Ecostoichiometry Characteristics And Spatial Variation Of Carbon,nitrogen And Phosphorus In Plant-soil Systems In Minqin Desert Area

Liangucheng Nation Reserve in Minqin county of Gansu Province is a typical desert ecological nature reserve.Its vegetation coverage and soil productivity are relatively low.Identifying the soil conditions and the adaptation and feedback mechanism of desert plants can effectively control and prevent desertification in the reserve.In this study,60 sampling sites were set up to collect 0-60 cm of soil profile samples and stem and leaf samples of five desert plants,including Ephedra przewalskii,Calligonum mongolicum,Nitraria tangutorum,Reaumuria songarica and Haloxylon ammodendron.The contents of organic carbon（C）,total nitrogen（N）and total phosphorus（P）were determined.Descriptive statistical analysis,one-way analysis of variance and spatial interpolation analysis were performed for the stoichiometric characteristics of soil.Two-factor analysis of variance was performed for the stoichiometric characteristics of five desert plants and their different organs,and their stoichiometric correlations with soil were further analyzed.The results are as follows:（1）The average content of C,N,P and C:N,C:P and N:P in 0-60cm soil were 2.22g·kg^-1,0.33g·kg^-1,0.25g·kg^-1,7.81,9.65 and 1.47,respectively,which were significantly lower than the national average,compared with other desert areas,the C,N and P contents were lower than those in the Korqin Sandy Land,and the C content,P content and C:N were lower than those in the Junggar Basin and Gurbantunggut Desert.N content and N:P were higher than those in the Junggar Basin and Gurbantunggut Desert,and C:P was higher than in the Gurbantunggut Desert（3.98）.It can be seen that the soil habitat conditions in the study area are poor,the decomposition rate of organic matter and soil N mineralization rate are high,the mineralization capacity of effective P in the soil is weak,which is not conducive to soil organic matter sequestration and plant growth,combined with low P content and relatively high N:P,the nutrient restriction in the study area is P>N.（2）In the vertical section,soil C content,N content,C:P and N:P decreased with the increase of soil depth,P content was relatively stable,and C:N first decreased and then increased with the increase of soil depth.Under the influence of litter,soil microorganisms and plants,the ecological stoichiometric characteristics of 0-30cm soil layer were significantly different from those of 30-60cm soil layer（P<0.05）.In terms of horizontal spatial distribution,the soil nutrient content in the northern part of the reserve was better than that in the southern area,among which,the Gaussian model with the most semivariogram fit with C content and the spherical model with the most fitting with N content,both of which showed the strongest total variation degree of 0-10cm soil layer,and the spherical model with the most fitting P content,and the partial abutment value of each soil layer was greater than the nugget value,and its spatial variation was structural variation.（3）The contents of C,N,P and C:N,C:P,C:N,C:P and N:P in the leaves of five desert plants were lower than the global average level.At different organ levels,the C content of the five desert plants showed stem>leaf,the N content and P content showed leaf>stem,the C:N and C:P content showed stem>leaf,and the N:P content showed leaf>stem.At the species level,the content of N and P of Nitraria tangutorum was significantly higher than other plants,and the content of N and P of Ephedra przewalskii and Calligonum mongolicum were relatively lower.The N:P of leaves and stems of Ephedra przewalskii and stems of Haloxylon ammodendron were greater than 14 and less than 16,which were jointly restricted by elements N and P in the growth process,while the N:P of other plants was greater than 16,which were more strongly restricted by elements P in the growth process.In addition,the contents of C,N,P and C:N,C:P and N:P of the five desert plants were significantly different at the species level and organ level（p<0.05）,indicating that the absorption and utilization of nutrient elements in different organs of different plants were selective,reflecting genetic differences.（4）At the same organ level,there was a significant negative correlation between the N content and C:N in the leaves of Ephedra przewalskii,itraria tangutorum,Reaumuria songarica and Haloxylon ammodendron.There was a significant negative correlation between the P content and C:P in the leaves of five desert plants,and a significant positive correlation between C:P and N:P in the leaves of Calligonum mongolicum and Reaumuria songarica.There was a significant negative correlation between stem N content and C:N,and also between stem P content and C:P.At different organ levels,there was significant positive correlation between the N and P contents of Ephedra przewalskii,Nitraria tangutorum and Haloxylon ammodendron in leaves and stems,but no significant correlation between the N and P contents of Calligonum mongolicum and Reaumuria songarica in different organs.（5）There was a positive correlation between the C content of the five plants’in different soil depths,and the positive correlation was significant between the C content of 0-10cm soil layer,and the correlation gradually weakened with the increase of soil depth.The content of N and P in leaves also showed a significant relationship with the content of N and P in surface soil.The relationship of C,N and P stoichiometric characteristics between plant stems and soil was basically consistent with that of leaves,and the relationship with surface soil stoichiometry was more significant.There was no uniform law between the C:N:P stoichiometric characteristics of five desert plants and the stoichiometric characteristics of soil at different depths,among which the relationship between Haloxylon ammodendron and soil was more obvious.In this paper,the nutrient restriction pattern and the nutrient interaction relationship between soil and plants in protected areas are clarified,and it is concluded that plant growth is more limited by P than N,and that Haloxylon ammodendron can better regulate soil productivity.In the later stage,the process of ecological restoration of protected areas can be promoted by artificially applying P fertilizer to increase biomass and continue to plant Haloxylon ammodendron to adjust soil nutrients.This paper is expected to provide data support for regulating and improving the productivity and ecological restoration of protected area ecosystems.