Effects Of Karst Soil Nutrient Resources On The CSR Strategies Of Woody Plant Communities

The framework of Grime(1974)regarding CSR strategy on competition,stress tolerance and ruderals concerning life reproduction reflects plant adaptabilities to their survival environments.Identifying ecological strategies based on plant functional traits can provide a better understanding of plant adaptations and changes in ecological processes and thus predict the impact of environmental changes on ecosystems.The highly heterogeneous karst habitat,combined with shallow and poorly water-holding soils,leads to poor soil nutrients;Plants develop different plant traits to adapt to this harsh habitat,resulting in different ecological strategies.However,the ecological strategies of karst plant communities and their response mechanisms to the soil nutrient resource mass are not clear at present.Here we sampled leaves of woody plants and soil from 53 typical karst plant communities and determined the leaf functional traits of 92 species,including plant diameter at breast height(DBH)and height,leaf area(LA),specific leaf area(SLA),and leaf dry matter content(LDMC),leaf carbon,nitrogen and phosphorus content(LC,LN,LP)and their stoichiometric ratio(leaf C:N,C:P,N:P).Soil physicochemical properties were measured to calculate soil nutrient resources mass and also calculated their stoichiometric ratio(soil C:N,C:P,N:P),the calculator "Strate Fy" was used to calculate the CSR component values of plant species and communities based on the mean and the community-weighted mean(CWM)values of LA,SLA and LDMC the CSR to explore the CSR strategies of karst plant species and communities,respectively.Subsequently,linear regression,Mantle’s test,principal component analysis(PCA)and Partial least squares path modeling(PLS-PM)disentangling were used to explore the relationship between plant community CSR strategies,plant functional traits and soil nutrient resources.The main research results are as follows:(1)Leaf functional traits of the karst plant community showed different trends with increased soil nutrient resource mass.In detail,with the increase of each soil nutrient resource mass(TN,TP,AN,AP and SOC),LA,SLA,LN,leaf N:P showed an increasing trend,while LDMC,leaf C:N showed a decreasing trend.In addition,with the increase of soil C:N,LA,SLA,LN,and leaf C:P and N:P gradually increased,and LC,LDMC,and leaf C:N gradually decreased;with the increase of soil C:P and N:P,LA and SLA,leaf C:N,C:P,and N:P increased,but LDMC,LN,and LP decreased.Moreover,Mantle’s test showed that different leaf functional traits had different key influencing factors.Specifically,SLA was mainly influenced by soil TP and AN,LDMC was mainly influenced by soil TP,AN and SOC,the key influencing factors of LN and leaf C:N were soil TP,LP and leaf C:P were soil C:P and N:P,and the main influencing factors of leaf N:P were soil SOC and C:P.The results indicated that soil N and P contents were the main influencing factors for leaf functional traits.(2)The CSR components mainly clustered on the C-S side bias to the S-side,whatever karst plant species and community.This indicates that karst plant species and communities mainly adopt stress tolerance strategies(S strategies),followed by competition and ruderals strategies(C and R strategies).Among the functional traits of karst plants,LA has the greatest variation,while LC has the smallest variation;The CSR strategy of woody plant community is regulated by plant functional traits,which also reflects the plants economic strategies in resource conservation and resource acquisition.In addition,with changes in plant functional traits,component S exhibits an opposite trend to C and R components,indicating a strategy trade-off of S strategy relative to C strategy and R strategy,which was related to plant functional traits.(3)The CSR components of karst plant community showed different trends with each soil nutrient resource mass.The S component decreased significantly with the increase of each soil nutrient resource mass(TN,TP,AN,AP and SOC),while the C and R component values showed a significant increasing trend,and the results indicated that the CSR strategies of plant communities gradually shifted from S strategies to C and R strategies with the increase of soil nutrient resources mass;In addition,the PLS-PMs showed that soil nutrient resources mass of N and P positively influenced the C and R strategies and negatively influenced the S strategy by affecting LA,SLA and LN,revealing soil nutrient resources lead to the change of CSR strategy by influencing the variation of leaf functional traits.In summary,soil resource mass in karst significantly affects the plant leaf functional traits of the plant community,and soil nitrogen and phosphorus contents were the main factors affecting the variation of leaf functional traits.Additionally,the stress tolerance strategy(S strategy)is mainly adopted by the karst plant community,followed by the competition strategy(C strategy)through the calculation and analysis of CSR strategy.Moreover,a strategic trade-off of the S strategy relative to the C and R strategies was associated with plant functional traits.Furthermore,with the increase of soil nutrient resources,the competition and reproduction of karst plant community gradually increased,and their tolerance decreased.Soil nitrogen and phosphorus nutrient resources affect the expression of leaf functional traits,leading to changes in CSR strategies.