Contrary to the countries of northern coast, the forest formations on Southern and East coast of the Mediterranean are in regression. With the combined action of the ax, fire and pasture, these ecosystems are subjecte...Contrary to the countries of northern coast, the forest formations on Southern and East coast of the Mediterranean are in regression. With the combined action of the ax, fire and pasture, these ecosystems are subjected to a pressure of permanent degradation. Indeed, the degradation of the forest ecosystems represents one of the most important causes of reduction and erosion of the biodiversity in the world. The massif of Aur6s is located in the North-East of Algeria. The analysis of the spatiotemporal dynamics of this vulnerable vegetation is not approached yet. This study proposes a focus on the analysis of the dynamics of this vegetation and to study the factors of its degradation. For that, a methodological approach of diachronic follow-up between two dates was adopted by using any kind of old information sources （archives, aerial photographs, topographic maps） and recent （Images satellite of American Landsat and data of land）. The results reveal a degradation of vegetable cover thus expressing a very thorough reduction of the formations forest replaced by herbaceous formations very sensitive and threatened by the overgrazing.展开更多
In order to evaluate the danger of debris flow properly, eight factors were selected as the risk assess- ment indexes of the debris flow, namely the vertical slope, valley relative difference, hillside slope, area of ...In order to evaluate the danger of debris flow properly, eight factors were selected as the risk assess- ment indexes of the debris flow, namely the vertical slope, valley relative difference, hillside slope, area of ba- sin, loose solid material reserves, the path length of sediment supply probability, silting and scouring derrieking and vegetation coverage. The improved Analytic Hierarchy Process （ AHP ） method was used to obtain the weights of the factors; and the efficacy coefficient method was adopted to evaluate the risks of six typical debris flow gullies. According to the research, the improved AHP method not only avoids the subjectivity in the indi- vidual factor valuation by comparing two factors of each layer, but also makes the subsequent consistency check unnecessary.展开更多
The study focused on one of the important contemporary environmental problems, land deterioration, carried out on a semi-desert rangeland constrained by aridity, in an area stretching between two small cities （Solouk...The study focused on one of the important contemporary environmental problems, land deterioration, carried out on a semi-desert rangeland constrained by aridity, in an area stretching between two small cities （Solouk and A1-Abyar） south of the city of Benghazi in north eastern Libya. The vegetation analysis revealed that the plant life is mainly confined to wadis （valleys）. Average vegetation cover was ranging between 39.53% and 69.20%. Biomass was ranging between 28.33 gm/m2 and 129.42 gm/m2, （average soil depth was between 30 cm and 50 cm）, meanwhile 25% of the area is covered by hummocks. The total number of sampled soil seed bank was 25,870 seed/m2, in which the important forage family Fabaceae constituted 450 seed/m2. Life forms spectrum was： 55.2% Therophytes, 26.3% Chamaeopytes, 11.4% Cryptophytes and 7.1% Phanerophytes. Alpha diversity 1.3%-3.4%, and Beta diversity 11.9%-77.6%. The soil showed low organic matter content an lean to alkalinity. The study showed that the area is characterized by harsh climate elements which led to land degradation in the form of low productivity, retrogressive succession, soil erosion, and sandy encroachment from the south desert area. In the last decades the land degradation was accelerated by the accumulative anthropogenic.展开更多
Post-fire field measurements of sediment and run off yield were undertaken in natural rainfall event-basis during five rainy months in Korea on a total of 15 small plots: four replica burned unseeded plots, six replic...Post-fire field measurements of sediment and run off yield were undertaken in natural rainfall event-basis during five rainy months in Korea on a total of 15 small plots: four replica burned unseeded plots, six replica burned seeded plots, and five replica unburned plots. The main aim was to evaluate the effects of vegetation recovery and spatial distribution patterns on sediment and runoff response between and within the treatment replica erosion plots. Sixyears after the wildfire, total sediment and runoff yield in the burned unseeded plots with 20%-30%vegetation cover was still 120.8 and 20.6 times higher than in the unburned treatment plots with 100%ground cover, 8.3 and 6.7 times higher than in the burned seeded plots with 70%-80% vegetation cover,while only 1.6 and 2.0 times higher than in the burned seeded plots with 50%-60% vegetation cover,respectively. The differences in sediment and runoff yield between the treatment plots was proportional to total vegetation cover, distance of bare soil to vegetation cover, magnitude of rainfall characteristics and changes in soil properties, but not slope gradient.Three out of the six within-treatment pairs of two replica plots showed large differences in sediment and runoff yield of up to 6.0 and 4.2 times and mean CV of up to 99.1% and 62.2%, respectively. This was due to differences in the spatial distribution patterns of surface cover features, including aggregation of vegetation and litter covers, the distance of bare soil exposed to vegetation cover closer to the plot sediment collector and micro topographic mounds and sinks between pairs of replica plots. Small differences in sediment and runoff of only 0.9-1.4folds and mean CV of 8.6%-25% were observed where the within-treatment pairs of replica plots had similar slope, total surface cover components and comparable spatial distribution pattern of vegetation and bare soil exposed surface covers. The results indicated that post-fire hillslopes undergoing effective vegetation recovery have the potential to reduce sediment and runoff production nearer to unburned levels within 6-years after burning while wildfire impacts could last more than 6-years on burned unseeded ridge slopes undergoing slow vegetation recovery.展开更多
