Stoichiometric Characteristics Of Caragana Korshinskii Leaves Of Different Planting Years In Ningxia Baijitan

Caragana korshinskii,as an important desert-controlling plant resource in the semi-arid loess hilly region and arid desert region of Ningxia,plays an important role in desertification control and soil and water conservation in the ecologically fragile region of Northwest China,the study on the relationship between leaf stoichiometry and environmental factors is of great significance to reveal the adaptation mechanism of Caragana Korshinskii plants and the restoration and control of desert vegetation.Caragana Korshinskii plantation under 9 different planting years(3a,5a,10a,20a,30a,40a,50a,60a,70a)was selected as the study object.Nine typical plots were set up along the growth year gradient with time gradient instead of space gradient,the relationship between leaf stoichiometric characteristics and soil factors was analyzed by measuring leaf stoichiometric characteristics,carbon stable isotope and soil physical and chemical properties,by using redundancy analysis(RDA),the main factors influencing the chemical stoichiometric characteristics Caraganag Korshinskiiskii leaves were revealed and quantified,and the main soil factors which had significant influence on the chemical stoichiometric characteristics of leaves were screened out.The main results are as follows:(1)The crown width,plant height and ground diameter of Caragana Korshinskii had significant difference in 9 different planting years,and the crown width,plant height and ground diameter increased with the increase of planting years.The crown width,plant height and ground diameter of Caragana Korshinskii had negative correlation with leaf stoichiometry,and had positive correlation with leaf stoichiometry.(2)Leaf δ13C value,leaf carbon content,leaf nitrogen content and leaf phosphorus content responded significantly with different planting years(P<0.01),the leaf stoichiometry of Caragana Korshinskii also showed significant response to planting age(P<0.01).(3)According to the correlation of leaf stoichiometry,there were significant positive correlations among leaf δ13C,leaf nitrogen content and leaf phosphorus content,which were negatively correlated with leaf C/N ratio,C/P ratio and N/P ratio;However,there were significant positive correlations among C/N,C/P and N/P ratios in leaves.(4)The variation of soil bulk density,total nitrogen and total phosphorus was not obvious,and the content of soil organic matter varied greatly,followed by water content and pH.(5)RDA analysis showed that soil factors explained 76.66%variance of leaf stoichiometric characteristics of Caragana Korshinskii,among which the first two order axes could well represent the correlation between leaf stoichiometric characteristics and soil factors,and the correlation is determined by the first axis.(6)The results showed that soil pH value,soil organic matter,total nitrogen in 40-60 cm soil layer and total phosphorus in 20-40 cm soil layer were the main factors affecting the leaf stoichiometry characteristics.Our results of this study enriched the nutrient and water adaptation mechanisms of sand control plant Caragana Korshinskii in Ningxia desert area,and clarified the ecological characteristics and functions of the Caragana Korshinskii Plantation,it is of great significance to the rational management of plantation in this area and has certain guiding function for the scientific management of Baijitan Nature Reserve.