Grazing intensity modulates carbohydrate storage pattern in five grass species from temperate grasslands

Regrowth after defoliation is an essential mechanism of plant tolerance to grazing. In grasses, non-structural carbohydrates (NSC) contained in tiller bases constitute a major substrate for regrowth after defoliation. Using a multi-specific approach, the present study aimed at testing the effect of grazing intensity on NSC concentration in tiller bases. We selected five grazing-tolerant grass species (Agrostis stolonifera, Cynosurus cristatus, Hordeum secalinum, Lolium perenne and Poa trivialis) and collected plants in a grassland subjected to two cattle grazing intensities (intensive versus moderate) for years. We measured NSC concentrations (starch, fructans, sucrose, glucose and fructose) in tiller bases. We found that fructan and sucrose concentrations before the grazing season (April) were higher under intensive than moderate grazing. By contrast, no significant effect of the grazing intensity on these NSC concentrations in tiller bases remained at the end of the grazing season (October). These results suggest that the level of reserves available before the onset of disturbance caused by grazing as well as the reserve replenishment capacity during the grazing season are modified by the intensity of grazing.