Soilscape analysis at different scales using pattern indices in the Jarama-Henares interfluve and Henares River valley, Central Spain

摘要

The Jarama-Henares interfluve is located south of the Ayllon range, one of the easternmost ranges of the "Sistema Central" mountains in central Spain. The Henares river valley is asymmetric, with 20 topographic benches along its right bank and a series of glacis-terraces on its left bank. We investigated the soil-geoform units in the Jarama-Henares interfluve and the Henares river valley using several indices to quantify and understand the evolution of soil and landscape patterns of the area during the Plio-Quaternary. Features such fragmentation, dominance, geopedologic unit diversity, relative spatial diversity, size and shape, neighbourhood and interaction were analysed in geopedologic maps prepared at two scales (1:18,000 and 1:50,000) using ancillary data, aerial photographs and field observations. Likewise, the taxonomic pedorichness and pedodiversity were assessed on plot maps at 1:100 scale representing three fluvial terrace areas of different age. Soil diversity analysis was carried out at the subgroup level of the USDA Soil Taxonomy using (1) the number of individuals included in a given pedotaxum, and (2) the areal proportion occupied by each soil taxum in a given map unit. One of the main findings was that the values of the indices were higher and the number of indices required to describe appropriately the soilscape patterns was smaller at the local than at the regional scale, the relative spatial diversity being one of the most useful indices. At the plot scale, taxonomic pedorichness and pedodiversity of soil subgroups increased from low/young to high/old terraces. Thus, pattern indices can be used to characterise soilscape evolution aspects such as diversification due to the behaviour of the depositional system or to relief dissection.