Abstract:

Soil microbiotic crusts cover extensive portions of the arid and semiarid regions of the world. Moss is one of the major components of the crusts. The reproduction and establishment of the mosses are crucial to the formation of moss crusts. Although many laboratory experiments have indicated that mosses can reproduce through spores, gemmae and fragmentation, the process of the dispersal and reproduction in natural conditions is not well understood in moss crusts. Bryum argenteum is the dominant species of moss crusts in the Shapotou region (37°27′ N, 104°57′ E) of the Tengger Desert. To examine characteristics of natural reproduction and establishment, 10 quadrats (10 cm×10 cm) were established on different positions of fixed dunes and the moss crust removed. These 10 quadrats were observed for three consecutive years and the species establishment and their coverage measured. In the third year, 2 quadrats (1 m×1 m) were established in a crust-absent area, and two different experiments were conducted, one on broadcast planting and the other on offshoots. The reproductive process was observed under the microscope, and the morphological indicators of new individuals measured. The results were compared with results from indoor experiments using the same methods. Our results showed that 70% of the quadrats (i.e., 7 of the 10 quadrats) recovered within 3-4 years. The quick recovery was most likely due to dispersal and reproduction of leaf and stem fragments of B. argenteum. Results from the artificial reproduction experiment showed that new plants occupied the uncovered space of the quadrats within one month. There were two main forms of reproduction: 1) stems continually branched and produced young plants; 2) young plants and the fragments of the stems and leaves repeatedly and extensively reproduced protonema which developed into a large number of new plants. The reproductive characteristics were identical between the two experiments although the protonema in the field was more robust and had more branches than the ones indoors. This research reveals the reproductive mechanism of the establishment of mosses in natural conditions in this region, and provides experimental evidence for the formation of moss crusts on fixed dunes.