茂兰喀斯特森林自然保护区凋落叶分解动态

目的]研究喀斯特森林生态系统凋落叶分解特征,为喀斯特森林区石漠化防治及水土保持提供科学依据。方法]采用1 mm网孔孔径分解袋,对茂兰喀斯特森林自然保护区不同树种凋落叶(落叶和常绿叶)在不同坡位的分解状况进行为期18个月的观测研究。研究茂兰喀斯特森林自然保护区凋落叶失重率和干重残留率动态变化、分解速率及养分释放特征。结果]凋落叶分解过程呈现"快—慢—快"的周期变化,春夏季分解速度快于秋冬季,落叶树种凋落叶分解速度快于常绿树种凋落叶,不同坡位凋落叶的分解速度表现为:下坡中坡上坡。利用Olson模型对凋落叶分解50%和95%所需时间进行估测,发现落叶树种凋落叶分解50%和95%所需时间分别为0.95～1.66 a和4.13～7.19 a,常绿树种凋落叶分解50%和95%所需时间分别为1.14～1.69 a和4.92～7.30 a,二者无显著性差异。凋落叶分解速率低于中亚热带东部常绿阔叶林和常绿落叶阔叶混交林,但比同区域喀斯特次生林与人工林高。落叶树种凋落叶和常绿树种凋落叶的N元素释放模式为富集—释放模式,C含量随分解时间的波动差异显著,总体在不断减少,而C/N比呈逐步下降的趋势。结论]由于不同树种凋落叶初始养分含量和叶片理化结构的差异,落叶比常绿叶具有更快的分解速率和养分释放速率,对促进喀斯特森林生态系统物质循环起着积极作用。

Decomposition Dynamics of Leaf Litters in Maolan Karst Forest Natrue Reserve

Objective] The characteristics of litter decomposition in karst forest ecosystems were studied in order to provide scientific basis for prevention and control of rocky desertification and soil and water conservation in karst forest natrue reserve.Methods] By using 1 mm mesh pore decomposition bag, the decomposition dynamics of different tree species of leaf litters(deciduous and evergreen leaf) in different slope position for 18 months were analyzed, including the dynamic change of litter loss rate and dry weight residue rate, decomposition rate and nutrient release characteristics of Maolan Karst Forest Natrue Reserve.Results] The decomposition process of litter showed a "fast-slow-fast" cycle, and the decomposition rate in spring and summer was faster than that in autumn and winter. The decomposition rate of deciduous tree litter was faster than that of evergreen tree litters, and the decomposition rate of litters on different slopes was characterized by downhill > mid slope > uphill. This study used the Olson model to estimate the time of decomposition of 50% and 95% leaf litters. The time required for decomposing 50% and 95% of deciduous tree litter is 0.95~1.66 a and 4.13~7.19 a, respectively. The time required for decomposing 50% and 95% of evergreen tree litter is 1.14~1.69 a and 4.92~7.30 a, respectively. The difference between them is not significant. The decomposition rate of leaf litter in the Maolan karst forest was lower than that of the evergreen broad-leaved forest and evergreen-deciduous broad-leaved mixed forest in the eastern subtropical zone, but higher than that of the karst secondary forest and plantation in the same region. The release pattern of N element in deciduous and evergreen leaves is enrichment-release mode, and the C content varies significantly with the decomposition time. The overall trend of C content is reduced, so the C/N ratio is decreasing.Conclusion] Due to the difference of initial nutrient content and leaf physical and chemical structure of different tree species, deciduous leaf had faster decomposition rate and nutrient release rate than evergreen leaf, which played an active role in promoting material circulation of karst forest ecosystem.