稀土矿尾砂地氮添加对樟树幼苗根系生长、生物量分配及非结构性碳水化合物的影响

[Objective]The southern regions of China,including Gannan,northern Guangdong,and western Fujian,possess a large amount of rare earth resources.Since the 1970s,due to the large demand for industry,rare earth resources have been extensively exploited.Due to the mining methods,the surrounding environment has been greatly damaged,resulting in a series of environmental problems.For many years,despite years of governance by government departments,the ecological restoration of rare earth tailings has been slow and lacks certain economic benefits due to the support of systematic scientific governance technology,which has limited the promotion and application of vegetation restoration measures.Cinnamomum camphora has been proven to be grown on rare earth tailings,and as a characteristic spice economic tree species in Jiangxi Province,its branches and leaves are rich in essential oil.Currently,it is widely planted in Yunnan,Sichuan,Hubei,Hunan,Guizhou,Guangxi and other provinces in China through dwarf cultivation.Due to the fact that the aboveground parts of camphor trees are flattened every year,the continuous growth of branches and leaves requires high nutrient requirements,and the barren rare earth tailings habitat is difficult to meet the growth needs of camphor trees.Therefore,in order to meet the continuous growth needs of plant branches and leaves,a large amount of nitrogen fertilizer needs to be supplemented every year.However,there is a certain degree of blindness in the application process of nitrogen fertilizer.In addition,the poor soil fertility in rare earth tailings mining areas can lead to more serious soil erosion and non-point source pollution problems due to the loss of excess nitrogen fertilizer.[Method]Based on this,this study takes camphor tree seedlings as the research object and sets three nitrogen levels:control(CK,0g/plant),low nitrogen(N1,1.8g/plant),and high nitrogen(N2,3.6g/plant).After 5 months of treatment,the differences in root growth indicators,biomass allocation,and non structural carbohydrates of camphor tree seedlings under different nitrogen addition levels are measured to explore the response mechanism of camphor tree seedlings to nitrogen addition,Furthermore,it provides a powerful and reliable reference for the ecological restoration of ionic rare earth ore tailings.[Result]The results showed that the leaf,stem,canopy,coarse root,fine root,and total biomass of camphor tree under N1 treatment were significantly higher than CK and N2(P<0.05),while the leaf branch ratio and leaf biomass proportion under N2 treatment were significantly higher than CK(P<0.05).The proportion of biomass of stems and fine roots under N2 conditions was significantly lower than that of CK(P<0.05).Under N1 treatment,the length and surface area of coarse and fine roots were significantly higher than those of CK(P<0.05);N2 treatment significantly increased specific root length and specific surface area compared to CK and N1 treatments(P<0.05);Under N1 treatment,the diameters of coarse and fine roots were significantly lower than those of CK(P<0.05).Under N1 treatment,the soluble sugars in leaves and stems were significantly higher than those in N2(P<0.05);Under N2 treatment,the starch and non structural carbohydrate(NSC)content in stems,coarse roots,and fine roots were significantly lower than those in CK(P<0.05).[Conclusion]In summary,under low nitrogen conditions,camphor tree seedlings mainly increase nutrient absorption by constructing root structures,while high nitrogen conditions inhibit the development of root length and root surface area,leading to a decrease in root nutrient absorption efficiency;The nutrient relief driven by N addition allocates more non structural carbohydrates to aboveground organs,thereby accumulating NSC in the aboveground portion.