Study On Functional Diversity Of Soil Yeast In The Main Forests Of The Changbai Mountain

In the forest ecosystem, microorganism, as the litter decomposer with mineralization,is the main power of transformation and cycle of soil organic matter and the nutrient, and also is anndispensable biological group in forest ecosystem.Microorganisms are widely distributed in the forest ecosystem, the fungi including yeastsbelongs to the microbial group with largest microbial biomass.The yeast with fermentation functions reproduced by budding or fission is called single-celled fungus, its fermentation products and its own cells can be used by plants or other microorganisms. Yeasts can be also used as research materials in biochemistry, genetics and molecular biology, and become hot research topic in microbiology.In recent years, the researches on yeast taxonomy areincreased rapidly, but ecological importance, especially the ecological function of yeasts in forest ecosystem is less known. Changbai Mountainis one of the most intact ecosystem in China, in which there are main forests including mixed broad-leaved and Pinus koraiensis forest(PKF), Picea and Abies forests(PAF) and Betula ermanii forest(BEF), etc.. It represents the typical natural vegetationcharacteristics in the northeast of Eurasia. In this pape, the yeasts from main forest stands of Changbai Mountain were taken as research materials, the techniques and methods based on Biolog micro tablet, GC-MS, HNMR, scanning electron microscope technology were used in this research to carry out experimental researches on distribution, functional diversity, ecological function of yeasts from main forest stands including PKF, Betula platyphylla forest(BPF), Populus davidiana forest(PDF), ACF, BEF and transition forest band trsnsmited forest between ACF tand BEF(ABF), and main achievments have been acquired, including following aspects:(1) The yeast distribution in the main forests in Changbai Mountainhad typical charicteristics. The vertical distribution from different soil layers in the profile accordedwith linear regression model and the linear equation wasy’=12.20683-0.35143x(x stands for the depth of soil as cm, y’stands for the logarithm value changed from the yeast number). On this basis of distribution pattern map of forest soil yeast in vertical profiled, the yeast distribution in vertical profiled was in accordance with the model of “needled neck”funnel and the quantity distribution of forest soil yeasts was mainly concentrated on the semidecomposition layer and top soils. The horizontal distribution was not uniform but in “cloud”typesconditioned by environmental heterogeneity.According to the results ofinvestigation, there are seasonal change rule in yeast quantitative distribution with the biggest richness in July, and began to decline from August to September, but increased again in October.(2) Charistics of fermnetation function from forest soil yeasts is funtional specificity. Under further researches, it was clear that there was similar fermentation characteristicsbetween BPF and PDF, ACF and ABF contained same species of coniferoustrees; their yeast fermentation charicteristics were similar. With the test designed by response surface analysis, the fermentation conditions of yeasts were estimated that when temperature was 22℃, moisture was 175% and inoculum was 7%, the degradation rate got to 9.16%. During fermentation, there was a synergy among yeasts, molds and bacteria. There werefour levels in yeasts(one group), molds(one group), yeasts+molds(two groups) and yeasts+molds+bacteria(three groups); degradation rate had the increasing trends with the increasing of group number of microbes. In this condition, composition of decomposed litter were grouped for three partitions as easy-decomposed partition, difficultdecomposed partitions and hard-decomposed partitions. On this basis, the changes of yeasts number in fermentation layer of forest soil was driven by the action-model TMLY, that is, under the driving of TMLY model, soil fermentatiton was controlled together by three factorsof temperatue factor(T), moisture factor(M), and existing ltter factor(L), the yeasts number in forest fermentation layer presented cyclical changes with the seasons.Onthe orthogonal experiment design, the decrasing rate of absorbance value(A275nm) for yeast-fermentation products and decomposition rate of barks were investigated. The results showed that the decomposition rate of absorbance value on fermented product was positively correlated with decomposition rate of barks. Forest soil yeasts were helpful to degradation of deciduous tree bark, of which,tree barkof Populus davidiana was most vulnerable to degradation. To abilities of yeasts for decomposition of bark from different forests, the overall trend were PDF>BPF>BEF>PKF and ABF, and there was a interaction between the bark decomposition of coniferous trees and the bark decomposition of broad-leaved trees.(3) Rich function diversitites of forest soil yeasts. Based on the method of Biology, the results showed that forest yeasts had abundant functional diversites with function for untilizing carbon source, producing volatile organic compounds, forming multiple chemical environment in fermentation and being enhanced in tranmiting compoumds by synergy with othermicroorganisms. Based on the Biolog method for functional diversity research, the results showed that Average Well Color Development(AWCD) value changesbegan to stable after culturing for 216 hours. AWCD value were significantly different indifferent forestsyeasts. Yeasts from PKF, PEF and PDF belonged to high decomposition abilities; the yeasts from PDF had the highest decomposition abilities. Based on GC-MS method for functional diversity research, the results showed that 216 chemical compounds were identified from VOC(volatile organic compound) from fermentation products. That reflected richness of VOC produced from fermentation of forest litter. Yeasts from PKA, PEF and PDF had similar abilities in VOC production from substances. Based on HNMR method for functional diversity research, the results showed that yeasts from PEF and PDFcontaining coniferous trees were similar in capacity of fermentation for model substance and yeasts from broad-leaved forests distributed in low attitude had similar capacity of fermentation for model substance.Based on UV-DPPH method for functional diversity research, the results showed that the order of fermentationcapacity from forests was PDF>BPF>BEF, ABF, and PKF>ACF and yeasts from PDF and BPF had similar characteristics and so did the yeasts from PKF and BEF.