Pathways of glyphosate effects on litter decomposition in grasslands

1. Grasslands store a third of global terrestrial carbon but are vulnerable to carbon loss due to inappropriate livestock grazing. Grasslands management can be improved with a mechanistic understanding of biogeochemical processes that determine carbon storage, such as plant litter decomposition.
2. Herbicides, such as glyphosate, are used to improve the quantity and quality of the forage. In the Flooding Pampa, the most extensive cattle-grazed natural grassland and one of the few remnant temperate grasslands in South America, glyphosate is applied to promote Lolium multiflorum, a forage grass associated with a fungal endophyte non-toxic for cattle.
3. We studied five mechanistic pathways in which the application of glyphosate can alter litter decomposition. We grouped them into single application pathways, through effects on living plants (1), leaf litter (2) and bare soil (3), and repeated annual application pathways, through legacies on ecosystem properties (4) and through the growth ..., Study site and application of glyphosate
The study site was a humid mesophytic grassland in the Flooding Pampa, a vast region of around 9 million hectares in the province of Buenos Aires, Argentina. The mean annual temperature is around 15°C and the mean annual rainfall is 885 mm (Soriano and Paruelo 1992). The landscape has a treeless physiognomy and an extremely flat topography with periodic flooding during autumn–spring in lowland, except in ridge areas with well-drained sandy soils (Burkart et al. 1998). The field experiment was carried out in a commercial livestock farm (35° 01´S, 57° 50´ W). The plant community is dominated by C3 and C4 grass species (see details in Druille et al. 2015). Soil is classified as a typical Natracuol (US Soil Taxonomy), characterized by having a nonsaline acid A1 horizon, and a highly alkaline saline B2 horizon (Lavado and Taboada 1988).
Glyphosate was not applied at the study site before, even though glyphosate application in the late summer is a comm...,