Discrimination Analysis Of Retrogressive Succession With Lipid Biomarkers From Plants And Soil On Alpine Meadow

Using lipid biomarkers as indicators of environment change and soil organic matter sourse is an emerging method. It has not yet been applied to the research related alpine meadow degradation. Based on the fact that there are different views about if the alpine meadow is degraded or not, the expenriments of isolating and identification of plant and soil fatty acids were conducted. The objectives were to find lipid biomarkers which reflect vegetation change, and provide envidenc and basis for studying alpine meadow degradation, protection and sustainable utilization.By comparing three different isolation methods and reaction conditions of plants and soil fatty acid, the optimal isolation method of fatty acids from plants and soil was determined. The general fatty acids distribution of plants and soil, fatty acids in plants and soil of degradated and non-degraded alpine meadow, seeded pasture, different depth of soil were analyzed. The kinds of fatty acids, concentration in soil and plants of degradated and no degraded alpine meadow was also compared. The main results and conclusions are as followings:1.Three pre-treatments, HCl/methanol methyl esterification,BF3/methanol methyl esterification and silanization were applied to extract plant fatty acids and GC-MS were used for isolation and identification. GC-MS detected and identified 32, 21 and 13 kinds of fatty acid after HCl/methanol esterification, BF3/methanol methyl esterification and silanization pretreatment with same samples. HCl-methanol methyl esterification is an easy-operation and short time-consuming pretreatment. GC-MS can detect and identify more kinds of fatty acid with this pretreatment,which is an ideal GC-MS plant fatty acid extraction and analysis method.2. The optimization of reaction conditions of HCl/methanol methyl esterification for plant are: KOH/methanol solution for 3 m L, saponification temperature is 75 ℃, saponification time is 5 min, HCl for 7 m L, temperature of methyl ester is 65 ℃, and its time is 10 min; And for soil, the optimal conditions are: KOH/methanol solution 1m L, saponification temperature 75 ℃ for 20 min, HCl for 7 m L, temperature of methyl ester 65 ℃ for 10 min.3. A total of 68 fatty acids was identified from 52 plant species, and can be cantigorized into four types, i. e. micro, and low, medium and high frequency distribution. Comparing the non-degraded and degraded alpine meadow suggests that degradated alpine meadow has more kinds of fatty acids than non-degraded does, and the fatty acids content of non-degradated alpine meadow is higher than degraded alpine meadow. There are 7 unique fatty acids, 15-tetracosenoic acid, 8,8-dimethoxy-octanoic acid,noanoic acid, 7,10,13-hexadecatrienoic acid, 12-methyl-tridecanoic acid, 12-methyl-tridecanoic acid, 3-benzenepropanoic acid, can be used as indicators of the succession of degraded alpine meadow. On different kinds of alpine meadow, plant eicosanoic acid content was measured. There are significant differences of content between seeded pasture, degradated and nondegraded alpine meadow(P<0.05), ant the content is 0.4930, 0.9470, 0.1585mg/g, respectively. The plant eicosanoic acid also can be used as one of the important evidence of alpine meadow degradation.4. Forty-one fatty acids were isolated from soil with carbon number of C3-C28. Among them 33 are saturated fatty, 5 are monounsaturated fatty acids and 3 are polyunsaturated fatty acids. The kinds of fatty acids in soil is in the order of 0-10cm≥10-20cm≥20-30 cm. Docosanoic acid content in 0-10 cm soil layer soil is 4.7 and 9.6mg/kg, respectively, and with significant difference(P<0.05) between non-degraded and degraded meadow. This fatty acid also can be used as one of the important evidence of degraded alpine meadow.5. Comparing plant and soil fatty acids on light degraded and non-degraded alpine meadow, plants have more fatty acids than soil and upper soil has more fatty acids than subsoil, i. e. plant≥0-10cm≥10-20cm≥20-30 cm soil layer. Either kinds or content of fatty acids has distinct differences between plants and soil on light degraded alpine meadow.