Pollen and non-pollen palynomorph signals of cultivation-related disturbance in a preservation-limited tropical soil profile, northern Thailand

This study examined pollen, spores, non-pollen palynomorphs, and associated microremains in a 118-cm tropical soil profile from Sri Nan National Park, northern Thailand, to evaluate depth-wise assemblage patterns and their relationship to surface disturbance. Nineteen subsamples yielded 691 observations, dominated by fungal remains (478; 69.18%), mostly Glomus -type morphotypes. Indeterminate morphotypes accounted for 95 observations (13.75%), helminth eggs for 53 (7.67%), and testate amoebae for 21 (3.04%). Terrestrial pollen was sparse, with only 25 grains recorded across the profile. The highest sample-level counts occurred in the upper sampled depths, which contained most helminth eggs and testate amoebae and all recorded spores, freshwater algal remains, rotifer remains, and indeterminate morphotypes, whereas several middle and lower samples yielded few or no remains. The upper assemblage is consistent with a disturbed terrestrial surface and, together with field observations and regional land-use evidence, is compatible with cultivation-related disturbance. However, the recovered proxies do not independently identify a specific crop or management practice. The absence of independent chronology, low terrestrial pollen recovery, and discontinuous recovery restrict interpretation to depth-wise patterns rather than a temporally resolved environmental history.