The mangrove carbon cycle- influence of below-ground processes and managed cutting

红树林是生长在咸水中的热带森林，通常生长在海岸。森林是宝贵的生态系统，提供木材作为燃料和木材，为鱼类、鸟类和无脊椎动物提供栖息地，并为防止海岸侵蚀和风暴潮提供实际保护。红树林还以泥炭的形式从大气中捕获碳，这些碳储存在它们生长的潮湿沉积物中;关于这个过程还有很多东西要了解。尽管它们很重要，但由于人们为了养虾、木材开采和其他用途而清除它们，它们正在遭受高比率的破坏。包括肯尼亚在内的许多国家都在寻找更好的方法来管理他们的红树林资源，比如允许有控制地砍伐这些森林，然后重新种植。重要的是，任何此类管理都应最大限度地提高森林的生态效益，并最大限度地减少任何生态损害-例如，管理应确保维持地下碳储存，并最大限度地减少温室气体排放。这项研究有两个相关的目标，都侧重于更好地了解红树林的碳循环和温室气体排放：1）研究控制采伐如何影响地下储存的碳和温室气体排放，控制采伐在小规模上重现了肯尼亚再次开始的商业采伐，沿着的还有其他对健康的红树林生态系统至关重要的因素，如生活在那里的鱼类和螃蟹群落。2)确定从红树林生态系统土壤中流失的二氧化碳和其他温室气体的来源-例如，这主要是来自根部的呼吸作用还是来自土壤中有机物质的分解。我们还将确定红树林根系的生产力，使我们能够估计这些根系生长和捕获碳的速度。除了这些主要目标外，我们还将培训肯尼亚科学家，并让当地妇女团体和学童参与红树林教育和恢复活动。实地研究将在距离肯尼亚海岸蒙巴萨约60公里的加齐湾进行。这个海湾被珊瑚礁环绕，并有海草床和红树林。海湾旁边的Gazi村是1000人的家园，他们利用红树林生产各种产品。方法使用天然森林，我们将清除5小块树木区域，并将这些区域的温室气体排放和根系分解与对照森林地块进行比较。通过研究稳定同位素，气体中的天然化学标记，我们将能够从我们的地块中大致区分气体的可能来源。我们亦会监察砍伐对蟹类和鱼类群落的影响，以及对红树林截留沉积物和保持稳定海拔高度的能力的影响。所有被砍伐的地区将重新种植当地人在苗圃种植的树木，当地学校和妇女团体将参加"红树林日"的重新种植和教育。

INTRODUCTION Mangroves are tropical forests that grow in salty water, usually at the coast. They are valuable ecosystems, providing wood for fuel and timber, habitat for fish, birds and invertebrates and physical protection against shore erosion and storm surges. Mangroves also trap carbon from the atmosphere in the form of peat, which is stored below ground in the wet sediments where they grow; there is still much to learn about this process. Despite their importance they are suffering high rates of destruction, as people clear them for shrimp farming, timber extraction and other uses. Many nations, including Kenya, are looking at better ways of managing their mangrove resources, such as allowing controlled cutting of these forests followed by re-planting. It is important that any such management maximises the ecological benefits of the forests and minimises any ecological damage - for example, management should ensure that below-ground carbon stocks are maintained and that the emission of greenhouse gases is minimised. AIMS This research has two related aims, both focused on a better understanding of carbon cycling and greenhouse gas emissions in mangroves: 1) To examine how controlled cutting, which reproduces on a small scale the commercial cutting that has started again in Kenya, affects carbon stored below the ground and greenhouse gas emissions, along with other factors of importance to a healthy mangrove ecosystem such as the communities of fish and crabs that live there. 2) To determine the sources of carbon dioxide and other greenhouse gases that are lost from the soil in mangrove ecosystems - for example, whether this is coming mostly from the respiration of the roots or from decomposition of organic matter in the soil. We will also determine the productivity of mangrove roots, allowing us to estimate how quickly such roots can grow and trap carbon. In addition to these main aims, we will also be training Kenyan scientists and involving a local women's group and school children in mangrove education and restoration events. FIELD SITE This research will be conducted at Gazi Bay, some 60km from Mombasa on the coast of Kenya. The bay is fringed by a coral reef, and contains seagrass beds and mangrove forests. Gazi village next to the bay is home to 1000 people who use their mangroves for a wide range of products. METHODS Using a natural forest we will clear 5 small areas of trees and compare the greenhouse gas emissions and root decomposition in these with control forested plots. By studying stable isotopes, natural chemical markers in the gases, we will be able to differentiate broadly between the possible sources of the gases coming from our plots. We will also monitor the effects of the cutting on crab and fish communities, and on the ability of the mangrove forests to trap sediment and to retain a stable height above sea level. All the cut areas will be replanted with trees grown by local people in a nursery, and the local school and women's group will participate in a 'mangrove day' of replanting and education.