| At present,the global planted forest area is showing an increasing trend year by year.Under the traditional management model,coupled with the poor stability and resilience of the planted forest’s own ecosystem,the soil fertility of planted forests has declined,and forest land degradation has become increasingly common and significant.Chinese fir plantations will go through mountain smelting before afforestation,releasing a large amount of nutrients into the soil,often resulting in the loss of nutrients.The stump is the main plant residue left over from logging,and its slow decomposition can continuously release nutrients during the entire growth process of the Chinese fir forest,which is of great significance for maintaining the nutrients of the forest.Coarse woody debris in plantation forests can effectively alleviate the problem of plantation degradation in improving forest soil fertility,maintaining biodiversity and conserving water and soil.At present,my country’s research on forest coarse woody debris mostly focuses on fallen and standing trees in temperate and tropical virgin forests,while research on stump decomposition in artificial forests in subtropical regions is still very rare.This paper adopts the space instead of time method and selects the 8 Chinese fir plantations established in 1985,1988,1991,1996,2001,2006,2009 and 2014 in Huitong,Hunan after logging and smelting,that is,the decomposition time of fir stumps.For 35,32,29,24,19,14,11 and 6 years,from October 2018 to October 2020,sample plots and samples were set up in the above eight forest stands respectively,and the decomposition of fir stumps and sapwood Analyze and study the dynamic changes of nutrient content of,heartwood,large roots and thick roots and the soil physical and chemical properties of the tree stump neighborhood and the clearing of the forest.Provide countermeasures for restoration and security,and provide a certain theoretical reference for the sustainable management of Chinese fir plantations.The results of the study are as follows:(1)With the increase of the decomposition time of the stump,the root density and moisture content of the above ground and underground parts change dynamically.The density and moisture content of the root are greater than the density and moisture content of the stump.The absolute density shows an upward trend with the increase of the decomposition time,and the moisture content shows a downward trend with the increase of time.There is no significant correlation between the density and the moisture content in different parts.The residual rate of stumps is continuously decreasing.The 35-year decomposition rate of fir stumps in the plantation is 0.043,and it is estimated that it will take 69.9 years to completely decompose.(2)The content of various elements is the largest when the stump is not decomposed,and there are obvious differences between the four parts.As time decomposes,the content gradually tends to be the same;the size order of the nutrient content in the stump is C>N>Ca>Fe>K>Mg>P>Mn,the order of the content of each nutrient element in the four parts is thick root,large root,sapwood and heartwood.The organic carbon content in the four parts of the stump increases with the decomposition time.Increases,all show an upward trend.The elements of N,P,K,Ca,Mg,Mn,and Fe in the four parts of the stump show a downward trend with the increase of the decomposition time;and there is a significant correlation between the nutrient contents of the stump.Only the stump organic carbon,nitrogen and calcium content did not have a significant correlation(P>0.05).(3)A three-factor variance analysis of soil physical and chemical properties with different decomposition times,different treatments and different soil depths found that the physical and chemical properties of soil are mainly affected by decomposition time and soil depth.In the four soil layers,the changes of different indicators of soil physical and chemical properties are different,and the stump group is relatively higher than the control group;the changes of different indicators in the same soil layer are also different,as the decomposition time increases,the difference is gradually become smaller.As the soil layer deepens,soil bulk density,Fe,Cu,and Zn continue to increase,and moisture content,C,N,P,K.Ca keeps getting smaller,Mn first drops and then rises,pH and Mg change little.The difference between the 0-15cm soil layer and other soil layers is the largest,and the difference between the nutrient content in each soil layer of the stump group and the open land group is not significant.(4)The indicators in the four soil layers are constantly changing as the time of stump decomposition changes.As the decomposition time increases,the content of organic carbon,N,and Mn continues to decrease,and the content of Zn continues to rise.The bulk density,P,K,and Fe first decrease and then rise,and the content of Fe first rises and then falls.The law of water content and Mg is not obvious.The value changes slightly.The correlation analysis between the soil physical and chemical properties shows that the correlation between the soil physical and chemical properties is significant.(5)The correlation analysis between the stump nutrient and the soil nutrient content found that the stump SOC content has a significant correlation with the soil nutrient element content,and the stump P content and the soil nutrient element content are not significantly correlated;soil K,Mg The correlation between the content of,Cu,Zn and the nutrient element content of tree stumps is significant.Comparing the comprehensive soil fertility index between the stump group and the control group in the four soil layers,in different soil layers,the soil fertility of the stump group is greater than that of the control group,and the decomposition of the stumps has a certain effect on the soil fertility in the neighborhood. |
