| The situation assessment of C,N and P in salinized degraded grassland is the basis of artificial restoration of degraded grassland,grassland ecological protection and rational development and utilization,especially in the background of soil fertilization and N deposition in our country.According to the spatial distribution patterns of the average precipitation in the past 50 years from 1961 to 2010,three different precipitation areas in the Songnen grassland were set up,namely,the east of the grassland in Xiangyang Township of Zhaodong City and the midwest in Shuiyuan Road,Ranghulu Area in Daqing City,which two both belong to Heilongjiang Province as well as the southwest of the grassland in Jiangjiadianzi Pasture,Dagangzi town,Daqing City,Jilin Province.We collected 169 samples of plant and soil samples,and the application of ecological chemical metrology theory and methods for analysis.The main results are as follows:1.C,N and P measurement of soil: soil salinization clearly negatived affected on the enrichment of C,N and P in soil,among them,the descending rates of soil organic C,total N,,soil available N,soil available P,soil total P were revealed,respectively.For the factors of soil salinization,soil bulk density contributed mostly,and followed by soil pH,meanwhile,soil conductivity weakly affected it.More concretely,soil bulk density primarily influenced the contents of organic C and total N in soil,while soil pH predominately affected soil total P,available P and soil N content.Based on Songnen grassland salinization,the distributed contents of soil C,N and P were 26.62,1.93 and 0.34 of g/kg,simultaneously,C:N,C:P and N:P were 18.13,237.15,14.75,respectively.There were low P content,C and N content of the medium involed in soil,which leading to C:P and N:P observed in elevation,ultimately,resulting in the imbalance of C:N:P.2.C,N and P in Leymus chinensis leaves: the variation range of Leymus chinensis leaf C,N and P content in Songnen grassland were 347.06 g/kg~493.01,12.04 g/kg,0.75 g/kg g/kg~34.02 g/kg~2.90 g/kg,respectively,among them,the average values were 462.51 g/kg,19.9 g/kg,1.31 g/kg,and the distribution of coefficient of variation between 3.34%~27.7%,belonging to the middle level of variation.In addition,the content of leaf P(18.30 g/kg)in the middle level of Leymus chinensis were lower than that in the northern China,and the leaf P content(1.32 g/ kg)as well as slightly higher N:P(15.83).Moreover,the leaf N content and N:P significantly displayed positive correlation with the soil total N and available N contents.Nevertheless,the leaf P content was negatively related with soil total N and available N content,whereas other soil factors were not observed a relationship with leaf N,P contents and N:P.The significant correlation between leaf P and soil N content and the deviation from soil P content indicated that there may be some P limitation in Leymus chinensis degraded grassland in Songnen Plain.3.The highest biomass and plant height in the Zhaodong area were the top of the study area,followed by the Daqing area in the middle and the lowest in the Da'an area.Daan sample has a higher C:P and lower C:N,with the unit N,P nutrient supply,Leymus chinensis on the use of high efficiency of P elements,while the use of N elements is relatively low efficiency,resulting in the more exacerbated phylogenetic relationship between element of Leymus chinensis leaf P and soil P.The distribution coefficients of P and C:P in leaves of Leymus chinensis were distributed in 20.16%-32.87% and 21.28%-25.83%,The variation coefficient of Da'an area is the highest,followed by Daqing area and the lowest in Zhaodong area,Under the premise of degradation of Leymus chinensis,the biomass of Leymus chinensis was the highest in Zhaodong area,and the utilization efficiency of P element was relatively stable,and the soil P content is the lowest in the Zhaodong plots that allowed the P limit will be more significant in the future.The C:P coefficient of variation(P <0.01)in Leymus chinensis grassland of Da'an area presented relatively high more vulnerable,in which,there was a significant positive correlation between soil organic C and soil C:P(P <0.01),similarily,leaf C content obviously related with leaf C:P(P <0.01),besides,between leaf C:N and soil C:N,it also revealed the negative relationship(P <0.05).In contrast,there was a evidently negative correlation between soil organic C and leaf C:N in Daqing plots,meanwhile,soil C:P was remarkably positively correlated(P <0.05).Ultimately,in terms of Zhaodong Area,the contents of soil organic C exhibited significant positive relations with soil C:P and soil C:N(P <0.01).Focused on the three research areas,they shared the similarities that the correlation between soil organic C and soil C:P,whereas the other factors is different in the three plots,with their own unique.In the actual production,the production guides for them also need to be treated separately. |
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