POLLEN RECORD OF VEGETATION CHANGES IN TIANCAI LAKE AREA OF NORTHWESTERN YUNNAN OVER THE PAST 400 YEARS
Modern global warming and intensified human activities have cast increasing pressure on vegetation change on alpine regions.Study palaeovegetation on change in alpine region and reveal their response to climate change gains priority on understanding the current vegetation statues and their likely variations under global warming.Tiancai Lake(26° 38′N,99°43′E)on Laojun Mountain in Jianchuan County,Yunnan Province,is a typical alpine lake with continuous lake sediments and surrounded by dense forest,which makes it a suitable region to study the vegetation change and the mechanism responding to modern climate warming.Here,we collected a 43-cm sediment core from Tiancai Lake and conducted pollen analysis,based on which,detailed changes in vegetation composition,plant functional traits,and functional diversity in the Laojun Mountain area over the past 400 years were discussed.The age-depth model,established by using 137Cs and 210Pb,yielded that the deposition age of the bottom sediment was 1635 A.D.(1592～1635 A.D.).A total of 91 pollen taxa had been identified,including 32 families and 59 genera.There were 47 woody plant pollen taxa,27 terrestrial herbaceous taxa,3 wet herbaceous taxa,and 14 fern taxa,with an average pollen concentration of 70891 grains per gram.Pollen composition indicated that coniferous forests dominated the vegetation since 1600 A.D.Although the regional vegetation remained stable,notable shifts in vegetation composition has been uncovered.Specifically,Pinus exhibited an expanding trend before 1900 A.D,after which this trend reversed.The vegetation components of Tsuga and Abies have generally shown a downward trend after 1900 A.D.Conversely,broad-leaved woody plant taxa have demonstrated a long-term increasing trend,peaking after 1960s.Reconstructed plant functional traits based on pollen taxonomy suggest that leaf dry matter content and leaf thickness were elevated before 1900 A.D.,followed by fluctuating decreasing trends.Leaf area and specific leaf area increased significantly after 1900 A.D.Furthermore,the functional dispersion(FDis)of plants,reconstructed based on changes in plant functional traits,transitioned from a fluctuating decrease to an increasing trend around 1900 A.D.Redundancy analysis indicates that mean annual temperature(MAT),total solar irradiance(TSI),and atmospheric CO2 concentration may have been the primary drivers on regional vegetation changes in Tiancai Lake area.Referring to modern ecological theory,heat(temperature),light,and CO2 concentration are crucial environmental factors that influence plant photosynthesis and growth.Over the past 400 years,increases in MAT and CO2 concentration,along with changes in TSI,may have continuously influenced plant functional traits,subsequently leading to alterations in plant composition and functional diversity.Our results manifested that the shifts in plant functional traits could be an important mechanism for plants responding to climate change,which would benefit our current knowledge of the long-term climate variations effects on vegetation change in the high-altitude regions of northwest Yunnan.
pollenvegetation changeplant functional traitspast 400 yearsTiancai Lake
万方数据
维普