Reconstructing long-term vegetation buffers along streams in agricultural landscapes has become a common environmental restoration strategy for improving water quality and wildlife habitat connectivity.This article de...Reconstructing long-term vegetation buffers along streams in agricultural landscapes has become a common environmental restoration strategy for improving water quality and wildlife habitat connectivity.This article developed a linear weighted model to rank the priority of agricultural sub-basins for the establishment of vegetative buffers.The method was applied to an agricultural watershed of 146 km2 in Ontario,Canada.The watershed was divided into 11 sub-basins as basic decision units.In each subbasin,four stream buffer schemes with widths of 5,10,15 and 20m were generated.For each buffer,three benefit-cost attributes of reconstructing vegetation cover were estimated,which include acreage per dollar,sediment abatement per dollar and habitat benefit per dollar.These attributes were first normalized using a linear normalization approach to eliminate the effects across different units.The normalized attributes were then integrated using a simple additive weighting method to rank the 11 sub-basins for prioritizing spatial restoration action.A sensitivity analysis was also conducted to observe the impact of a change in attribute weights on the management decisions.The results suggest that vegetation buffers reconstructed for achieving the water quality goal are not effective in improving habitat connectivity and vice versa.展开更多
Vegetation and rainfall are two important factors affecting soil erosion and thus resulting in nutrient loss in the Chinese Loess Plateau.A field experiment was conducted to investigate the effects of rainfall intensi...Vegetation and rainfall are two important factors affecting soil erosion and thus resulting in nutrient loss in the Chinese Loess Plateau.A field experiment was conducted to investigate the effects of rainfall intensities(60,100 and 140 mm h-1) and vegetation(Caragana korshinskii) coverages(0%,30% and 80%) on soil loss,nutrient loss,and the composition and volume fractal dimension of eroded sediment particles under simulated rainfall conditions.The results showed that vegetation cover,rainfall intensity and their interaction all had significant effects on sediment transport and the sedimentbound nutrient loss.Higher rainfall intensity and lower coverage led to higher sediment and nutrient losses.Positive linear relationships were observed between soil loss and nutrient loss.The treatments showed more significant effects on the enrichment ratio(ER) of nitrogen(ERN) than organic matter(EROM) and phosphorus(ERP).Compared with the original surface soil,the eroded sediment contained more fine particles.Under the same coverage,the clay content significantly decreased with increasing rainfall intensity.The ER of sediment-bound nutrients was positively correlated with that of clay,suggesting that the clay fraction was preferentially eroded and soil nutrients were mainly adsorbed onto or contained within this fraction.There were increments in the fractal dimension of the sediment particles compared to that of the original surface soil.Moreover,the fractal dimension was positively correlated with clay,silt,and sediment-bound OM,N,and P contents,whereas it was negatively correlated with sand content.This study demonstrated that fractal dimension analysis can be used to characterize differences in particle-size distribution and nutrient loss associated with soil erosion.展开更多
文摘Contrary to the countries of northern coast, the forest formations on Southern and East coast of the Mediterranean are in regression. With the combined action of the ax, fire and pasture, these ecosystems are subjected to a pressure of permanent degradation. Indeed, the degradation of the forest ecosystems represents one of the most important causes of reduction and erosion of the biodiversity in the world. The massif of Aur6s is located in the North-East of Algeria. The analysis of the spatiotemporal dynamics of this vulnerable vegetation is not approached yet. This study proposes a focus on the analysis of the dynamics of this vegetation and to study the factors of its degradation. For that, a methodological approach of diachronic follow-up between two dates was adopted by using any kind of old information sources （archives, aerial photographs, topographic maps） and recent （Images satellite of American Landsat and data of land）. The results reveal a degradation of vegetable cover thus expressing a very thorough reduction of the formations forest replaced by herbaceous formations very sensitive and threatened by the overgrazing.
