| Guizhou Baili Rhododendron is located in the subtropical evergreen broad-leaved forest subzone.Guizhou Baili Rhododendron National Forest Park is one of the few intact high-altitude rhododendron forest zones in China.It is an important resource bank of rhododendron germplasm.Rhododendron delavayi is the dominant species in rhododendron forest of Bali Rhododendron National Forest Park.It has strong ability to utilize soil nutrient and light energy.The results showed that the population of Rhododendron was in the period of vigorous growth,but the population structure was unreasonable and the natural regeneration was slow,especially the Rhododendron delavayi population.So it is important to protect the Rhododendron delavayi population to understand the ecological adaptation mechanism of Rhododendron delavayi.Microorganisms play an important role in the adaptation of plants to different habitats.The study on soil microorganisms of Rhododendron,rhizosphere microorganisms and root endophyte helps to reveal the role of microorganisms in the process of rhododendron plants adapting to different habitats.It has positive significance for the rational utilization and resource protection of Rhododendron plants.In consideration of little is known about the effects of different altitudes on soil fungi,rhizosphere fungi and endophyte fungi of rhododendron delavayi,This study Rehe(105°53?39.9552??E 27°15?26.136??N,1820 m),Pudi(105°51?40.0212??E 27°13?58.4076??N,1642m)and Baili Rhododendron Grassland(106°2?26.3652??E 27°13?0.4188??N,1448 m)were selected as subjects,1,820 meters,1,642 meters,1,448meters above altitude,the community structure,distribution,composition,diversity and correlation of different soil physical and chemical properties of rhododendron delavayi,rhizosphere fungi and endophyte fungi were analyzed by Illumina high-throughput sequencing technique in order to reveal the adaptive mechanism of soil fungi,rhizosphere fungi and endophytic fungi of rhododendron delavayi at different altitudes.The findings are as follows:1.The soils of rhododendron grassland,pudi and Ren He three rhododendron delavayi forests were slightly acidic,p H was 4.2-5.56,and the soil physical and chemical properties of Rhododendron delavayi forests varied with different altitudes.Soil total nitrogen(TN)(R~2=0.77,p<0.001),soil total phosphorus(TP)(R~2=0.85,P<0.001),nitrate nitrogen(NN)(R~2=0.69,P<0.001),soil available phosphorus(AP)(R~2=0.93,P<0.001)were all significantly correlated with altitude.Soil Organic Carbon(SOC)first decreased and then increased with the elevation gradient,and the content of TN was the lowest at 1820 m,which was 1.26mg/g.with the elevation gradient increasing,the content of TN decreased by 59%at 1448-1820 m,and TP decreased with the elevation increasing,from 1.8 mg/g to 0.78 mg/g,the content of NN decreased to 0.46 mg/g at last,while the content of NN decreased first and then increased with the elevation.The highest content of NN was 0.013 mg/g at the elevation of1448 meters.Ammonia nitrogen decreased at first and then increased with the increase of altitude,and reached the highest value at 1820 m,0.033mg/g.The content of AP decreased from 0.028 mg/g at 1448 m to 0.012mg/g at 1820 m.2.The Shannon Index of soil and rhizosphere fungal communities decreased with the elevation gradient,the diversity of soil and rhizosphere fungal communities decreased,the Shannon index of rhizosphere fungal communities increased with the elevation gradient,and the diversity of rhizosphere fungal communities increased.Altitude had significant effect on Shannon index of fungal community in roots.The Richness of soil fungal community decreased firstly and then increased with the elevation.the Richness of rhizosphere fungal community decreased with the elevation gradient,the Richness of root endophyte fungal community increased with the elevation gradient.The results of two-factor analysis showed that the effects of DAG and DS on Shannon index and abundance were not significant(P<0.001),but the effects of DS were significant(P<0.001).Ascomycota(62.8%,58.0%,66.1%),Basidiomycota(18.1%,27.6%,13.3%),Mortierellomycota(7.4%,5.5%,0.0098%)and Rozelomycota(0.3%,2.9%,0.6%)were the main representative phyla in soil,rhizosphere and rhizosphere fungi at 1448 m altitude At 1643 m altitude,Ascomycota(58.3%,47.7%,58.0%),Basidiomycota(23.3%,30.9%,14.4%),Morellomycota(3.3%,4.3%,0.05%)and Rozelomycota(0.3%,1.3%,0.005%)were the main representatives of soil,rhizosphere and rhizosphere fungi.Ascomycota(58.3%,47.7%,58.0%),Basidiomycota(23.3%,30.9%,14.4%),Mortierellomycota(3.3%,4.3%,0.05%)and Rozelomycota(0.3%,1.3%,0.005%)were the main representative phyla./n3.The results of RDA analysis showed that SOC and AN,p H,TN were positively correlated with soil fungi at 1448m,1643m and 1821m above sea level,and AN(P=0.026)accounted for38.72%,soil fungi and soil nutrient interpretation were 52.59%and 27.68%at different altitudes.TN,TP,NN and AP showed positive correlation,while SOC,AN and p H showed negative correlation.TN(P=0.069)had the largest single interpretation capacity(31.67%).The variation of soil nutrients and endophytes in different altitudes was 47.23%and 30.72%,respectively.TP,TN,AP and PH showed positive correlation,while SOC,AN and NN showed negative correlation.The variation of AN(P=0.026)was the largest(38.72%).Ascomycota,Chytridiomycota and Mortierelomycota were negatively correlated with TN and Kickxellomycota was negatively correlated with AP(P=0.046).Chytridiomycota and glomercota were negatively correlated with TN(P=0.02 and P=0.002),while Chytridiomycota and glomercotta were positively correlated with p H(P=0.001 and P=0.040).In soil below 1821m,there was a positive correlation between TP and Glomeromycota,Kickxellomycot and Mucoromycota(the results of the sub-structural equation model showed that altitude accounted for 85%of the change in total phosphorus(P<0.001),while total phosphorus accounted for 77%of the change in the abundance of endophyte fungi(P=0.048). |
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