizantha for 225 days; 2) Ninety days after the influence of CMN, two adult B. brizantha prunings were carried out, the first occurring 90 days after emergence and the second 180 days after the first pruning; 3) Ninety days after the influence of the CMN, the communication network was severed by the weekly rupture of the fungal hyphae; 4) The control treatment consisted of the isolated growth of five seedlings of each species without contact with the CMN. The CMN originated from B. brizantha suppressed the growth of seedlings of the three species. CMN severing completely eliminated the suppressive effects of adult B. brizantha on seedlings. The adult B. brizanta pruning mitigated the negative effects on seedlings, however after regrowth, suppression returned. The seedlings of H. popayanensis connected to the CMN originated from adult B. brizantha died, while the seedlings of C. estrellensis and B. brizantha itself survived, altough suppressed.