Biological sand-fixation characteristics of Carex brunnescens in Yellow River source region

Carex brunnescens is a pioneer plant that has an excellent ability to fix sand and plays an important role in maintaining the ecosystem stability of the Maqu desertified alpine grassland of the source area of the Yellow River. In this study, the biological characteristics (phenological characters, the above- and belowground growth processes, and the morphological characters of belowground organs) of C. brunnescens was studied in a field observation experiment. The results showed that C. brunnescens has the characteristics of turning green earlier than other plants, a long growth period, and two flowering and fruiting cycles. The leaf width, length, and count of individual plants, and the community plant density and leaf density showed significant increases from the leaf growth stage to the fruit maturity stage, and then tended to be stable in the withering stage, while the plant height, leaf areas of individual plants, and community leaf areas showed significant increases at first and then decreases. Underground stems (horizontal and vertical stems) and roots of C. brunnescens could survive in sand of depths 0-60 cm. There were more mid-sized roots (0.2~0.5 mm) than other root size classes in all soil layers (0-20, 20-40, and 40-60 cm). The total length of fine roots with <0.2 mm diameter was maximal in the 20-40 cm sand layer and, 0.2~0.5 mm diameter roots maximed in the 0-20 cm sand layer. The length and fresh and dry weights of the main root and horizontal and vertical stems was maximal in the 10-30 cm sand layer, and minimal in the 40-50 cm sand layer. These results showed that C. brunnescens has unique biological characteristics which could well adapt to the Maqu alpine sandy habitats, and is a species that has good potential for ecological restoration in Maqu desertified Alpine grassland.