Major Forest Changes in Subtropical China since the Last Ice Age

Abstract

In the subtropical zone of southern China, there was a considerable conversion of forests from deciduous to evergreen broadleaf in the early Holocene. However, the exact timing of this vegetation change and its relationship to climate are still unclear. We examined a high-resolution pollen record collected in the mid-subtropical zone and then performed a correlation with regional data to reconstruct the history of forest ecosystems since the last deglaciation. Our data show that the expansion of the evergreen plant component already occurred at low elevations during the last deglaciation. The subtropical mountain landscape was not recolonized by evergreen forests until the mid-Holocene at about 8.1 ka BP. Based on fossil pollen reconstruction and climate model simulation, we conclude that the primary increase in evergreen components of subtropical ecosystems was triggered by postglacial temperature increase, and that a complete conversion from deciduous to evergreen forest ecosystems did not occur until Holocene winter temperatures and seasonal temperature contrast reached a threshold suitable for the growth and persistence of evergreen tree species.