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

研究了密克罗尼西亚波纳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基于区域的评价。通过植物社会学分析，确定了3种主要的红树林植被类型，即在沿岸狭窄地带发现的柱茎根（Rhizophora stylosa）先锋群落和具有密集高脚根或呼吸植物的海桑（Sonneratia alba）群落，以及广阔的尖根根（Rhizophora apiculata - Bruguiera gymnorrhiza）群落。浅层泥炭沉积深度为0 ~ 0.5m的先锋林分各类型估算年龄小于400年，而泥炭沉积深度为1 ~ 2 m的主要林分估算年龄约为1700年。据估计，建立在珊瑚礁上的红树林的直立生物量约为560吨/公顷，河口沿岸红树林的生物量约为700吨/公顷。年常绿碳储量估计在160 ~ 300吨碳/公顷之间，固定率估计在0 ~ 3吨碳/公顷之间。地下固碳以泥炭积累为主，少量凋落物的贡献可以忽略不计。地下泥炭储量巨大，约2000吨碳/公顷。通过精确的监测，我们认识到大林隙的发生对更新的重要性。研究了木材分解的过程和相关因素，发现了它们对恶劣条件的耐受性。然后，我们对整个波纳佩岛的森林类型进行了检测，并对每种红树林的碳储量进行了评估。

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.