Yang Long, Wang Jun, Huang Yuhui, Hui Dafeng, Wen Meili
Centre of Resource and Environment, Guangzhou Institute of Geography, Guangzhou, China; Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China.
Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China.
PLoS One. 2014 Jun 24;9(6):e100464. doi: 10.1371/journal.pone.0100464. eCollection 2014.
For the purposes of forest restoration, carbon (C) fixation, and economic improvement, eucalyptus (Eucalyptus urophylla) has been widely planted in South China. The understory of eucalyptus plantations is often occupied by a dense community of the fern Dicranopteris dichotoma, which intercepts tree canopy leaf litter before it reaches the ground. To understand the effects of this interception of litterfall on C cycling in eucalyptus plantations, we quantified the mass of intercepted litter and the influences of litterfall interception on litter decomposition and soil respiration. The total mass of E. urophylla litterfall collected on the understory was similar to that collected by the traditional litter trap method. All of the eucalyptus litterfall is intercepted by the D. dichotoma canopy. Of the litterfall that was intercepted by D. dichotoma, 20-40% and 60-80% was intercepted by the top (50-100 cm) and bottom (0-50 cm) of the understory canopy, respectively. Intercepted litterfall decomposed faster at the bottom of understory canopy (at the base of the plants) than at the top, and decomposition was slower on the soil surface in the absence of understory than on any location in the understory canopy. Soil respiration was highest when both the understory and litter were present and was lowest when both the understory and litter were absent. These results indicate that litterfall interception changed carbon flow between aboveground and belowground through litter decomposition and soil respiration, which changed carbon cycling in eucalyptus plantations. The effects of the understory on litter decomposition and soil respiration should be considered in ecosystem carbon models.
出于森林恢复、碳固定和经济改善的目的，尾叶桉（Eucalyptus urophylla）已在中国南方广泛种植。尾叶桉人工林的林下通常被茂密的芒萁（Dicranopteris dichotoma）群落占据，芒萁在树冠层落叶到达地面之前就将其拦截。为了解这种对凋落物的拦截对尾叶桉人工林碳循环的影响，我们对拦截凋落物的质量以及凋落物拦截对凋落物分解和土壤呼吸的影响进行了量化。林下收集的尾叶桉凋落物总质量与传统凋落物收集器方法收集的质量相似。所有尾叶桉凋落物都被芒萁冠层拦截。在被芒萁拦截的凋落物中，分别有20 - 40%和60 - 80%被林下冠层顶部（50 - 100厘米）和底部（0 - 50厘米）拦截。林下冠层底部（植株基部）的拦截凋落物分解速度比顶部快，且在没有林下植被的情况下，土壤表面的分解速度比林下冠层的任何位置都慢。当林下植被和凋落物都存在时，土壤呼吸最高，而当林下植被和凋落物都不存在时，土壤呼吸最低。这些结果表明，凋落物拦截通过凋落物分解和土壤呼吸改变了地上和地下之间的碳流，从而改变了尾叶桉人工林的碳循环。在生态系统碳模型中应考虑林下植被对凋落物分解和土壤呼吸的影响。
