The objective of this study is to analyze the dendrochronological potential of two Sahelian species (<i><span style="font-family:Verdana;">B. senegalensis</span></i><span style=&qu...The objective of this study is to analyze the dendrochronological potential of two Sahelian species (<i><span style="font-family:Verdana;">B. senegalensis</span></i><span style="font-family:Verdana;"> and </span><i><span style="font-family:Verdana;">S. birrea</span></i><span style="font-family:Verdana;">) and to evaluate the rela</span><span style="font-family:Verdana;">tionships between their growth rings and the climate. The study was con</span><span style="font-family:Verdana;">ducted in 2016 in the Ferlo area of Senegal. The biological material consists of wood slices, taken from the trunks of these adult woody species at 0.30 m and 1.30 m from the ground after they have been felled. The technique used to examine the slices consists in identifying their rings, establishing their structures, inter-dating them and studying the relationship between the identified rings and climatic factors. The results showed that the species had thin, clear, highly visible and sharp rings. The limit of growth is marked by a line of parenchyma. Intradatation series carried out on the chronologies made it possible to estimate the ages of the individuals, which vary from 10 to 38 years for </span><i><span style="font-family:Verdana;">B. senegalensis</span></i><span style="font-family:Verdana;"> and from 29 to 50 years for </span><i><span style="font-family:Verdana;">S. birrea</span></i><span style="font-family:Verdana;">. Their average growth </span><span style="font-family:Verdana;">rates are estimated at 0.906 mm/year and 0.89 mm/year respectively. The </span><span style="font-family:Verdana;">chronological sequences are 29 years (1987-2016) for </span><i><span style="font-family:Verdana;">B. senegalensis</span></i><span style="font-family:Verdana;"> and 38 years (1964-2012) for </span><i><span style="font-family:Verdana;">S. birrea</span></i><span style="font-family:Verdana;">. The results revealed that there is no significant correlation between the growth chronologies of </span><i><span style="font-family:Verdana;">B. senegalensis</span></i><span style="font-family:Verdana;"> and the </span><span style="font-family:Verdana;">climatic regressors (temperature and precipitation). In contrast, the ring-</span><span style="font-family:Verdana;">climate relationship shows that in </span><i><span style="font-family:Verdana;">S. birrea</span></i><span style="font-family:Verdana;"> winter precipitation positively influences ring growth while temperature has no effect on ring growth in this species. This study provides a better understanding of the response of forest ecosystems to possible climate change, particularly in the current context of sustainable forest management.</span>展开更多
Since the 50s, many changes are observed in the climate of the globe, the warming of the atmosphere and the ocean, the decrease in the extent of snow and ice, and rising sea levels. In addition to the demographic pres...Since the 50s, many changes are observed in the climate of the globe, the warming of the atmosphere and the ocean, the decrease in the extent of snow and ice, and rising sea levels. In addition to the demographic pressure, the Maghreb countries are suffering from the drought, which accentuates the phenomenon of desertification and soil erosion, as well as their salinity, which leads to the salinization and depletion of water resources. In Morocco, the climate change leads to the erosion of the soil under the effect of desertification resulting in siltation of reservoirs and the increased salinization of soil and water resources. The Essaouira basin, which is the subject of this study, is located at the Western extremity of the High Atlas to the Southeast of the Essaouira city;between 31°20' to 31°30'N and between 9°00' to 9°46'W. The basin is characterized by a semi-arid climate with average annual rainfall of around 300 mm·year<sup>-1</sup> and an average temperature of 20°C. Considering the importance of the aquifer in Essaouira in the supply of the region's groundwater, a study was conducted to assess quantitatively and qualitatively the impact of climate change on water resources in this area. The aquifers present in this region are one of cenomano-turonian upstream and plio-quaternary downstream, separated by the diaper of Tidzi. A piezometric map of the basin was made (1990-2009) and the hydrochemical method of the waters shows that they present a facies Na-Cl with an electrical conductivity ranging from 700 to 7000 μs/cm. The isotopic tracers like <sup>18</sup>O, <sup>2</sup>H, <sup>3</sup>H and <sup>14</sup>C were analyzed to determine the age of groundwater, and a right local meteoric close to the right meteoric world characterizing the precipitation of oceanic origin has been determined. The Essaouira basin turns out to be very vulnerable and sensitive to climate change because its recharge is entirely dependent on the rainwater. These results should be taken in consideration for the future water management in the region.展开更多
