造林密度对米老排凋落物量及动态的影响

Effects of Planting Densities on Production and Dynamics of Litter of Mytilaria laosensis Plantation

在2015年10月~2016年9月,采用90个凋落物收集器,研究不同造林密度对米老排人工林凋落物总量、组分及动态特征的影响。结果表明:年凋落物总量及各组分的产量与造林密度呈线性相关。随着造林密度的增加,林分的年凋落物总量、叶、花果和杂物的年凋落物量均呈现降低的趋势,而枝条的年凋落物量呈增加的趋势。不同造林密度米老排人工林的年凋落物量为6.52~8.17 t·hm^(-2)·a^(-1),其中叶为主要组分,占总量的86.2%~87.85%,枝条占0.35%~5.43%,花果占0.46%~4.67%,杂物占6.69%~8.89%。不同造林密度叶凋落物量的月动态变化均呈单峰型,最大值出现在9月,最小值在3~4月。枝条凋落物量的月动态变化呈不规则型,花果和杂物凋落物量均呈双峰型,花果的凋落主要集中在5和10月,而杂物的凋落量高峰在6和9月。凋落物总量与叶凋落物量的月动态变化基本相似,但在6月杂物凋落物量的影响下,有些密度的林分也会呈双峰型。当林分完全郁闭后,随着造林密度的增加,林分枝下高的增加,胸径、树冠比以及冠幅的减小,可能会导致凋落物总量、叶、花果及杂物凋落物量的下降,而枝条的凋落物量增加。

Field investigations were made on the production,components and dynamics of litter of Mytilaria laosensis plantation at different planting densities from October 2015 to September 2016 by using 90 litter traps.The production of litter and its components was linearly correlated with the planting densities; the production of total litter,leave,flower and fruit,and miscellaneous litter decreased,but that of branch litter increased with the increasing of planting densities. The annual litter production of M. laosensis plantation at different planting densities varied from 6. 52-8. 17 t · hm^（-2）·a^（-1）. The leave constituted the highest proportion（ 86. 2%-87. 85%）,followed by miscellaneous components（ 6. 69%-8. 89%） while the branch made up 0. 35%-5. 43%,and flower and fruit accounted for 0. 46%-4. 67% of annual yield of the litter. The monthly variation of the litter production of leave at different planting densities 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 had bimodal seasonal patterns. Flower and fruit fell mainly in May and October,and miscellaneous litter peaked in June and September. The monthly variation of total litter was almost similar to that of leaf litter,but double peaks would occur in some densities under the influence of miscellaneouslitter fall in July. With the increase of the planting densities,the height under living branch would be higher,but DBH,crown ratio and crown width would be lower,which might lead to much decline in total litter,leaf,fruit and miscellaneous litter but there would be great enhance in branch litter after the crown.