This study describes the floristic composition and structure of a woody stand in the Senegalese Sahel, paying particular attention to the edaphic factors of its floristic composition. A stratified inventory considerin...This study describes the floristic composition and structure of a woody stand in the Senegalese Sahel, paying particular attention to the edaphic factors of its floristic composition. A stratified inventory considering the different relief units was adopted. Woody vegetation was surveyed using a dendrometric approach. The results obtained show that the flora is dominated by a few species adapted to drought, such as Balanites aegyptiaca (L.) Del., Calotropis procera Ait. and Boscia senegalensis (Pers.). The distribution of this flora and the structure of the ligneous plants are linked to the topography. In the lowlands, the flora is more diversified and the ligneous plants reach their optimum level of development compared with the higher relief areas. In the lowlands, there are a few woody species which, in the past, were indicative of better climatic conditions. These are Anogeissus leiocarpus (DC.), Commiphora africana (A. Rich.), Feretia apodanthera Del., Loeseneriella africana (A. Smith), Mitragyna inermis (Willd.) and Sclerocarya birrea (A. Rich). It is important that their reintroduction into reforestation projects takes account of their edaphic preference.展开更多
The main objective of the study was to investigate the diversity of the woody stratum of the vegetation in intercommunity rangelands in the department of Koungheul based on an ecological inventory using vegetation sur...The main objective of the study was to investigate the diversity of the woody stratum of the vegetation in intercommunity rangelands in the department of Koungheul based on an ecological inventory using vegetation surveys. The results indicate a rich flora of 70 species divided into 54 genera and 27 families where Ceasalpiniaceae and Rubiaceae are dominant (5 genera each). They are followed by Combretaceae and Euphorbiacea (4 genera each) and by Capparaceae, Fabaceae and Mimosaceae (3 genera for each family). But at the specific level, it is the Combretaceae which dominates with 10 species and Rubiaceae (7 species). It is more representative at the level of the rural community of Lour Esacale. The different values of vegetation parameters from one site to another indicate variability in community rangeland management practices. The woody stand, dominated by small Combretaceae, shows a relatively stable level of organization with an average equitability of about 45% for the two rural communities studied. Species such as Cordyla pinnata, Sclerocarya birrea, Adansonia digitata and Sterculia setigera contributed strongly to the basal and aerial cover of the overall stand. The regeneration of the stand is very good (about 85% on average) but it represents very few species, especially of the Combretaceae family. This shows a tendency to a progressive loss of species richness in the woody stratum.展开更多
The objective of this study was to develop allometric models for estimating the biomass of Sclerocarya birrea (A.Rich) Hoscht and Boscia senegalensis (Pers.) Lam. ex Poir. The inventory of these ligneous was carried o...The objective of this study was to develop allometric models for estimating the biomass of Sclerocarya birrea (A.Rich) Hoscht and Boscia senegalensis (Pers.) Lam. ex Poir. The inventory of these ligneous was carried out at Widou Thiengoly (North of Senegal). The sample consists of 43 individuals of Boscia senegalensis and 15 individuals of Sclerocarya birrea. The selected individuals were dendrometrically characterized before being cut, compartmentalized (trunk, branches, and twigs) and weighed entirely. Simple regression tests were performed to examine the most explanatory dendrometric parameter (x) for biomass (y) according to two types of models: the linear model (y = ax + b) and the polynomial model of degrees 2 (y = ax<sup>2</sup> + bx + c). The criteria for selection and validity of the models are based firstly on the tests of normality, nullity, heterogeneity and autocorrelation of the residues. The results showed that the most explanatory dendrometric parameter of the biomass was the crown surface for Boscia senegalensis and the 1.30 m diameter for Sclerocarya birrea of all the tests performed, the second-order Polynomial model is the best predictor of above ground biomass for these two species. Thus, the allometric models established to predict the biomass of these two species are: y = 0.0023x<sup>2</sup> + 0.4851x - 0.0519 for Boscia senegalensis and y = 0.35x<sup>2</sup> + 10.35x - 12.90 for S. birrea;with very significant correlation coefficients (R<sup>2</sup>) of 0.85 and 0.94 respectively. These results can be used for a sequestered carbon assessment study and will play a role in monitoring the carbon market in Africa.展开更多
The objective of this study is to characterize and assess the risk of collapse of woody plant formations in the Fathala forest. In recent years, this forest has suffered a sharp reduction in its plant cover to the poi...The objective of this study is to characterize and assess the risk of collapse of woody plant formations in the Fathala forest. In recent years, this forest has suffered a sharp reduction in its plant cover to the point of compromising the survival of populations of certain animal species such as the Red colobuses. The methods used are respectively constituted by the transect method, the dendrometric statements method and that of establishing the red list of ecosystems of the IUCN. The specific richness comprises 56 species divided into 47 genera and 22 families. The density is higher in the unfenced area (369 ind/ha in clear forest and 53 ind/ha in gallery forest) compared to the fenced area (160 ind/ha in clear forest versus 48 ind/ha in gallery forest). A study of the plant