Effects of arbuscular mycorrhizal fungi on aggregate stability,GRSP,and carbohydrates of white clover

The effects of two arbuscular mycorrhizal fungi(Glomus versiforme and Paraglomus occultum)on size distribution of soil water-stable aggregate and aggregate stability,glomalin-related soil protein(GRSP),and carbohydrates of white clover(Trifolium repens)were analyzed.Root mycorrhizal infection ranged from35%to 75%after 85 days of mycorrhizal inoculation.The inoculated treatments significantly increased shoot,root,and total dry biomass and chlorophyll content.White clover was more dependent on P.occultumthan on G.mosseae.The treatments inoculated with arbuscular mycorrhizal fungi also notably increased the content of water-stable aggregate in the size ranges 0.25-0.5mm and 0.5-1mm but significantly reduced them in the1-2mm size range.There was no effect on water-stable aggregate content in the 2-4mm size and mean weight diameter(an indicator of soil aggregate stability).Inoculated treatments markedly increased rhizospheric soil easily-extractable GRSP,total GRSP,hot-water extractable and hydrolyzed carbohydrate contents.Correlation analysis showed that root mycorrhizal colonization was highly positively correlated with GRSP production,and GRSP had a positive effect on1mm size water-stable aggregates.In addition,the contribution of GRSPs to aggregate stability mainly depends on total GRSP but not on easily-extractable GRSP.GRSP fractions had different contributions to soil carbohydrates.