Study Of Plant Community Secondary Succession On Abandoned Farmland In The Lower Reaches Of Shiyang River

In this paper, related survey of plant communities and soil physical and chemical properties of different restoration years of abandoned farmland in plant communities in the lower reaches of Shiyang Rive were analyzed used bytemporal substitution. The following results were obtained.(1)Plants of 37 species spread over 13 families and 31 genera appeared in different years of abandoned farmland in the lower reaches of Shiyang Rive. Among them, the Asteraceae(6 genera,7 species), Zygophyllaceae(5 genera,7 species),Gramineae(5 genera,5 species) and Chenopodiaceae(4 genera,6 species) plant species, accounted for total genera and species of 64.51 and 67.57%。the dominant species of herbaceous layer for Atriplex patens, Eragrostis pilosa, Suaeda glauca, Peganum harmala and Bassia dasyphylla, and those of Shrub layer were Nitraria tangutorum, Reaumuria soongarica, Tamarix ramosissima, Lycium ruthenicum and Salix wilhelmsiana.(2) During the period of returning farmland to land in 1-50 years, with increasing year of afforestation in the lower reaches of Shiyang River,the plant communities had the Atriplex patens- Peganum nigellastrum- Phragmites australis- Suaeda glauca+ Peganum nigellastrum- Lycium ruthenicum- Nitraria tangutorum- Kalidium foliatum succession process;In succession, the main species in plant communities is started by weeds Atriplex patens, followed by a succession of annual herbaceous communities, perennial herbaceous and perennial herbaceous and woody plant communities. After returning farmland to 50 years, the succession is a shrub community. With the increase of the cultivated land, he Margalef index, Shannon-Wiener index, Simpson index, Pielou index, and Alatalo index of the community were in a volatility reduction trend.(3)With the increase years of vegetation restoration, soil organic matter have differences with total N content, the change trend is similar to a fluctuation change; available P and available K have similar change trend and have no obvious difference, showing a slow growth state. The Species diversity index and soil nutrient show various degree of difference during succession period. Margalef index was highly significantly correlated with organic matter and significantly negative correlation with available K, significantly correlated with total N, non-significant with Quick acting P; Shannon index was significantly correlated with organic matter, and non-significant with total N, available P, and available K; Simpson index was non-significant with other index; Pielou index was significantly negatively correlated with total N, Alatalo index was significantly correlated with the whole N, and both non-significant with organic matter, available P, and available K.