Louzada Rômullo Oliveira, Bergier Ivan, McGlue Michael M, de Oliveira Roque Fabio, Rasbold Giliane, Domingos-Luz Leandro, Lo Edward, Assine Mario Luis
Federal University of Mato Grosso do Sul, Campo Grande, MS, Brazil; Environmental Institute of Mato Grosso do Sul, Campo Grande, MS, Brazil.
Embrapa Digital Agriculture, Campinas, SP, Brazil.
Sci Total Environ. 2024 May 20;926:172127. doi: 10.1016/j.scitotenv.2024.172127. Epub 2024 Apr 2.
River avulsions drive important changes in the Pantanal wetlands, owing to their role in the hydro-sedimentology of the region. Although relevant to numerous ecosystem services, few studies have analyzed the influence of river avulsions on soil fertility in the Pantanal. Here, we use the largest ongoing avulsion in the Taquari River (Caronal region) to evaluate the effects on soil fertility, considering two factors: avulsion stage (1) and aquatic-terrestrial succession (2). Since both factors are influenced by macrophyte abundance, an incident map was created through tasseled cap indices from Sentinel 2 images to guide sampling efforts in flooded soils. The mapped area was split into two zones of alluvial processes, the first from the apex of the Caronal lobe corresponding to the Taquari River megafan (TRM), and the second as the distal Paraguay River floodplain (PRF). Soil macro- and micronutrient levels were evaluated from 42 surface samples (0-0.2 m) distributed across the two alluvial process zones. The macrophyte map's overall accuracy (OA) was analyzed by a confusion matrix using the Sentinel 2 imagery. Finally, we used Random Forest regressions to determine the influence of response variables on soil attributes, including tassel indices, distance from the Caronal crevasse, macrophyte density, and an existing soil fertility map. The macrophyte map obtained an OA of 93 %. Some parameters such as pH (r = -0.62; R2 = 0.57), effective cation exchange capacity (r = -0.49; R2 = 0.79), Mn (r = -0.71; R2 = 0.6), Zn (r = -0.69; R2 = 0.54), and base saturation (r = -0.7; R2 = 0.93) were influenced by the distance or level of maturation of the avulsion stage in the TRM. Our scattering of soil collections was insufficient to test the terrestrialization hypothesis (2). The study results show that river channel avulsions influence the accumulation of mineral and organic nutrients in tropical floodplain soils, which has implications for fertility and biodiversity.
由于河流改道在该地区水沙学中所起的作用，它推动了潘塔纳尔湿地的重要变化。尽管河流改道与众多生态系统服务相关，但很少有研究分析其对潘塔纳尔湿地土壤肥力的影响。在此，我们利用塔夸里河（卡罗纳尔地区）正在发生的最大规模改道来评估对土壤肥力的影响，考虑两个因素：改道阶段（1）和水陆演替（2）。由于这两个因素都受大型植物丰度的影响，通过哨兵2号影像的缨帽变换指数创建了一幅影像图，以指导对淹水土壤的采样工作。测绘区域被划分为两个冲积过程区，第一个区从卡罗纳尔河叶的顶点开始，对应塔夸里河巨型扇（TRM），第二个区是巴拉圭河下游泛滥平原（PRF）。从分布在两个冲积过程区的42个表层样本（0 - 0.2米）评估土壤大量和微量养分水平。利用哨兵2号影像通过混淆矩阵分析大型植物影像图的总体精度（OA）。最后，我们使用随机森林回归来确定响应变量对土壤属性的影响，包括缨帽指数、距卡罗纳尔决口的距离、大型植物密度以及现有的土壤肥力图。大型植物影像图的总体精度为93%。一些参数，如pH值（r = -0.62；R2 = = 0.57）、有效阳离子交换容量（r = -0.49；R2 = 0.79）、锰（r = -0.71；R2 = 0.6）、锌（r = -0.69；R2 = 0.54）和碱基饱和度（r = -0.7；R2 = 0.93）受TRM改道阶段的距离或成熟程度影响。我们采集的土壤样本分布不足以检验陆地化假说（2）。研究结果表明，河道改道影响热带泛滥平原土壤中矿物质和有机养分的积累，这对土壤肥力和生物多样性具有重要意义。