formations shows a strong degradation of the ecosystems passing from a clear and dry Sudanese forest to a wooded savannah. The cover rate in the fenced area is 20% in gallery forests and 25% in clear forests;in the unfenced area, it is 19% and 23% in gallery forests and clear forests, respectively. The application of the IUCN criteria shows an annual rate of collapse is -<span style="font-family:Verdana;">6 ind/ha in gallery forests and </span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">4 ind/ha in clear forests. The annual rate of cover collapse would be </span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">3.75% and </span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">2.9% for gallery forests and clear forests, respectively. These results classify the forest in the Critically Endangered category. The main factors responsible for this degradation are, among others, anthropogenic actions and climatic pejoration. These results could constitute a basic tool for undertaking an improvement in the management of this forest, which is a living environment for an animal species.</span>展开更多
The find for the optimal slide of water to bring to the plot during the irrigated onion crop was important in order to limit the recharge of the water table close to the soil surface. The quantities of water supplied ...The find for the optimal slide of water to bring to the plot during the irrigated onion crop was important in order to limit the recharge of the water table close to the soil surface. The quantities of water supplied during onion irrigation were estimated from measurements made with a metal crest to the plot positioned at the tertiary canal. The flow rates at the tertiary canal directly irrigating the plot were recorded during irrigation. From this flow rate, the quantity of water supplied to each plot was determined. From then, the performance of the irrigated system in onion cultivation should pass on the management of this water slide at the level of the hydroagricultural facilities. The integrated soil water mass, salinity and water table dynamics monitoring system was used to assess the water requirements of onion following the irrigation. The daily water requirement of onion in the holland soil of the delta was estimated to average 0.45 g/m<sup>3</sup>. These requirements were varied according to the development stage of the crop. The water level between the ridges was between 6 and 9 mm during irrigation. This was not permanent, it infiltrated between 12 and 18 hours. This type to the stingray irrigation did not favour the arrival of the water table on the surface. The only fluctuations in the water table were observed during the bulb maturation phase. During this phase, the soil water masses were important. The electrical conductivity recorded varied during the campaign. At the beginning of irrigation, it was 3.62 mS/cm on a 30 cm profile, it decreased towards the end of the irrigations to reach 2.06 mS/cm. The quantities of salt recorded on a 30 cm profile varied from one month to the next;they were 0.468 t/ha at the beginning of irrigation (January) and 0.275 t/ha at the end of the campaign (April). From these results we can say that land degradation in the Senegal river delta would be linked to the arrival of salty groundwater on the surface.展开更多
文摘This study describes the floristic composition and structure of a woody stand in the Senegalese Sahel, paying particular attention to the edaphic factors of its floristic composition. A stratified inventory considering the different relief units was adopted. Woody vegetation was surveyed using a dendrometric approach. The results obtained show that the flora is dominated by a few species adapted to drought, such as Balanites aegyptiaca (L.) Del., Calotropis procera Ait. and Boscia senegalensis (Pers.). The distribution of this flora and the structure of the ligneous plants are linked to the topography. In the lowlands, the flora is more diversified and the ligneous plants reach their optimum level of development compared with the higher relief areas. In the lowlands, there are a few woody species which, in the past, were indicative of better climatic conditions. These are Anogeissus leiocarpus (DC.), Commiphora africana (A. Rich.), Feretia apodanthera Del., Loeseneriella africana (A. Smith), Mitragyna inermis (Willd.) and Sclerocarya birrea (A. Rich). It is important that their reintroduction into reforestation projects takes account of their edaphic preference.
文摘The main objective of the study was to investigate the diversity of the woody stratum of the vegetation in intercommunity rangelands in the department of Koungheul based on an ecological inventory using vegetation surveys. The results indicate a rich flora of 70 species divided into 54 genera and 27 families where Ceasalpiniaceae and Rubiaceae are dominant (5 genera each). They are followed by Combretaceae and Euphorbiacea (4 genera each) and by Capparaceae, Fabaceae and Mimosaceae (3 genera for each family). But at the specific level, it is the Combretaceae which dominates with 10 species and Rubiaceae (7 species). It is more representative at the level of the rural community of Lour Esacale. The different values of vegetation parameters from one site to another indicate variability in community rangeland management practices. The woody stand, dominated by small Combretaceae, shows a relatively stable level of organization with an average equitability of about 45% for the two rural communities studied. Species such as Cordyla pinnata, Sclerocarya birrea, Adansonia digitata and Sterculia setigera contributed strongly to the basal and aerial cover of the overall stand. The regeneration of the stand is very good (about 85% on average) but it represents very few species, especially of the Combretaceae family. This shows a tendency to a progressive loss of species richness in the woody stratum.
