Study On Ecological Stoichiometric Characteristics Of Plant Leaf-Litter-Soil In The Process Of Natural Restoration In Maolan Karst Forest

Based on the theory of ecological stoichiometry,by the method of spatial sequence instead of time successional sequence,this paper selected herb stage,shrub stage,arbor stage and climax stage with the process of natural restoration of Maolan karst forest as the object,studied the C,N,P,K content and stoichiometric characteristics of plant leaves,litter and soil,and the N,P resorption efficiencies,community diversity indices and the specific leaf area.The main results were as follows:1.The overall distribution of C,N,P,K content and stoichiometric characteristics of plant leaves?1?The contents of C,N,P and K in 68 dominant plants in Maolan karst area were range in 309.57 573.21 g·kg^-1,5.01 41.62 g·kg^-1,0.56 5.79 g·kg^-1,2.50 39.11 g·kg^-1,respectively;with the variation coefficient were 10.16%,29.61%,52.33% and 62.72%,respectively,thereinto content of C belonged to the weak variability,content of N was medium variability,and content of P,K were strong variability.The ranges of variation of C:N?C:P?C:K?N:P?N:K and P:K of plant leaves were 11.06⁵7.39,58.20⁸86.69,9.94²17.80,3.57³0.88,0.38⁶.31 and 0.04⁰.56,with variation coefficient of 31.11%,39.58%,54.86%,35.06%?49.18% and 50.71%,respectively;thereinto C:K and P:K belonged to the strong variability,the rest were medium variability.?2?C,N,P,K content of plant leaves and correlation of stoichiometric characteristics were different due to the difference of growth stage.But on the whole,the content of C was significantly and negativelycorrelated with N?P<0.01?,butwith no significant correlation between the P?P>0.05?,and the content of N was significantly and positively correlated with P?P<0.05?.In addition to the P:K,nutrient content of plant leaves and the rest of the stoichiometric characteristics basic were significantly?P<0.05?or extremely significantly?P<0.01?negative correlation;and through further function model fitting,found that between them were nonlinear coupling relationship of quadratic function,exponential function,or ghost function.?3?C,N,P,K content of plant leaves and stoichiometric characteristics because of life forms,phylogenesis,growth phases with the big difference.Compared with shrubs and arbor,herbaceous plants with high N,P content and lower C:N,C:P and N:P,which accord with the “growth rate hypothesis”of ecological stoichiometry;and C:N and P:Kof different stages of each function?class?group plant basically maintain a relatively stable level,which maybe the embodiment of “homeostatic mechanism”.In addition,through redundancy analysis?RDA?,the results showed that the biggest effect on stoichiometric characteristics was life form,the interpretation degree as high as 61.86%;SLA and phylogenesis were 16.67% and 12.43%,respectively;the growth stage was the lowest,only 9.04%.2.Nutrient content and stoichiometric characteristics of plantleaves,litter,soil in different successionstage?1?The change tendency for C,N,P,K content and stoichiometric characteristics of plantleaves,litter,soil with the progress of succession exist certain differences,because of community layers,litter decomposition level,plant growth stage and soil depth.Among them: in addition to the SS,the rest of different community layer of each succession stages the nutrient content of plant leaves and stoichiometric characteristics coefficient of variation of the basic characteristic of variability were weak,to a certain extent,also was the embodiment of the “homeostatic mechanism”;compared with the main community layer of the rest succession stages?herb of HS,arbor of AS and CS?,plant leaves of shrub layer of SS with high N,P content and lower C:N,C:P and N:P,which maybe in response to the changes in species composition and community structure and formed a nutrient utilization strategy,and accord with the “growth rate hypothesis”.?2?C and N content of plantleaves,litter and soil of each growth stage in different succession community were characterized by plant leaves>itter>soil;C:P?C:K?N:P?N:K ?P:K were characterized by litter>plant leaves>soil;P,K content and C:N were different due to the different growth stage or succession stage.3.The limiting nutrient factors of different succession stagesBy comparing the plant leaves N:P,N:K and P:K of main community level in each succession stage,combined with the scope of its