Soil eutrophication reduces fungal colonization in Berberis microphylla roots in Patagonia (Argentina)

Abstract

Soil eutrophication can trigger drastic changes in biological interactions. However, it is notclear, particularly in forest ecosystems, how different symbiotic microorganisms respond toeutrophication or how responses might differ according to the nutrients involved (e.g., additive vs.interactive effects). In this study we evaluated how arbuscular mycorrhiza (AM) and dark septateendophyte (DSE) colonization of Berberis microphylla, a native shrub, was affected by the addition ofinorganic nitrogen, phosphorus and potassium. We used a factorial experimental design (8 fertilizationtreatments applied to 31.5 x 45m plots) in Río Negro (Argentina). We found that N and P fertilizationreduced mycorrhizal colonization, while N, P and K fertilization reduced DSE colonization; however, wefound no additive effect on either mycorrhizal or DSE colonization. Mycorrhization percentages wereclose to 20% in the control and potassium-only plots, and between 3 and 5% in the remaining treatments.DSE colonized over 50% of plants in the control plots, whereas this value fell below 20% withfertilization. Our results show that changes in even a single soil nutrient can severely affect these fungal-plant associations, evidencing the high impact of eutrophication on forest soils. Considering the crucialrole of these symbiotic interactions, it is essential to control anthropogenic eutrophication.