文摘The objective of this study was to develop allometric models for estimating the biomass of Sclerocarya birrea (A.Rich) Hoscht and Boscia senegalensis (Pers.) Lam. ex Poir. The inventory of these ligneous was carried out at Widou Thiengoly (North of Senegal). The sample consists of 43 individuals of Boscia senegalensis and 15 individuals of Sclerocarya birrea. The selected individuals were dendrometrically characterized before being cut, compartmentalized (trunk, branches, and twigs) and weighed entirely. Simple regression tests were performed to examine the most explanatory dendrometric parameter (x) for biomass (y) according to two types of models: the linear model (y = ax + b) and the polynomial model of degrees 2 (y = ax<sup>2</sup> + bx + c). The criteria for selection and validity of the models are based firstly on the tests of normality, nullity, heterogeneity and autocorrelation of the residues. The results showed that the most explanatory dendrometric parameter of the biomass was the crown surface for Boscia senegalensis and the 1.30 m diameter for Sclerocarya birrea of all the tests performed, the second-order Polynomial model is the best predictor of above ground biomass for these two species. Thus, the allometric models established to predict the biomass of these two species are: y = 0.0023x<sup>2</sup> + 0.4851x - 0.0519 for Boscia senegalensis and y = 0.35x<sup>2</sup> + 10.35x - 12.90 for S. birrea;with very significant correlation coefficients (R<sup>2</sup>) of 0.85 and 0.94 respectively. These results can be used for a sequestered carbon assessment study and will play a role in monitoring the carbon market in Africa.
文摘The objective of this study is to characterize and assess the risk of collapse of woody plant formations in the Fathala forest. In recent years, this forest has suffered a sharp reduction in its plant cover to the point of compromising the survival of populations of certain animal species such as the Red colobuses. The methods used are respectively constituted by the transect method, the dendrometric statements method and that of establishing the red list of ecosystems of the IUCN. The specific richness comprises 56 species divided into 47 genera and 22 families. The density is higher in the unfenced area (369 ind/ha in clear forest and 53 ind/ha in gallery forest) compared to the fenced area (160 ind/ha in clear forest versus 48 ind/ha in gallery forest). A study of the plant formations shows a strong degradation of the ecosystems passing from a clear and dry Sudanese forest to a wooded savannah. The cover rate in the fenced area is 20% in gallery forests and 25% in clear forests;in the unfenced area, it is 19% and 23% in gallery forests and clear forests, respectively. The application of the IUCN criteria shows an annual rate of collapse is -<span style="font-family:Verdana;">6 ind/ha in gallery forests and </span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">4 ind/ha in clear forests. The annual rate of cover collapse would be </span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">3.75% and </span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">2.9% for gallery forests and clear forests, respectively. These results classify the forest in the Critically Endangered category. The main factors responsible for this degradation are, among others, anthropogenic actions and climatic pejoration. These results could constitute a basic tool for undertaking an improvement in the management of this forest, which is a living environment for an animal species.</span>
文摘The find for the optimal slide of water to bring to the plot during the irrigated onion crop was important in order to limit the recharge of the water table close to the soil surface. The quantities of water supplied during onion irrigation were estimated from measurements made with a metal crest to the plot positioned at the tertiary canal. The flow rates at the tertiary canal directly irrigating the plot were recorded during irrigation. From this flow rate, the quantity of water supplied to each plot was determined. From then, the performance of the irrigated system in onion cultivation should pass on the management of this water slide at the level of the hydroagricultural facilities. The integrated soil water mass, salinity and water table dynamics monitoring system was used to assess the water requirements of onion following the irrigation. The daily water requirement of onion in the holland soil of the delta was estimated to average 0.45 g/m<sup>3</sup>. These requirements were varied according to the development stage of the crop. The water level between the ridges was between 6 and 9 mm during irrigation. This was not permanent, it infiltrated between 12 and 18 hours. This type to the stingray irrigation did not favour the arrival of the water table on the surface. The only fluctuations in the water table were observed during the bulb maturation phase. During this phase, the soil water masses were important. The electrical conductivity recorded varied during the campaign. At the beginning of irrigation, it was 3.62 mS/cm on a 30 cm profile, it decreased towards the end of the irrigations to reach 2.06 mS/cm. The quantities of salt recorded on a 30 cm profile varied from one month to the next;they were 0.468 t/ha at the beginning of irrigation (January) and 0.275 t/ha at the end of the campaign (April). From these results we can say that land degradation in the Senegal river delta would be linked to the arrival of salty groundwater on the surface.
