LARCH (LARIX GMELINII) BULK SOIL PHENOLIC ACIDS PROMOTE MANCHURIAN WALNUT (JUGLANS MANSHURICA) GROWTH AND SOILMICROORGANISM BIOMASS

摘要

The current study investigated the effect of seasonal variation on larch root exudates and the impact of some phenolic acids allelopathic on soil microbes and seedling growth. The soil microbial profiles were determined by phospholipid fatty acids (PLFA) digest method, whereas phenolic acids identification and their concentration in larch rhizosphere and bulk soil was determined by HPLC during spring, summer and autumn 2011. Combinations of four phenolic acids concentration (2, 4-2 hydroxy acid, 7-hydroxy coumarin, ferulic acid and abietic acids) were added to Manchurian walnut seedling pot soil and their PLFA profile and seedling biomass was measured after seedling harvest. Results indicated that seasonal variation of larch total root exudates was highest in soil in autumn and summer than spring . Bulk phenolic acids exerted stimulation effect on the microbial biomass and Manchurian seedling biomass. The rhizosphere soil phenolic acids had a negative impact on the microbial biomass and seedling growth due to high phenolic acids concentration. Principal component analysis explained 63.6% and 65.5% of total variation in PLFA composition in larch rhizosphere and bulk soil. Thus, bulk soil phenolic acid combination, particularly 7-hydroxyl coumarin + ferulic acid, has considerable stimulative impact on seedling and microbial biomass.