A statistical evaluation of the origin of cypress domes in Florida

© 2020 Elsevier B.V. Two competing explanations exist for the origin of one type of karstic landform found in Florida called the cypress dome. One explanation relies on complex ecological feedbacks stemming from nutrient cycling suggesting biota contribute more significantly to processes of landscape evolution in Florida than anywhere else in the world. The second explanation is that the landforms are sinkholes that completely preclude the biological explanation while fitting more parsimoniously with the surrounding geological narrative. This work puts forward geostatistical analyses and a model linking the landforms to sinkholes, thus bolstering the geological explanation for origin of the landform. Satellite imagery of sinkholes occurring in limestone from locations spanning the planet was analyzed. Measurements of globally distributed limestone sinkhole surface areas are best characterized by an exponential distribution indicating sinkhole formation is robust to starting conditions (i.e., climate, tectonics). This observation is supported by an analysis of sinkhole geometry and geospatial dispersion. This demonstrates the geospatial parameters space for globally distributed groups of sinkholes forming in limestone are statistically indistinguishable despite sinkhole formation in different climates, tectonic regimes, and at different times. Employing this observation as a tool, sinkholes are directly compared to the cypress domes in Florida and are found to be statistically indistinguishable. From the striking similarity in spatial parameter spaces in conjunction with the geologic history of the area, it is interpreted that these landforms originate through geologic, not biologic, processes

A statistical evaluation of the origin of cypress domes in Florida

Two competing explanations exist for the origin of one type of karstic landform found in Florida called the cypress dome. One explanation relies on complex ecological feedbacks stemming from nutrient cycling suggesting biota contribute more significantly to processes of landscape evolution in Florida than anywhere else in the world. The second explanation is that the landforms are sinkholes that completely preclude the biological explanation while fitting more parsimoniously with the surrounding geological narrative. This work puts forward geostatistical analyses and a model linking the landforms to sinkholes, thus bolstering the geological explanation for origin of the landform. Satellite imagery of sinkholes occurring in limestone from locations spanning the planet was analyzed. Measurements of globally distributed limestone sinkhole surface areas are best characterized by an exponential distribution indicating sinkhole formation is robust to starting conditions (i.e., climate, tectonics). This observation is supported by an analysis of sinkhole geometry and geospatial dispersion. This demonstrates the geospatial parameters space for globally distributed groups of sinkholes forming in limestone are statistically indistinguishable despite sinkhole formation in different climates, tectonic regimes, and at different times. Employing this observation as a tool, sinkholes are directly compared to the cypress domes in Florida and are found to be statistically indistinguishable. From the striking similarity in spatial parameter spaces in conjunction with the geologic history of the area, it is interpreted that these landforms originate through geologic, not biologic, processes

Lithologic, tectonic, and climatic controls on chemical weathering, soil production, and erosion in New Zealand

Over geologic timescales, chemical weathering in mountain landscapes may play an important role in regulating atmospheric CO2. Understanding the feedbacks between climate, tectonics, erosion rates, biota, and weathering has been a recent focus of research, but disentangling these complex relationships remains a challenge. One area of particular interest has been the potential for a kinetic limit to weathering and soil production. Studies in New Zealand's Southern Alps were among the first to clearly exceed proposed kinetic limits on soil production and demonstrate thresholds in the influence of precipitation on chemical weathering. Here we present a new dataset that addresses chemical weathering, soil production rates, and surface erosion rates, measured across an altitudinal transect in the Tararua Range on New Zealand's North Island. The transect spans a kilometer in relief, and receives 3.5-5.5 m of annual precipitation. Underlying bedrock comprises silty and sandy members of the same Cretaceous Greywacke, but subtle lithologic changes correspond to abrupt shifts in soil production rates and total weathering. Total weathering across the transect is roughly invariant for each lithology and reflects near-complete depletion of weatherable species, consistent with a previously proposed threshold in the influence of precipitation. However, spatial patterns in weathering differ markedly in saprolite and in soils. Deep weathering in saprolite decreases with elevation and makes up a large fraction of the total weathering. This pattern suggests that climate may influence saprolite weathering, even where the total weathering is supply-limited. Spatial patterns in saprolite and total weathering do not correlate with an abrupt vegetation transition from dense forest to alpine tussock, which may suggest that biota are more strongly affected by a temperature threshold or more complex biogeochemical cycling. We contrast these results with new and previously published data from the Southern Alps, which have a similar climate but experience rapid tectonic uplift. There, the fresh supply of minerals to soils provided by uplift and erosion may enable much faster weathering and soil production rates. Taken together, these observations suggest a strong lithologic and tectonic control on soil production and weathering rates in humid climates

Chemical Weathering and Organic Carbon Turnover in Soil

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