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Soil-atmosphere exchange of nitrous oxide, nitric oxide, methane, and carbon dioxide in logged and undisturbed forest in the Tapajos National Forest, Brazil.

机译:巴西塔帕霍斯国家森林的原木和未受干扰的森林中一氧化二氮,一氧化氮,甲烷和二氧化碳的土壤-大气交换。

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摘要

Selective logging is an extensive land use in the Brazilian Amazon region. The soil?atmosphere fluxes of nitrous oxide (N2O), nitric oxide (NO), methane (CH4), and carbon dioxide (CO2) are studied on two soil types (clay Oxisol and sandy loam Ultisol) over two years (2000?01) in both undisturbed forest and forest recently logged using reduced impact forest management in the Tapajos National Forest, near Santarem, Para, Brazil. In undisturbed forest, annual soil?atmosphere fluxes of N2O (mean ± standard error) were 7.9 ± 0.7 and 7.0 ± 0.6 ng N cm?2 h?1 for the Oxisol and 1.7 ± 0.1 and 1.6 ± 0.3 ng N cm?2 h?1 for the Ultisol for 2000 and 2001, respectively. The annual fluxes of NO from undisturbed forest soil in 2001 were 9.0 ± 2.8 ng N cm?2 h?1 for the Oxisol and 8.8 ± 5.0 ng N cm?2 h?1 for the Ultisol. Consumption of CH4 from the atmosphere dominated over production on undisturbed forest soils. Fluxes averaged ?0.3 ± 0.2 and ?0.1 ± 0.9 mg CH4 m?2 day?1 on the Oxisol and ?1.0 ± 0.2 and ?0.9 ± 0.3 mg CH4 m?2 day?1 on the Ultisol for years 2000 and 2001. For CO2 in 2001, the annual fluxes averaged 3.6 ± 0.4 ?mol m?2 s?1 on the Oxisol and 4.9 ± 1.1 ?mol m?2 s?1 on the Ultisol. We measured fluxes over one year each from two recently logged forests on the Oxisol in 2000 and on the Ultisol in 2001. Sampling in logged areas was stratified from greatest to least ground disturbance covering log decks, skid trails, tree-fall gaps, and forest matrix. Areas of strong soil compaction, especially the skid trails and logging decks, were prone to significantly greater emissions of N2O, NO, and especially CH4. In the case of CH4, estimated annual emissions from decks reached extremely high rates of 531 ± 419 and 98 ± 41 mg CH4 m?2 day?1, for Oxisol and Ultisol sites, respectively, comparable to wetland emissions in the region. We calculated excess fluxes from logged areas by subtraction of a background forest matrix or undisturbed forest flux and adjusted these fluxes for the proportional area of ground disturbance. Our calculations suggest that selective logging increases emissions of N2O and NO from 30% to 350% depending upon conditions. While undisturbed forest was a CH4 sink, logged forest tended to emit methane at moderate rates. Soil?atmosphere CO2 fluxes were only slightly affected by logging. The regional effects of logging cannot be simply extrapolated based upon one site. We studied sites where reduced impact harvest management was used while in typical conventional logging ground damage is twice as great. Even so, our results indicate that for N2O, NO, and CH4, logging disturbance may be as important for regional budgets of these gases as other extensive land-use changes in the Amazon such as the conversion of forest to cattle pasture.
机译:选择性伐木是巴西亚马逊地区广泛的土地利用。在两年(2000?01)的两种土壤类型(粘土Oxisol和砂壤土Ultisol)上研究了一氧化二氮(N2O),一氧化氮(NO),甲烷(CH4)和二氧化碳(CO2)的土壤大气通量。 )在巴西帕拉州圣塔伦附近的塔帕霍斯国家森林中,在未受干扰的森林和最近使用减少影响的森林管理方式伐木的森林中。在未受干扰的森林中,Oxisol的年土壤气态通量N2O(平均值±标准误差)分别为7.9±0.7和7.0±0.6 ng N cm?2 h?1,以及1.7±0.1和1.6±0.3 ng N cm?2 h Ultisol在2000年和2001年分别为?1。 2001年,Oxisol的未扰动森林土壤NO的年通量为9.0±2.8 ng N cm?2 h?1,Ultisol为8.8±5.0 ng N cm?2 h?1。在未受干扰的森林土壤上,大气中的CH4消耗量占生产总量的主导地位。 2000年和2001年,Oxisol的通量平均为?0.3±0.2和?0.1±0.9 mg CH4 m?2 day?1,Ultisol的通量平均为?1.0±0.2和?0.9±0.3 mg CH4 m?2 day?1。在2001年的二氧化碳中,Oxisol的年通量平均为3.6±0.4μmolm?2 s?1,Ultisol的年通量平均为4.9±1.1μmolm?2 s?1。我们分别测量了2000年的Oxisol和2001年的Ultisol上两个最近采伐的森林在一年中的通量。对采伐区域的采样从最大到最小地面干扰进行了分层,覆盖了原木甲板,滑道,树木倒空和森林矩阵。土壤密实性强的地区,特别是滑道和伐木平台,容易产生大量的N2O,NO,尤其是CH4排放。就CH4而言,Oxisol和Ultisol站点的甲板每年估计排放量分别达到531±419和98±41 mg CH4 m?2·day?1的极高比率,与该地区的湿地排放量相当。我们通过减去背景森林矩阵或未扰动森林通量来计算伐木区的多余通量,并针对地面扰动的比例面积调整这些通量。我们的计算表明,根据条件的不同,选择性测井会将N2O和NO的排放量从30%增加到350%。虽然未受干扰的森林是CH4汇,但砍伐的森林倾向于以中等速率排放甲烷。伐木对土壤大气CO2通量的影响很小。不能简单地根据一个站点推断测井的区域影响。我们研究了使用减少影响采伐管理的地点,而在典型的常规伐木中,地面破坏的损失是其两倍。即便如此,我们的结果表明,对于N2O,NO和CH4,伐木扰动对于这些气体的区域预算而言可能与亚马逊地区其他广泛的土地利用变化(例如从森林转变为牧场)一样重要。

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