Phytolith evidence for changes in the vegetation diversity and cover of a grassland ecosystem in Northeast China since the mid-Holocene

Abstract

Accurate estimates of changes in the composition and diversity of grassland ecosystems, and an understanding of the mechanisms responsible, are essential for predicting future changes and for conservation planning. Here, we synthesize stratigraphic records of phytoliths, together with previously published pollen, diatom, carbonate and grain-size records, from a peat profile (LDBS) in the Songnen region of Northeast China. The results demonstrate that since the mid-Holocene this region was occupied by grassland, with C3 grasses always dominant but with C4 grasses progressively increasing. The species richness and plant cover were high and relatively stable for most of the studied interval, but they decreased significantly in the last ∼1,000 years. The long-term evolution of this grassland ecosystem was dominated by climate changes, but it was also affected by human activities and local habitat factors. The plant cover and several dominant plant taxa were climatically sensitive, while the C4 grasses also responded to changes in the water table and human activities. Species richness was relatively stable but it responded to long-term climatic changes. Phytolith-based reconstruction of Holocene plant community composition and diversity and their driving mechanisms can potentially be used to facilitate conservation planning in this temperate grassland ecosystem.