In a context of climate change characterized by rising temperatures, increased greenhouse gases and frequent droughts, the Sahel is presented as one of the most vulnerable areas to the adverse effects of climate chang...In a context of climate change characterized by rising temperatures, increased greenhouse gases and frequent droughts, the Sahel is presented as one of the most vulnerable areas to the adverse effects of climate change. The Sahel is presented as one of the most vulnerable areas to the adverse effects of climate change. The objective of this study is to assess the above-ground biomass and carbon stock of three Sahelian species: Acacia raddiana tortilis (Forsk.) hayne ssp. raddiana (savi) Brenan, Acacia senegal (L.) Willd and Balanites aegyptiaca (L.). The study was carried out in northern Senegal commonly known as Ferlo. Biomasses of the populations of the three target species were first assessed by harvesting the entire epigenetic part of the species and then modelled by correlation using dendrometric parameters measured on each individual of the sample. Two models, mono-specific and multi-species, were used. The results obtained showed that the diameter at breast height (x) and the parameter best correlated to the epigeal biomass (y). The dry biomass of woody plants was 31.4 ± 15.2 kg/tree for B. aegyptiaca, 30.6 ± 13.2 kg/tree for A. senegal and 26.2 ± 11.1 kg/tree for A. raddiana;i.e. carbon equivalents of 14.75 - 14.38 - 12.31 kg/tree respectively. The amount of carbon contained in the above-ground woody biomass is estimated at 4.48 t/ha. The carbon equivalent, atmospheric CO<sub>2</sub> is estimated at 16.44 tons of CO<sub>2</sub>/ha and based on the actual density of Ferlo (108.08 ± 49.79 ind/ha) the sequestered carbon of the area is estimated at 1777.008 tons of CO<sub>2</sub>. The comparison between the models developed in this study and the multispecific or mono-specific models from the literature showed substantial differences. This study contributes to a better understanding of the contribution of Sahelian woody species to carbon sequestration and the results could be used in the framework of adaptation to climate change.展开更多
Sediments spanning the last 30000 yr BP wereobtained from two sections in the southern part of the Teng-ger Desert, northwestern China (3810′46″N, 10245′53″E). The pollen assemblage suggested a Picea forest domina...Sediments spanning the last 30000 yr BP wereobtained from two sections in the southern part of the Teng-ger Desert, northwestern China (3810′46″N, 10245′53″E). The pollen assemblage suggested a Picea forest domination under a wetter and cooler environment from 27580 to 23510 yr BP. During the following period from 23510 to 21880 yr BP a Cyperaceae meadow occurred under a wet and coldclimate. Wetter and cooler conditions returned and a Piceaforest re-occupied this region between 21880 and 20910 yrBP. From 20910 to 15590 yr BP a steppe under a dryenvironment dominated the region. The first temperatureincrease started at ca.15590 yr BP. The pollen assemblagecovering the period between 15590 and 10890 yr BP can be divided into six minor zones, suggesting that the vegetation compositions changed rapidly under unstable climate.Between 10710 and 10370 yr BP the climate became cold and dry again. The climatic conditions became warmer and more humid between 10260 and 9140 yr BP. From 8450 to 7950 yr BP a steppe landscape under a dry climate occupied this region. Between 7950 and 7290 yr BP climate seemed more humid. The following period from 7290 to 5670 yr BP wasgenerally warm. The period between 5670 and 3510 yr BPwas characterized by dramatic climatic oscillations.Relatively cold intervals appeared around 7760 and 7380,6490—6290, 5670—5010, 4470—3510 yr BP. Twopronounced dry events occurred in 6290—5670 and 5010—4470 yr BP with a marked wet spell from 3510 to 3000 yr BP.展开更多
