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Controls on heterotrophic soil respiration and carbon cycling in geochemically distinct African tropical forest soils
Soil ( IF 6.8 ) Pub Date : 2021-02-04 , DOI: 10.5194/soil-2020-96 Benjamin Bukombe , Peter Fiener , Alison M. Hoyt , Sebastian Doetterl
Soil ( IF 6.8 ) Pub Date : 2021-02-04 , DOI: 10.5194/soil-2020-96 Benjamin Bukombe , Peter Fiener , Alison M. Hoyt , Sebastian Doetterl
Abstract. Heterotrophic soil respiration is an important component of the global terrestrial carbon (C) cycle, driven by environmental factors acting from local to continental scales. For tropical Africa, these factors and their interactions remain largely unknown. Here, using samples collected along strong topographic and geochemical gradients in the East African Rift Valley, we study how soil chemistry and soil fertility, derived from the geochemical composition of soil parent material, can drive soil respiration even after many millennia of weathering and soil development. To address the drivers of soil respiration, we incubated soils from three regions with contrasting geochemistry (mafic, felsic, and mixed sedimentary) sampled along slope gradients. For three soil depths, we measured the potential maximum heterotrophic respiration under stable environmental conditions as well as the radiocarbon content (Δ14C) of the bulk soil and respired CO2. We found that soil microbial communities were able to mineralize C from fossil as well as other poor quality C sources under laboratory conditions representative of tropical topsoils. Furthermore, despite similarities in terms of climate, vegetation, and the size of soil C stocks, soil respiration showed distinct patterns with soil depth and parent material geochemistry. The topographic origin of our samples was not a main determinant of the observed respiration rates and Δ14C. In situ, however, soil hydrological conditions likely influence soil C stability by inhibiting decomposition in valley subsoils. Our study shows that soil fertility conditions are the main determinant of C stability in tropical forest soils. Further, in the presence of organic carbon sources of poor quality or the presence of strong mineral related C stabilization, microorganisms tend to discriminate against these sources in favor of more accessible forms of soil organic matter as energy sources, resulting in a slower rate of C cycling. Our results demonstrate that even in deeply weathered tropical soils, parent material has a long-lasting effect on soil chemistry that can influence and control microbial activity, the size of subsoil C stocks, and the turnover of C in soil. Soil parent material and its lasting control on soil chemistry need to be taken into account to understand and predict C stabilization and rates of C cycling in tropical forest soils.
中文翻译:
地球化学独特的非洲热带森林土壤中异养土壤呼吸和碳循环的控制
摘要。异养土壤呼吸是全球陆地碳(C)循环的重要组成部分,受局部到大陆尺度的环境因素驱动。对于热带非洲来说,这些因素及其相互作用仍然未知。在这里,我们使用在东非大裂谷沿强烈的地形和地球化学梯度收集的样本,研究了由土壤母体物质的地球化学成分得出的土壤化学和土壤肥力如何即使在经历了几千年的风化和土壤发育后仍能促进土壤呼吸。为了解决土壤呼吸的驱动因素,我们将三个地区的土壤与沿斜坡梯度采样的地球化学对比(镁铁质,长英质和混合沉积)进行了温育。对于三个土壤深度,14 C)的土壤和呼吸的CO 2。我们发现,在代表热带表土的实验室条件下,土壤微生物群落能够从化石以及其他劣质碳源中矿化碳。此外,尽管在气候,植被和土壤碳储量的大小方面相似,但土壤呼吸在土壤深度和母质地球化学方面表现出截然不同的模式。我们的样品的产地地形不是观察呼吸速率和Δ的主要决定因素14C.然而,就地而言,土壤水文条件可能会通过抑制山谷底土的分解而影响土壤C的稳定性。我们的研究表明,土壤肥力条件是热带森林土壤碳稳定性的主要决定因素。此外,在存在质量较差的有机碳源或与矿物质有关的强碳稳定性的情况下,微生物往往会歧视这些碳源,而倾向于使用更易获得的土壤有机质形式作为能源,导致碳的速率降低循环。我们的结果表明,即使在深度风化的热带土壤中,母体材料也对土壤化学具有长期影响,可以影响和控制微生物活性,土壤中C碳储量的大小以及土壤中C的周转率。
更新日期:2021-02-04
中文翻译:
地球化学独特的非洲热带森林土壤中异养土壤呼吸和碳循环的控制
摘要。异养土壤呼吸是全球陆地碳(C)循环的重要组成部分,受局部到大陆尺度的环境因素驱动。对于热带非洲来说,这些因素及其相互作用仍然未知。在这里,我们使用在东非大裂谷沿强烈的地形和地球化学梯度收集的样本,研究了由土壤母体物质的地球化学成分得出的土壤化学和土壤肥力如何即使在经历了几千年的风化和土壤发育后仍能促进土壤呼吸。为了解决土壤呼吸的驱动因素,我们将三个地区的土壤与沿斜坡梯度采样的地球化学对比(镁铁质,长英质和混合沉积)进行了温育。对于三个土壤深度,14 C)的土壤和呼吸的CO 2。我们发现,在代表热带表土的实验室条件下,土壤微生物群落能够从化石以及其他劣质碳源中矿化碳。此外,尽管在气候,植被和土壤碳储量的大小方面相似,但土壤呼吸在土壤深度和母质地球化学方面表现出截然不同的模式。我们的样品的产地地形不是观察呼吸速率和Δ的主要决定因素14C.然而,就地而言,土壤水文条件可能会通过抑制山谷底土的分解而影响土壤C的稳定性。我们的研究表明,土壤肥力条件是热带森林土壤碳稳定性的主要决定因素。此外,在存在质量较差的有机碳源或与矿物质有关的强碳稳定性的情况下,微生物往往会歧视这些碳源,而倾向于使用更易获得的土壤有机质形式作为能源,导致碳的速率降低循环。我们的结果表明,即使在深度风化的热带土壤中,母体材料也对土壤化学具有长期影响,可以影响和控制微生物活性,土壤中C碳储量的大小以及土壤中C的周转率。