Abstract. In Southeast Asia, oil palm plantations have largely replaced tropical forests. The impact of this shift in land-use on greenhouse gas (GHG) fluxes and soil microbial communities remains highly uncertain, mainly due to a relatively small pool of available data. The aim of this study is to quantify differences of nitrous oxide (N₂O) and methane (CH₄) fluxes as well as soil carbon dioxide (CO₂) respiration rates from logged forests, oil palm plantations of different ages and an adjacent small riparian area. The focus of this study is on N₂O fluxes, as these emissions are expected to increase significantly due to the introduction of nitrogen (N) fertiliser application. This study was conducted in the SAFE (Stability of Altered Forest Ecosystems) landscape in Malaysian Borneo (Sabah) with measurements every two months over a two-year period. GHG fluxes were measured by static chambers; at the same time soil samples were collected for analysis of the key soil physicochemical parameters and for analysis of microbial biodiversity using next generation sequencing in dry and wet season. N₂O fluxes were highly variable across the different sites, with the highest mean flux from OP (46.2 ± 166 µg m⁻² h⁻¹ N₂O-N) and riparian (31.8 ± 220 µg m⁻² h⁻¹ N₂O-N) sites, compared to lower fluxes from logged forest (13.9 ± 171 µg m⁻² h⁻¹ N₂O-N). Methane fluxes were generally small; −2.6 ± 17.2 µg CH₄-C m⁻² h⁻¹ for OP and 1.3 ± 12.6 µg CH₄-C m⁻² h⁻¹ for riparian with the range of measured CH₄ fluxes largest in logged forests (2.2 ± 48.3 µg CH₄- m⁻² h⁻¹). Soil respiration rates were larger from riparian areas (157.7 ± 106 mg m⁻² h⁻¹ CO₂-C) and logged forests (137.4 ± 95 mg m⁻² h⁻¹ CO₂-C) than OP plantations (93.3 ± 70 mg m⁻² h⁻¹ CO₂-C) due to larger amounts of decomposing leaf litter. Microbial communities were distinctly different between the different land-use types and sites, bacterial communities linked to soil pH and fungal and eukaryotic communities to land-use. Despite measuring a number of environmental parameters, mixed models could only explain up to 17 % of the variance of measured fluxes for N₂O, 3 % of CH₄ and 25 % of soil respiration. Scaling up measured N₂O fluxes to Sabah using land areas for forest and OP resulted in emissions increasing from 7.6 Mt (95 % confidence interval, −3.0–22.3 Mt) per year in 1973 to 11.4 Mt (0.2–28.6 Mt) per year in 2015 due to the increasing area of forest converted to OP plantations over the last ~40 years.

中文翻译：

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热带森林及邻近油棕人工林在矿物土壤上的温室气体通量和微生物群落的比较

摘要。在东南亚，油棕种植已基本取代了热带森林。这种土地利用方式的变化对温室气体（GHG）通量和土壤微生物群落的影响仍然高度不确定，这主要是由于可用数据量相对较小。这项研究的目的是量化伐木森林，不同年龄的油棕人工林和邻近的小林中一氧化二氮（N ₂ O）和甲烷（CH ₄）通量的差异以及土壤二氧化碳（CO ₂）的呼吸速率。河岸地区。这项研究的重点是N ₂O流量，因为由于引入了氮（N）肥料应用，预计这些排放量将显着增加。这项研究是在马来西亚婆罗洲（沙巴州）的SAFE（森林生态系统改变的稳定性）景观中进行的，每两年进行两次测量。温室气体通量通过静态室测量；同时收集土壤样品，以利用旱季和湿季的下一代测序技术分析关键的土壤理化参数和微生物多样性。N ₂ O通量在不同位置之间变化很大，OP的平均通量最高（46.2±166 µg m ^-2  h ^-1 N ₂ O-N）和河岸通量（31.8±220 µg m ^-2  h^-1 N ₂ O-N）站点，而采伐森林的通量较低（13.9±171 µg m ^-2  h ^-1 N ₂ O-N）。甲烷通量一般很小；对于OP为-2.6±17.2 µg CH ₄ -C m ^-2  h ^-1，对于河岸为-1.3 ±12.6 µg CH ₄ -C m ^-2  h ^-1，测得的CH ₄通量范围在伐木森林中最大（2.2±48.3 µg CH ₄ -m ^-2  h ^-1）。河岸地区的土壤呼吸速率更高（157.7±106 mg m ^-2  h ^-1 CO ₂-C）和伐木森林（137.4±95 mg m ^-2  h ^-1 CO ₂ -C），比OP人工林（93.3±70 mg m ^-2  h ^-1 CO ₂ -C）大，这是因为分解的叶子凋落物较多。不同土地利用类型和地点之间的微生物群落明显不同，与土壤pH相关的细菌群落以及与土地利用相关的真菌和真核生物群落。尽管测量了许多环境参数，但混合模型最多只能解释N ₂ O，3％CH ₄和25％土壤呼吸的通量变化的17％。放大测量的N ₂使用林地和OP的土地流向沙巴的O通量导致排放量从1973年的每年7.6 Mt（95％置信区间，−3.0-22.3 Mt）增加到1973年的每年11.4 Mt（0.2-28.6 Mt），这是由于在过去约40年中，越来越多的森林转化为OP人工林。