Screening trial for the suitable plant species growing on sand dunes in the alpine valley and its recovery status in the Yarlung Zangbo River basin of Tibet,China

There was a total of 273 697.54 hm2 of aeolian sandy lands in the Yarlung Zangbo River basin of Tibet in 2008.The fast development of aeolian sand lands has caused immense damages to its social and economic development,it is urgent to choose appropriate plant species for vegetation restoration of the moving sand dunes in the basin.Thus,we carried out a continuous trial of the field artificial seeding on sand dunes in the middle reaches of the Yarlung Zangbo River basin,the main testing plant species included the northern China′s psammophyte species and the Tibet′s native species.The germination,emergence,growth processes and reproduction of the testing plant species were observed from 2008 to 2011,based on these,the best suitable species on sand dunes in the alpine valley were determined,which could be used to guide the ongoing vegetation recovery and reconstruction on aeolian sandy land in the studied area.The results showed that the plant height and plant size growth of northern China′s psammophyte species were larger than that of native psammophyte species in the field artificial seeding trial,and the species such as Artemisia sphaerocephala,Hedysarum scoparium,Calligonum mongolicum,H.fruticosum var.mongolicum and Sophora moorcroftiana all exhibited good adaptability to moving sand land.So far as the status of reproduction of the testing species,Artemisia sphaerocephala began to flower and seed in the second year,while H.scoparium and C.mongolicum began to flower and seed in the third year,it was the most important finding that A.sphaerocephala,H.scoparium and C.mongolicum were all able to complete the life cycle in the alpine valley under the special climate zone on the Tibetan Plateau,however,the reproducibility of A.sphaerocephala was weak,but H.scoparium and C.mongolicum both showed strong reproducibility.The morphological characteristics and different parts of sand dunes influenced the trial results of field artificial seeding greatly,and the vegetation coverage varied from 5% to 40% on different sand dune types.The approach which sowed seeds into footprints trampled on slope sand land by feet following the contours of mountain artificially proved to be a good measure to improve the results of field artificial seeding trial.The observed results showed that habitat conditions such as precipitation,soil temperature of sand dune,soil moisture content and sand movement affected the germination,emergence and plant growth greatly,but these need to be discussed in detail in the next step.