文摘In order to evaluate the danger of debris flow properly, eight factors were selected as the risk assess- ment indexes of the debris flow, namely the vertical slope, valley relative difference, hillside slope, area of ba- sin, loose solid material reserves, the path length of sediment supply probability, silting and scouring derrieking and vegetation coverage. The improved Analytic Hierarchy Process （ AHP ） method was used to obtain the weights of the factors; and the efficacy coefficient method was adopted to evaluate the risks of six typical debris flow gullies. According to the research, the improved AHP method not only avoids the subjectivity in the indi- vidual factor valuation by comparing two factors of each layer, but also makes the subsequent consistency check unnecessary.
文摘The study focused on one of the important contemporary environmental problems, land deterioration, carried out on a semi-desert rangeland constrained by aridity, in an area stretching between two small cities （Solouk and A1-Abyar） south of the city of Benghazi in north eastern Libya. The vegetation analysis revealed that the plant life is mainly confined to wadis （valleys）. Average vegetation cover was ranging between 39.53% and 69.20%. Biomass was ranging between 28.33 gm/m2 and 129.42 gm/m2, （average soil depth was between 30 cm and 50 cm）, meanwhile 25% of the area is covered by hummocks. The total number of sampled soil seed bank was 25,870 seed/m2, in which the important forage family Fabaceae constituted 450 seed/m2. Life forms spectrum was： 55.2% Therophytes, 26.3% Chamaeopytes, 11.4% Cryptophytes and 7.1% Phanerophytes. Alpha diversity 1.3%-3.4%, and Beta diversity 11.9%-77.6%. The soil showed low organic matter content an lean to alkalinity. The study showed that the area is characterized by harsh climate elements which led to land degradation in the form of low productivity, retrogressive succession, soil erosion, and sandy encroachment from the south desert area. In the last decades the land degradation was accelerated by the accumulative anthropogenic.
