The effects of sand encroachment on composition,diversity,and functional patterns of vegetation in drylands are rarely studied,and yet addressing these aspects is important to deepen our understanding of the biodivers...The effects of sand encroachment on composition,diversity,and functional patterns of vegetation in drylands are rarely studied,and yet addressing these aspects is important to deepen our understanding of the biodiversity conservation.This study aimed to investigate the effect of sand encroachment on plant functional biodiversity of desert pavements(gravel deserts)in the Sahara Desert of Algeria.Plants were sampled and analyzed in three desert pavements with different levels of sand encroachment(LSE)and quantity of aeolian deposits(low,LLSE;medium,MLSE;and high,HLSE).Within the sample-plot area(100 m^(2)),density of every plant species was identified and total vegetation cover was determined.Plant taxonomic and functional diversity were analyzed and compared between LSE.Result showed that 19 plant species in desert pavements were classified into 18 genera and 13 families.Asteraceae and Poaceae were the most important families.The species Anabasis articulata(Forssk)Moq.characterized LLSE desert pavements with 11 species,whereas Thymelaea microphylla Coss.&Durieu ex Meisn.and Calobota saharae(C&D)Boatwr.&van Wyk were dominant species of desert pavements with MLSE(14 species)and HLSE(10 species),respectively.The highest values of species richness and biodiversity were recorded in desert pavements with MLSE,while low values of these ecological parameters were obtained in desert pavements with HLSE.Desert pavements with LLSE were characterized with the highest values of species abundances.Plant communities were dominated by chamaephytes,anemochorous,arido-active,and competitive stress-tolerant plants.The increase in LSE along the gradient from LLSE to HLSE induced significant changes in plant community variables including decreases in plant density,plant rarity,lifeform composition,morphological type,and aridity adaptation.Desert pavements with HLSE favor the degradation of vegetation and trigger biodiversity erosion.展开更多
With lots of indoor and outdoor experiments, several key technical issues in construc-tion of the Desert Highway have been solved satisfactorily, on the basis of great achievements ofthe studies in respects of dry com...With lots of indoor and outdoor experiments, several key technical issues in construc-tion of the Desert Highway have been solved satisfactorily, on the basis of great achievements ofthe studies in respects of dry compaction on sand base, design parameters, structure combinationof subgrade and pavement, stabilization analysis of sand base strengthened with geotextile and acomplete set of construction techniques. It is the first time the achievements of the study weresuccessfully applied in the Taklimakan Desert where the natural condition is extremely harsh. Ithas been proved that it is economic and reasonable with reliable techniques and simple construc-tion methods. The Desert Highway constructed with the achievements is the first-grade highwayrunning through huge migratory desert for long distance in the world.展开更多
Three cold desert soil sites were first found in the southern Mount Harding, Grove Mountains, East Antarctica. The soils are characteristics of the widespread occurrence of surface desert pavement, abundant water-solu...Three cold desert soil sites were first found in the southern Mount Harding, Grove Mountains, East Antarctica. The soils are characteristics of the widespread occurrence of surface desert pavement, abundant water-soluble salts, strongly stained upper portion of soil profile, slightly acid and negligible organic matter content. A 1:5 soil-water extracts analysis indicates that the dominant cations are Mg2+ and Na+, followed by Ca2+ and K+, and the main anion is SO 4 2? , then Cl? and NO 3 2? . The accumulation of water-soluble salts indicates ion transportation in the frigid and arid Antarctica environment. The distribution of the salts is related to the maximum content of moisture and clay mineral. Clay fraction migration occurs in the soils, which is different from that of other cold desert soils. The upper horizons of some profiles are generally stained, namely rubification, primarily because of the weathering of iron-bearing minerals. The reddish hues of cold desert soils have been attributed to relatively high concentrations of dithionite-extractable Fe (Fed). The weathering features of soils suggest that the soil age of this area is 0.5–3.5 Ma. No remnants of glaciations were found on the soil sites of Mount Harding, which suggests that the Antarctic glaciations have not reached the soil sites since at least 0.5 Ma, even during the Last Glacial Maximum.展开更多
