| Decomposition and fire disturbance are important ecological processes in nutrient cycling of forest litter,and slow decomposition rates can promote the accumulation of litter,leading to a significant increase in the probability of forest fire occurrence.The role of black carbon,a byproduct produced after the fire,in the decomposition process of litter is still unknown.Therefore,in order to better explore the impact of fire and black carbon on litter decomposition,this article takes the needle leaf litter of Larix gmelinii in the Greater Xing’an Mountains region of Inner Mongolia,China as the research object,and explores the impact mechanism of fire disturbance,black carbon addition,and the combined effect of fire disturbance and black carbon addition on litter decomposition,as well as the main factors affecting decomposition.The main conclusions are as follows:(1)Fire interference has a promoting effect on the decomposition of litter,and under the influence of low intensity fire disturbance,litter decomposition is faster.The residual rates of unburned,mild fire disturbance,and severe fire disturbance litter during the entire decomposition process were significantly reduced by 10.60%,15.20%,and 11.50%(p<0.05),respectively.The percentage of reduction by mild fire disturbance was higher than that of other treatments.The main factor affecting litter decomposition under light fire disturbance is the phenoloxidase activity of litter,and the main factor affecting litter decomposition under heavy fire disturbance is the hemicellulose content of litter.(2)Black carbon addition has a promoting effect on the decomposition of litter,and the larger the black carbon gradient,the faster the decomposition of litter.The residual rate of litter mass decreased by 10.61%,11.70%,13.76%,and 9.46%(p<0.05)during the entire decomposition process under the treatments of no black carbon control,low gradient black carbon addition,high gradient black carbon addition,and black carbon removal,respectively.The main influencing factor after adding and removing black carbon is the activity of phenolic oxidase in the litter.(3)The combined effects of fire disturbance and black carbon addition have a promoting effect on the decomposition of litter,and the decomposition is faster under the influence of high gradient black carbon addition after low intensity fire disturbance.Mild fire disturbance promoted the decomposition of litter by removing black carbon,while severe fire disturbance inhibited the decomposition of litter by removing black carbon.The control group without burning and without adding black carbon,the low gradient and high gradient after mild fire disturbance,the removal of black carbon,the low gradient and high gradient after severe fire disturbance,and the removal of black carbon treatment decreased the entire decomposition process by 10.61%,16.72%,17.96%,12.93%,13.53%,14.14%,and 10.61%,respectively(p<0.05).The main influencing factor is the addition of low gradient black carbon and litter lignin after mild fire disturbance;The main influencing factors were the addition and removal of high gradient black carbon after mild fire disturbance,and the addition of litter phenoloxidase after heavy fire disturbance;The addition and removal of low gradient black carbon and organic carbon content in black carbon litter after severe fire disturbance are the main influencing factors.In summary,under the joint influence of fire disturbance,black carbon addition,fire disturbance,and black carbon addition,the decomposition of litter is directly and indirectly affected by changes in soil factors,litter chemical composition,enzyme activity,etc.The indirect effect is stronger than the direct effect,and under the joint influence of fire disturbance and black carbon,the effect of black carbon addition is stronger.Therefore,the role of black carbon,a byproduct produced by fire disturbance and fire disturbance,in the decomposition process of litter deserves attention.The results of this study are conducive to providing a theoretical basis for developing appropriate planned burning forest management methods in the future.While promoting the restoration of forest ecosystems and nutrient cycling,it can also reduce a portion of combustible load and thereby reduce the probability of forest fires. |
