近日，国际知名古气候学刊物《全新世》（The Holocene）发表了中科院地质与地球物理研究所新生代地质与环境重点实验室的研究成果，研究人员发现太阳辐射影响高原气候变化和植被演替。
青藏高原中部草原、草甸植被对气候变化非常敏感。前人通过该地区全新世孢粉记录重建了高寒草原、高寒草甸植被带的水平迁移与气候变化过程。但是，有关高原中部孢粉记录中莎草科花粉的植被和气候指示意义尚存争议，迄今对高原中部垂直植被带迁移与气候变化的关系了解甚少。
博士研究生李泉与导师吕厚远研究员及其合作者对青藏高原中部纳木错湖区37个表土和NMLC-1湖芯198个沉积物样品开展了孢粉分析。研究显示，该区表土孢粉组合可指示并区分念青唐古拉山北坡沿海拔梯度分布的高寒草原和高寒草甸植被带。高寒草原表土孢粉组合以蒿属花粉的高含量（平均25.1%）为特征，蒿属与莎草科花粉比值（A/Cy）平均为4.9；高寒草甸表土孢粉组合以莎草科占绝对优势（56.8%），A/Cy平均值为0.1。A/Cy比值可区分高寒草原带（>1.0）和高寒草甸带（<1.0），并作为垂直植被带迁移和气候温度变化的指示。
通过纳木错NMLC-1孔全新世化石孢粉记录，结合A/Cy比值变化与判别分析结果，研究人员重建了距今8400年以来伴随气候温度的持续降低，念青唐古拉山北坡垂直植被带逐渐向下迁移的过程。该区全新世植被带迁移和温度变化的趋势，与同时期北半球夏季太阳辐射变化较一致，反映了太阳辐射直接影响了高原中部全新世气候变化和植被演替；对比同时期高原不同区域植被与气候变化序列，他们认为全新世西南季风的进退主要影响了高原中部湿度的变化。（生物谷Bioon.com）
doi:10.1177/0959683611400218
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Pollen-inferred climate changes and vertical shifts of alpine vegetation belts on the northern slope of the Nyainqentanglha mountains (central Tibetan Plateau) since 8.4 kyr BP
Li, Quan; Lu, Houyuan; Zhu, Liping; Wu, Naiqin; Wang, Junbo; Lu, Xinmiao
Fossil pollen from Nam Co and modern pollen from altitudinal vegetation belts around the lake are investigated to reveal alpinevegetation succession in response to climate changes during the Holocene in the central Tibetan Plateau. The discriminantanalysis on 37 topsoil samples shows that pollen samples from alpine steppe at lower elevations (<4800 m) and alpine meadowon upper slopes (4800–5200 m) can be distinguished by their pollen assemblages. Samples from alpine steppe contain more Artemisia (25.1%) and Poaceae pollen (11.5%), whereas those from alpine meadow are dominated by Cyperaceae pollen (>60%). Our resultindicates that the pollen ratio of Artemisia to Cyperaceae (A/Cy) can be used as an indicator of the vertical shift of vegetation belts and temperature changes in thecentral Tibetan Plateau as suggested by previous studies. A history of the vertical shift of vegetation belts on the northernslope of Nyainqentanglha Mountains and climate changes since 8.4 kyr BP are thus recovered by 198 fossil pollen assemblagesfrom a 332 cm core of Nam Co. Paleovegetation reconstructed from fossil pollen assemblages through discriminant analysis showsa general downward shift of altitudinal vegetation belts, suggesting a decline in the temperature trend since 8.4 kyr BP.This result is consistent with the reduction of A/Cy ratios. The fossil pollen record also reveals warm and wet climate duringthe early to mid Holocene, and cold and dry conditions during the late Holocene in the Nam Co area. A comparison of Holoceneclimatic reconstructions across the Plateau indicates that termination of maximum moisture at around 6–5.5 kyr BP in our recordis associated with the southeastward retreat of the Southwest Monsoon.