threshold,the restrictive factors of nutrient were discriminated,the results showed that:succession community in different growth stages existed different nutrient limiting factor;in growth stage?,in prometaphase of succession?by HS to SS?communities were susceptible toN limit,middle and late succession?by AS to CS?communities were susceptible toN,P,K limit,and along with the progress of succession the more restricted by P element.In growth stage?,the succession community were mainly restricted by N element.And K:P critical value may not be suitable for as the limiting factor of nutrient discrimination on the basis of the region.Of course,for a more scientific and reasonable identifying the limiting nutrient,must be supplemented by fertilization experiment.4.N and P nutrients resorption characteristics of different succession stagesIn the?and ?growth stage,the resorption efficiencies of N in different succession stages was 15.82%⁵5.06% and 12.35%⁶1.14%,respectively,the resorption efficiencies of P was 51.19% 75.69% and 54.72% 71.31%,respectively,and with the process of succession showed a decreasing tendency.From the point of different growth stage,the resorption efficiencies of N of HS and AS showed ?>?,while SS and CS were ?>?.The resorption efficiencies of P showed ?>?except for CS.The resorption efficiencies of P was higher than that of N in different successional stages.Comprehensive the limiting nutrient factor of succession stages,further demonstrated the restricted by N or P of the community does not necessarily had high N or P resorption efficiencies.5.The interaction between plant leaves-litter-soil in different succession stages?1?The nutrient contents of litter and soil were negatively correlated with the content of C plants in different growth stage of different succession stages,and the correlation of ? was significant?P<0.05?or extremely significant?P<0.01?.P_litter ofI as well as C_litter of ?was extremely significant?P<0.01?and significant?P<0.05?correlated with N_plant,respectively.There was no significant correlation between soil nutrient content and N_plant content.P_litter and P_plant were positively correlated,and the correlation of ? was significant?P<0.05?;TP_soil and P_plant content were negatively correlated,but the correlation was not significant?P>0.05?.There was no significant correlation between K_litter and TKsoil and K_plant content?P>0.05?,but there was a significant?P<0.05?or extremely significant?P<0.01?negative correlation between SOC and TP_soil and K_plant content.C_litter and P_litter content were negatively correlated with N:P_plant,Nlitter and K_litter content were positively correlated,and the correlation between C_litter and Nlitter content of ? and N:P_plant was significant?P<0.05?.The nutrient contents of soil were positively correlated with N:P_plant,and the correlation of ?was significant?P<0.05?or extremely significant?P<0.01?.In addition,there was a significant positive correlation between N:P_litter and N:P_plant?P<0.01?.N:P_soil was negatively correlated withN:P_plant,but the correlation was not significant?P>0.05?.?2?The correlation between nutrient contents and stoichiometric characteristics of Plant leaves and litter,litter and soil,the soil and plant leaves,reflected inheritance and degeneration between nutrient content;Due to the factors were different such as the research area,scale,vegetation types and growth stage,leading to the correlation of nutrient content of plant,litter,soil and stoichiometric characteristics were difference,which maybe a flexible adaptive mechanism for plant to the environment changes.?3?Comprehensive succession stage,growth stage,the community diversity index,biomass of forest litterand soil hydro-physical propertiessuch as impact factor,the influence degree of leaf,litter and soil stoichiometric characteristics of different succession stages was analyzed by RDA.The results showed that: the effects of SLA,P_litter content and Presorption efficiencieson plant leaves were the highest,and the explanations were 41.78%,17.84% and 17.54%,respectively.The factors that had the greatest influence on litter were N resorption efficienciesand P_plant content,the interpretive degree was 49.65% and 14.62%,respectively.The depth of the soil and the succession stage had the greatest influence on the soil,and the explanations was 32.82% and 32.19% respectively,accounting for more than 65% of the total interpretation.