Study On The Nitrogen Utilization And Root Foraging Among Six Species In Soft Sandstone Areas Of Ordos Plateau

The Arsenic sandstone areas of Ordos Plateau has fragile ecological environment due to barren soil and severe erosion.As we all know,soil nutrients are important limiting factors for plant growth.Therefore,studies on the nitrogen use efficiency and root morphology response of plants under different nutrient control have important theoretical and practical significance for species selection in the process of soil and water conservation and vegetation restoration and reconstruction in the sandstone area.The study is based on the environmental and climatic conditions of the sandstone area of Ordos Plateau,from the perspective of plant nutrient utilization characteristics,selecting three kinds of native plants Achnatherum splendens,Amygdalus pcdunculata and Hippophae rhamnoides and three kinds of exotic species Rheum palmatum,Pennisetum americanum × P.purpureum and Elaeagnus pungens as studies' objects,using the internal growth method(nylon mesh bag method)to set the heterogeneous nitrogen fertilizer spot,also including four nitrogen levels of high(0.3g N/kg dry soil),medium(0.2g N/kg dry soil),low(0.1g N/kg dry soil))and control treatment.The species with strong root foraging ability and good nutrient utilization function were selected to provide a basis for the introduction and selection of resistant plant material in the sandstone area by calculating the nitrogen use efficiency of six different plants under different nutrient control and the foraging responses of different plant roots to different nitrogen fertilizer patches,aboveground biomass,rooting biomass and morphological parameters in ingrowth cores were determined and comparing the difference of nutrient utilization efficienc and root foraging ability of different plants.The results show:(1)Nitrogen use efficiency(NUE)is expressed as the product of nitrogen productivity(NP)and mean residency time(MRT).There were significant interspecies differences in nitrogen productivity,mean residency time(except Elaeagnus pungens)and nitrogen use efficiency among the six plants used in this study.The order of NP from high to low is Pennisetum americanum ×P.purpureum>Rheum palmatum >Hippophae rhamnoides>Achnatherum splendens>Amygdalus pcdunculata >Elaeagnus pungens,the order of MRT from long to short is Amygdalus pcdunculata >Hippophae rhamnoides>Achnatherum splendens>Rheum palmatum > Pennisetum americanum × P.purpureum,the order of NUE is Hippophae rhamnoides>Amygdalus pcdunculata >Rheum palmatum >Pennisetum americanum × P.purpureum>Achnatherum splendens>Elaeagnus pungens.The nitrogen utilization strategies of the six plants were also different.Rheum palmatum and Pennisetum americanum × P.purpureum have higher NP and shorter MRT,while Amygdalus pcdunculata,Hippophae rhamnoides and Achnatherum splendens are on the contray(lower NP and longer MRT).Compared with the non-nitrogen control plants,the aboveground biomass and NUE of these six plants increased in the plaque nitrogen-bearing habitats,particularly,Pennisetum americanum × P.purpureum increased most after nitrogen application,which was the fast-growing plant.(2)Compared with the roots of the untreated nitrogen plants,the heterogeneous nitrogen fertilizer plaques of roots of six plants has increased,which showed an increase in root biomass,root length elongation and root surface area.The roots of the Amygdalus pcdunculata increased significantly and fine root proliferation has certain sensitivity to plaque habitat.Among the heterotrophic nitrogen plaques,the biomass density of Pennisetum americanum × P.purpureum roots was the highest in high nitrogen,and the biomass density,root length and surface area of Rheum palmatum,Achnatherum splendens,Amygdalus pcdunculata and Elaeagnus pungens were the most abundant in the treatment of nitrogen.There were interspecies differences in the response of six plants to heterogeneous plaques.Compared with the control growth bags,the biomass density of Rheum palmatum roots increased by a maximum of 489.29%,and the root length of Amygdalus pcdunculata increased by a maximum of 95.35%.The root surface area of Achnatherum splendens increased by a maximum of 170.02%.There was a negative correlation between the accuracy and spread of the roots among these five plants of Rheum palmatum,Achnatherum splendens,Pennisetum americanum × P.purpureum,Amygdalus pcdunculata and Elaeagnus pungens.(3)It is also shown that there were significant differences in nitrogen uptake among the six plants after the analysis of the fate of fertilizer nitrogen at the end of the study: the nitrogen uptake of Pennisetum americanum × P.purpureum and Hippophae rhamnoides were relatively more,and the nitrogen uptake of Rheum palmatum was less.Compared with the control treatment,in nitrogen treatment,the amount of nitrogen absorbed by plants and the amount of nitrogen lost by soil were both increased significantly while there was no significant difference in soil residual nitrogen.There were also significant differences in soil residual nitrogen fertilizer of the ingrowth cores of heterogeneous fertilization(high fertilizer,medium fertilizer,low fertilizer and control).Interspecies differences exist among soil residual total nitrogen,nitrate nitrogen and ammonium nitrogen.