文摘The effects of sand encroachment on composition,diversity,and functional patterns of vegetation in drylands are rarely studied,and yet addressing these aspects is important to deepen our understanding of the biodiversity conservation.This study aimed to investigate the effect of sand encroachment on plant functional biodiversity of desert pavements(gravel deserts)in the Sahara Desert of Algeria.Plants were sampled and analyzed in three desert pavements with different levels of sand encroachment(LSE)and quantity of aeolian deposits(low,LLSE;medium,MLSE;and high,HLSE).Within the sample-plot area(100 m^(2)),density of every plant species was identified and total vegetation cover was determined.Plant taxonomic and functional diversity were analyzed and compared between LSE.Result showed that 19 plant species in desert pavements were classified into 18 genera and 13 families.Asteraceae and Poaceae were the most important families.The species Anabasis articulata(Forssk)Moq.characterized LLSE desert pavements with 11 species,whereas Thymelaea microphylla Coss.&Durieu ex Meisn.and Calobota saharae(C&D)Boatwr.&van Wyk were dominant species of desert pavements with MLSE(14 species)and HLSE(10 species),respectively.The highest values of species richness and biodiversity were recorded in desert pavements with MLSE,while low values of these ecological parameters were obtained in desert pavements with HLSE.Desert pavements with LLSE were characterized with the highest values of species abundances.Plant communities were dominated by chamaephytes,anemochorous,arido-active,and competitive stress-tolerant plants.The increase in LSE along the gradient from LLSE to HLSE induced significant changes in plant community variables including decreases in plant density,plant rarity,lifeform composition,morphological type,and aridity adaptation.Desert pavements with HLSE favor the degradation of vegetation and trigger biodiversity erosion.
文摘With lots of indoor and outdoor experiments, several key technical issues in construc-tion of the Desert Highway have been solved satisfactorily, on the basis of great achievements ofthe studies in respects of dry compaction on sand base, design parameters, structure combinationof subgrade and pavement, stabilization analysis of sand base strengthened with geotextile and acomplete set of construction techniques. It is the first time the achievements of the study weresuccessfully applied in the Taklimakan Desert where the natural condition is extremely harsh. Ithas been proved that it is economic and reasonable with reliable techniques and simple construc-tion methods. The Desert Highway constructed with the achievements is the first-grade highwayrunning through huge migratory desert for long distance in the world.
基金This work was supported by the Chinese Academy of Sciences(Grant No.KZCX2-303)he State Key Project during the 9th Pive Year Plan Period(Grant No.98-927-01-06).
文摘Three cold desert soil sites were first found in the southern Mount Harding, Grove Mountains, East Antarctica. The soils are characteristics of the widespread occurrence of surface desert pavement, abundant water-soluble salts, strongly stained upper portion of soil profile, slightly acid and negligible organic matter content. A 1:5 soil-water extracts analysis indicates that the dominant cations are Mg2+ and Na+, followed by Ca2+ and K+, and the main anion is SO 4 2? , then Cl? and NO 3 2? . The accumulation of water-soluble salts indicates ion transportation in the frigid and arid Antarctica environment. The distribution of the salts is related to the maximum content of moisture and clay mineral. Clay fraction migration occurs in the soils, which is different from that of other cold desert soils. The upper horizons of some profiles are generally stained, namely rubification, primarily because of the weathering of iron-bearing minerals. The reddish hues of cold desert soils have been attributed to relatively high concentrations of dithionite-extractable Fe (Fed). The weathering features of soils suggest that the soil age of this area is 0.5–3.5 Ma. No remnants of glaciations were found on the soil sites of Mount Harding, which suggests that the Antarctic glaciations have not reached the soil sites since at least 0.5 Ma, even during the Last Glacial Maximum.
