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

这项研究将调查北美中部大平原和南非大草原草原生态系统中生物硅(植物来源的二氧化硅)沿气候和地质梯度的数量和化学。将确定影响不同地理多样性草原生态系统中生物硅的生产、储存和化学行为的因素。此外，还将评估草原放牧和火烧对生物硅的影响。陆地上二氧化硅的生产、移动和循环与全球碳循环密切相关。在海洋中，某些微小的海藻(硅藻)是控制二氧化硅分布的主要因素，而且由于其光合作用活性，在控制大气中的二氧化碳浓度方面也发挥着重要作用。生物控制在陆地环境中二氧化硅循环的重要性鲜为人知，但可能是由于植物和土壤中生物成因二氧化硅的形成和储存，特别是在草原上。最近的估计表明，陆地植被对生物成因二氧化硅的全球吸收与海洋系统生物活跃部分的储存数量不相上下。更重要的是，陆地系统中最大的生物成因硅储藏库不是存在于生物量中，而是存在于土壤中，特别是草原土壤中。生物成因二氧化硅在植物材料死亡和分解后积累在地下。这一巨大的草原生物成因硅储藏库可能受到全球变化因素的很大影响，对全球生物地球化学循环产生未知的后果。

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.