Evaluation of the carbon fixation and organic matter decomposition functions in natural mangrove forests

本文研究了密克罗尼西亚波恩佩岛红树林固碳的能力、功能和过程，并应用卫星图像分析方法对红树林碳储量进行了面积评价。通过植物社会学分析，确定了3种主要的红树林植被类型，即先锋海棠群落和海桑群落，它们的高脚根或气孔都密集分布在沿海狭长地带，以及广袤的细根海桑-木本植物群落。红树林泥炭浅层沉积深度为0~0.5m的先锋林分，每种类型的年龄估计都在400年以内，而泥炭沉积深度为1~2m的主要类型估计为1700年左右。建立在珊瑚礁上的红树林的现存量估计约为560吨/公顷，河口河流红树林的现存量约为700吨/公顷。固定碳储量估计在160至300吨C/ha之间，固定速率估计为每年0至3吨C/ha。地下碳汇大部分是泥炭积累，小凋落物的贡献可以忽略不计。地下泥炭储量非常大，约为2000吨/公顷。通过精确监测，我们认识到大树冠空隙的出现对更新的重要性。研究了与木材分解有关的工艺和助剂，发现了它们对恶劣条件的耐受性。然后，我们对整个波恩佩岛的每种类型的红树林进行了森林类型检测和碳储量评估。

We studied on the capacity, function and process of carbon sequestration by mangrove forests in Pohnpei Island, Micronesia, and applied satellite image analysis for area based evaluation of carbon stock by mangroves. Three main mangrove vegetation types were identified by phyto-sociological analysis i.e. pioneer Rhizophora stylosa community and Sonneratia alba community with dense stilt root or pneumatopher both found in narrow zone along shore as well as vast Rhizophora apiculata - Bruguiera gymnorrhiza community. The estimated age of each type was less than 400 years for pioneer stand with shallow deposit of mangrove peat as 0-0.5m in depth while major type was estimated as ca, 1700 years owing to 1 to 2 m deep peat deposit. Standing biomass was estimated as ca. 560 ton/ha for mangroves established on coral reef and as ca. 700 ton/ha for estuary riverine mangrove. Standing carbon stocks were estimated between 160 to 300 ton C/ha and fixation rate was estimated 0 to 3 ton C/ha annually. Most belowground carbon sequestration was made of peat accumulation and the contribution of small litter was negligible. Belowground peat deposit was, very huge as ca. 2000 ton C/ha. We recognized the importance of large canopy gap occurrence for regeneration through precise monitoring. The process and agents concerning to wood decomposition were also studied and their tolerance to severe conditions was found. Then we detected forest types and evaluated carbon stocks by each type of mangrove over whole Pohnpei Island.