RESPONSE OF FIRE TO VEGETATION AND CLIMATE CHANGE DURING THE PLIOCENE-PLEISTOCENE IN THE NIHEWAN BASIN
The Pliocene-Pleistocene is an important period for the climate to change from the warm Pliocene to the glacial-interglacial cycle in Quaternary.It is also a key stage for the formation of modern climate and ecosystem.As an indispensable part of the Earth's ecosystem,fire is universal phenomenon,which directly affects the evolution of the structure and function of the Earth's ecological environment,and plays an important role in maintaining ecological balance.By analyzing the charcoal from 333 sediment samples from the NHA drill core during the Pliocene-Pleistocene(2.89～1.78 Ma),combined with the previous results of pollen analysis,this study revealed the fire activity process,the response characteristics of fire activity to vegetation and climate change and the relationship between fire intensity and fire frequency in the Nihewan Basin.The samples were taken from the 175.2～106.0 m depth of the NHA drill core(40° 13′0.4″N,114° 38′32.3″E;938 m a.s.l.)with a total length of 69.2 m,which was located in Haojiatai in the eastern part of the Nihewan Basin.The samples used in this study were mainly composed of horizontally-bedded bluish-grey,brownish-black and reddish-brown clays and silts,containing abundant mollusk fossils and charcoal in several samples(such as ca.132m and 148 m).The lithology and fossil assemblages indicate that the depositional environment was lacustrine-swamp facies.The results showed that:(1)The fire intensity can be divided into one period with high intensity(2.74～2.32 Ma)and two periods with low intensity(2.89～2.74 Ma and 2.32～1.78 Ma)during the Pliocene-Pleistocene in Nihewan Basin.(2)The concentration of total charcoal and coarse charcoal(＞125 μm)showed a significant 41 ka cycle,indicating that the fire intensity in Nihewan Basin was significantly influenced by the ice volume in high latitude region.(3)Plant richness is the most important factor affecting fire intensity,while vegetation type had little effect.(4)The change of fire intensity and frequency is not completely synchronized,which can be classified into three modes:high intensity-high frequency,high intensity-low frequency and low intensity-high frequency.(5)2.60～2.14 Ma,fire activity was the strongest during the study section,showing high fire intensity and high fire frequency.During this period,the Nihewan Basin was affected by global climate cooling and frequent climate fluctuation,the vegetation was mainly coniferous forest,with large plant richness,thus lead to the strong wildfire activity.(6)High intensity-high frequency fire activities usually occurred in climatic transition or paleomagnetic reverse periods,such as the peaks of fire intensity and frequency during 2.60～2.56 Ma,2.15～2.14 Ma and 1.82～1.78 Ma corresponding respectively to the Matuyama/Gauss,Reunion and Olduvai.It may be related to the increase of fire activity in the Nihewan Basin due to climate fluctuation caused by paleomagnetic reverses.
Nihewan BasinPliocene-Pleistocenecharcoalfire intensityfire frequency
万方数据
维普
