Academic journal article Borneo Research Bulletin

Climatic and Lithogenic Controls on Soil Organic Matter-Mineral Associations

Academic journal article Borneo Research Bulletin

Climatic and Lithogenic Controls on Soil Organic Matter-Mineral Associations

Article excerpt

Interactions of organic matter (OM) with soil mineral phases strongly affect the storage and dynamics of soil OM as well as other ecosystem processes. This study examined aspects of organo-mineral associations in soils at different scales. First, I assessed the potential controls of climate and parent rock type on organo-mineral associations using two sets of undisturbed tropical forest soils developed on two contrasting rocks along an altitudinal gradient in Borneo, Southeast Asia. Density fractionations showed that OM stored in surface mineral soils partitioned towards plant detritus fraction under cooler climates on both rock types. Thus climate exerted stronger control on soil OM storage and partitioning patterns than parent rock in the study area. The plant detritus associated with soil mineral grains also increased its standing stock under cooler climates, suggesting that abundance of mineral-free detritus and its comminution had stronger control than soil mineralogical factors. Second, gas sorption approaches were applied to the same sets of soils to assess OM associations with soil mineral surfaces. Surface characterization before and after OM removal revealed that, with increasing altitude and OM loading, OM appear to accumulate in globular forms that incidentally encapsulate fine mineral grains, rather than accumulating via sorption onto all mineral surfaces. …

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