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Abstract: Fluorapatite-solubilizing bacteria were isolated from the hyphosphere of the ectomycorrhizal (ECM) fungus Wilcoxina sp., a dominant species in the Picea glauca (Moench) Voss rhizosphere. Hundreds of strains isolated from [...]

The rock weathering literature contains the hypothesis that case hardening exemplifies equifinality, where the same end state can be reached by many potential processes in an open system. We present analytical data from six different sites in the western USA to assess the hypothesis of equifinality. Case hardening can be produced on: (1) sandstone in Petrified Forest National Park, Arizona, from the addition of silica glaze, rock varnish and heavy-metal skins; (2) sandstone in Whoopup Canyon, Wyoming, from silica glaze that formed originally inside subsurface joints combined with externally applied iron film, silica glaze, and rock varnish; (3) welded tuff in Death Valley, California, from the accumulation of rock varnish and heavy metal skins of Mn and Fe; (4) sandstone in Sedona, Arizona, from the protective effects of rock varnish accretion and heavy metal skins of Mn and Fe; (5) basalt on the Big Island, Hawai'i, from the accumulation of silica glaze inside vesicles; and (6) sandstone at Point Reyes, California, from a lithobiont mat of fungi and lichen. Each developed the general form of a case-hardened shell, protecting the surface from erosion. In accordance with the hypothesis of equifinality, the processes that led to similar appearance differ., Introduction DIFFERENTIAL WEATHERING of rocks leads to varying degrees of resistivity of different rock types to erosion. Such differences in weathering provide a fundamental control on Earth's topography (Ollier 1984, [...]

Studies across a broad range of drainage basins have established a positive correlation between mean slope gradient and denudation rates. It has been suggested, however, that this relationship breaks down for catchments where slopes are at their threshold angle of stability because, in such cases, denudation is controlled by the rate of tectonic uplift through the rate of channel incision and frequency of slope failure. This mechanism is evaluated for the San Bernardino Mountains, California, a nascent range that incorporates both threshold hill slopes and remnants of pre-uplift topography. Concentrations of in situ-produced cosmogenic [sup.10]Be in alluvial sediments are used to quantify catchment-wide denudation rates and show a broadly linear relationship with mean slope gradient up to ~30[degrees]: above this value denudation rates vary substantially for similar mean slope gradients. We propose that this decoupling in the slope gradient-denudation rate relationship marks the emergence of threshold topography and coincides with the transition from transport-limited to detachment-limited denudation. The survival in the San Bernardino Mountains of surfaces formed prior to uplift provides information on the topographic evolution of the range, in particular the transition from slope-gradient-dependent rates of denudation to a regime where denudation rates are controlled by rates of tectonic uplift. This type of transition may represent a general model for the denudational response to orogenic uplift and topographic evolution during the early stages of mountain building. Keywords: cosmogenic nuclides, denudation, erosion rates, erosion control, orogenesis, San Bernardino Mountains.

The rate of weathering of feldspar, an abundant mineral, requires quantification to accurately estimate carbon dioxide fluxes over geological timescales. Weathered albite surfaces are sodium and aluminium depleted, and microtopography images were found to be consistent with dissolution occurring at specific surface sites.

An analysis of century-old marble tombstone slab weathering reveals that air pollution from high-sulfur coal, charcoal, space heating and arc smelting cause marble decay. A marble-damage function correlates tombstone weathering to the SO2 released from industrialized and urban areas in the US. Spatial correlation methods grade the various marble decay processes on the basis of importance.

In a process that takes from thousands to millions of years, tree roots in mountainous areas may be influencing C[O.sub.2] levels, and thus global temperatures, according to two recent studies. [...]

Minerals are destroyed after some time due to acidic and leaching conditions in soils and leave behind ghostly shapes with structures similar to original crystal. Secondary minerals form the substance of these mineral ghosts. The weathering process can be known by studying these remnants of minerals. Such studies show that weathering is not a linear process in space and time. Minerals that could develop during the weathering process can be known by studying crystal remains.