Earthquake-induced structural deformations enhance long-term solute fluxes from active volcanic systems.

Evidence for relationships between seismotectonic activity and dissolved weathering fluxes remains limited. Motivated by the occurrence of new springs emerging after the 2016 Kumamoto earthquake and supported by historical groundwater data, this study focuses on the long-term effect of near-surface structural deformation on the contribution of deep, highly saline fluids to the solute fluxes from the Aso caldera, Kyushu, Japan. Available hydrologic and structural data suggest that concentrated, over-pressured groundwaters migrate to the surface when new hydraulic pathways open during seismic deformation. These new springs have a hydrochemical fingerprint (including δDH2O, δ18OH2O, δ7Li, δ11B, δ18OSO4, and δ34SSO4) indistinguishable from long-established confined groundwater that likely reflects a mixture of infiltrated meteoric water with high-sulfate hydrothermal fluids. A comparison of historical hydrochemistry data and patterns of past seismicity suggests that discharge of deep fluids is associated with similar deformation structures to those observed during the Kumamoto earthquake, and that seismic activity plays an important role over historic timescales in delivering the majority of the solutes to the caldera outlet, sustaining fluxes that are amongst the world's highest. This upwelling mechanism might be relevant for other systems too, and could contribute to the over-proportional share of active volcanic areas in global weathering fluxes.

Increasing biomass demand enlarges negative forest nutrient budget areas in wood export regions.

Energy production from biomass is one of the adopted strategies in different European countries to limit global warming to within the 1.5-2° targets after the 2015 UN climate agreement. This will motivate enhanced forest harvest rates and whole tree harvest to supply the increasing biomass demand. Negative nutrient budgets for certain timberland areas where geogenic nutrient supply cannot cope with harvesting rates will be one consequence. A spatially explicit analysis for a U.S. timberland area of 33,570 km2 reveals that for a minimum nutrient loss and supply scenario, negative nutrient budgets occur in 17, 20, 16, and almost 94% of the studied areas for Ca, K, Mg, and P, respectively. For a maximum nutrient loss (considering intensive harvesting) and supply assumptions, the affected areas increase to 50, 57, 45 and 96% for Ca, K, Mg, and P, respectively. In general, atmospheric nutrient deposition is of minor importance for the high weathering supply cases. Increasing global woody biomass demand may cause additional pressure on forested ecosystems, enlarging negative nutrient budget areas. If woody biomass demand rises, strategies to counterbalance nutrient gaps might be needed, for example, by preparing harvested areas with rock products, designed to replenish growth limiting nutrients, and/or implementing forest management strategies to minimize nutrient export.