| Litter is an important part of the forest ecosystem.Its yield,existing stock,seasonal dynamics,nutrient element reserves,decomposition characteristics,etc.,are an important manifestation of forest ecosystem productivity and nutrient dynamic balance.Compared with normal landforms,there are obvious differences in the habitat conditions,appearance and structural characteristics of plant communities in karst forests.At the same time,the types of karst forest landforms are complex and diverse,and there are obvious differences in habitat conditions between different terrains.Terrain,as the main factor affecting the structure and function of the karst forest ecosystem,has an impact on the forest microclimate,surface runoff and evapotranspiration,and changes the soil The attributes,vegetation composition,growth and development status,etc.,in turn have an important impact on the quantitative characteristics,nutrient content,and decomposition dynamics of forest litter.Based on this,this study takes Guizhou Maolan Karst Forest Nature Reserve as the research area,and selects three typical terrains of slopes,troughs and funnels in the area to carry out the positioning and dynamic monitoring of litter output,and the collection and determination of litter stock.And litter decomposition bag test.Research and analysis of litter composition and yield of each component,litter rhythm,litter layer existing quantity and nutrient characteristics,litter decomposition dynamics and other characteristics and influencing factors,and analyzed the influence of litter on soil nutrients and soil enzyme activities,In order to reveal the nutrient cycling and soil fertility maintenance mechanism of Maolan karst forest ecosystem,and provide scientific theoretical basis for forest management.The main conclusions are as follows:(1)By comparing the annual output of forest litter under three terrain conditions,it is found that the total output of litter is funnel> slope>trough.Leaf litter is the main body of litter,and leaf litter is dominated by deciduous leaves.The proportions of leaf litter in the three terrains are70.01%,71.96%,and 76.12% of the total litter,which are represented by trough> funnel> slope land;The proportions of deciduous leaf litter to the total leaf litter are 55.68%,59.56% and 57.50%,respectively,which is represented by funnel>trough>slopeland.(2)The littering rhythms of the total amount of forest litter and leaf litter of the three terrains are bimodal,with the first peak in April and the second peak in October.The monthly change of leaf litter quantity is consistent with the change of total litter quantity,and the monthly change of branch and other litter quantity fluctuates irregularly.The first peak of leaf litter fall was dominated by evergreen tree species,while the second peak of leaf litter fell was dominated by deciduous tree species,among which the leaf litter was dominated by deciduous tree species.(3)There are big differences in the existing litter layer between different terrains and different decomposition layers,which are expressed as slope> trough> funnel and decomposed layer> semi-decomposed layer>undecomposed layer.The nutrient element contents and reserves of each decomposition layer of the litter are in the order of carbon>calcium>nitrogen>magnesium>potassium>phosphorus.There are significant differences in the total reserves of each nutrient element of the litter between different terrains,and the slopes are the highest,and each nutrient element is also the highest.The release rate is different due to the difference of topography and decomposition layer.(4)The decomposition characteristics of litter are obviously different between different terrains.The weight loss rate of litter in the decomposition bag under the three terrain conditions is trough> slope>funnel from 0 to 360 days;in the first 90 days,There was no significant difference in the weight loss rate of litter from the three terrains;in90-360 days,the litter weight loss rate of the funnel terrain was significantly lower than that of slopes and troughs.During the decomposition process,changes in the content of carbon,nitrogen,and phosphorus in the litter show different states over time.The total carbon content shows a release pattern,and the total nitrogen and total phosphorus contents show different patterns due to different topography.Under the three terrain conditions,the carbon-nitrogen ratio of the litter decomposition bag showed a downward trend with the decomposition of the litter.The carbon-phosphorus ratio and the nitrogen-phosphorus ratio of the litter showed different trends due to different terrains.(5)Topography,plant community characteristics,soil and other factors have a significant impact on the yield,existing amount,nutrient characteristics,and decomposition characteristics of the Maolan Karst forest litter.Topographic factors produce significant effects on forest microclimate,surface runoff,and evapotranspiration.Influence,change the properties of soil and the composition of vegetation,growth and development status,etc.,and then have an indirect impact on the yield,existing amount,nutrient characteristics,and decomposition characteristics of forest litter.The plant diversity index has a significant impact on the total amount of litter and the yield of each component,the litter layer and the content of each nutrient element,and the species diversity of the tree layer is the main factor.(6)The litter has a significant impact on the physical and chemical properties of the soil,which in turn affects the physical and chemical properties of the soil.The results show that forest litter can improve the physical and chemical properties of soil to a certain extent,which is reflected in the influence of litter input and total nitrogen content on soil organic carbon,total nitrogen,alkali hydrolyzable nitrogen,p H,water content and other physical and chemical indicators;soil enzymes The activity is regulated by soil total nitrogen content,p H value,carbon-nitrogen ratio,nitrogen-phosphorus ratio,etc.,of which total nitrogen content is the key influencing factor. |
PDF Full Text Request