Abandoned Farmland Soil Seed Bank And Its Relationship With The Aboveground Vegetation In The Eastern Margin Of The Qinghai-Tibet Plateau

All the viable seeds existed in the soil or mixed in the litter forms a seed bank..Research on the size,composition and number of soil seed bank is of great theoretical and practical significance.The past research of the soil seed bank concentrated in the temperate regions,and few in the Alpine region,such as the Qinghai-Tibet Plateau.soil seed bank of grassland abandoned different period of Qinghai-Tibet Plateau were studied.The method is:Select abandoned 1,10 and20 year and the control turf as four treatment each treatment 20 m×20m,Respectly,select 10 sub- plots of 2m×2 m in four treatment randomly.Further divided each sub-plots into ten 0.4×1m~2 sample.Sample in three layers in each sample(sampling depth:0-2 cm,2-7cm and 7-12 cm),Shipped the samples back with the bags prepared and dry freely.It is used the germination method to research the abandoned farmland soil seed bank of the alpine grasslands on the eastern edge of Qinghai-Tibet Plateau.Its purpose is to examine the difference among soil seed bank of different abandoned-year farmland and the relationship between the soil seed bank and the corresponding ground vegetation and the succession relationship of different abandoned-year farmland in general,so as to provide important theoretical basis for the rehabilitation and reconstruction of abandoned farmland.Respectly,we mark abandoned 1 year farmland,10 years farmland,20 years farmland and control grassland of the four treatment as:A,B,C and D.Main results is:25 familis 65 generas 93 species 20813 seedlings was recordedin the 4 treatment with 5 month-long germinations.With the increasing of succession age,seed number in the 4 treatment was reducing gradually,the difference significance analysis indicates that:only the differences between C the D was not remarkable,the difference between the others was remarkable(p＜0.05).Seeds from 0-2 cm layer to 2-7 cm layer in all four treatments increased with soil depth,and the difference was significant(p＜0.05),and from 2-7 cm layer to 7-12 cm layer,seeds number between the two soil layers of the treatments is reduced exept that of abandoned one-year farmland which is increased slightly,although the difference is not significant(p＞0.05).With the increasing of succession years,species in soil seed bank maintain stability basically after abandoned 10 years,and to the life-time,with the abandon of the increase,the proportion of annual species or biennial species in the seed bank was decreasing gradually. The number of species in aboveround vegetation was increasing in general,and the difference between four treatment was significant(p＜0.05),The similarity between soil seed bank and the corresponding ground vegetation is from 36.56 of the abandoned one-year farmland,48.28%of abandoned 10 years farmland,to 57.58%of abandoned 20 years farmland,and decreased to 48.53%of control grassland. Available conclusion is as following:the seeds of soil seed bank mainly concentrated in 0-2 cm layer,and the buried seed follows a downward trend with soil depth.The number of species and plants in aboveground vegetation was increasing with abandoned years.The relationship between soil seed bank and the corresponding vegetation was a gradually increasing trend generally with the increasing abandoned years.