| Guizhou Baili Rhododendron National Forest Park(abbreviation:Baili Rhododendron)has the largest subtropical evergreen broad-leaved primary Rhododendron forest identified in China and even the world.It is the only nature reserve in China to protect Rhododendron plants of Rhododendron family,and has unique and rich Rhododendron forest resources.Rhododendron delavayi(RD),Rhododendron irroratum(RI)and Rhododendron agastum(RA)are the main constructive species and dominant species in the region.According to the previous investigation,the Rhododendron in Baili Rhododendron is generally older,there are few new seedlings under the forest,and the litter layer,especially the humus layer,is thick,but its annual seed setting is enough.Litter under the forest has an impact on the natural regeneration of Rhododendron.However,there are few reports on the decomposition characteristics of Rhododendron litter.Through the study on the amount and decomposition of litter of Rhododendron delavayi,Rhododendron irroratum and Rhododendron agastum three evergreen broad-leaved forests and deciduous broad-leaved mixed forests in Baili Rhododendron,this paper provides a scientific basis for the balance of ecosystem and the rational development and utilization of resources in Baili Rhododendron forest area,which is of great significance in the protection and sustainable utilization of Rhododendron forest resources.In this study,the method of location collection was used to continuously collect the new litter produced during the experiment through the litter net,and the yield characteristics of litter in different stands were studied.Through the litter bag method,the field observation and indoor experiment of litter decomposition process under three Rhododendron forests and mixed forests were carried out for 16 months(July 2020 to November 2021).The litter bags of 0.5,1,2.36 and 4.75 mm were used to study the decomposition rate and nutrient dynamic characteristics of litter,and the role of soil environment and litter nutrients in the process of litter decomposition was analyzed.The results show that:(1)The average annual yield of Baili Rhododendron is 3311.1 kg/hm~2,and the average monthly yield can reach 298.26 kg/hm~2.The order of annual and monthly average litter is:Rhododendron delavayi>Rhododendron irroratum>Rhododendron agastum>Mixed forest.The dynamic change of monthly litter yield of Mixed forest?Rhododendron irroratum and Rhododendron agastum is single peak,and the dynamic change of monthly litter yield of Rhododendron delavayi is double peak.(2)There are many factors affecting the litter yield of Baili Rhododendron forest.Season,air temperature,soil HN and AK had significant effects on litter yield.Moreover,rainfall and moisture content will not limit the yield of litter.(3)The time pattern of litter decomposition process in different forests was obvious.According to the litter decomposition rate,it can be divided into three stages.The first stage is the rapid decomposition stage(0-3months);The second stage is the slow decomposition stage(4-8 months);The decomposition speed of the third stage is between the first and second stages(9-16 months).(4)The effect of stand type on litter decomposition is extremely significant.According to the litter decomposition model,it took 1.09?2.56years for 50%decomposition.And it took 5.59 years for mixed forest 95%decomposition,4.72 years for RD,7.4 years for RA,and 10.35 years for RI.(5)In the process of litter decomposition,the migration mode of N?P and cellulose of litter is accumulation-release,and the decomposition mode of lignin and hemicellulose presents a degradation trend;air temperature,soil moisture content,soil available phosphorus,plant N concentration,hemicellulose concentration,hemicellulose/N and hemicellulose/P are significantly affect the litter decomposition rate of the four forests. |
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