The Effect And Mechanism Of Warming On Soil Phosphorus Components Of Cunninghamia Lanceolata Forest In Different Forest Ages

Phosphorus is one of the important nutrients that limit the productivity of subtropical forest.Moreover,the changes of energy,water and nutrients brought by warming will directly or indirectly affect the biogeochemical cycle of phosphorus,and there is still uncertainty about the impact on the supply capacity of phosphorus.In addition,different forest ages can change the processes of phosphorus nutrient demand,return and turnover of plants,leading to significant differences in soil phosphorus supply capacity.However,most of the existing studies have been based on the results of microcosm seedling control experiments,there are a few reports on whether the phosphorus supply capacity of soil at different forest ages at the level of the ecosystem changes due to the soil warming.Besides,the following two scientific questions are unclear:1)is there a difference in the response of soil phosphorus components at different forest ages to warming?2)what are the abiotic and biotic factors that affect the migration and transformation of phosphorus components in soil at different forest ages under warming?This research was conducted at Saming experimental site of the Research Station of Forest Ecosystems and Global Change of Fujian Province,South China.Based on the same parent material,we selected the young(5 years)and mature(45 years)forest stand of Cunninghamia lanceolata as the research object,and we adopt the soil heating cable to realize that soil temperature increase by 4?,by comparing the differences of effect of physical and chemical properties(p H,Fe/Al oxides and base cations),and microbial factors(phospholipid fatty acid method,PLFA,microbial biomass C\N\P)on the occurrence form of phosphorus components(Hedley P)in the soil of Cunninghamia lanceolata at different forest age under soil warming,so as to elucidate the effect and mechanism of warming on soil phosphorus components of Cunninghamia lanceolata in different forest ages.The main results and conclusions are as follows:(1)In terms of forest ages,the contents of labile phosphorus(Labile-P),organic phosphorus(Po),Fe/Al phosphorus(Fe/Al-P),Residual-P and total phosphorus(TP)in the soil of young Cunninghamia lanceolata forest were all lower than that of the mature forest,indicating that the mature forest had higher P availability and P supply capacity.Soil warming has caused the decrease of soil Labile-P content in the 0-10 cm and 10-20cm soil layers of the young Cunninghamia lanceolata forest,and it has no significant effect on the content of Labile-P in the 0-10 cm soil layer of the mature forest,which indicate that the effect of the soil warming on soil phosphorus availability of Cunninghamia lanceolata at different development stages was inconsistent and the climate warming may lead to the reduction of the phosphorus supply capacity of subtropical young forest,therefore the phosphorus limitation status of young Cunninghamia lanceolata forest also may be intensified.(2)The biomass and enzyme activity of soil microorganisms were significant affected by forest ages and warming treatments.In terms of forest ages,soil microbial biomass carbon(MBC)and microbial biomass phosphorus(MBP)in young forest were significant lower than that in 0-10 cm layer of mature forest,while soil microbial community biomass of total and each part were larger than that in 0-10 cm and 10-20 cm layers of mature forest.The effect of forest age on soil enzyme activity was not reach the significant level.In addition,the soil warming significantly reduced different funtional properties of microbial biomass(PLFA)of the young forest,but the effect of soil warming on enzyme activity in young and mature forests were inconsistent,manifesting that soil warming significantly reduced the?-1,4-glucosidase(?G),?-1,4-N-acetylglucosaminidase(NAG),Leucine aminopeptidase(LAP),and Acid phosphatase(AP)activities of young forest,whereas increased the?G,NAG,AP activities of mature forest.Above all,it showed that soil warming would lower the soil microorganisms on the soil C,N,and P conversion rate of young forest and improve the soil C,N,and P conversion rate of mature forest.(3)The content of Fe/Al oxides and base cations in soil were significant affected by forest ages and warming treatments.In terms of forest age,the content of Fe/Al oxides and base cations in soil of young forest was lower than that of mature forest.Soil warming increased the content of K⁺,Ca²⁺,Na⁺,and Al³⁺in the soil of the layer of0-10 cm of young forest,but it has no significant effect on mature forest,indicating that soil warming may add the loss of base cations of young forest and accelerate the process of soil acidification.(4)The results of the Correlation analysis manifested that Labile-P,Po,Fe/Al-P,Residual-P and TP had significant positive correlation with soil water content(SWC),Fe/Al oxides and base cations(except Na⁺).Besides,Labile-P and Fe/Al-P had positive correlation with enzyme activities and different funtional properties of microbial biomass.In addition,the Redundancy analysis(RDA)revealed that Al complexation(Al_p),Al cation(Al³⁺),and SWC were the main environmental factors causing the difference of phosphorus components.Therefore,the effect of soil warming on phosphorus components of Cunninghamia lanceolata forest in different forest ages was the results of joint regulation of abiotic factors and biotic factors,and the effect of abiotic factors was stronger than that of biotic factors.