(4)Three strains of functional yeasts have some ecological functions. Based on culture media containing plant wax, astrain of yeast L1 Cryptococcus musci was screened as yeast for decomposing plant wax.It was tested respectively for decomposition in the corn(Zea mays) strawand leaves from Quercus mongolica. The results showed that this yeast with ability to using plant wax could decomposing some chemical components of plant wax led to the outermost layer density wax on plant skins was formed verrucous bulges, these verrucous bulges were composed of particles like sweet potatoes pilled up. Based on such a action, plant wax layer became to soft layers by forming verrucous bulges composed of particles like sweet potatoes pilled up, this soft layers were easy to be decomposed by mix microbial. Based on culture media containing water abstract from Pinus korainsis bark, a strain of yeast H1 Kuraishia capsulatawas screened as yeast for decomposition of coniferous tannins. Test were carried out on water abstracted tannin respectively from leaves of Quecus mongolica and bark of Pinus korainsis, the decomposition charicteristics were estimated by IR spectrum. The results showed that the screened yeast had the capacity of transmationfor plant tannins from, bark of Pinus korainsis butless effect for tannin from leaves of Quecus mongolica. That to say,the screened yeast had the ability to changing tannin but had selectivity. Based on culture media containing fresh fruit juice from Lonicera edulis,a strain of yeast DG1 Cyberlindnera sp.was screened as yeast for decomposition of acids. The screened yeast has the effects of reduction organic acids.(5) Degradation model of forest litter was based on yeasts as pioneer microbia. Forest litter decomposition was carried out from yeast as a pioneer microbia to attack wax layer of litter at thin wax layer on the surface of litter skin, and continued to be decomposed by mix microbia, and then, the yeast continue attack the thin wax layer by thin wax layer to continue the processing for wax layer decomposition thin wax layer. This model can be used to explain the start stage of litter decomposition wasa long time distance in the whole decomposition process. In this research, components changes from substance containing saccharides, glycosides, organic acids, amino acids to products containing VOCssuch as amines, alkanes, alkenes by means of substance transformation including tannins. These VOCs distributed in fermentation layer can be used up by plants or microbia, this combination effect drived the carbon cycle in fermentation layer of ferest soil.In this research, a setof tests were carried out for distribution charcteristics of yeast number, functional diversities based on multiple method, and three functional yeast strains were screened for decomposing or transforming plant wax, tannin or organic acid and main results were obtained for further understanding on the function and distribution of forest soil yeasts. Forest yeast has the typical distribution characteristics and diverse function properties. Forest soil yeasts, mainly distributed in soil fermentation layer in forest soil, using the soluble saccharides from litter, decomposing litter wax layer to destroy litter’s natural defense system,which plays a positive role in the ecosystem.This study introduced the new method for estimating microbial functional diversity to experiments, enriched the research. Drawing the model image of yeast vertical distribution in profile layer of forest soil by “needle neck” funnel, and the model image of yeast horizontal distribution in different forests by yeast “cloud” image. Three action models were discovered,the first isthe model of yeast co-decomposing litter by mixing yeast with molds, mold and bacteria, the second is the model of TMLY drivenby environmental factors,the third is the model of litter decompositiom in thin layer by thin layer. This research could develop forest soil ecological theory on yeasts, effectively carry out soil ecology research and promote the development of disciplines, as well as providedreferences for other research onmicrobial functional diversity of ecosystems, there are important theoretical value and practical significance in research on carbon cycle of forest ecosysytem.The main innovations in this research have two aspecets including method innovation and results innovation.Firstly, four methods were eatablished to evaluate yeast functional diversities. By these methods, the properties of products components or substace components of composite litter or dandelion(Taraxacum SP.) fermented by yeasts were determined by these methods to evaluate yeast functional diversities from changes chemical components.Secondly, Someresults innovation have been achieved. Mapped the image of vertical distribution model on forest soil profile of yeast and found that the vertical distribution of yeast on forest soil profile with the “needled neck” funnel type distribution patterns; With soil layer yeast fermentation "cloud" shape distribution, described yeast plane distribution in the soil. Estimated that there was about272 billion to 519 billion yeast Colony Forming Unit(CFU) per hectare in forest soil fermentation layer of the Changbai Mountain; Founded that TMLY role model on the number of yeast(Y) distribution in forest soil fermentation layer were driven by temperature(T) of soil fermentation layer, water(M) of soil fermentation layer and existing litter content(L) of soil fermentation layer, and another model was found as the model of forest litter layer degradation with yeast as the forerunner.