Characteristics Of Secondary Successive Vegetation And Soil Changes In High Altitude Agricultural Areas In Eastern Qinghai Province

Due to the lack of water resources,the spread of wind and sand and other factors,water and soil loss in northwest China is very serious.Returning farmland to forests and grasslands is an important governance model to prevent and control water and soil loss.This study selected Dongshan Township,Huzhu County,Qinghai Province,to study potato farmland,broad bean farmland,Oat farmland,2,5,20 year old returned farmland,2,5 year old abandoned land,12 characteristic plots such as native meadow,seabuckthorn,Caragana microphylla and Artemisia annua were used as research objects to study the vegetation communities and soil physical and chemical characteristics of the area with different restoration years.This paper discusses which model of returning farmland to forest and grassland is more suitable for northwest China,and provides important reference for ecological restoration in northwest China.The main conclusions are as follows:(1)Leymus chinensis and Pennisetum centrasiaticum were dominant species in the middle school of the conversion succession,but in the late succession period,Pennisetum centrasiaticum was replaced by Caragana with developed roots,drought tolerance and strong adaptability.The number of plants tended to decrease,and the plant types tended to be simple.Artemisia annua and Artemisia hedinii were dominant species in succession after two years of abandonment,and Leymus chinensis and Artemisia annua were dominant species in succession after five years of abandonment.The growth range of dominant plants was gradually expanded,and the plant richness was also greatly increased.(2)The content of soil p H,organic matter,organic carbon,total nitrogen,total potassium and alkali hydrolyzable nitrogen did not change significantly within 20 years of the land conversion succession.After 5 years of the land conversion succession,the content of total phosphorus increased significantly.Within 20 years of the land conversion succession,the content of available potassium in the soil surface layer 0-15 cm increased significantly first and then decreased significantly.After 5years of abandonment,the content of soil p H,organic matter,organic carbon,alkali hydrolyzable nitrogen and available phosphorus in the soil within 30 cm increased significantly;The proportion of clay,fine silt,medium silt and extremely fine sand in the soil remained stable within 20 years of returning farmland,while the proportion of silt in the soil surface layer of 15-30 cm remained unchanged after being increased.The proportion of clay and fine silt in the soil surface layer of 0-30 cm within 5 years of abandonment decreased significantly,and the proportion of silt and extremely fine sand in the soil surface layer of 0-30 cm within 5 years of abandonment increased significantly.(3)Soil p H is significantly negatively correlated with alkali hydrolyzable nitrogen,total nitrogen,organic matter,and organic carbon;p H is significantly positively correlated with available phosphorus;alkali hydrolyzable nitrogen,total nitrogen,organic matter,and organic carbon are significantly positively correlated;total phosphorus is significantly positively correlated with alkali hydrolyzable nitrogen,total nitrogen,organic matter,organic carbon,and available phosphorus;vegetation coverage and species evenness are significantly negatively correlated;species evenness and p H are significantly negatively correlated,There was a significant negative correlation between species richness and available phosphorus,and a significant positive correlation between species richness and available potassium.(4)According to the grey correlation degree method,the soil fertility of the land in the 20 years after the conversion of farmland increased first and then remained unchanged,and the soil fertility of the land in the 5 years after the abandonment showed an increasing trend.Classification of soil fertility stages: according to the overall difference of soil physical and chemical profiles,it can be divided into three main stages: initial fertility stage,medium fertility stage,and fertility fertility stage.