In the past 30 years,observational climate datasets reveal a significant a drying and warming trend over in North China.Understanding of climatic variability over North China and its driving mechanism in a long-term p...In the past 30 years,observational climate datasets reveal a significant a drying and warming trend over in North China.Understanding of climatic variability over North China and its driving mechanism in a long-term perspective is,however,limited to a few sites only,especially the lack of temperature reconstructions based on latewood density and blue intensity.In this study,we developed a 281-year latewood blue intensity chronology based on 45 cores of Picea meyeri in western North China.Based on the discovery that the warm season(May–August)mean maximum temperature is the main controlling factor affecting the change in blue light reflection intensity,we established a regression model that explained 37%of the variance during the calibration period(1950–2020),allowing to trace the mean maximum temperature up to 1760 CE.From the past 261 years,we identified seven persistent high temperature periods(1760–1773,1778–1796,1805–1814,1869–1880,1889–1934,1984–2000,2004–2020)and three persistent low temperature periods(1815–1868,1935–1963,1969–1983)in North China.Comparisons of a nearby temperature reconstructions and climate gridded data indicate that our reconstruction record a wide range of temperature variations in North China.The analysis of links between large-scale climatic variation and the temperature reconstruction showed that there is a relationship between extremes in the warm season temperature and anomalous SSTs in the equatorial eastern Pacific,and implied that the extremes in the warm season temperature in North China will be intensified under future global warming.展开更多
Background:Trees and forests in drylands help mitigate the challenges through provision of economic products and vital environmental services such as habitat for biodiversity,prevention of erosion and desertification,...Background:Trees and forests in drylands help mitigate the challenges through provision of economic products and vital environmental services such as habitat for biodiversity,prevention of erosion and desertification,regulation of water,microclimate,and soil fertility.The condition and changes in dry forests can be assessed by using ecological indicators able to quantify spatial and temporal changes in vegetation.One of the ways to determine the condition of the forest is to study the dominant tree species and its regeneration.Our study aimed to assess whether the abundance of Prosopis flexuosa saplings is affected by environmental and biological factors.Results:To evaluate the first variables we used data from remote sensing such as satellite images and Aster Global Digital Model(GDEM).The second set of variables was about exotic and native ungulates and we used feces of these animals and camera traps to take data.We found that sapling abundance related positively to sandy substrates and negatively to Wetness Index.On the other hand,in relation to biological variables,the abundance of saplings was positively affected by density of adult trees and by number of seeds dispersed by equines,but space use by Lama guanicoe had a negative relationship with saplings.This research shows that P.flexuosa saplings are benefited from sandy substrates and the conditions around adult trees.In addition to this,we found that exotic ungulates in low densities have neutral(i.e.cattle)or positive(i.e.equines)effects on sapling abundance.Conclusions:Based on these findings,we conclude that regeneration of the population of P.flexuosa in our study area has no major problems.In addition,we corroborated that the presence of exotic and domestic ungulates in low densities does not have deleterious consequences for saplings of the dominant tree,P.flexuosa.展开更多
The main objective of this research is to recognize several geological structures associated with the shear zones of the MFFS（Magallanes-Fagnano fault system） by the analysis and interpretation of gravimetric anomal...The main objective of this research is to recognize several geological structures associated with the shear zones of the MFFS（Magallanes-Fagnano fault system） by the analysis and interpretation of gravimetric anomalies. Besides, to compare the gravimetrical response of the cortical blocks that integrate the region under study, which is related to the different morphotectonic domains recognized in the region. This research was developed employing data obtained from World Gravity 1.0, which includes earth and satellite gravity data derived from the EGM2008 model. The study and interpretation of the MFFS from the analysis and processing of the gravimetric data, allowed appreciation of a noticeable correlation with the most superficial cortical structure.展开更多
