Effect of canal blocking on biodiversity of degraded peatlands: Insight from West Kalimantan

PLOS One | https://doi.org/10.1371/journal.pone.0334014 October 8, 2025 11 / 23 The highest plant individual count was recorded in less disturbed peat forests, followed by disturbed peat forests, estate crops, and disturbed wet shrubs. Similarly, less disturbed peat forests exhibited the highest species count, with dis- turbed wet shrub recording the lowest. The species count was comparable between forested (disturbed and less disturbed peat forests) and non-forested (estate crop and disturbed wet shrub) areas. Forested areas had higher species count than non-forested area. However, the pattern did not apply to the plant individual counts, as disturbed peat forests, estate crop, and disturbed wet shrubs all had similar numbers. Dissimilarity between forested and non-forested areas was observed in plant species composition and thus reflected in Shannon diversity index. NMDS plot shows overlap between disturbed peat forests with less disturbed peat forest and estate crop with disturbed wet shrubs (Fig 7). The separation between forested or non-forested areas using NMDS indicate that there are still species we found only specific to a habitat types. As many as 65 species recorded were only found in less disturbed peat forests, 56 species in disturbed peat forests, 15 in estate crops, and 7 species only occur at disturbed wet shrub. Disturbed peat forests and less disturbed peat forests have higher plant diversity index compared to estate crop areas and disturbed wet shrub.

On average, tree height and diameter were higher in forested areas compared to disturbed wet shrub. However, within forested areas, trees with diameter wider than 45 cm and height above 30 m were only found in less disturbed peat forest. Canopy cover was present in all habitat types but very low number in disturbed wet shrub (mean = 1.97%). In estate crops, canopy cover was due to shade from oil palm stands. Estate crops had lower canopy cover than disturbed and less disturbed peat forest. All our survey areas in estate crop took place in palm oil plantations with height of each plant reach up to more than 2 m. Ground cover was observed across all habitat types. Mean percentage of canopy and ground cover was highest in less disturbed peat forest followed by disturbed peat forest. Among all habitats, less disturbed peat forest had the highest average of tree height, tree diameter, ground cover and canopy cover. Temperature and humidity were relatively stable across months in less disturbed forest (Fig 8). Temperature ranges from 20° to 44°C. The highest humidity was 99.99% while the lowest was in 40.3%. Temperature and humidity tend to have an inverse relationship. In both survey months, humidity was lower during dawn to morning time and peaked when approaching noon, usually around 10:00–15:00. Temperature declined after noon approaching nighttime and remained Fig 7. NMDS ordination plot showing plant species composition of four habitat types. https://doi.org/10.1371/journal.pone.0334014.g007