Genesis and soil environmental implications of intact in-situ rhizoliths in dunes of the Badain Jara

• 作者: Qingfeng Sun Kazem Zamanian Arnaud Huguet Omid Bayat Hong Wang Hanan S. Badawy
• 来源期刊: 地球化学学报(英文）
• 学科: 地球科学
• 关键词: Rhizoliths Calcification Leptic regosols Artemisia roots Decomposition Soil moisture
• 年，卷（期）: 2023,（5）
• 页码范围: 811-822
• 页数: 11页
• 语种: 中文
• DOI: 10.1007/s11631-022-00543-0

摘要

Desert rhizoliths are generally found as weathered, broken and scattered samples on dune field surface, but rarely insitu in their initial states buried under the soil of desert in the Badain Jaran Desert, northwest China. This study offers an assessment of the morphological, mineralogical, and chemical properties of intact and in-situ rhizoliths found in soils of swales and depressions among dune chains. The characteristics of these rare and precious objects were assessed using optical polarizing microscopy, cathodoluminescence, scanning electronic microscopy, radiocarbon dating, and stable isotopic analyses, providing the opportunity for discussion of the rhizolith formation mechanisms and associated environmental conditions. Field and laboratory investigations showed that the in-situ intact rhizoliths were formed only in the places where Artemisia shrubs are living, and the remaining root relicts within rhizoliths belong to this species. The spatial distribution of rhizoliths also suggested that low topographic positions on a landscape provided soil moisture, and redox environments favored rhizolith formation. A semi-closed redox environment in the subsoil at swales and depressions, where water is always present, along with the sandy soil texture, facilitated fast water percolation to deeper depths and condensation. Such a soil environment not only provides water for Artemisia growth, but also for the weathering of minerals such as felspars and calcite from primary carbonates, and for the decomposition of root relicts. Furthermore, harsh climatic conditions, such as strong winds and solar radiation, led to water evaporation through dead root channels and triggered the calcification along the root relicts. The entrapped lithogenic carbonates and to a lesser extent the decomposition of Artemisia roots provided the carbon sources for the rhizoliths formation, while the weathering of soil minerals, particularly feldspars and carbonates, was the main source of Ca.