茂兰喀斯特森林退化区凋落物的分解动态

Decomposition of litters in Maolan karst forest degradation area

关键词:  茂兰, 喀斯特, 凋落物, 分解动态, 养分释放

Key words:  Maolan, karst forest, litter, decomposition of dynamic, nutrient release

摘要:

为了解亚热带气候型的茂兰喀斯特森林退化区次生林和灌木林的凋落物分解动态过程,该研究采用分解袋法,对茂兰喀斯特森林退化区不同类型的凋落物在不同坡位的分解状况进行了为期18个月的观测,并通过分析凋落物分解时的失重量和失重率的动态变化,比较了次生林和灌木林的凋落叶的失重率变化,探讨了不同坡位对凋落物分解的影响。结果表明:各种类型凋落物的分解速率和失重率在退化区内存在明显的差异, 落叶>常绿叶>枯枝(P<0.05),三种凋落物整体变化趋势在分解过程中大致相同, 它们在早期都快速分解,中期分解变慢,后期开始加速; 落叶在次生林与灌木林中的前期分解速率基本同步,后期为灌木林落叶>次生林落叶,而常绿叶在灌木林与次生林中的分解速率则表现为基本同步; 利用回归方程对凋落叶分解50%和95%所需时间进行估测,得出落叶和常绿叶在灌木林中分解50%和95%所需时间少于次生林的; 在不同坡位,三种凋落物分解速率的总体趋势为中坡>上坡; 三种凋落物的C含量波动性较大,但总体变化趋势是随分解时间的增加而减少,随着分解时间增加,N含量增加,而C/N比则降低。

Abstract:

In order to study the dynamic process of litter decomposition of secondary forest and shrubbery in Maolan karst forest degradation area of subtropical climate type, the decomposition bag method was used to observe the litter decomposition of different types in different slopes in Maolan karst forest degradation area for 18 months. By analyzing the dynamic changes of weight loss and weight loss rate during the decomposition of litters, comparing the changes of weight loss rate of litters in secondary forest and shrubbery and the effects of different slope positions on litters decomposition. The results showed that there were significant differences in the decomposition rate and weight loss ratio of all types of litters in the degradation zone, fallen leaves>often leaves>deadwood(P<0.05), the overall change trend of the three litters was roughly the same in the decomposition process, they all decomposed rapidly in the early stage, slowed down in the middle stage and accelerated in the later stage. The decomposition rate of leaves in secondary forest and shrubbery was basically synchronized at the earlier stage, deciduous shrub>secondary forest leaves in the later, while the decomposition rate of the common green leaves in secondary forest and shrubbery was basically synchronous. The regression equation was used to estimate the time required for the decomposition of litter leaves by 50% and 95%, and it was concluded that the time required for the decomposition of deciduous leaves and evergreen leaves in shrubbery by 50% and 95% was less than that of secondary forests. At different slope positions, the general trend of decomposition rate of three kinds of litters is mesoslope>upslope. The C content of the three litters fluctuates greatly, but the overall change trend is to decrease with the increase of decomposition time, with the increase of decomposition time, the N content increases, while the C/N ratio decreases.