Study On Ecological Stoichiometry Characteristics In Soil And Plants Of Robinia Pseudoacacia And Caragana Korshinskii Forest On The Loess Plateau

In order to understand the sustainable development of typical plantations in the Loess Plateau,as well as the relationship between the distribution pattern and the ecological stoichiometry of soil and plants carbon and nitrogen and phosphorus,we selected Robinia pseudoacacia and Caragana korshinskii forest on the loess plateau as the objects.This research was related to the ecological stoichiometry characteristics of carbon,nitrogen,phosphorus in leaves,steams,roots,litter and soil of Robinia pseudoacacia and Caragana korshinskii forest,as well as the responsibility of ecological stoichiometry to environmental factors,which revealed the relationships between plant and soil.This research was benefitial for evaluating the ecological benefits and guiding the ecological reconstruction.The results showed that:(1)With the increase of forest age,the soil carbon and nitrogen and phosphorus content of Robinia pseudoacacia plantation increased significantly;while the phosphorus content was highest in the mid-mature plantation;the content of carbon,nitrogen and phosphorus in plants was higher than that in soil;the carbon content of aboveground biomass was higher than that in litter;The variation of nitrogen and phosphorus in different organs showed as follows: leaves>litter>roots>steams;The N/P of Robinia pseudoacacia leaves were 17.70,13.49 and 12.70 in the young plantation,mid-mature plantation and mature plantation,respectively.N/P of leaves decreased with the increase of forest age.(2)The average contents of soil carbon,nitrogen and phosphorus in Robinia pseudoacacia forest were 7.49?0.78 and 0.77g·kg-1,respectively,the average contents of soil carbon,nitrogen and phosphorus in Caragana korshinskii forest were 5.08 ? 0.58 and 0.49g·kg-1,respectively.The contents of carbon and nitrogen in the soil of Robinia pseudoacacia and Caragana korshinskii were enriched in the surface,and the phosphorus content was relatively uniform;The contents of carbon,nitrogen and phosphorus in the soil of Robinia pseudoacacia andCaragana korshinskii showed that Robinia pseudoacacia>Caragana korshinskii,which showed that the Robinia pseudoacacia storage capacity of carbon and nitrogen was higher than that of Caragana korshinskii.(3)The content of nitrogen and phosphorus in leaves is higher,and the content of nitrogen and phosphorus in roots and steams is lower.The average N/P value of Robinia pseudoacacia leaves was 14.08,and the average N/P value of Caragana korshinskii leaves was 20.13,which indicated that the growth of Robinia pseudoacacia was limited by nitrogen and phosphorus,while the growth of Caragana korshinskii was limited by phosphorus;Based on the Garnier theory,the growth of Robinia pseudoacacia root was limited by nitrogen,and the growth of steams was limited by the content of nitrogen and phosphorus;the growth of Caragana korshinskii was limited by phosphorus,and the growth of stems was limited by nitrogen.There was a significant correlation between carbon,nitrogen and phosphorus of stems,soil and roots,and illustrate the relationship between stems,roots and soil more closely.(4)Different organs have different stability,different elements or elements ratio have the different the homeostasis indexes.There have no stability of carbon and nitrogen elements in leaves and roots,the phosphorus homeostasis indexes was higher in roots and steams of Robinia pseudoacacia,the stability of nitrogen element in Caragana korshinskiileaves was higher,and the stability of phosphorus in roots and stems was higher.The homeostasis indexes of carbon and nitrogen was higher than that in Robinia pseudoacacia,while the phosphorus homeostasis index was less than Robinia pseudoacacia.The stability index of C/P in Robinia pseudoacacia was higher,and C/N did not have stability,the stability index of C/N and N/P in Caragana korshinskii leaves was higher,and the stability index of stem C/P was higher.(5)The contents of carbon,nitrogen and phosphorus in soil of Robinia pseudoacacia and Caragana korshinskii decreased with the increase of latitude,at 37 degrees north latitude south of Caragana korshinskii forest soil carbon and nitrogen content is higher than that of Robinia pseudoacacia,at 37 degrees north latitude north of Robinia pseudoacacia forest soil carbon and nitrogen contents higher than Caragana korshinskii;Precipitation 400 mm is a critical point,which is less than this value,the precipitation has little effect on the soil nutrients of Robinia pseudoacacia forest,more than 400 mm,significantly increased;The soil of Robinia pseudoacacia plantation was more sensitive to the change of annual precipitation,Caragana korshinskii forest soil was more sensitive to altitude change.(6)The contents of carbon,nitrogen and phosphorus in litter of Robinia pseudoacacia decreased with the increase of latitude,the content of nitrogen and phosphorus in litter of Robinia pseudoacacia and Caragana korshinskii decreased with the increase of altitude,and increased with the increase of annual temperature and annual precipitation.The contents of carbon,nitrogen and phosphorus in leaves of Robinia pseudoacacia and Caragana korshinskii had no significant correlation with latitude,which did not accord with the hypothesis of temperature plant physiology.The nitrogen content of Robinia pseudoacacia leaves increased with the increase of altitude,and the content of carbon and phosphorus increased with the increase of annual precipitation,and there was no significant correlation with the average annual temperature;The nutrient content of Robinia pseudoacacia roots increased with the increase of latitude,and was negatively correlated with temperature,that was supported by the hypothesis of temperature plant physiology.