| The desertification of Qinghai-Tibet plateau was severe,especially in areas along the Qinghai-Tibet railway.The desertification areas along the Qinghai-Tibet Railway were selected,including Wulan section and the Beiluhe section,to study the changes of vegetation characteristics and soil nutrient content in different vegetation restoration forestland,relationship between degraded vegetation characteristics and soil trace elements in sandy grassland,and effects of sand burial on seed germination,seedling emergence and growth of native plants.Results of this study would provide reference for the restoration and reconstruction of desertification land on the Qinghai-Tibet Railway.1?The study on the vegetation restoration of different vegetation in the Wulan desertification area.The results showed that both in the number of unrecovered sand or vegetation restoration plots.There were fewer shrubs and herbs under vegetation restoration.With the restoration of vegetation growth,the number of species increased;Hippophae rhamnoides had the highest number of species,the most complex community structure and the best biological diversity.The soil bulk density under the restored vegetation was significantly reduced,soil porosity,capillary porosity increased,soil water holding capacity increased;The organic matter,total nitrogen,total phosphorus,total potassium,instant phosphorus and available potassium in soil were significantly improved compared with the unrestored sand land.The soil surface nutrient content was higher than the unrestored land,and the soil element converge on thesurface.The sequence of 0-20cm soil fertility in the soil layer was as follows:Tamarix chinensis>Hippophae rhamnoides>Populus bolleana>Populus simonii>Caragana korshinskii.It was the best to obtain the effect of Hippophae rhamnoides and Tamarix chinensis on the restoration of the sand land by the investigation of vegetation restoration and soil sampling.2?The grassland degradation of Qinghai-Tibet plateau was serious,land degradation along the qinghai-tibet railway was particularly concerned.The experiment investigated the characteristics of degraded vegetation community and its relationship with soil physical and chemical properties of Carex moorcroftii steppe in the Beiluhe section of Qinghai-Tibet Railway.The results showed that the species of vegetation in the steppe of the grassland of Carex moorcroftiis decreased gradually,Carex moorcroftii was dominant plant in non-degraded,replaced by the coexistence of Carex moorcroftii,Kobresia pygmaea and Kobresia humilis in the lightly and moderately degraded ones,with obvious dominant plant identified in the highly degraded steppe.The succession of high-density tussock communities to low,creeping weed communities,desert plants appeared.Plant species evenness index firstly increased and then decreased,species richness and diversity index decreased.The content of silt,clay,total P,available Cu content and available Fe content in soil decreased significantly(P<0.05),and the available Zn content increased significantly(P<0.05),and the soil pH,total potassium and gravel ratio remained unchanged.Correlation analysis showed that the species diversity index,evenness index and species richness index of Carex moorcroftiisteppe were significantly correlated with the content of clay,pH and Zn in soil(P<0.05).There was a positive correlation between available Fe and species evenness index,which was mainly reflected in the more significant effect of vegetation aggregation,and the available Zn content could be used as a key indicator of the vegetation degradation.3?To promote the restoration and reconstruction of desertified land in Qinghai-Tibet Plateau,the effects of different depth of sand burial(0,1,2,3,4 and 6 cm)on seed germination,seedling emergence and growth of four native plants(Festuca sinensis,Elymus breviaristatus,Elymus nutan and Poacrymophila cv Qinghai)were studied.The results showed that sand burial had a significant effect on the emergence rate,root length,root shoot ratio,plant height and biomass allocation of four plant seedlings(P<0.05);seed germination and seed mass was significantly positive correlated(P<0.05),and the seed with high 1000-grain weight had high probability of germination.With increasing of burial depth,the probability of seedling emergence,plant height,root length,the root and shoot biomass of Festuca sinensis,Elymus breviaristatus,Elymus nutan increased firstly,followed by decreasing,however Poacrymophila cv Qinghai of more than 4 cm depth of sand burial failed to emergence.It indicated that the optimum depth of sand burial for seeding emergence and growth for Festuca sinensisis 1-3 cm,Elymus breviaristatus was 2-3 cm,Elymus nutans was 1-3 cm,Poacrymophila cv Qinghai was 1-3cm respectively.Plant with larger seed mass and moderate sand depth of 1-3 cm should be considered during vegetation recovery to improve emergence and growth of seedling,further benefit to establishment of species. |
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