Vertical dynamics of Ombrogenous peat physical properties on Bengkalis island, Indonesia

Peat depth reflects the humification process and the diversity of physical properties. The study examined vertical physical properties and their dynamic relationship with peat depth in an ombrogenous peat dome system. Observations were made on five profiles representing a variety of land elevations. These profiles are arranged sequentially from the edge of the dome to its peak. Profile locations were extracted from DTM LiDAR, while thickness was measured using an Eijkelkamp drill. Profile descriptions were made at every 20 cm interval above the drill bit, totaling 123 layers. Laboratory analysis included moisture content (gravimetric), bulk density/BD (ring), and fiber content (syringe). Statistical analysis employed Pearson correlation and simple linear regression at a 5% significance level. Vertical autocorrelation of peat properties is expected to be evident in adjacent peat depth layers. Profile P3 at the top of the dome I showed the strongest and most significant relationship, with the distributions of fiber content, moisture content, and BD strongly influenced by depth. A relatively deeper groundwater table promotes greater surface aeration and enhanced humification. Profile P4 in dome II also shows a significant relationship, indicating the role of BD in shaping the vertical distribution of peat. In contrast, the low coefficients of determination for P1, P2, and P5 indicate that variations in moisture content and BD are influenced more by groundwater-level fluctuations than by depth alone, whereas fiber content remains strongly correlated with depth. Although Profiles P4 and P5 are located within the same dome, they display different vertical patterns. At Profile P4, moisture content and fiber content do not vary systematically with depth. This deviation is attributed to intensive mixed-crop cultivation, which disrupts the peat dome structure and weakens the natural relationship between depth and peat physical properties.