文摘The objective of this study is to analyze the dendrochronological potential of two Sahelian species (<i><span style="font-family:Verdana;">B. senegalensis</span></i><span style="font-family:Verdana;"> and </span><i><span style="font-family:Verdana;">S. birrea</span></i><span style="font-family:Verdana;">) and to evaluate the rela</span><span style="font-family:Verdana;">tionships between their growth rings and the climate. The study was con</span><span style="font-family:Verdana;">ducted in 2016 in the Ferlo area of Senegal. The biological material consists of wood slices, taken from the trunks of these adult woody species at 0.30 m and 1.30 m from the ground after they have been felled. The technique used to examine the slices consists in identifying their rings, establishing their structures, inter-dating them and studying the relationship between the identified rings and climatic factors. The results showed that the species had thin, clear, highly visible and sharp rings. The limit of growth is marked by a line of parenchyma. Intradatation series carried out on the chronologies made it possible to estimate the ages of the individuals, which vary from 10 to 38 years for </span><i><span style="font-family:Verdana;">B. senegalensis</span></i><span style="font-family:Verdana;"> and from 29 to 50 years for </span><i><span style="font-family:Verdana;">S. birrea</span></i><span style="font-family:Verdana;">. Their average growth </span><span style="font-family:Verdana;">rates are estimated at 0.906 mm/year and 0.89 mm/year respectively. The </span><span style="font-family:Verdana;">chronological sequences are 29 years (1987-2016) for </span><i><span style="font-family:Verdana;">B. senegalensis</span></i><span style="font-family:Verdana;"> and 38 years (1964-2012) for </span><i><span style="font-family:Verdana;">S. birrea</span></i><span style="font-family:Verdana;">. The results revealed that there is no significant correlation between the growth chronologies of </span><i><span style="font-family:Verdana;">B. senegalensis</span></i><span style="font-family:Verdana;"> and the </span><span style="font-family:Verdana;">climatic regressors (temperature and precipitation). In contrast, the ring-</span><span style="font-family:Verdana;">climate relationship shows that in </span><i><span style="font-family:Verdana;">S. birrea</span></i><span style="font-family:Verdana;"> winter precipitation positively influences ring growth while temperature has no effect on ring growth in this species. This study provides a better understanding of the response of forest ecosystems to possible climate change, particularly in the current context of sustainable forest management.</span>
文摘Since the 50s, many changes are observed in the climate of the globe, the warming of the atmosphere and the ocean, the decrease in the extent of snow and ice, and rising sea levels. In addition to the demographic pressure, the Maghreb countries are suffering from the drought, which accentuates the phenomenon of desertification and soil erosion, as well as their salinity, which leads to the salinization and depletion of water resources. In Morocco, the climate change leads to the erosion of the soil under the effect of desertification resulting in siltation of reservoirs and the increased salinization of soil and water resources. The Essaouira basin, which is the subject of this study, is located at the Western extremity of the High Atlas to the Southeast of the Essaouira city;between 31°20' to 31°30'N and between 9°00' to 9°46'W. The basin is characterized by a semi-arid climate with average annual rainfall of around 300 mm·year<sup>-1</sup> and an average temperature of 20°C. Considering the importance of the aquifer in Essaouira in the supply of the region's groundwater, a study was conducted to assess quantitatively and qualitatively the impact of climate change on water resources in this area. The aquifers present in this region are one of cenomano-turonian upstream and plio-quaternary downstream, separated by the diaper of Tidzi. A piezometric map of the basin was made (1990-2009) and the hydrochemical method of the waters shows that they present a facies Na-Cl with an electrical conductivity ranging from 700 to 7000 μs/cm. The isotopic tracers like <sup>18</sup>O, <sup>2</sup>H, <sup>3</sup>H and <sup>14</sup>C were analyzed to determine the age of groundwater, and a right local meteoric close to the right meteoric world characterizing the precipitation of oceanic origin has been determined. The Essaouira basin turns out to be very vulnerable and sensitive to climate change because its recharge is entirely dependent on the rainwater. These results should be taken in consideration for the future water management in the region.
