Effects Of Different Forests Intercropping With Bletilla Striata On Soil Physicochemical Properties And Microbial Community Structure

To explore suitable tree-medicinal plant intercropping models for promotion of the regional sustainable development,an experimental study was conducted at Qiucun in Guangde city,Anhui Province,including different intercropping models such as bamboo?Phyllostachys pubescens?-Bletilla striata,sycamores?Platanus acerifolia?-B.striata,pecan?Carya cathayensis?-B.striata,and pure B.striata.The objectives of the study were to make comprehensive analysis of the different models along with different intercropping years on soil physical and chemical properties and microbial community structure.The main results are as follows.?1?Different intercropping models had significant effects on SWC,pH,EC,NH₄⁺-N,NO₃^--N,DOC,DON,SOC,TN and TP contents?P<0.05?,but no significant effects on C/N?P>0.05?.Different soil layers had significant effects on SWC,pH,NH₄⁺-N,NO₃^--N,DON,SOC,TN and TP?P<0.05?,but no significant effects on EC,DOC,C/N?P>0.05?.The interaction between model and soil layer had significant effects on pH,NH₄⁺-N,NO₃^--N,DOC,DON,SOC and TN?P<0.05?,but no effects on SWC,EC,TP and C/N?P>0.05?.Most of the soil nutrient contents in different stands were Ca+B>B>Ph+B>Pl+B.With the exception of SWC and EC,the soil nutrient content was obviously enriched in surface layer,with decrease with increase of soil depth.?2?Different models had significant effects on MBC,MBN and MBC/SOC?P<0.01?,but no effect on MBC/MBN.Soil layer had significant influence on MBC/SOC?P<0.01?,but no influence on MBC,MBN or MBC/MBN?P>0.05?.The interaction between model and soil layer had no effect on microbial biomass?P>0.05?.The soil MBC and MBN in different stands showed a trend of Ca+B>B>Ph+B>Pl+B,and decreased with the soil depth.The difference between MBC/MBN and MBC/SOC is not significant and increased with soil depth.?3?There existed differences in utilization of single carbon-source in soil microbial community among the different intercropping models.The microbial community had the highest AWCD value for the utilization of amino acid,followed by carboxylic acids,polyphenolic acids and polymers,and the lowest for sugars and polyamines.There was a significant difference between Shannon and Simpson indices in different models?P<0.05?,and Shannon and Simpson indices in Pl+B model were significantly lower than the other three models?P<0.05?.There was no significant difference between Mc Intosh indices in different models?P>0.05?.Principal component analysis?PCA?showed that utilization of carbohydrates and amino acids played a major role in differentiation.?4?In the bamboo-Bletilla striata model,the intercropping years had significant effects on soil physical and chemical properties?P<0.05?.The soil layer had significant effects on SWC,EC,NH₄⁺-N,NO₃^--N,SOC,TN and TP?P<0.05?.The sampling month had significant effects on SWC,EC,NH₄⁺-N,NO₃^--N,DOC,DON,SOC,TN,TP and C/N?P<0.05?.The interaction between the intercropping year and soil layer and between the intercropping year and sampling month had significant effects on pH,NH₄⁺-N,NO₃^--N,DOC,SOC,TN and TP?P<0.05?.The interaction between the soil layer and sampling month had significant effect on NH₄⁺-N and NO₃^--N?P<0.05?.The interaction between the intercropping year,soil layer and sampling month had significant effects on pH,EC,NH₄⁺-N and NO₃^--N?P<0.05?.The soil nutrient content in Ph+B model was the highest,and most of the soil nutrient contents decreased with the increase of soil depth.The seasonal variations of nutrient elements in the bamboo-Bletilla striata model with different intercropping years were obvious?except NH₄⁺-N,NO₃^--N and DON?,all of which showed that the nutrient contents in September were higher than that in May.?5?The intercropping years in the bamboo-Bletilla striata model had significant effects on MBC,MBN and MBC/SOC?P<0.05?.Soil layer had no effect on microbial biomass?P>0.05?.The sampling month had significant influence on MBC,MBC/MBN and MBC/SOC?P<0.05?.The interaction between the composite mode and the soil layer had a significant effect on MBC/MBN?P<0.05?.The interaction between intercropping year and sampling month has significant influence on MBC,MBN,MBC/MBN and MBC/SOC?P<0.01?.The interaction between soil layer and sampling month and intercropping year,soil layer and sampling month had no effect on microbial biomass?P>0.05?.The soil microbial biomass in May and September was significantly higher in Ph+B4 model than in other models,with obvious seasonal changes and gradually decrease with soil depth.?6?The diversity index and structural composition of soil bacterial community were different in the bamboo-Bletilla striata model with different intercropping years.On the phylum level,Proteobacteria,Acidobacteria,Chloroflexi and Actinobacteria were the four major phyla of soil bacteria,accounting for more than 75%of the relative abundance in the models of B4,Ph+B4 and Ph+B3.Bacteroidetes and Latescibacteria were significantly lower in B4 than in Ph+B4 and Ph+B3?P<0.05?.Nitrospirae were significantly different between B4 model and Ph+B3 models.Cyanobacteria were significantly different in the three models?P<0.05?.The relative abundance was the highest in B4,followed by Ph+B3.Result from the redundancy analysis?RDA?showed that DON is the main controlling factor affecting soil bacteria.In summary,different tree-medicinal plant intercropping models,soil depths and seasonal changes had significant effects on soil physicochemical properties,microbial biomass,microbial functional metabolism and bacterial community diversity.The results of the study provide basis for the selection of suitable tree-medicinal plant intercropping models.