Soil microbiotic crusts cover extensive portions of the arid and semiarid regions of the world and play an important ecological role.Moss is one of the major components in the crusts.The reproduction and establishment...Soil microbiotic crusts cover extensive portions of the arid and semiarid regions of the world and play an important ecological role.Moss is one of the major components in the crusts.The reproduction and establishment of the mosses are crucial to the formation of moss crusts.Bryum argenteum is the dominant species of moss crusts in the Shapotou region(104°57′E,37°27′N)of the Tengger Desert.In search for the characteristics of natural reproduction and establishment of the mosses,10 quadrates(10×10 cm for each)were obtained by removing the moss crusts in different positions of fixed dunes.These 10 quadrates were observed for 3 years depending on the species’components and coverage.Meanwhile,in the third year,two quadrates(1×1 m for each)were set up in a crustabsent area and two different experiments of the asexual reproduction(broadcast planting and offshoots)were conducted,respectively.The reproductive process was observed under the microscope,and the morphological indicators of the new individuals were measured.The results were compared with the ones from indoor experiments using the same methods.All the results showed the following:(1)70%of the quadrates(i.e.,7 of the 10 quadrates)were recovered within 3–4 years;thus,the quick recovery might be due to the dispersal and reproduction of the fragments of stems and leaves of B.argenteum;(2)as for the two quadrates in the artificial reproduction test,the new plants occupied the uncovered space of the quadrates in 1 month,and there were two main reproduction approaches,one of which was that the stems continually branched and produced young plants,and the other was that the young plants and the fragments of the stems and leaves repeatedly and extensively reproduced protonema,which finally developed into a large number of new plants;(3)the reproductive characteristics were identical,though the protonema in the field was more robust and had more branches than the ones indoors.展开更多
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
基金funded by the National Nature Science Fund Project (30060021)the Fund Project of the Shapotou Station of Desert Research,Chinese Academy of Science (No.200014).
文摘Soil microbiotic crusts cover extensive portions of the arid and semiarid regions of the world and play an important ecological role.Moss is one of the major components in the crusts.The reproduction and establishment of the mosses are crucial to the formation of moss crusts.Bryum argenteum is the dominant species of moss crusts in the Shapotou region(104°57′E,37°27′N)of the Tengger Desert.In search for the characteristics of natural reproduction and establishment of the mosses,10 quadrates(10×10 cm for each)were obtained by removing the moss crusts in different positions of fixed dunes.These 10 quadrates were observed for 3 years depending on the species’components and coverage.Meanwhile,in the third year,two quadrates(1×1 m for each)were set up in a crustabsent area and two different experiments of the asexual reproduction(broadcast planting and offshoots)were conducted,respectively.The reproductive process was observed under the microscope,and the morphological indicators of the new individuals were measured.The results were compared with the ones from indoor experiments using the same methods.All the results showed the following:(1)70%of the quadrates(i.e.,7 of the 10 quadrates)were recovered within 3–4 years;thus,the quick recovery might be due to the dispersal and reproduction of the fragments of stems and leaves of B.argenteum;(2)as for the two quadrates in the artificial reproduction test,the new plants occupied the uncovered space of the quadrates in 1 month,and there were two main reproduction approaches,one of which was that the stems continually branched and produced young plants,and the other was that the young plants and the fragments of the stems and leaves repeatedly and extensively reproduced protonema,which finally developed into a large number of new plants;(3)the reproductive characteristics were identical,though the protonema in the field was more robust and had more branches than the ones indoors.
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.
