Abstract:

The species diversity of halophytic vegetation and its distribution changes with salt content of soil were studied by the spot investigation and referred literatures in this paper. The results showed that there were about 305 species 15 varieties and 7 subspecies of halophytes,which belong to 38 families and 124 genera in Xinjiang. The halophytes concentratively distributed in the groundwater overflowing zone of alluvial fan,outer area of riverside oasis and desert skirts. Richness of halophyte in communities was mainly controlled by salt content of soil. The relationships between halophyte richness as well as β-diversity and salt content can be simulated by quadratic equation. The highest richness of halophyte occurred at the habitat with salt content of 4% and it decreased while the salt content exceeded or below the threshold. The most species of halophytic shrub,sub-shrub and annual herb was observed at the habitat with salt content of 4%. The species richness and β-diversity of halophytic community decreased sharply while the salt content of habitat exceeded 5 to 6 percent. At habitat of salt content exceeding 12 percent,none annual herb but 2 to 4 species of halophytic shrub and sub-shrub were observed and the halophyte richness decreased by minimum. The component of life forms of halophytes in communities varied with salt content of soil,I.e. the annual herbs decreased and the shrubs increased with the increasing of salt content of soil. In addition,the study on distribution characteristics of 12 community-constructed species,such as Tamarix hispida,Nitraria sibirica,Kalidium foliatum,Phragmites australia,Suaeda glauca,Halocnermum strobilaceum,Halostachys caspica,Salsola ferganica,Lycium ruthenicum,Alhagi sparsifolia,Karelinia caspica and Reaumuria soongorica,showed that the salt adaptabilities of plant to salt are very different among the species T. hispida,N. sibirica,and H. caspica widely distributed in the habitat from 0.2% to 27.0% of salt content. H. strobilaceum was mainly found in the habitat exceeding 2% of salt content and rarely found in low saline environments,P. australia was found only in the habitat below 17% of salt content,K. foliatum and A. sparsifolia usually survived in the soil below 8% of salt content,L. ruthenicum and K. caspica were usually found in the habitat below 6% of salt content,S. glauca and S. ferganica were only found in the habitat below 8% of salt content and R. soongorica generally grew in the saline soil below 4% of salt content. Distribution frequency of different halophytes showed different trends with salt content in their distribution salt interval. The distribution frequency of T. hisipa,H. caspica,H. strobilaceum,A. sparsifolia and K. caspica increased linearly in the salt interval they distributed. Frequency of S. glauca,S. ferganica and R. soongorica decreased linearly in the habitat below 8.0% of salt content and 4% of salt content,respectively. However,the relationships of distribution of P. australia,N. sibirica,K. foliatum and L. ruthenicum with soil salt could be expressed by quadratic equation and the frequency of N. sibirica and P. australia got a peak at about 10% of salt content,frequency of K. foliatum got a peak at about 4% of salt content and frequency of L. ruthenicum got a peak at about 2.5% of salt content.

Key words: Xinjiang, halophytic vegetation, species diversity, distribution, soil salt