The Effect Of Moisture And Iron On Soil Organic Carbon Content In Zoige Peatland

Peatland,covering approximately 30%of the global terrestrial carbon content,is an important“carbon sink”and has great potential to become a“carbon source.”Environmental factors play an important role in protecting soil carbon in peatlands.The effect of key factors on soil carbon was different in different types of peatland,such as phenol oxidase and ferrous(Fe²⁺)mentioned in the“enzymatic latch”and“iron gate”mechanisms.However,the above two key factors on soil carbon transition in peatland soil remain debated.Therefore,this study selected Zoige Peatland as the research object and collected soil samples of different types（drained and waterlogged）,different seasons（dry and rainy season）,and different depths（0-100 cm）to confirm the key environmental factor on soil organic carbon（SOC）content based on the“enzymatic latch”and“iron gate”mechanism.Moreover,the potential impact mechanism of soil moisture and iron on SOC was investigated via room incubation.The main results show as follows:（1）There was no significant correlation among phenol oxidase,Fe²⁺,and SOC（p>0.05）,suggesting that the“enzymatic latch”and“iron gate”were not key mechanisms in Zoige peatland soil.However,soil moisture and SOC were significantly correlated（p<0.05）.Moisture was the highest effect（0.87）on SOC through partial least squares paths model（PLS-PM）analysis,indicating that moisture was the key environmental factor in Zoige peatland soil.（2）Moisture change could cause SOC decomposition acceleration in two soil types.Phenol oxidase activity and Fe²⁺content positively correlated with moisture（p<0.05）.The effect pathway of moisture on SOC content according to structure equation model（SEM）.Moisture could affect SOC content by regulating the contents of iron oxides and phenol oxidase or mediating Fe³⁺content which affects microorganisms.（3）Iron（Fe（Ⅱ）and Fe（Ⅲ））addition decreased SOC content in drained soils but increased SOC content in waterlogged soils.In drained soil,Fe（Ⅱ）and Fe（Ⅲ）addition increased the soil redox potential and the oxidation of dissolved organic carbon,thus causing SOC content to decrease by 3.88%and 7.35%on average.However,Fe（Ⅱ）and Fe（Ⅲ）addition decreased soil p H（from 7.71-8.24 to below 6.50）and microbial abundance,thus causing the accumulation of dissolved organic carbon and the increase of SOC（increased by 11.78%and 13.62%on average）in waterlogged soil.This study confirmed that moisture was the key environmental factor on SOC in Zoige peatland soil,revealed the potential impact mechanism of moisture and iron on SOC,provided a theoretical basis for soil carbon conservation in peatland,and was of great significance for protecting peatland soil through moisture and iron management.