Department of Biology and Geology, University of Almería, Spain; Andalusian Centre for the Monitoring and Assessment of Global Change (CAESCG), University of Almería, Almería, Spain.
Andalusian Centre for the Monitoring and Assessment of Global Change (CAESCG), University of Almería, Almería, Spain; Department of Agronomy, University of Almería, Almería, Spain.
Sci Total Environ. 2022 Jun 20;826:154111. doi: 10.1016/j.scitotenv.2022.154111. Epub 2022 Feb 24.
Water availability controls the functioning of dryland ecosystems, driving a patchy vegetation distribution, unequal nutrient availability, soil respiration in pulses, and limited productivity. Groundwater-dependent ecosystems (GDEs) are acknowledged to be decoupled from precipitation, since their vegetation relies on groundwater sources. Despite their relevance to enhance productivity in drylands, our understanding of how different components of GDEs interconnect (i.e., soil, vegetation, water) remains limited. We studied the GDE dominated by the deep-rooted phreatophyte Ziziphus lotus, a winter-deciduous shrub adapted to arid conditions along the Mediterranean basin. We aimed to disentangle whether the groundwater connection established by Z. lotus will foster soil biological activity and therefore soil fertility in drylands. We assessed (1) soil and vegetation dynamics over seasons (soil CO efflux and plant activity), (2) the effect of the patchy distribution on soil quality (properties and nutrient availability), and soil biological activity (microbial biomass and mineralization rates) as essential elements of biogeochemical cycles, and (3) the implications for preserving GDEs and their biogeochemical processes under climate change effects. We found that soil and vegetation dynamics respond to water availability. Whereas soil biological activity promptly responded to precipitation events, vegetation functioning relies on less superficial water and responded on different time scales. Soil quality was higher under the vegetation patches, as was soil biological activity. Our findings highlight the importance of groundwater connections and phreatophytic vegetation to increase litter inputs and organic matter into the soils, which in turn enhances soil quality and decomposition processes in drylands. However, biogeochemical processes are jeopardized in GDEs by climate change effects and land degradation due to the dependence of soil activity on: (1) precipitation for activation, and (2) phreatophytic vegetation for substrate accumulation. Therefore, desertification might modify biogeochemical cycles by disrupting key ecosystem processes such as soil microbial activity, organic matter mineralization, and plant productivity.
水的可利用性控制着旱地生态系统的功能，导致植被分布不均匀、养分可利用性不均衡、土壤呼吸呈脉冲式以及生产力有限。依赖地下水的生态系统（GDE）被认为与降水无关，因为它们的植被依赖于地下水源。尽管它们对于提高旱地生产力具有重要意义，但我们对 GDE 不同组成部分（即土壤、植被、水）之间的相互作用的理解仍然有限。我们研究了由深根肉质旱生植物骆驼刺主导的 GDE，这是一种适应地中海盆地干旱条件的冬季落叶灌木。我们旨在阐明骆驼刺建立的地下水连接是否会促进土壤生物活性，从而提高旱地的土壤肥力。我们评估了（1）土壤和植被随季节的动态变化（土壤 CO 排放和植物活动），（2）斑块分布对土壤质量（性质和养分可利用性）和土壤生物活性（微生物生物量和矿化速率）的影响，这些是生物地球化学循环的基本要素，以及（3）在气候变化影响下保护 GDE 及其生物地球化学过程的意义。我们发现，土壤和植被动态对水的可利用性有响应。虽然土壤生物活性会迅速响应降水事件，但植被功能依赖于较不浅层的水，并在不同的时间尺度上响应。植被斑块下的土壤质量更高，土壤生物活性也是如此。我们的研究结果强调了地下水连接和肉质旱生植物的重要性，它们增加了枯枝落叶输入和有机物到土壤中的积累，从而提高了旱地的土壤质量和分解过程。然而，由于土壤活性依赖于（1）降水的激活和（2）肉质旱生植物的基质积累，气候变化影响和土地退化对 GDE 的生物地球化学过程构成了威胁。因此，荒漠化可能通过扰乱土壤微生物活性、有机质矿化和植物生产力等关键生态系统过程来改变生物地球化学循环。
