| In the orchard ecosystems, soil microorganisms participate in many biochemical processes, such as the element circulation, orgaic matter decomposition and synthesis, soil formation and humus formation and so on. Sequentially, the abovegraound vegetations are also influenced. Soil managements in orchards can alter soil microbial community structure and composition through changing soil physicochemical parameters what they live by. Ultimately, soil managements may influence the circulation of materials and energy transformation of the ecosystems, and the sustainable development of fruit industry. Therefore, researches on the response of soil microorganisms to orchard soil managements and on the change rule of soil microorganisms and the correlations between the change and soil parameters are important for the scientific application of these soil managements and for the improvement of orchard ecological environment. This research adopted PCR-DGGE(Poleymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis), 16 S r RNA clone libraries and Illumina high-throughput sequencing to study the effects of different ground mulching managements(grass mulch, cornstalk mulch, film mulch, bareland) on soil bacterial and fungal community structure, compositions and diversity as well as the their changes rule along with the apple growth. This study also analyzed the correlation between soil microbial communities and soil parameters and the major factors which have significant effects on apple yield and quality. The main results were as follows:The DGGE fingerprint indicated that bacterial communities in this region were quite abundant because the tested 36 soil samples obtained 70 predominant OTUs. Cloning and sequencing of the predominant bands observed in the DGGE fingerprint suggested that the predomiant groups in the soil bacterial communities were proteobacteria(45.5%) and bacteroidetes(18.2%), followed by acidobacteria(9.1%), firmicute(9.1%) and actinobacteria(9.1%). There were 383 positive clones obtianed from the clone libraries. The results of multiple sequence alignment indicated that the predominant phyla were proteobacteria(41%), bacteroidetes(11.48%) and acidobacteria(13.58%), which was consistent with the results of DGGE fingerprint analysis. Moreover, the percents of ?-proteobacteria, ?-proteobacteria, ?-proteobacteria and actinobacteria were significantly different among treatments. Predominant groups were quite different among periods of apple growth, for example, firmicute was the predominant group at mature period but no so abundant at yong fruit period and expanding period, another was that the degree of fusobacteria dominance at young fruit period was obviously higher than those at other periods.(2) The analysis of shannon-wiener diversity(H'), richness(S) and evenness(E) indicated that mulched treatments significantly increased soil bacterial diversity and richness than CK at young fruit period and expanding period of apple growth. The cornstalk mulch treatment obtained the hgihest diversity and richness values. However, the bacterial diversity was the highest in CK at mature period.(3) The results of clutering analysis and DCA(Detrended Correspondence Analysis) indicated that apple growth periods were the major strength to change soil bacterial communities because 36 soil samples clustered 3 groups according to apple growth periods except for some exceptions. At the same growth period, grass mulch treatment and cornstalk mulch treatment clustered together, while the film mulch treatment clustered with CK. Therefore, grass mulch and cornstalk mulch managements more significantly influenced soil bacterial communities.We adopted P-test and PCo A(Principal Coordinate Analysis) to determine the similarity of soil bacterial communities obtained from clone libraries under different ground mulching managements and the results indicated that soil bacterial communities under mulched treatments were altered prominently. Bacterial community under film mulch management was significantly different(P<0.05) from others, while the similarity between grass mulch treatment and cornstalk mulch treatment was relatively high(P>0.5).(4) Multivariate statistical analysis of soil bacterial communities and environmental factors(soil physicochemical parameters) suggested that the influence factors which remarkably affected soil bacterial communities were soil temperature(ST), soil water content(SM), available nitrogen(AN), soil organic matter(SOM) and total potassium(TK). The bacterial principal component 5 and 7 positively related with soil nutrients including SOM, total nitrogen(TN), TK and availabe potassium(AK).(5) According to the results of Illumina high-throughput sequencing, it was concluded that the predominat phyla in soil fungal communities were ascomycota(55.92%) and basidiomycetes(1.95%), followed by some other phya including blastocyst(0.67%) and chytrid(0.01%). In addition, there was a good deal of unclassifed fungi(20.66%). There was no obvious difference among treatment at the phylum level. Whereas, the result of two-way clustering analysis at genus level indicated that soil fungal communities were apparently different aomg treatments at each period of apple growth because the predominat genera in soil samples were totally different: the predominat genera(abudance level >3) in the grass mulch treatment were cryptococcus, Myrothecium and Parasola; those in the cornstalk mulch treatment were Coprinopsis, Kendrickiella, Eurotium and Exophiala; film mulch treatment, Colletotrichum, Geastrum and Metarhizium; there were no genus whose abuandance level was >3 in CK, while the relatively abundant genera(abundance level >2) were Alternaria, Chaetomium and Cadophra. The two-way clustering analysis also indicated that ground mulching managements had greater effects on soil fungal communities than apple growth periods because treatments under the same mulching managements clustered together.(6) Results of clustering analysis were consistent with the results of two-way clustering analysis at the genus level. The P-test results showed that soil fungal communities were significantly different(P<0.01) among treatments at each period of apple growth.(7) At young fruit period, soil fungal diversities were the highest in the film mulch treatment, followed by cornstalk mulch treatment, grass mulch treatment and CK. At expanding period, soil fungal diversities from high to low were cornstalk mulch > grass mulch > film mulch > CK, excepting that H' in the grass mulch treatment was lower than CK. At mature period, Chao1 in the grass mulch treatment was the highest while diversities in the film mulch treatment were significantly lower than others.(8) The results of the redundancy analysis(RDA) showed that the major soil parameters which signally influnced soil fungal communities were AN, ST, TK, SM, AP, and so on. There were complex correlation between soil physicochemical parameters and soil fungal communities. Soil fungal diversities were mianly influenced by ST, AN, SD, SM and STP. Chao1 was positively or significantly positively related to SM and STP. Soil fungal richness(S) was highly correlated with TP and SOM. The Shannon-Wiener index was positively correlated with TN and TK at P<0.05. The RDA analysis also indicated that cornstalk mulch and grass mulch treatments obtianed higher diversities.(9) Ground mulching managements increased apple yield, fruit firmness and sacchrinity(SAC) at different level, compared with CK. The weight per 100 fruits was the highest in the cornstalk mulch treatment, which was highly prominently different from others. The fruit firmness from high to low was film mulch > cornstalk mulch > grass mulch > CK. The apple sacchrinity was the highest in the cornstalk mulch treatment followedby grass mulch, film mulch and CK.(10) The results of correaltion analysis between apple yield and quality and environmental factors(including soil physicochemical parameters and microbial communities) indicated that soil physicochemical parameters and microbial communities together influence apple yield and quanlity. The environmental factors highly related to apple yield and quanlity were bacterial richness(Sb), bacterial community principal component 2(PC2b), bacterial community principal component 5(PC5b), bacterial community principal component 6(PC6b), fungal diversity(H'f), fungal richness(Sf), fungal community principal component 2(PC2f), fungal community principal component 3(PC3f), fungal community principal component 5(PC5f), fungal community principal component 7(PC7f), soil density(SD), soil total porosity(STP), capillary porosity(CP), soil organic matter(SOM), toatl nitrogen(TN), total phosphorus(TP), available phosphorus(AP), and available potassium(AK). The stepwise regression analysis indicated that the major factors influencing apple yield were CP, PC2 b and Sf, in order, while those obviously affecting fruit firmness were AK, AN, PC5 f and PC2 f and those having great effects on apple sacchrinity were PC7 f, TK and AN. In conclusion, both soil physicochemical conditions and soil microbial communities have great effects on apple yield and quality or they influenced apple yield and quality together. |
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