干旱区生态环境知识资源中心

In order to ensure the smooth operation of the Baotou-Lanzhou railway in Shapotou region of China (southeast edge of the Tengger Desert), vegetation protecting system was established, and then substantial biological soil crusts (BSCs) gradually developed there, however so far little study has focused on the refined crust community types and their related ecological functions. In this study, eight main crust community types were distinguished from the restoration region, and their pigment composition and photosynthetic performance were compared through spectrophotometry, chlorophyll fluorescence and infrared gas analysis technologies. The results showed that crust chlorophyll-a and carotenoids contents had a good linear relationship (R-2 = 0.964; P < 0.001), generally increased with the development and succession of BSCs, while crust scytonemin content was highest in cyanolichen soil crusts. When chlorophyll-a content was less than 15 mu g cm(-2), crust original fluorescence (Fo) linearly increased with the increasing chlorophyll-a content (R-2 = 0.758; P = 0.001), providing a convenient approach to monitor crust photosynthetic biomass in situ, but without crust destruction. Compared with cyanobacterial and cyanolichen soil crusts, chlorolichen and moss soil crusts had the higher photosynthetic activities (Fv/Fm), although the chlorolichen soil crusts performed the lowest net photosynthetic carbon fixation (average 1.5-1.8 mmol CO2 m(-2) h(-1)), while moss soil crusts had the greater carbon fixation efficiency, about 2.4-7.5 fold higher according to the different community types. Conclusively, a finely divided classification of BSCs will not only improve the estimation of crust carbon fixation, but also strengthen the accuracy and importance of crust community types at the landscape scale. (C) 2016 Elsevier B.V. All rights reserved.