Comparing soil taxonomy and WRB systems to classify soils with clay-enriched horizons (A case study: arid and semi-arid regions of Iran) مقاله
DESERT Summer & Autumn 2018, Volume 23 - Number 2 علمی-پژوهشی (وزارت علوم) (11 صفحه - از 315 تا 325 )
Comparing the ability of ST and WRB systems to describe soils with clay-enriched horizons was the aim of the present research. In arid and semi-arid regions of Iran, two study sites were considered. Three pedons at each study site were selected, described and sampled. Soils were classified based on ST (2014) and WRB (2015) systems. The micro-morphological investigations were done to confirm the illuvial clay accumulation in Bt horizons. Results showed that the required characteristics of an argillic horizon were not met in any of the Bt horizons. The poor correlation between ST and WRB systems was related to the different definition and criteria of clay-enriched horizons in the systems. Using “Differentic” and “Cutanic” qualifiers, the WRB system could describe properties of an argic horizon more efficiently than the ST system. Although the evidence of clay illuviation was observed as lamellae in some argillic horizons in the arid study site, the ST system could not display this characteristic. The WRB system indicates the presence of lamellae using a “Lamellic” qualifier in some cases. These issues are disadvantages for both classification systems in describing the soils with clay-enriched horizons. Defining Natrisalids great group and new subgroups including Calcic Natrisalids, Lamellic Argigypsids and Lamellic Calciargids seems necessary to improve deficiencies of both classification systems. Adding the “Lamellic” qualifier for Calcisols in the WRB system is highly suggested.خلاصه ماشینی:
Comparing soil taxonomy and WRB systems to classify soils with clay-enriched horizons (A case study: arid and semi-arid regions of Iran) I. Although about 85 % of the Iranian's territory is located in the arid and semi-arid belt of the world (NCCO, 2003), but many researchers reported the presence of clay-enriched horizons under different environmental conditions of Iran (Khademi and Mermut, 2003; Khormali et al. The objective of this study is to investigate the ability of ST and WRB systems to describe soils with clay-enriched horizons in arid and semi-arid regions of Iran. The addition of the “Panto-” specifier to “Loamic” qualifier shows that the horizon starts at the mineral soil surface and has its lower limit ≥ 100 cm from the soil surface (IUSS Working Group WRB, 2015, page 18) (Table 4). The presence of an argic horizon with a CEC ≥ 24 cmolc kg-1 clay and BS ≥ 50 % starting ≤ 100 cm from the soil surface was considered using the “Luvic” qualifier (IUSS Working Group WRB, 2015, page 128). Meanwhile, the “Endo-” specifier combined with “Loamic” qualifier is a proof that the layer ≥ 30 cm thick with a silty clay loam textural class starts ≥ 50 and ≤ 100 cm from the soil surface (IUSS Working Group WRB, 2015, page 128). Although no evidence of clay illuviation was observed, the WRB system described the presence of an argic horizon well within 100 cm of the soil surface at the RSG level.کلیدواژه ها:
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