An adaptive strategy for current afforestation in the forest-steppe ecotone, north China, inferred from the Holocene geo-ecology dynamics

The current afforestation in the forest-steppe ecotone of northern China to reduce continental desertification is hindered by a problem of what vegetational assemblage would adapt to local environment. Here we attempted to address the issue by investigating the long-term geo-ecological background in the Saihanba Forest Farm region, using pollen, biomarker, and radiocarbon dating analysis. Results show that natural arboreal species over the past 10,000 years were mainly composed of Quercus, Betula, Ulmus, Pinus and Juglans. Shrub species consisted of Prunus sibirica, and Ericaceae, while herbs included Artemisia, Chenopodiaceae, and Poaceae. The regional vegetation was profoundly altered by anthropogenic factors since ∼300 a B.P., as evidenced by an abrupt increase in coniferous trees. The Holocene climate in this region generally fluctuated from a cold-dry to a warm-humid condition and finally returned to cold and dry, suggesting a similar climatic status between the Holocene optimum (∼6 ka) and the modern warming periods. Therefore, we propose an adaptive vegetational assemblage for current afforestation, enhancing the sustainability of the Three-North Shelterbelt Project.