基金support of‘Forest Science and Technology Projects(Project No.S211216L020210)provided by Korea Forest Service
文摘Post-fire field measurements of sediment and run off yield were undertaken in natural rainfall event-basis during five rainy months in Korea on a total of 15 small plots: four replica burned unseeded plots, six replica burned seeded plots, and five replica unburned plots. The main aim was to evaluate the effects of vegetation recovery and spatial distribution patterns on sediment and runoff response between and within the treatment replica erosion plots. Sixyears after the wildfire, total sediment and runoff yield in the burned unseeded plots with 20%-30%vegetation cover was still 120.8 and 20.6 times higher than in the unburned treatment plots with 100%ground cover, 8.3 and 6.7 times higher than in the burned seeded plots with 70%-80% vegetation cover,while only 1.6 and 2.0 times higher than in the burned seeded plots with 50%-60% vegetation cover,respectively. The differences in sediment and runoff yield between the treatment plots was proportional to total vegetation cover, distance of bare soil to vegetation cover, magnitude of rainfall characteristics and changes in soil properties, but not slope gradient.Three out of the six within-treatment pairs of two replica plots showed large differences in sediment and runoff yield of up to 6.0 and 4.2 times and mean CV of up to 99.1% and 62.2%, respectively. This was due to differences in the spatial distribution patterns of surface cover features, including aggregation of vegetation and litter covers, the distance of bare soil exposed to vegetation cover closer to the plot sediment collector and micro topographic mounds and sinks between pairs of replica plots. Small differences in sediment and runoff of only 0.9-1.4folds and mean CV of 8.6%-25% were observed where the within-treatment pairs of replica plots had similar slope, total surface cover components and comparable spatial distribution pattern of vegetation and bare soil exposed surface covers. The results indicated that post-fire hillslopes undergoing effective vegetation recovery have the potential to reduce sediment and runoff production nearer to unburned levels within 6-years after burning while wildfire impacts could last more than 6-years on burned unseeded ridge slopes undergoing slow vegetation recovery.
基金supported by "SUST Spring Bud" Project (Grant no.2008AZZ110)National Key Technology R&D Program of China project (Grant no.2006BAJ15B02)
文摘Reconstructing long-term vegetation buffers along streams in agricultural landscapes has become a common environmental restoration strategy for improving water quality and wildlife habitat connectivity.This article developed a linear weighted model to rank the priority of agricultural sub-basins for the establishment of vegetative buffers.The method was applied to an agricultural watershed of 146 km2 in Ontario,Canada.The watershed was divided into 11 sub-basins as basic decision units.In each subbasin,four stream buffer schemes with widths of 5,10,15 and 20m were generated.For each buffer,three benefit-cost attributes of reconstructing vegetation cover were estimated,which include acreage per dollar,sediment abatement per dollar and habitat benefit per dollar.These attributes were first normalized using a linear normalization approach to eliminate the effects across different units.The normalized attributes were then integrated using a simple additive weighting method to rank the 11 sub-basins for prioritizing spatial restoration action.A sensitivity analysis was also conducted to observe the impact of a change in attribute weights on the management decisions.The results suggest that vegetation buffers reconstructed for achieving the water quality goal are not effective in improving habitat connectivity and vice versa.
基金Supported by the National Basic Research Program (973 Program) of China (No.2007CB407205)the National Key Technologies Research and Development Program of China during the 11th Five-Year Plan Period (No.2006BAD09B03)the CAS Action Plan for the Development of Western China (No.KZCX2-XB2-05)
文摘Vegetation and rainfall are two important factors affecting soil erosion and thus resulting in nutrient loss in the Chinese Loess Plateau.A field experiment was conducted to investigate the effects of rainfall intensities(60,100 and 140 mm h-1) and vegetation(Caragana korshinskii) coverages(0%,30% and 80%) on soil loss,nutrient loss,and the composition and volume fractal dimension of eroded sediment particles under simulated rainfall conditions.The results showed that vegetation cover,rainfall intensity and their interaction all had significant effects on sediment transport and the sedimentbound nutrient loss.Higher rainfall intensity and lower coverage led to higher sediment and nutrient losses.Positive linear relationships were observed between soil loss and nutrient loss.The treatments showed more significant effects on the enrichment ratio(ER) of nitrogen(ERN) than organic matter(EROM) and phosphorus(ERP).Compared with the original surface soil,the eroded sediment contained more fine particles.Under the same coverage,the clay content significantly decreased with increasing rainfall intensity.The ER of sediment-bound nutrients was positively correlated with that of clay,suggesting that the clay fraction was preferentially eroded and soil nutrients were mainly adsorbed onto or contained within this fraction.There were increments in the fractal dimension of the sediment particles compared to that of the original surface soil.Moreover,the fractal dimension was positively correlated with clay,silt,and sediment-bound OM,N,and P contents,whereas it was negatively correlated with sand content.This study demonstrated that fractal dimension analysis can be used to characterize differences in particle-size distribution and nutrient loss associated with soil erosion.
