近日，國(guó)際知名古氣候?qū)W刊物《全新世》（The Holocene）發(fā)表了中科院地質(zhì)與地球物理研究所新生代地質(zhì)與環(huán)境重點(diǎn)實(shí)驗(yàn)室的研究成果,，研究人員發(fā)現(xiàn)太陽(yáng)輻射影響高原氣候變化和植被演替,。
青藏高原中部草原、草甸植被對(duì)氣候變化非常敏感,。前人通過(guò)該地區(qū)全新世孢粉記錄重建了高寒草原,、高寒草甸植被帶的水平遷移與氣候變化過(guò)程。但是,，有關(guān)高原中部孢粉記錄中莎草科花粉的植被和氣候指示意義尚存爭(zhēng)議,，迄今對(duì)高原中部垂直植被帶遷移與氣候變化的關(guān)系了解甚少。
博士研究生李泉與導(dǎo)師呂厚遠(yuǎn)研究員及其合作者對(duì)青藏高原中部納木錯(cuò)湖區(qū)37個(gè)表土和NMLC-1湖芯198個(gè)沉積物樣品開(kāi)展了孢粉分析,。研究顯示,，該區(qū)表土孢粉組合可指示并區(qū)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帶。高寒草原表土孢粉組合以蒿屬花粉的高含量（平均25.1%）為特征,，蒿屬與莎草科花粉比值（A/Cy）平均為4.9,；高寒草甸表土孢粉組合以莎草科占絕對(duì)優(yōu)勢(shì)（56.8%），A/Cy平均值為0.1,。A/Cy比值可區(qū)分高寒草原帶（>1.0）和高寒草甸帶（<1.0）,，并作為垂直植被帶遷移和氣候溫度變化的指示。
通過(guò)納木錯(cuò)NMLC-1孔全新世化石孢粉記錄,，結(jié)合A/Cy比值變化與判別分析結(jié)果,，研究人員重建了距今8400年以來(lái)伴隨氣候溫度的持續(xù)降低,，念青唐古拉山北坡垂直植被帶逐漸向下遷移的過(guò)程。該區(qū)全新世植被帶遷移和溫度變化的趨勢(shì),，與同時(shí)期北半球夏季太陽(yáng)輻射變化較一致,，反映了太陽(yáng)輻射直接影響了高原中部全新世氣候變化和植被演替；對(duì)比同時(shí)期高原不同區(qū)域植被與氣候變化序列,，他們認(rèn)為全新世西南季風(fēng)的進(jìn)退主要影響了高原中部濕度的變化,。（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.
