HOLOCENE FLORISTIC DIVERSITY AND ITS RELATIONSHIP WITH PALEOCLIMATE IN THE WENQUAN WETLAND OF THE TIANSHAN MOUNTAINS,XINJIANG,CHINA
Floristic diversity in mountains of the arid region is highly sensitive to global climate change.In order to predict the possible impact of climate change on floristic diversity in the future,it is necessary to study the evolution of floristic diversity over the past and its response mechanism to climate change at different spatial and temporal scales.This study was based on 89 fossil pollen spectra from the lower part(126.75～50.25 cm)of the sediment core(length of 126.75 cm)collected from the Wenquan wetland(44° 58′N,80°01′E;1300 m a.s.l.)that is located in the western part of the Tianshan Mountains,Xinjiang,China.We reconstructed the overall variations of floristic diversity during the last 10300 years for the Wenquan region using multiple diversity indices including Shannon-Wiener index(H),Simpson index(D),palynological richness(E(T300))and Evenness(E).The results showed that the average values of different diversity indices of the Early Holocene(10300～7500 cal.a B.P.)were 1.46(Htotal),0.66(Dtotal),13.32(E(T300))and 0.33(E),respectively,suggesting a low floristic diversity;the average values of different diversity indices of the Middle Holocene(7500～4200 cal.a B.P.)increased to 1.99(Htotal),0.82(Dtotal),15.78(E(T300))and 0.48(E),respectively,suggesting a higher floristic diversity;and the average values of different diversity indices of the Late Holocene(4200～81 cal.a B.P.)were 1.84(Htotal),0.78(Dtotal),15.59(E(T300))and 0.43(E),respectively,and suggesting a slight decrease in plant diversity but still maintaining a relatively hight level.The palynological diversity largely depends on the vegetation communities within and surrounding the Wenquan wetland,and its response mechanism to paleoclimate change has been controlled by the coupled water-energy balance.This study showed that the overall floristic diversity was high with humid climate,but it was much lower with comparatively drier climate.The overall response of the diversity of all plants to climate change has been suggested to be stable,when compared with an individual plant.In addition,different pollen-based records for floristic diversity at various altitudes and vegetation zones have exhibited diverse patterns and trends over the Holocene,due to the marked differences in hydrothermal conditions.Therefore,more relevant studies in many geographical regions are needed to be carried out for exploring the past evolution of floristic diversity and its response mechanism to climate change with different hydrothermal conditions on various spatial-temporal scales.
万方数据
维普
