Polygenetic soils of montane cloud forest in Sierra Gorda, Mexico

Abstract

The aim of the study was to fill the gap in the knowledge on soils of montane cloud forest: until recently the soils formed in base-rich parent material under this forest type were insufficiently studied. We provided pedogenetic analysis of soils of two localities under montane cloud forest ecosystems in Sierra Gorda Mountains, Quirétaro state, Mexico. The site San Agustin had the annual rainfall of about 3000mm and more diverse vegetative community. Soils formed in the debris and colluviums of silicate shales. The soils at this site were classified as Umbric Alisol (Cutanic, Humic). The pedogenesis of these soils included the stage of accumulation of polymerized organic matter and illuviation of clay rich in organic C, followed by the stage of progressing hydroconsolidation. Current clay illuviation occurs mainly under the consolidated fragipan-like layer. The site Yerba Buena had the annual rainfall of about 1000mm and less diverse vegetation. Soils formed in a mixture of silicate shale and limestone-derived materials. The soils at this site were classified as Albic Fragic Luvisol (Calcaric, Cutanic). Initially these soils underwent the stage of leaching of bases and simultaneous hydroconsolidation that resulted in the formation of fragic horizon. Currently clay illuviation can be detected in these soils, but the process is not very active due to the compaction of the EBx and Btx horizons and the presence of residual calcite in the BC horizon. Both Alisols and Luvisols are seldom reported in montane cloud forest: they form mainly in base-rich parent material. For Luvisols under this forest type carbonate-rich parent material seems to be a pre-requisite for their formation.