| Mytilaria laosensis is a kind of evergreen valuable native broad-leaved trees in the southern subtropical region of China.It has the characteristic of fast growth and large litter amount and is a kind of good timber,paper making and ecological tree species.Litter is an important component of forest ecosystem function,which has great significance for maintain soil fertility and nutrient cycling.In the process of forest cultivation,stand density control is an important management measure,which affects the stand productivity and ecosystem function.In order to investigate the relationship between stand density and litter,this paper we studied the effects of five planting densities(625 tree·hm-2,833 tree·hm-2,1111 tree·hm-2,1667 tree·hm-2,2500 tree·hm-2;D1,D2,D3,D4,D5)on litter production,nutrient content and nutrient return of 6-year-old M.laosensis plantation.It can provide the basic data for the ecological function,and also provide reference for the density control in the cultivation process of M.laosensis plantation.The main conclusions were as follows:(1)The production of total litter,leave,flower and fruit,and miscellaneous litter decreased but that of branch litter increased when the planting densities increased.The annual litter production of M.laosensis plantation at different planting densities varied from 6.52 to 8.17 t·hm-2·a-1,among which the leave constituted the highest proportion(86.2%~87.85%),followed by miscellaneous components(6.69%~8.89%),the branch(0.35%~5.43%),and flower and fruit(0.46%~4.67%).In the different planting densities,the monthly variation of the litter production of leave showed a unimodal mode with the maximum in September and the minimum in March or April.Monthly variation of branch litter was irregular while that of flower and fruit,miscellaneous litter exhibited bimodal seasonal patterns.Flower and fruit fell mainly in May and October,and miscellaneous litter peaked in June and September.The total litter of D1 and D2 stands were the bimodal peak type,and the peak values were June and September,respectively,while the total litterfall of D3,D4 and D5 stands were single peak type and the peak appeared in September.(2)The order of nutrient content of litter in different planting densities was: C> N,Ca> Mg> K> P.With the increase of planting density,the content of C,N and P in the leaves showed a tendency to increase,and the K content showed a decreasing tendency,while the Ca and Mg content were higher in the medium density.The effect of planting density on nutrient content in litter components such as branches,flowers and fruits and miscellaneous was relatively small.The order of nutrient element content in litter was: C> Ca> N> K,Mg> P.The content of nutrient elements in flower and fruit,miscellaneous litter were: C> N> K,Ca> Mg> P.(3)With the increase of planting density,the return amount of C,N,P,K,Ca and Mg in litter decreased,but the difference of N,P and Ca return amount among different densities was not significant.The total amount of nutrient return amount in the litter of different planting densities was 3516.0 ~ 4363.10 kg·hm-2.The order of the nutrient return amount is: C> N> Ca> K> Mg> P.Among them,the amount return of C element is 3332.5 ~ 4139.12 kg·hm-2,the return amount of N element is 72.79 ~ 85.37 kg·hm-2,the return amount of the Ca element is 61.47 ~ 68.48 kg·hm-2,the return amount of K element is 29.52 ~ 51.55 kg·hm-2,and the return amount of Mg element is 12.20 ~ 14.91 kg·hm-2,and the return amount of P element is 3.04 ~ 3.66 kg·hm-2. |
PDF Full Text Request