The superlative environmental conditions in Southern Amazonia, i.e. high temperatures and annual rainfall, create ideal conditions for high soil organic matter turnover rates and therewith the soil-atmosphere exchanges of greenhouse gases. In this study, we present daily observations of soil-related carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) emissions from the dominant land use types in Mato Grosso (cerrado, gallery forest, cattle pasture, and cropland under soybean) and Pará (rainforest and cattle pastures) during the early rain season. We followed the hypothesis that precipitation events provoke hot moments for CO2 and N2O, and lead to alternating uptake and emission for CH4, respectively. Observed fluxes differed significantly between land use types and underlying soil type. CO2 fluxes from soils under natural vegetation ranged from 101 mg m-2 h-1 in the cerrado to 160 mg C m-2 h-1 in the rainforest. Fluxes from cattle pastures varied between locations and were 79 mg C m-2 h-1 from the pasture in Mato Grosso and between 120 and 180 mg C m-2 h-1 from pastures in Pará. For N2O, fluxes were highest from rainforest (16 μg N m-2 h-1) and lowest from cerrado soil (-0.05 μg N m-2 h-1). Similar to CO2, the pastures in Pará emitted higher fluxes of N2O (2–8 μg N m-2 h-1) compared to the pasture in Mato Grosso (0.09 μg N m-2 h-1). CH4 fluxes were negative on all sites, except for two pasture sites in Pará, where recorded fluxes amounted to 10 and 53 μg C m-2 h-1, respectively. The dynamic behavior during the measurement period, as determined by an indicator function, was moderate for N2O, low for CO2 and CH4, and depended on the site and measurement chamber, respectively. Nevertheless, N2O fluxes from the cropland increased during the end of the vegetation period of soybean, likely as a result of increased nitrogen availability due to ceasing plant roots. At the same time cattle pastures showed an age-related decrease of N2O emissions, whereas they turned out to being considerable sources for CH4. Generally, the low dynamics and missing reactions to precipitation events demonstrate poor process understanding and need to be further investigated.

中文翻译：

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错过亚马逊南部温室气体的炎热时刻

亚马逊南部最高级的环境条件，即高温和年降雨量，为土壤有机质的高周转率以及温室气体的土壤-大气交换创造了理想的条件。在这项研究中，我们展示了马托格罗索州主要土地利用类型（塞拉多、画廊森林、牛牧场和农田）的土壤相关二氧化碳 (CO2)、一氧化二氮 (N2O) 和甲烷 (CH4) 排放量的每日观察结果。大豆下）和帕拉（热带雨林和牛牧场）在雨季早期。我们遵循以下假设，即降水事件引发了 CO2 和 N2O 的高温时刻，并分别导致 CH4 的交替吸收和排放。观测到的通量在土地利用类型和下伏土壤类型之间存在显着差异。来自天然植被下土壤的 CO2 通量范围从塞拉多的 101 mg m-2 h-1 到雨林中的 160 mg C m-2 h-1。牛牧场的通量因地点而异，来自马托格罗索州牧场的 79 mg C m-2 h-1 和来自帕拉州牧场的 120 至 180 mg C m-2 h-1。对于 N2O，雨林的通量最高（16 μg N m-2 h-1），而塞拉多土壤的通量最低（-0.05 μg N m-2 h-1）。与 CO2 类似，与马托格罗索州的牧场（0.09 μg N m-2 h-1）相比，帕拉州的牧场排放出更高的 N2O 通量（2–8 μg N m-2 h-1）。除了帕拉州的两个牧场，记录的通量分别为 10 和 53 μg C m-2 h-1，所有地点的 CH4 通量均为负值。测量期间的动态行为，由指标函数确定，N2O 适中，CO2 和 CH4 低，并分别取决于站点和测量室。然而，在大豆植被期结束时，农田的 N2O 通量增加，这可能是由于植物根系停止导致氮可用性增加所致。与此同时，牛牧场显示出与年龄相关的 N2O 排放量减少，而它们却是 CH4 的重要来源。通常，对沉淀事件的低动力学和缺失反应表明对过程的理解很差，需要进一步研究。而事实证明它们是 CH4 的重要来源。通常，对沉淀事件的低动力学和缺失反应表明对过程的理解很差，需要进一步研究。而事实证明它们是 CH4 的重要来源。通常，对沉淀事件的低动力学和缺失反应表明对过程的理解很差，需要进一步研究。