Fikri Mehdi, Joulian Catherine, Motelica-Heino Mikael, Norini Marie-Paule, Hellal Jennifer
BRGM, DEPA/GME, Orléans, France.
ISTO, UMR 7327, CNRS-Université d'Orléans-Brgm, Orléans, France.
Front Microbiol. 2021 Dec 22;12:727468. doi: 10.3389/fmicb.2021.727468. eCollection 2021.
In the context of climate change and biodiversity loss, rehabilitation of degraded urban soils is a means of limiting artificialization of terrestrial ecosystems and preventing further degradation of soils. Ecological rehabilitation approaches are available to reinitiate soil functions and enhance plant development. However, little is known about the long-term stability of rehabilitated soils in terms of soil functions when further natural or anthropogenic perturbations occur. Based on rehabilitated urban soils, the present study sought to evaluate the resistance and resilience of soil functions linked to carbon cycling and phosphate dynamics in addition to nitrogen cycling and related microbial communities after a heat and drought stress. A laboratory experiment was conducted in microcosms under controlled temperature conditions, with four contrasted soils collected from a rehabilitated urban brownfield; an initial, non-rehabilitated soil (IS), a technosol with a high organic matter level (HO), and two technosols with less organic matter (LO1 and LO2), together with their respective controls (no stress). Changes in potential denitrification (PDR), nitrification (PNR) rates, and their interactive relationships with soil microbial activities and soil physicochemical properties were determined following a combined heat (40°C) and drought stress period of 21 days. Measurements were carried out immediately after the stress (resistance), and then also 5, 30, and 92 days after soil rewetting at 60% water holding capacity (resilience). Microbial activities involved in soil functions such as carbon cycling and phosphate dynamics proved to be of low resistance in all soils except for IS; however, they were resilient and recovered rapidly after rewetting. On the other hand, the microbial activities and gene abundances that were measured in relation to nitrogen cycling processes showed that for denitrification, activities were more rapidly resilient than gene abundances whereas for nitrification the activities and gene abundances were resilient in the same way. Results suggest that, unless the soils contain high amounts of organic matter, microbial communities in imported soils can be more vulnerable to environmental pressures such as drought and heat than communities already present. This should be considered when rehabilitating degraded soils.
在气候变化和生物多样性丧失的背景下，退化城市土壤的修复是限制陆地生态系统人工化以及防止土壤进一步退化的一种手段。有生态修复方法可用于重新启动土壤功能并促进植物生长。然而，对于修复后的土壤在遭受进一步自然或人为干扰时土壤功能的长期稳定性，人们了解甚少。基于修复后的城市土壤，本研究旨在评估热旱胁迫后，除了氮循环及相关微生物群落外，与碳循环和磷动态相关的土壤功能的抗性和恢复力。在可控温度条件下的微观世界中进行了一项实验室实验，从一个修复后的城市棕地采集了四种对比土壤；一种初始的未修复土壤（IS）、一种有机质含量高的技术土壤（HO）以及两种有机质含量较低的技术土壤（LO1和LO2），并设置了各自的对照（无胁迫）。在经历21天的联合热（40°C）旱胁迫期后，测定了潜在反硝化（PDR）、硝化（PNR）速率及其与土壤微生物活动和土壤理化性质的交互关系。在胁迫后立即（抗性）进行测量，然后在土壤以60%持水量重新湿润后的第5天、30天和92天也进行测量（恢复力）。除IS外，参与碳循环和磷动态等土壤功能的微生物活动在所有土壤中抗性都较低；然而，它们具有恢复力，重新湿润后迅速恢复。另一方面，与氮循环过程相关的微生物活动和基因丰度表明，对于反硝化，活动的恢复力比基因丰度更快，而对于硝化，活动和基因丰度以相同方式具有恢复力。结果表明，除非土壤含有大量有机质，否则外来土壤中的微生物群落可能比已存在的群落更容易受到干旱和高温等环境压力的影响。在修复退化土壤时应考虑这一点。
