Biological soil crusts （BSCs） play an important role in surface soil hydrology. Soils dominated with moss BSCs may have higher infiltration rates than those dominated with cyanobacteria or algal BSCs. However, it is...Biological soil crusts （BSCs） play an important role in surface soil hydrology. Soils dominated with moss BSCs may have higher infiltration rates than those dominated with cyanobacteria or algal BSCs. However, it is unnown whether improved infiltration in moss BSCs is accompanied by an increase in soil hydraulic conductivity or water retention capacity. We investigated this question in the Tengger Desert, where a 43-year-old revegetation program has promoted the formation of two distinct types of BSCs along topographic positions, i.e. the moss-dominated BSCs on the interdune land and windward slopes of the fixed sand dunes, and the al- gal-dominated BSCs on the crest and leeward slopes. Soil water retention capacity and hydraulic conductivity were measured using an indoor evaporation method and a field infiltration method. And the results were fitted to the van Genuchten-Mualem model. Unsaturated hydraulic conductivities under greater water pressure （〈-0.01 MPa） and water retention capacities in the entire pressure head range were higher for both crust types than for bare sand. However, saturated and unsaturated hydraulic conductivities in the near-saturation range （〉-0.01 MPa） showed decreasing trends from bare sand to moss crusts and to algal crusts. Our data suggested that topographic differentiation of BSCs significantly affected not only soil water retention and hydraulic conductivities, but also the overall hydrology of the fixed sand dunes at a landscape scale, as seen in the reduction and spatial variability in deep soil water storage.展开更多
Biological soil crusts （BSCs） are an important type of land cover in arid desert landscapes and play an important role in the carbon source-sink exchange within a desert system. In this study, two typical BSCs, moss...Biological soil crusts （BSCs） are an important type of land cover in arid desert landscapes and play an important role in the carbon source-sink exchange within a desert system. In this study, two typical BSCs, moss crusts and algae crusts, were selected from a revegetated sandy area of the Tengger Desert in northern China, and the experiment was carried out over a 3-year period from January 2010 to November 2012. We obtained the effec- tive active wetting time to maintain the physiological activity of BSCs basing on continuous field measurements and previous laboratory studies on BSCs photosynthesis and respiration rates. And then we developed a BSCs carbon fixation model that is driven by soil moisture. The results indicated that moss crusts and algae crusts had significant effects on soil moisture and temperature dynamics by decreasing rainfall infiltration. The mean carbon fixation rates of moss and algae crusts were 0.21 and 0.13 g C/（m2.d）, respectively. The annual carbon fixations of moss crusts and algae crusts were 64.9 and 38.6 g C/（m2.a）, respectively, and the carbon fixation of non-rainfall water reached 11.6 g C/（m2.a） （30.2% of the total） and 8.8 g C/（m2.a） （43.6% of the total）, respectively. Finally, the model was tested and verified with continuous field observations. The data of the modeled and measured CO2 fluxes matched notably well. In desert regions, the carbon fixation is higher with high-frequency rainfall even the total amount of seasonal rainfall was the same.展开更多
Algae and mosses are not only two of the familiar communities in the process of desert vegetational succession,but also have the highest biomass in biological soil crusts.Meanwhile,being the pioneer plants,algae and m...Algae and mosses are not only two of the familiar communities in the process of desert vegetational succession,but also have the highest biomass in biological soil crusts.Meanwhile,being the pioneer plants,algae and mosses are involved in the establishment of biological soil crusts,which have great importance in arid environments and play a major role in desert ecosystems,such as being the indicator of the vegetation type,soil-holding,preventing erosion by water and wind,and sand fixation.This paper reviews the advances in the study of algae and mosses in arid and semi-arid areas.It mainly describes the ecological functions of algae and mosses including their influences on water cycle,circulation of substances,and community succession.In addition,the relationships between algae and mosses are discussed.Finally,some suggestions are proposed for the research orientations of algae and mosses in biological soil crusts.Ecologically,algae and mosses have significant ecological importance in arid areas,especially in those areas where environmental problems are becoming increasingly serious.展开更多
