Vicente Gómez-Miguel

QUANTIFYING THE RELATIONSHIP BETWEEN DRAINAGE NETWORKS AT HILLSLOPE SCALE AND PARTICLE SIZE DISTRIBUTION AT PEDON SCALE

Nowadays, translating information about hydrologic and soil properties and processes across scales has emerged as a major theme in soil science and hydrology, and suitable theories for upscaling or downscaling hydrologic and soil information are being looked forward. The recognition of low-order catchments as self-organized systems suggests the existence of a great amount of links at different scales between their elements. The objective of this work was to research in areas of homogeneous bedrock material, the relationship between the hierarchical structure of the drainage networks at hillslope scale and the heterogeneity of the particle-size distribution at pedon scale. One of the most innovative elements in this work is the choice of the parameters to quantify the organization level of the studied features. The fractal dimension has been selected to measure the hierarchical structure of the drainage networks, while the Balanced Entropy Index (BEI) has been the chosen parameter to quantify the heterogeneity of the particle-size distribution from textural data. These parameters have made it possible to establish quantifiable relationships between two features attached to different steps in the scale range. Results suggest that the bedrock lithology of the landscape constrains the architecture of the drainage networks developed on it and the particle soil distribution resulting in the fragmentation processes.

Soil Distribution and Classification

This chapter describes the main soil types and their geographical distribution based on the soil map of the Atlas of Spains National Geographic Institute, at a scale of 1:1,000,000. It was written according to the guidelines of the Soil Survey Manual and the methodology of Soil Taxonomy. Spanish soils are developed under a wide range of temperatures and moisture regimes–cryic, mesic, and thermic in the first case, and udic, ustic, xeric and aridic (or torric) with an occasional aquic regime in the second. Entisols (39.9 %) and Inceptisols (37.9 %) comprise more than three-quarters of Spain’s surface, while Alfisols (12.3 %) and Aridisols (5.6 %) account for only a bit more than one-sixth of the land. The remaining orders do not reach 5 % of the total land (Vertisols 2.4 %, Mollisols 1.5 %, Ultisols 0.2 %, Spodosols 0.1 %, Andisols 0.1 %, and Histosol 0.02 %). In this chapter, special attention is paid to the description of soil properties related to land management. Furthermore, their relationship with soil-forming factors is indicated. For each order, hectares and distribution of soil groups are indicated, down to the Spanish province scale. The text is accompanied by tables and maps, displaying the distribution of soil orders in Spain, including the synonyms of equivalent units in the WRB system.