The Guandacol Formation corresponds to glacial episode 4 of the“Late Paleozoic Ice Age”in western Gondwana.It represents the final glaciation of westernmost Gondwana and the beginning of deglaciation that swept acro...The Guandacol Formation corresponds to glacial episode 4 of the“Late Paleozoic Ice Age”in western Gondwana.It represents the final glaciation of westernmost Gondwana and the beginning of deglaciation that swept across the supercontinent throughout the rest of the Paleozoic.A succession of transitional sedimentary facies associations characterizes the eastern outcrops of the Guandacol Formation.These facies associations are interlayered with several deposits of mass-transport complexes(MTC)and present the occasional opportunity to conduct a deep-time analysis of the effect of tectonism in what is interpreted to be glacially-influenced deposits.Six sedimentary facies associations were recognized in the lower part of the Guandacol Formation.Facies association 1(interbedded diamictites,sandstones,and mudstones)overlies MTC 1 and is interpreted as sedimentation into a marine glacially-influenced outwash fan.Facies association 2(ponded interbedded sandstones,mudstones,and diamictites)was deposited as subaqueous underflows/turbidites and debris flows covering the irregular paleotopography of MTC 2.Facies association 3(white medium-to coarse-grained sandstones and conglomerates)represents a small deltaic system.Facies association 4(rhythmites with dropstones and sandstones)was deposited in a partially ponded water body resulting from the collapse and paleotopography of MTC 3.Facies association 5(coarsening-upward cycles of mudstones and sandstones)was deposited in prodelta to delta front environments.Finally,facies association 6(conglomerates,sandstones,and mudstones)corresponds to the subaerial deltaic platform.The evolution of depositional environments suggests three glacially-linked stages:Stage 1—Initial retreat of the nearby ice masses(facies association 1);Stage 2—Further retreat of glaciers and the progressive decoupling between ice masses and sea(facies associations 2 and 3);and Stage 3—Postglacial sedimentation dominated by deltaic progradation during highstand conditions(facies associations 4 to 6).The importance of the paleogeographic context is emphasized in which the tectonism triggered recurrent events of MTC that continually modified the topography and sedimentary patterns,interrupting and complicating the stratigraphy of the interpreted glacial and postglacial sedimentation.展开更多
基金National Natural Science Foundation of China,No.32061123008。
文摘In the past 30 years,observational climate datasets reveal a significant a drying and warming trend over in North China.Understanding of climatic variability over North China and its driving mechanism in a long-term perspective is,however,limited to a few sites only,especially the lack of temperature reconstructions based on latewood density and blue intensity.In this study,we developed a 281-year latewood blue intensity chronology based on 45 cores of Picea meyeri in western North China.Based on the discovery that the warm season(May–August)mean maximum temperature is the main controlling factor affecting the change in blue light reflection intensity,we established a regression model that explained 37%of the variance during the calibration period(1950–2020),allowing to trace the mean maximum temperature up to 1760 CE.From the past 261 years,we identified seven persistent high temperature periods(1760–1773,1778–1796,1805–1814,1869–1880,1889–1934,1984–2000,2004–2020)and three persistent low temperature periods(1815–1868,1935–1963,1969–1983)in North China.Comparisons of a nearby temperature reconstructions and climate gridded data indicate that our reconstruction record a wide range of temperature variations in North China.The analysis of links between large-scale climatic variation and the temperature reconstruction showed that there is a relationship between extremes in the warm season temperature and anomalous SSTs in the equatorial eastern Pacific,and implied that the extremes in the warm season temperature in North China will be intensified under future global warming.
基金supported by“The chica,the retamo,and the algarrobo:umbrella species for the conservation of the Native Forest of the Ischigualasto Provincial Park and nearby zones.Biological interactions,effects of human activities and their mitigation”,Plan for the Conservation of Native Forests Law 26.331.
