COLLABORATIVE RESEARCH: Ecological Controls on Biogenic Silica in Grasslands - The Role of Long-term Fire and Grazing History on Two Continents

这项研究将调查生物硅（植物来源的二氧化硅）的数量和化学沿着气候和地质梯度在草原生态系统的北美中部大平原和南非的稀树草原。影响生物硅的生产，存储和化学行为在地理上不同的草地生态系统的因素将被确定。 此外，放牧和火灾在草原上的生物硅的影响将进行评估。 二氧化硅的陆地生产、移动和循环与全球碳循环密切相关。 在海洋中，某些微小的海洋藻类（硅藻）是二氧化硅分布的主要控制者，由于它们的光合作用活性，它们在控制大气CO2浓度方面也发挥着重要作用。 在陆地环境中的二氧化硅循环的生物控制的重要性是鲜为人知的，但可能的结果从植物和土壤中，特别是在草原的生物硅的形成和存储。最近的估计表明，全球陆地植被对生物硅的吸收量与海洋系统生物活性部分储存的数量相当。更重要的是，在陆地系统中最大的水库生物硅驻留在生活生物量，但在土壤中，特别是草原土壤。 生物硅在植物材料死亡和分解时在地下积累。 草原中生物硅的巨大储存库可能受到全球变化因素的巨大影响，对全球地球化学循环的影响尚不清楚。

This research will investigate the quantities and chemistry of biogenic Si (plant-derived silica) along climatic and geologic gradients in grassland ecosystems of the central Great Plains of North America and the savannas of the South Africa. Factors that affect the production, storage, and chemical behavior of biogenic Si in geographically diverse grassland ecosystems will be identified. Furthermore, the influence of grazing and fire in grasslands on biogenic Si will be assessed. The terrestrial production, movement and cycling of silica is closely linked to the global carbon cycle. In the oceans, certain minute marine algae (diatoms) are a major control on the distribution of silica and also play a major role in controlling atmospheric CO2 concentration due to their photosynthetic activity. The importance of biological controls on silica cycling in the terrestrial environment is much less well known, but likely results from the formation and storage of biogenic silica in plants and soils, particularly in grasslands. Recent estimates suggest that the global uptake of biogenic silica by terrestrial vegetation rivals quantities stored in the biologically active portions of the ocean systems. More importantly, the largest reservoir of biogenic Si in terrestrial systems resides not in living biomass but in soils and, in particular, grassland soils. Biogenic silica accumulates belowground upon death and decomposition of plant materials. This large reservoir of biogenic Si in grasslands may be greatly influenced by global change factors, with unknown consequences for global biogeochemical cycles.