Warming risks Tibetan meadow collapse

The researchers studied a 1,084.67-m core (ZB19-C1) from the basin’s sedimentation centre. Combined with a previously drilled core (ZB13-C2), this provided a uniquely continuous palynological archive that spans approximately the past 3.5 million years. Using numerical analysis and statistical modelling on the pollen data, the team identified three major vegetation transformations at approximately 2.73 Ma, approximately 1.54 Ma and approximately 0.62 Ma. These shifts were superimposed on a gradual long-term trend from forest to grassland.

The first transformation occurred in the mid-late Pliocene (3.5–2.73 Ma), and was characterized by a shift from stable forest to a codominant mix of forest and steppe during the early Quaternary (2.73–1.54 Ma). A second transformation then shifted the vegetation towards a meadow-dominated ecosystem, which established after about 1.54 Ma according to biomization analysis. Tree taxon richness was highest before 3.5 Ma and declined drastically after about 0.62 Ma, which coincided with major Pleistocene glaciation. These vegetation dynamics occurred alongside glacial–interglacial cycles and millennial-scale grassland–forest shifts.