Louisiana Tech University, School of Biological Sciences, 1 Adams Blvd., Ruston, LA 71272, USA.
Virginia Tech, Department of Entomology, 170 Drillfield Drive, Blacksburg, VA 24061, USA.
Sci Total Environ. 2022 Feb 1;806(Pt 4):151392. doi: 10.1016/j.scitotenv.2021.151392. Epub 2021 Nov 2.
Terrestrial and freshwater secondary salinization is a global phenomenon arising partially from anthropogenic activities. How low-level direct (e.g., sodium exposure through irrigation runoff) or indirect (e.g., sodium exposure through sodium-enriched leaves as riparian plants uptake sodium that via senescence enters detrital systems) impacts detrital processes in riparia have received little attention. Based on the sodium ecosystem respiration hypothesis, we predicted low-level salinization of an inland mesic riparia would result in increased detrital processing and increased leachate dissolved organic carbon (DOC) and conductivity. Two riparian soil mesocosm experiments tested how low-level salinization affects leachate chemistry and conductivity and riparian decomposition rates and detritivore community structure: 1) direct low-level NaCl deposition in water (weekly additions of 300 ml of 0.05% NaCl or just HO (controls)), and 2) indirect low-level NaCl deposition through Na-enriched artificial litter (0.05% NaCl or just HO (controls)). After three months, leachate Na concentrations were 12-fold and 1.5-fold higher in Na-addition than control mesocosms for direct and indirect Na-addition experiments, respectively. Contrary to predictions, decomposition rate was 1.3-fold lower in indirect Na-addition than control mesocosms but invertebrate communities were similar. Decomposition rate did not differ in direct Na-addition experiments, and although invertebrate abundance was lower, diversity was 1.4-fold higher in Na-addition than control mesocosms. Leachate DOC did not differ between Na-addition and control mesocosms for either direct or indirect Na-addition experiments. This study adds to the growing evidence that even low-level Na addition can stress inland mesic terrestrial systems and demonstrates that even Na-enriched detritus alone can induce salt-stress in riparian soil systems. These results suggest that even low-level salinization of riparia can impact riparian ecosystem function and leachate chemistry through direct exposure and indirectly through Na-enriched detritus, a previously overlooked pathway.
陆生和淡水次生盐渍化是一种全球性现象，部分是由人为活动引起的。低水平的直接（例如，通过灌溉径流暴露于钠）或间接（例如，通过作为河岸植物吸收钠的富钠叶子暴露于钠，通过衰老进入碎屑系统）影响河岸碎屑过程的情况受到的关注很少。基于钠生态系统呼吸假说，我们预测内陆湿润河岸的轻度盐渍化将导致碎屑处理增加，并增加淋出液溶解有机碳（DOC）和电导率。两项河岸土壤中尺度实验测试了轻度盐渍化如何影响淋出液化学性质和电导率以及河岸分解速率和碎屑食性动物群落结构：1）直接在水中进行低水平 NaCl 沉积（每周添加 300ml 0.05%NaCl 或仅为 HO（对照）），以及 2）通过富钠人工凋落物进行间接低水平 NaCl 沉积（0.05%NaCl 或仅为 HO（对照））。三个月后，与对照中尺度实验相比，直接和间接添加 Na 实验中淋出液 Na 浓度分别高出 12 倍和 1.5 倍。与预测相反，间接添加 Na 的分解速率比对照中尺度实验低 1.3 倍，但无脊椎动物群落相似。直接添加 Na 的分解速率在实验中没有差异，尽管无脊椎动物丰度较低，但多样性在添加 Na 的中尺度实验中比对照高出 1.4 倍。直接或间接添加 Na 实验中，淋出液 DOC 均无差异。本研究增加了越来越多的证据表明，即使是低水平的 Na 添加也会对内陆湿润陆地系统造成压力，并表明即使是单独的富钠碎屑也会引起河岸土壤系统的盐胁迫。这些结果表明，即使是河岸的轻度盐渍化也可以通过直接暴露和通过富钠碎屑的间接途径影响河岸生态系统功能和淋出液化学性质，这是以前被忽视的途径。
