Soil formation and its implications for stabilization of soil organic matter in the riparian zone
Soil formation and its implications for stabilization of soil organic matter in the riparian zone
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DOI：
10.1016/j.catena.2015.11.010
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发表时间：
2016-04
期刊：
影响因子：
6.2
通讯作者：
Markus Graf‐Rosenfellner;A. Cierjacks;B. Kleinschmit;F. Lang
中科院分区：
文献类型：
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作者：
Markus Graf‐Rosenfellner;A. Cierjacks;B. Kleinschmit;F. Lang
河岸林地由不同的景观单元组成，具有不同的水文生态地貌条件，这反映在土壤和树种的分布上。这些条件是由洪水频率和持续时间、到河道的距离、海拔和水流速度决定的。这些环境驱动因素对土壤有机质(SOM)稳定性的影响尚未得到研究。因此，我们研究的目的是将土壤形成及其驱动因素与河岸泛滥平原森林土壤有机质的稳定过程联系起来。我们调查了奥地利维也纳附近多瑙河河岸带内的白蜡枫榆树冲积林带(AMEO站点)和柳杨冲积林带(WIP站点)中的两个地点的土壤和沉积物。根据质地、有机碳(OC)、氮、铁氧化物和土壤pH的含量对沉积物和土壤进行了表征。根据稳定过程和由此产生的有机质(OM)周转时间，采用密度分级法分离有机碳组分：自由轻组分(快速周转)、团聚体中的轻组分(中周转)和与矿物表面紧密结合的重组分(慢周转)。在这两个地点，土壤和沉积物特性反映了河岸带景观单元形成的水文生态立地条件：AMEO地点的土壤在细质沉积物持续沉积期间发育，而水流速度较低。随着土壤发育的不断深入，土壤有机碳含量随着土壤深度的增加而不断降低，主要来源于速效和中速周转的组分。因此，重质组分明显占优势，约占有机碳的90%。在WIP站点发现的随时间变化的洪水条件和发生的湍流导致土壤性质随着土壤深度的增加而不连续地变化。以前被大量沉积物掩埋的表土层似乎保持了典型的有机碳分级，表土层具有极高的轻组分OM(游离态和闭塞态)，占总有机碳的20%-40%。这些结果证实了AMEO场地的沉积和土壤形成是同时进行的。在WIP站点，这两个过程似乎与沉积和土壤形成的交替阶段无关。因此，在WIP地点形成的表土物质的频繁埋藏似乎能够保护这一部分活跃的泛滥平原的不稳定有机质组分。
Riparian woodlands consist of different landscape units characterized by different hydroecomorphological site conditions that are reflected in the distribution of soils and tree species. These conditions are determined by flooding frequency and duration, distance to river channels, elevation and water flow velocity. The influence of these environmental drivers on the stabilization of soil organic matter (SOM) has as yet not been investigated. Hence, the aim of our study is to link soil formation and its drivers with stabilizing processes of SOM in riparian floodplain forests. We investigated soils and sediments at two sites in the ash–maple–elm–oak alluvial forest zone (AMEO sites) and two sites in the willow-poplar alluvial forest zone (WiP sites) within the riparian zone of the Danube near Vienna (Austria). Sediments and soils were characterized based on texture, contents of organic carbon (OC), nitrogen, Fe oxides, and soil pH. Density fractionation was used to separate OC fractions in terms of stabilization process and resulting organic matter (OM) turnover time: the free light fraction (fast turnover), the light fraction occluded in aggregates (intermediate turnover) and the heavy fraction of OM associated tightly to mineral surfaces (slow turnover).At both sites, soil and sediment properties reflect the hydroecomorphological site conditions for formation of the landscape units in the riparian zone: Soils at AMEO sites develop during constant deposition of fine-textured sediment while water flow velocity is low. Progressing soil development causes a continuous decrease in OC content with increasing soil depth, mainly from fractions with fast and intermediate turnover. As a consequence the heavy fraction clearly dominates with around 90% of OC. Temporally variable flooding conditions with occurring turbulences found at WiP sites result in a discontinuous change of soil properties with increasing soil depth. Former topsoil horizons buried by huge amounts of sediments seem to keep the OC fractionation typical for topsoil horizons with extraordinarily high amounts of light fraction OM (free and occluded) representing 20–40% of total OC. The presented results confirm that sedimentation and soil formation are simultaneous processes at AMEO sites. At WiP sites both processes seem uncoupled with alternate phases of sedimentation and soil formation. Thus, the frequent burial of topsoil material formed at WiP sites seems to enable the conservation of unstable organic matter fractions at this part of active floodplains.