Mangroves accumulate sedimentary sequences, where cores can provide historical records of mangrove evolution with past climate change and human activity. The study traced the history of mangrove evolution during the p...Mangroves accumulate sedimentary sequences, where cores can provide historical records of mangrove evolution with past climate change and human activity. The study traced the history of mangrove evolution during the past one hundred years in a mangrove swamp of Maowei Sea, SW China. The sedimentation rates(0.38-0.95 cm yr^(-1)) were calculated on the basis of ln(^(210)Pb_(xs)/Al) and mass depth in the core sediments. Chemical tracers, such as δ^(13)C_(org) and C:N values, were utilized to trace the contribution of mangrove-derived organic matter using a ternary mixing model. Because of potential diagenetic alteration and / or overlap in the isotopic signatures of different components, simultaneous use of mangrove pollen diagrams can help to supplement some of these limitations. Combined with mangrove pollen, mangrove evolution was reconstructed and could be divided into three stages: flourishment(1886-1905 AD), slight degradation(1905-1949 AD) and rapid degradation period(1949-2007 AD), which was consistent with previous reports. The reclamation of mangrove swamps to shrimp ponds was the major reason for rapid degradation of mangrove ecosystems in recent years, rather than climate change in the region.展开更多
In order to reconstruct the paleoproductivity evolution history of the West Philippine Sea during the last 700 ka, the vertical gradient of Δδ13C in dissolved inorganic carbon Δδ13C between those of foraminifera P...In order to reconstruct the paleoproductivity evolution history of the West Philippine Sea during the last 700 ka, the vertical gradient of Δδ13C in dissolved inorganic carbon Δδ13C between those of foraminifera Pulleniatina obliquiloculata and Cibicidoides wuellerstorfi） and planktonic foraminiferal assemblages were analysed in piston Core MD06-3047 retrieved from the Benham Rise （east of the Luzon Island）. Paleoproductivity evolution in the West Philippine Sea during the last 700 ka is closely related to glacial-interglacial cycles and precession-controlled insolation. Controlling factors ofpaleoproductivity could have been both thermocline fluctuations related with ENSO-Iike processes and eolian input associated with East Asian winter monsoon, and the former could have been the primary factor. A higher productivity and a shallower thermocline coeval with the occurrence of low CO2 concentrations in the EPICA Dome C ice core might indicate that biological export production in the low-latitude could act as a significant sink in the global carbon cycle, and modify atmospheric CO2 concentrations. Spectral analysis further reveals that the paleoproductivity is mainly controlled by thermocline fluctuations subjected to ENSO processes responding to processional variability of insolation. High coherences in eccentricity, obliquity and precession periods fiuther revealing the close link between thermocline fluctuations, paleoproductivity and atmospheric CO2 levels.展开更多
基金supported by the National Key Scientific Research Project on Global Climate Change (Grant No. 2010CB 951203)the National Natural Science Foundation of China (Grant Nos. 41206057, 41576067, 41376075 and 41576061)
文摘Mangroves accumulate sedimentary sequences, where cores can provide historical records of mangrove evolution with past climate change and human activity. The study traced the history of mangrove evolution during the past one hundred years in a mangrove swamp of Maowei Sea, SW China. The sedimentation rates(0.38-0.95 cm yr^(-1)) were calculated on the basis of ln(^(210)Pb_(xs)/Al) and mass depth in the core sediments. Chemical tracers, such as δ^(13)C_(org) and C:N values, were utilized to trace the contribution of mangrove-derived organic matter using a ternary mixing model. Because of potential diagenetic alteration and / or overlap in the isotopic signatures of different components, simultaneous use of mangrove pollen diagrams can help to supplement some of these limitations. Combined with mangrove pollen, mangrove evolution was reconstructed and could be divided into three stages: flourishment(1886-1905 AD), slight degradation(1905-1949 AD) and rapid degradation period(1949-2007 AD), which was consistent with previous reports. The reclamation of mangrove swamps to shrimp ponds was the major reason for rapid degradation of mangrove ecosystems in recent years, rather than climate change in the region.
基金Supported by the National Natural Science Foundation of China(Nos.41230959,41076030,40906038,41106042,41006032)the Pilot Project of the Knowledge Innovation Program of Chinese Academy of Sciences(No.KZCX2-YW-221)the Foundation of Key Laboratory of Marine Geology and Environment of Chinese Academy of Sciences(No.MGE2011KG01)
文摘In order to reconstruct the paleoproductivity evolution history of the West Philippine Sea during the last 700 ka, the vertical gradient of Δδ13C in dissolved inorganic carbon Δδ13C between those of foraminifera Pulleniatina obliquiloculata and Cibicidoides wuellerstorfi） and planktonic foraminiferal assemblages were analysed in piston Core MD06-3047 retrieved from the Benham Rise （east of the Luzon Island）. Paleoproductivity evolution in the West Philippine Sea during the last 700 ka is closely related to glacial-interglacial cycles and precession-controlled insolation. Controlling factors ofpaleoproductivity could have been both thermocline fluctuations related with ENSO-Iike processes and eolian input associated with East Asian winter monsoon, and the former could have been the primary factor. A higher productivity and a shallower thermocline coeval with the occurrence of low CO2 concentrations in the EPICA Dome C ice core might indicate that biological export production in the low-latitude could act as a significant sink in the global carbon cycle, and modify atmospheric CO2 concentrations. Spectral analysis further reveals that the paleoproductivity is mainly controlled by thermocline fluctuations subjected to ENSO processes responding to processional variability of insolation. High coherences in eccentricity, obliquity and precession periods fiuther revealing the close link between thermocline fluctuations, paleoproductivity and atmospheric CO2 levels.
