Effects Of Acid Treatment On Mineral Elements Release Characteristic And Bacterial Community In Granite Soil

In China, acid deposition is increasingly more serious in subtropical granite region of China. Ecological constraints do impact the function and stability of ecosystem due to the soil acidification and the fast weathering of soil minerals. It is very important fact for the estimate accurately the soil mineral weathering rate and soil acidification rate through the stoichiometric relationship of silicon (Si) released from mixed minerals and soil base drived by the acid deposition. Meanwhile, the response process of soil bacterial community structure and diversity affected by soil acidification also was one of the key factors influence the ecosystem. Therefore, profile soil samples were collected from granite region, soil exchangeable bases were replaced entirely by EDTA-ammonium acetate solution, then the soil without exchangeable base cation was completely preparation. The release amount of base cation, Si, Fe3+ and Al3+ in natural soil and soil without exchangeable base cations were determined after treated with NH4CI-HCl solution in different pH. Meanwhile, the bacterial 16S rRNA of soil without exchangeable base cations and natural soil were also measured through the high-throughput sequencing technique. We aimed to (1) illustrate the release characteristics of soil mineral elements in granite soil after without cationic exchangeable function; (2) clarify the stoichiometric relationship between silicon and base cations after soil mineral weathering; (3) discuss the effect of acid treatment on bacterial community and diversity. The results showed that:(1) Soil exchangeable base cations were replaced completely by EDTA-ammonium acetate solution.(2) During the continuous reaction with soil solution in different pH, the release amount of K+、Ca2+、Mg2+、Na+、Al3+ of natural soils presents the decline firstly and then show down trend. In the soil without exchangeable base cation, Ca2+、Mg2+ release amount no obvious changed with the addition of acid solution, but K+ release amount appears rising trend of fluctuations, Na+ release amount appears declining trend of fluctuations. Release amoutn of Al3+ in A layer profile soil appears continuously decline, which of in B and C layer profile soil appear rise at first and then decline. Fe3+ release amount in soil without exchangeable base cations no obvious change with the addition of acid solution, but which in A layer soil without exchangeable base cations was continuously decreased, and in B, C layer were firstly increased and then decreased trend.Si release amount was higher than the release amount of Al3+ and Fe3+ during the mineral weathering in the soil without exchangeable base cations.(3) The stoichiometric relationship of silicon and base cations during mineral weathering in natural soil were 3:13-7:26 (A layer) and 5:16-11:29 (B, C layer), respectively. But in soil without exchangeable base cation, the stoichiometric relationship were 7:8-1:1 (A layer) and 9:13-1:1 (B^ C), respectively. There no significant effects of the three profile soil layers and acidity of treatment solution on the stoichiometric relationship.(4) Acid solution (pH=3.5,4.5,5.5) can significant reduced soil bacterial diversity. The dominate population were changed from Acidobacteria to Proteobacteria in A layer soil and from Proteobacteria to Actinobacteria in B and C layer soil.(5) There no significant difference in soil bacterial diversity affected by acid solution in pH3.5, pH4.5, pH5.5, but the soil bacterial community structure in three soil profile layers response to the same simulated acid solution showed significant difference, which maybe caused by different acid buffer function and the different release amount of Al3+ in profile layer soils.