Abstract:

Precipitation and seed burial depth are the key environmental factors affecting the emergence and early growth of exotic plant seedlings. To explore the response mechanism of the growth of exotic plant seedlings to precipitation and burial depth， in this paper， Cenchrus pauciflorus was used as the experimental material to study four types of precipitation respectively. A， first precipitation of 30 mm， no subsequent precipitation. B， first precipitation of 30 mm， subsequent precipitation of 6 mm every 5 days Total precipitation 60 mm. C， first precipitation 20 mm， subsequent precipitation 6 mm every 3 days， total precipitation 80 mm and D， first precipitation 10 mm， subsequent precipitation 6 mm every 1 day， The effects of total precipitation of 100 mm and eight burial depths （0， 0.5， 1， 3， 5， 7， 9 and 13 cm） on the emergence process and growth of C. pauciflorus seedlings. The results show that： （1） The depth of seed burial significantly affects the emergence process of C. Pauciflorus seeds. The emergence time of C. pauciflorus and the number of days reaching the peak of emergence are both delayed with the increase of soil cover thickness， and the number of seedlings at the peak of emergence shows a changing pattern of first increasing， then decreasing， and then increasing again. （2） The amount of initial precipitation affects the emergence time of C. Pauciflorus seedlings at shallow burial depth （≤3 cm）， while the total precipitation plays a regulatory role in the emergence of C. pauciflorus seeds and seedlings at deep burial depth （≥5 cm）. （3） Under each precipitation treatment， the plant height， aboveground and underground biomass， and root-crown ratio of the seedlings of C. pauciflorus reached the maximum value at a burial depth of 1cm and the minimum value at a burial depth of 9 cm. Moreover， the higher the total precipitation， the better the growth of the above indicators. The root growth of the young C. pauciflorus seedlings reached its maximum value at a burial depth of 0 cm and its minimum value at a burial depth of 9 cm. The germination of C. pauciflorus seeds and the growth of subsequent seedlings perform better in a shallow burial depth （≤3 cm）， while a burial depth that is too deep is not conducive to their germination and growth. Therefore， the following control strategies are proposed： Suppress the germination of C. pauciflorus seeds by deep ploughing； Or after the rainy season arrives， spray herbicides on areas severely invaded by C. pauciflorus， thereby consuming the C. pauciflorus seed bank. Or by rationally intercropping other competitive plants to consume soil moisture， the growth space of the low-flowered C. pauciflorus can be restricted.

Key words: precipitation, burial depth, seedling growth, Cenchrus pauciflorus