SOIL PROPERTIES AND CARBON STOCK ALONG THE TOPOSEQUENCE OF LALMAI HILL ECOSYSTEM OF BANGLADESH

Abstract

A study was carried out in the Lalmai hill ecosystem of Bangladesh
regarding their soil properties and soil organic carbon (SOC) stocks. The Lalmai
hill ecosystem consists of three toposequence arrangements as hills, piedmonts,
and floodplains. Forty-five soil samples covering nine soil profiles were selected
to conduct the present study. Soil samples were collected at five different depths
of 0-20 cm, 20-40 cm, 40-60 cm, 60-80 cm and 80-100 cm intervals from each pit of
the study sites. Soil pH, percent SOC, percent total nitrogen (TN), bulk density,
cation exchange capacity (CEC), particle size distribution, and SOC storage
(kg/m2) dataset indicates that piedmont deposits and floodplain soils are more
enriched than the upper hill soils. Regarding SOC storage, the post hoc test
indicates that hill soils are significantly different from the other two
physiographic units, but there is no significant difference between piedmont
deposits and floodplain soils. The soil property varies differently depending on
their depth level at different physiographic units. Estimation on SOC stock
revealed that 2.01Tg, 21.75Tg, 12.68Tg carbon remains in the hill soils, piedmont
soils, and estuarine floodplain soils, respectively. The total SOC stock was
estimated at 36.44 Tg in the Lalmai hill ecosystem of Bangladesh, where
piedmont deposits contained the highest level of SOC stock. It is assumed that
more clay-organic substances are washed in at the foot of piedmont units due to
the well-drained nature of upper Pleistocene hill soils. Thus, fine soil textural
nature, diverse land and land cover accelerates to sequester more carbon in
piedmont zone rather than hill or floodplain zones.