Pedogenesis of Horizons and Profiles

Jenny, Hans

doi:10.1007/978-1-4612-6112-4_7

Cited by 2 publications

(1 citation statement)

References 31 publications

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“…However, the Spodosol map used as categorical variable had little variation within it and showed only a moderate influence in the model. Also, many pedological observations suggested that the Bh horizon in spodosol do not act as hardpans, not always restrictive of root penetration, and typically do not have low permeability (Jenny, 1980).…”

Section: Discussionmentioning

confidence: 99%

Assessment on latitudinal tree species richness using environmental factors in the southeastern United States

Kwon

Lee

Lang

et al. 2019

PeerJ

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The southeastern region of the United States exhibits an unusual trend of decreasing tree species richness (TSR) from higher to lower latitudes over the Florida peninsula. This trend contradicts the widely marked latitudinal diversity gradient where species richness is highest in tropical zones and decreases towards extratropical regions. This study aims to assess the environmental factors that prompt this atypical inverse latitudinal gradient seen in TSR using the USDA Forest Service’s Forest Inventory and Analysis (FIA) database. Fifteen variables under four categories of forested area, groundwater, soil properties, and climate groups were examined to model TSR in the region. Generalized linear models (GLMs) with Poisson distributions first assessed individual variables to test explanatory power then the LASSO regularization method was utilized to extract two subsets of the most influential variables to predict TSR. Forest area and four climate variables (mean annual temperature, precipitation seasonality, mean temperature of coldest quarter, and mean precipitation of driest quarter) were the top five variables during the initial GLM assessment implying their potential individual influence in regulating TSR. Two subsets of LASSO models contained seven and three predictor variables, respectively. Frist subset includes seven predictors, presented in highest to low standardized coefficient, mean temperature of coldest quarter, forested area, precipitation seasonality, mean precipitation of driest quarter, water table depth, spodosol, and available water storage. The other subset further excluded four lowest influential variables from the first set, leaving the top three variables from the first subset. The first subset of the LASSO model predicted TSR with 63.4% explained deviance while the second subset reproduced 60.2% of deviance explained. With only three variables used, the second model outperformed the first model evaluated by the AIC value. We conclude that forest patch area, mean temperature of coldest quarter, and precipitation seasonality are the highly influential variables of TSR among environmental factors in the southeastern region of U.S., but evolutionary or historic cause should be further incorporated to fully understand tree species diversity pattern in this region.

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Section: Discussionmentioning

confidence: 99%

Assessment on latitudinal tree species richness using environmental factors in the southeastern United States

Kwon

Lee

Lang

et al. 2019

PeerJ

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Kaolin Mineralogy of Clays in Paleosol Profiles on the Late-Miocene Sediments in Penghu Islands (Pescadores), Taiwan

Wang

Yeh

Chen

et al. 1998

Clays and clay miner.

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Abstract--Clay mineral compositions from 2 paleosol profiles (Chu-Wan, CW, and Shiao-Men Yu, SMY, profiles) on the late-Miocene sediments in Penghu Islands (Pescadores), Taiwan, are characterized by random X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). By the clay assemblage of the paleosol profile, we want to explore the probable formation mode of the Penghu paleosols.The paleosol profiles in study are overlain by a layer of basalt flow. However, the clay mineralogy of the 2 paleosols was not altered metasomatically after burial. Results show that 3 distinctive zones of different dominating kaolin-group minerals are apparent in the profiles. In descending order, they are: 1) spheroidal, hollow 7A-halloysite, 2) platy, irregular-shaped and disordered kaolinite, and 3) platy, irregular-shaped, disordered kaolinite. The relative crystallinity of kaolin minerals of the 3 layers is: layer 2 > layer 3 > layer 1. On the basis of the XRD, TEM analyses and the crystallinity calculations, the distribution of kaolin in Penghu paleosol profiles appears to be unique. Penghu paleosol profiles show systematic change in kaolin crystallinity and polymorphs with depth. Because the clay type is heterogeneous within the profile, this represents that Penghu paleosol profiles were polypedogenic.The contact between the upper basalt and the paleosol is the erosion surface, so we do not know exactly what the thickness of the original paleosol was. The first layer (about 20 cm) of the profiles appears to be constituents of the original paleosol. It contains high contents of pedogenic (in situ weathering) hematites and 7/*k-halloysites, which implies that the local climate of the Penghu Islands at late Miocene was warm and humid. Intense leaching and dry/wet cycle should be the reason for high contents of halloysite (>60%) in the Penghu paleosols. Laterization was the probable pedogenic process for the formation of the paleosols.

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Pedogenesis of Horizons and Profiles

Cited by 2 publications

References 31 publications

Assessment on latitudinal tree species richness using environmental factors in the southeastern United States

Assessment on latitudinal tree species richness using environmental factors in the southeastern United States

Kaolin Mineralogy of Clays in Paleosol Profiles on the Late-Miocene Sediments in Penghu Islands (Pescadores), Taiwan

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