School of Molecular and Life Sciences, Curtin University, Kent Street, Bentley, WA 6102, Australia; EcoHealth Network, 1330 Beacon St, Suite 355a, Brookline, MA 02446, United States.
School of Biological Sciences, The University of Western Australia, 35 Stirling Highway, Perth, WA 6009, Australia.
Sci Total Environ. 2021 May 10;768:145373. doi: 10.1016/j.scitotenv.2021.145373. Epub 2021 Feb 2.
Rates of tailings production and deposition around the world have increased markedly in recent decades, and have grown asynchronously with safe and environmentally suitable solutions for their storage. Tailings are often produced in regions harbouring biodiverse native plant communities adapted to old, highly-weathered soils. The highly-altered edaphic conditions of tailings compared with natural soils in these areas will likely select against many locally endemic plant species, making phytostabilisation, rehabilitation or ecological restoration of these landforms challenging.
We established four substrate cover composition treatments on a dry-stacked magnetite tailings storage facility in semi-arid Western Australia, representative of standard industry practices for rehabilitating or restoring post-mining landforms in the region. Plots were seeded with a selection of locally native plant species and monitored for five years to determine whether different substrate cover treatments yielded different edaphic conditions (soil moisture, substrate surface temperature and substrate chemistry) and influenced soil development and the success of native vegetation establishment.
No vegetation established from seeds on unamended tailings with no surface cover, and substrate chemistry changed minimally over five years. In contrast, rock-containing surface covers allowed establishment of up to 11 native plant species from broadcast seeds at densities of ca. 1.5 seedlings m, and up to 3.5 seedlings m of five native pioneer chenopods from capture of wind-dispersed seeds from surrounding undisturbed native vegetation. Greater vegetation establishment in rock-containing surface covers resulted from increased heterogeneity (e.g., lower maximum soil temperature, greater water capture and retention, surface microtopography facilitating seed capture and retention, more niches for seed germination). Soil development and bio-weathering occurred most rapidly under the canopy of native pioneer plants on rock-containing surface covers, particularly increases in organic carbon, total nitrogen, and organo-bound aluminium and iron.
Seed germination and seedling survival on tailings were limited by extreme thermal and hydrological conditions and a highly-altered biogeochemical environment. The design of surface cover layers appears crucial to achieving closure outcomes on tailings landforms, and designs should prioritise increasing surface heterogeneity through the incorporation of rock or other structure-improving amendments to assist the establishment of pioneer vegetation.
近几十年来，全球尾矿产量和堆积量显著增加，且与安全且环境适宜的尾矿储存解决方案不同步增长。尾矿通常在拥有适应旧、高度风化土壤的生物多样性本地植物群落的地区产生。与这些地区的天然土壤相比，尾矿的高度改变的土壤条件可能不利于许多本地特有植物物种，使得这些地貌的植物稳定、修复或生态恢复具有挑战性。
我们在西澳大利亚半干旱地区的一个干堆磁铁矿尾矿储存设施上建立了四种基质覆盖组成处理，代表了该地区修复或恢复矿山后地貌的标准工业实践。这些地块播种了一些本地特有植物物种，并进行了五年监测，以确定不同的基质覆盖处理是否产生不同的土壤条件（土壤湿度、基质表面温度和基质化学），并影响土壤发育和本地植被的建立。
未经改良的尾矿上没有表面覆盖物且没有种子，没有植被从种子中建立，且五年内基质化学变化极小。相比之下，含有岩石的表面覆盖物允许从广播种子中建立多达 11 种本地植物物种，密度约为 1.5 株/平方米，从周围未受干扰的本地植被中随风传播的种子中捕获的五种本地先锋藜科植物的密度可达 3.5 株/平方米。含有岩石的表面覆盖物中更多的植被建立是由于增加了异质性（例如，最低土壤温度更高、水捕获和保留更多、表面微地形有利于种子捕获和保留、更多种子萌发的生境）。在含有岩石的表面覆盖物下，原生先锋植物的树冠下，土壤发育和生物风化发生得最快，特别是有机碳、总氮以及有机结合的铝和铁的增加。
种子萌发和幼苗存活受到极端热和水文条件以及高度改变的生物地球化学环境的限制。表面覆盖层的设计似乎对实现尾矿地貌的封闭结果至关重要，设计应优先通过掺入岩石或其他结构改良剂来增加表面异质性，以协助先锋植被的建立。
