| Fire is one of the most common disaster factors in shrub forests that are the difficulty of vegetation restoration and study focus on ecological management in karst rocky desertification area of southwest China,and fire effect in this area is poor research.This study was by controlling the fire to karst desert shrubs as the research object in Puding county,Anshun city,Guizhou province,and fire frequency for 4processing levels as control(CK),burning it year after year(1a),the next year(2a)and every 2 years(3a),respectively,3 repeat Settings.Before and after the fire,main physical and chemical indicators,enzyme activity and microorganism quantity of soil and plant diversity indexes of shrub forest were measured,it is analyzed that evaluation of fire values and the effects of fire on shrub plant diversity indexes and soil fertility in the Guizhou central karst stony desert area.This research result is providing theoretical basis and technical support to further explore the scientific use of fire to promote forest vegetation restoration in stone desert area.The main conclusions are as follows:(1)Compared with that before fire,two-times fires improved soil pH value and soil catalase activity,reduced soil available phosphorus content,soil urease activity and alkaline phosphatase activity,and increased the content of organic matter and available potassium and reduced the content of total phosphorus in surface soil.The activity of sucrase in surface soil increased after primary fire and decreased after secondary fire.Before and after two fires,the pH value trends of soil were surface layer < bottom layer,and the pH values between soil layers in the first fire were significantly different,but the difference was not significant in the second fire.The soil indicators in the bottom layer > surface layer were organic matter,total nitrogen,total phosphorus,total potassium,available phosphorus and available potassium,as well as the number of bacteria,fungi and actinomycetes.The number of soil bacteria,fungi and actinomycetes in different soil layers decreased after the first fire,while thenumber of soil bacteria,fungi and actinomycetes increased after the second fire.(2)There were significant differences in soil sucrase and alkaline phosphatase activity,soil microbial number and the corresponding background value after nearly one year’s recovery after fire.The soil total nitrogen content was significantly different between soil layers,and the available phosphorus and total nitrogen content of surface layer and bottom layer increased after restoration,while the contents of soil pH value,organic matter,total phosphorus,total potassium,hydrolyzed nitrogen and available potassium decreased.The activities of urease and catalase in surface soil decreased,while the activities of sucrase and alkaline phosphatase increased,the activities of urease,sucrase and alkaline phosphatase in bottom soil increased,and the activities of catalase decreased.The number of soil microorganisms decreased in presented > bottom soil layer.Before fire,the number of soil microorganisms was sequenced by actinomycetes > and bacteria > fungi.After recovery,the number of soil microorganisms was sequenced by bacteria > and actinomycetes > fungi.(3)The effects of fire frequency on the contents of soil organic matter,total phosphorus,total potassium,hydrolyzed nitrogen and available phosphorus,the activities of soil sucrase,alkaline phosphatase and catalase,and the number of soil actinomycetes were significantly different.With the increase of the frequency of fire,the content of soil organic matter and available phosphorus increased,the activity of urease in surface soil decreased.the activity of sucrase and catalase in soil increased,and the number of bacteria and actinomyces decreased.(4)The surface soil loss rate(DFS)in the first fire < the second fire was indexes of soil total nitrogen,total phosphorus,effective phosphorus,soil urease,invertase and alkaline phosphatase,profile influence the loss rate(IFP1)in the first fire > the second fire index of soil organic matter,total phosphorus,hydrolyzed nitrogen,hydrogen peroxide enzyme,alkaline phosphatase,invertase and actinomyces quantity,other physical and chemical index,microorganism quantity and enzyme activity index change trend.(5)There were significant differences in the index values of shrub and herb diversity between the experimental forest background and the restoration of shrub andherb after fire in the past year,while there were no significant differences in the index values of shrub and herb diversity between the experimental forest control and the restoration of fire in the same year.In the process of natural restoration,the values of shrub Margalef index and Shannon-wiener index increased significantly,while the values of Pielou index decreased significantly.The Simpson index,Shannon-wiener index and Pielou index of herb decreased significantly,while the Margalef index increased significantly.(6)After 0-1 treatment,it was found that there was no significant difference in surface soil fertility indexes between different years and within the same year.The soil comprehensive fertilizer,effective fertilizer and enzyme activity reached the maximum value in the first year of fire,continuous fire was beneficial to microbial growth,and the total fertilizer increased after 1 year of recovery after fire.(7)By principal component analysis,the annual soil fertility indexes before and after fire were divided into 5 principal components include general fertilizer consumption,effective fertilizer consumption,microorganism,enzyme activity and other factors,the total variance of 87.14% and 83.09% respectively,shrub plant diversity indexes were divided into plant diversity and evenness of two principal components,the total variance is 97.81%,the linear regression equations of shrub plant diversity principal components and soil fertility principal components were significantly,Contribution rate of the main component of total fertilizer consumption on shrub plant diversity and enzyme activity of shrubs plants uniformity principal component were the highest before fire,and other factors on the main component of shrub plant diversity and microorganisms of shrub plant uniformity principal component contribution rate is highest after fire. |
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