Effects Of Nitrogen And Phosphorus Addition On The Soil Properties And Functional Traits Of Dicranopteris Dichotoma

Dicranopteris dichotoma plays an important role in the process of ecological restoration and reconstruction in the eroded area of southern red soil because it can survive in nutrient-poor or excess environment.In this study,the red soil in the eroded area of the southern red soil was used as the substrate.Pot experiments were carried out with the method of control variables to reveal the morphological and physiological response mechanism of Dicranopteris dichotoma under nitrogen and phosphorus addition in order to provide relevant scientific basis for ecological restoration and soil erosion control in the eroded area of red soil in southern China.The main results of this study are as follows:(1)Soil nitrogen and phosphorus significantly changed the soil nutrient status and physical and chemical properties,but also affected the distribution of carbon,nitrogen and phosphorus in different organs of Dicranopteris dichotoma.With the increase of soil nitrogen gradient,soil pH value decreased,which increased soil acidification.With the addition of phosphorus,the pH value of soil increased.Soil nitrogen addition significantly increased the availability of soil nitrogen,especially the increase of soil ammonium nitrogen.the content of total phosphorus and available phosphorus increased significantly with the increase of phosphorus gradient,which alleviated the phosphorus deficiency in red soil.Under the addition of soil nitrogen and phosphorus,the internal stability of nitrogen and phosphorus in all organs of Dicranopteris dichotoma showed the characteristics of leaf > petiole > root of underground stem,and the relationship between soil N:P and N:P of each organ of Dicranopteris dichotoma were in accordance with the quadratic function model.(2)Addition of soil nitrogen and phosphorus decreased the root / shoot ratio of Dicranopteris dichotoma.With the increase of nitrogen gradient,the ratio of root to shoot decreased first and then increased,while that of phosphorus increased.The root-shoot ratio of Dicranopteris dichotoma decreased with the increase of the additive gradient.The addition of nitrogen to a certain extent may contribute to the growth of root system and increase the biomass of Dicranopteris dichotoma,but excessive nitrogen supplementation may have a toxic effect on Dicranopteris dichotoma,which limits the extension of root length and the growth of abovegroundpart of Dicranopteris dichotoma.Moderate nitrogen addition promoted the increase of leaf area and chlorophyll content of Dicranopteris dichotoma,while the chlorophyll content of Dicranopteris dichotoma decreased obviously with the addition of excess nitrogen.The leaf area and plant height of Dicranopteris dichotoma increased significantly(p < 0.01),but chlorophyll increased first and then decreased with the increase of the adding gradient of Dicranopteris dichotoma under a certain degree of soil phosphorus addition.(3)There was a negative correlation between growth rate and leaf N:P,but no significant correlation with leaf C:P,and there was a significant positive correlation between leaf growth rate and growth rate.Therefore,the growth characteristics of Dicranopteris dichotoma basically accord with the hypothesis of plant growth rate.There was no significant correlation between leaf chlorophyll and total carbon,total nitrogen and available nitrogen in soil,but negative correlation with total phosphorus and available phosphorus in soil.Chlorophyll content in leaves of Dicranopteris dichotoma increased with the increase of soil nitrogen content to a certain extent,and then decreased after the increase of soil nitrogen content.In addition,the content of chlorophyll in Dicranopteris dichotoma There was a positive correlation between nitrogen content and phosphorus content in leaves of Dicranopteris dichotoma.(4)There was a significant negative correlation between leaf tissue density and specific leaf area(p < 0.01).Leaf area was positively correlated with leaf N content and leaf N:P content.The content of N:P in the root of underground stem and N:P content in leaves of Dicranopteris dichotoma changed parabola.Soil phosphorus and available phosphorus are the most important factors affecting the leaf functional characters of Dicranopteris dichotoma.The content of soil available phosphorus is the most important factor affecting the root functional characters of Dicranopteris dichotoma,followed by soil available nitrogen and soil N:P.