文摘In a context of climate change characterized by rising temperatures, increased greenhouse gases and frequent droughts, the Sahel is presented as one of the most vulnerable areas to the adverse effects of climate change. The Sahel is presented as one of the most vulnerable areas to the adverse effects of climate change. The objective of this study is to assess the above-ground biomass and carbon stock of three Sahelian species: Acacia raddiana tortilis (Forsk.) hayne ssp. raddiana (savi) Brenan, Acacia senegal (L.) Willd and Balanites aegyptiaca (L.). The study was carried out in northern Senegal commonly known as Ferlo. Biomasses of the populations of the three target species were first assessed by harvesting the entire epigenetic part of the species and then modelled by correlation using dendrometric parameters measured on each individual of the sample. Two models, mono-specific and multi-species, were used. The results obtained showed that the diameter at breast height (x) and the parameter best correlated to the epigeal biomass (y). The dry biomass of woody plants was 31.4 ± 15.2 kg/tree for B. aegyptiaca, 30.6 ± 13.2 kg/tree for A. senegal and 26.2 ± 11.1 kg/tree for A. raddiana;i.e. carbon equivalents of 14.75 - 14.38 - 12.31 kg/tree respectively. The amount of carbon contained in the above-ground woody biomass is estimated at 4.48 t/ha. The carbon equivalent, atmospheric CO<sub>2</sub> is estimated at 16.44 tons of CO<sub>2</sub>/ha and based on the actual density of Ferlo (108.08 ± 49.79 ind/ha) the sequestered carbon of the area is estimated at 1777.008 tons of CO<sub>2</sub>. The comparison between the models developed in this study and the multispecific or mono-specific models from the literature showed substantial differences. This study contributes to a better understanding of the contribution of Sahelian woody species to carbon sequestration and the results could be used in the framework of adaptation to climate change.
基金supported by the National Natural Science Foundation of China(Grant No.40171094)the Ministry of Science and Technology of China(Grant No.G2000048701).
文摘Sediments spanning the last 30000 yr BP wereobtained from two sections in the southern part of the Teng-ger Desert, northwestern China (3810′46″N, 10245′53″E). The pollen assemblage suggested a Picea forest domination under a wetter and cooler environment from 27580 to 23510 yr BP. During the following period from 23510 to 21880 yr BP a Cyperaceae meadow occurred under a wet and coldclimate. Wetter and cooler conditions returned and a Piceaforest re-occupied this region between 21880 and 20910 yrBP. From 20910 to 15590 yr BP a steppe under a dryenvironment dominated the region. The first temperatureincrease started at ca.15590 yr BP. The pollen assemblagecovering the period between 15590 and 10890 yr BP can be divided into six minor zones, suggesting that the vegetation compositions changed rapidly under unstable climate.Between 10710 and 10370 yr BP the climate became cold and dry again. The climatic conditions became warmer and more humid between 10260 and 9140 yr BP. From 8450 to 7950 yr BP a steppe landscape under a dry climate occupied this region. Between 7950 and 7290 yr BP climate seemed more humid. The following period from 7290 to 5670 yr BP wasgenerally warm. The period between 5670 and 3510 yr BPwas characterized by dramatic climatic oscillations.Relatively cold intervals appeared around 7760 and 7380,6490—6290, 5670—5010, 4470—3510 yr BP. Twopronounced dry events occurred in 6290—5670 and 5010—4470 yr BP with a marked wet spell from 3510 to 3000 yr BP.
