Photosynthetic pathway types of forage species along grazing gradient from the Songnen grassland, Northeastern China

Photosynthetic pathway types (C-3 and C-4 Species) and their dynamics along grazing gradient were determined for 42 plant species in 30 genera and 13 families from the Songnen grassland, Northeastern China. Of the total, 10 species in 9 genera and 4 families had C-4 photosynthesis; 32 species in 21 genera and 12 families had C-3 photosynthesis. The proportion of C-4 species in total plants and C-4/C-3 increased with grazing intensity, and peaked in overgrazed plot. Most of the increased C-4 species (6 of 10) along the grazed gradient were annual grasses and halophytes. This indicated that the C-4 species had greater capacity to tolerate environmental stresses (e.g. drought and saline) caused by animal grazing in the Songnen grassland, Northeastern China.