基金funded by the National Basic Research Program of China (2013CB429901)the National Natural Science Foundation of China (41471434, 31170385)the Foundation for Excellent Youth Scholars of CAREERI, Chinese Academy of Sciences
文摘Biological soil crusts （BSCs） play an important role in surface soil hydrology. Soils dominated with moss BSCs may have higher infiltration rates than those dominated with cyanobacteria or algal BSCs. However, it is unnown whether improved infiltration in moss BSCs is accompanied by an increase in soil hydraulic conductivity or water retention capacity. We investigated this question in the Tengger Desert, where a 43-year-old revegetation program has promoted the formation of two distinct types of BSCs along topographic positions, i.e. the moss-dominated BSCs on the interdune land and windward slopes of the fixed sand dunes, and the al- gal-dominated BSCs on the crest and leeward slopes. Soil water retention capacity and hydraulic conductivity were measured using an indoor evaporation method and a field infiltration method. And the results were fitted to the van Genuchten-Mualem model. Unsaturated hydraulic conductivities under greater water pressure （〈-0.01 MPa） and water retention capacities in the entire pressure head range were higher for both crust types than for bare sand. However, saturated and unsaturated hydraulic conductivities in the near-saturation range （〉-0.01 MPa） showed decreasing trends from bare sand to moss crusts and to algal crusts. Our data suggested that topographic differentiation of BSCs significantly affected not only soil water retention and hydraulic conductivities, but also the overall hydrology of the fixed sand dunes at a landscape scale, as seen in the reduction and spatial variability in deep soil water storage.
基金supported by the Knowledge Innovation Project of the Chinese Academy of Sciences (KZCX2-EW-301-3)the National Program on Key Basic Research Project (2013CB429905)+1 种基金the National Natural Scientific Foundation of China (41201084 31170385)
文摘Biological soil crusts （BSCs） are an important type of land cover in arid desert landscapes and play an important role in the carbon source-sink exchange within a desert system. In this study, two typical BSCs, moss crusts and algae crusts, were selected from a revegetated sandy area of the Tengger Desert in northern China, and the experiment was carried out over a 3-year period from January 2010 to November 2012. We obtained the effec- tive active wetting time to maintain the physiological activity of BSCs basing on continuous field measurements and previous laboratory studies on BSCs photosynthesis and respiration rates. And then we developed a BSCs carbon fixation model that is driven by soil moisture. The results indicated that moss crusts and algae crusts had significant effects on soil moisture and temperature dynamics by decreasing rainfall infiltration. The mean carbon fixation rates of moss and algae crusts were 0.21 and 0.13 g C/（m2.d）, respectively. The annual carbon fixations of moss crusts and algae crusts were 64.9 and 38.6 g C/（m2.a）, respectively, and the carbon fixation of non-rainfall water reached 11.6 g C/（m2.a） （30.2% of the total） and 8.8 g C/（m2.a） （43.6% of the total）, respectively. Finally, the model was tested and verified with continuous field observations. The data of the modeled and measured CO2 fluxes matched notably well. In desert regions, the carbon fixation is higher with high-frequency rainfall even the total amount of seasonal rainfall was the same.
基金The project was supported by the National Natural Science Foundation of China(Grant Nos.40571085 and 30670152)the National Infrastructure of Natural Resources for Science and Technology(No.2005DKA21403)Science and Social Practice Foundation of Graduate Students in Chinese Academy of Sciences(Investigation on Algal Distribution in Gurbantunggut Desert,Xinjiang,China)。
文摘Algae and mosses are not only two of the familiar communities in the process of desert vegetational succession,but also have the highest biomass in biological soil crusts.Meanwhile,being the pioneer plants,algae and mosses are involved in the establishment of biological soil crusts,which have great importance in arid environments and play a major role in desert ecosystems,such as being the indicator of the vegetation type,soil-holding,preventing erosion by water and wind,and sand fixation.This paper reviews the advances in the study of algae and mosses in arid and semi-arid areas.It mainly describes the ecological functions of algae and mosses including their influences on water cycle,circulation of substances,and community succession.In addition,the relationships between algae and mosses are discussed.Finally,some suggestions are proposed for the research orientations of algae and mosses in biological soil crusts.Ecologically,algae and mosses have significant ecological importance in arid areas,especially in those areas where environmental problems are becoming increasingly serious.