文摘Background:Trees and forests in drylands help mitigate the challenges through provision of economic products and vital environmental services such as habitat for biodiversity,prevention of erosion and desertification,regulation of water,microclimate,and soil fertility.The condition and changes in dry forests can be assessed by using ecological indicators able to quantify spatial and temporal changes in vegetation.One of the ways to determine the condition of the forest is to study the dominant tree species and its regeneration.Our study aimed to assess whether the abundance of Prosopis flexuosa saplings is affected by environmental and biological factors.Results:To evaluate the first variables we used data from remote sensing such as satellite images and Aster Global Digital Model(GDEM).The second set of variables was about exotic and native ungulates and we used feces of these animals and camera traps to take data.We found that sapling abundance related positively to sandy substrates and negatively to Wetness Index.On the other hand,in relation to biological variables,the abundance of saplings was positively affected by density of adult trees and by number of seeds dispersed by equines,but space use by Lama guanicoe had a negative relationship with saplings.This research shows that P.flexuosa saplings are benefited from sandy substrates and the conditions around adult trees.In addition to this,we found that exotic ungulates in low densities have neutral(i.e.cattle)or positive(i.e.equines)effects on sapling abundance.Conclusions:Based on these findings,we conclude that regeneration of the population of P.flexuosa in our study area has no major problems.In addition,we corroborated that the presence of exotic and domestic ungulates in low densities does not have deleterious consequences for saplings of the dominant tree,P.flexuosa.
基金funded through Project lE/750 CS-CICITCA and the permanent programs"South American Tectonics"and"Neotectonic of Argentina"executed by the Gabinete de Geomorfología y Neotectónica(INGEO-UNSJ)
文摘The main objective of this research is to recognize several geological structures associated with the shear zones of the MFFS（Magallanes-Fagnano fault system） by the analysis and interpretation of gravimetric anomalies. Besides, to compare the gravimetrical response of the cortical blocks that integrate the region under study, which is related to the different morphotectonic domains recognized in the region. This research was developed employing data obtained from World Gravity 1.0, which includes earth and satellite gravity data derived from the EGM2008 model. The study and interpretation of the MFFS from the analysis and processing of the gravimetric data, allowed appreciation of a noticeable correlation with the most superficial cortical structure.
基金supported by the Agencia Nacional de Promoción de la Investigación,el Desarrollo Tecnológico y la Innovación (PICT, 2020-01294)the University of Wisconsin-Milwaukee Center for Latin American and Caribbean Studies,the Nelson Cherkauer Lasca Legacy Scholarshipthe National Science Foundation (Grant No. 1559231)
文摘The Guandacol Formation corresponds to glacial episode 4 of the“Late Paleozoic Ice Age”in western Gondwana.It represents the final glaciation of westernmost Gondwana and the beginning of deglaciation that swept across the supercontinent throughout the rest of the Paleozoic.A succession of transitional sedimentary facies associations characterizes the eastern outcrops of the Guandacol Formation.These facies associations are interlayered with several deposits of mass-transport complexes(MTC)and present the occasional opportunity to conduct a deep-time analysis of the effect of tectonism in what is interpreted to be glacially-influenced deposits.Six sedimentary facies associations were recognized in the lower part of the Guandacol Formation.Facies association 1(interbedded diamictites,sandstones,and mudstones)overlies MTC 1 and is interpreted as sedimentation into a marine glacially-influenced outwash fan.Facies association 2(ponded interbedded sandstones,mudstones,and diamictites)was deposited as subaqueous underflows/turbidites and debris flows covering the irregular paleotopography of MTC 2.Facies association 3(white medium-to coarse-grained sandstones and conglomerates)represents a small deltaic system.Facies association 4(rhythmites with dropstones and sandstones)was deposited in a partially ponded water body resulting from the collapse and paleotopography of MTC 3.Facies association 5(coarsening-upward cycles of mudstones and sandstones)was deposited in prodelta to delta front environments.Finally,facies association 6(conglomerates,sandstones,and mudstones)corresponds to the subaerial deltaic platform.The evolution of depositional environments suggests three glacially-linked stages:Stage 1—Initial retreat of the nearby ice masses(facies association 1);Stage 2—Further retreat of glaciers and the progressive decoupling between ice masses and sea(facies associations 2 and 3);and Stage 3—Postglacial sedimentation dominated by deltaic progradation during highstand conditions(facies associations 4 to 6).The importance of the paleogeographic context is emphasized in which the tectonism triggered recurrent events of MTC that continually modified the topography and sedimentary patterns,interrupting and complicating the stratigraphy of the interpreted glacial and postglacial sedimentation.
