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 5 / 23 To collect soundscape data, we deployed a set of SwiftOne (The Cornell Lab of Ornithology K. Lisa Yang Center for Conservation Bioacoustics) passive acoustic recorders across four habitat types. Each recorder was systematically positioned at the beginning and end of each transect, affixed to tree trunks at approximately 130 cm off the ground. Each device was set at minimum 500 m apart to ensure acoustics sampling were independent [50,51]. The acoustic devices were programmed to continuously capture sounds for 59 minutes every hour over a span of three days (equivalent to 3 x 24 hours), synchronized with the visual surveys conducted by human observers. Sound data collection occurred consis- tently in May and August, employing uniform tool settings and recorder placement. Habitat features. 1. Vegetation We collected vegetation data using nested plots, each with a specific plot size designated for different vegetation and tree growth stages. We used 1x1 m plots to observe understory which includes non-woody plant species, 2x2 m plots to observe woody seedlings, 5x5 m plots to observe woody saplings (those with diameter less than 10 cm), 10x10 m to observe woody pole (diameter ranging from 10–20 cm), and 20x20 m plots to observe tree (i.e., tree with diameter exceeding 20 cm). These nested plots were systematically placed within a transect, with each transect containing six plots spaced 200 meters apart. During each observation, we recorded essential vegetation attributes, including plant species,

individual counts, and tree height and diameter (specifically for saplings, poles, and mature trees). Additionally, we mea- sured canopy cover and ground cover using HabitApp. 2. Environmental data We used data loggers (Mini USB, model BTH81, Bonajay Technology Co., Ltd.) to document local temperature and humidity were also placed in the same spot as acoustic recorders. We set the loggers to note the information every 5 Table 1. Characteristics of each study sites. Landscape Habitat type Site information Mempawah Disturbed peat forest • Located in two villages: Sungai Bakau Besar Darat and Sejegi • Still actively logged by the local people to collect pilling wood • Surrounded by palm oil plantation and wet shrub • Canal blocking was established in 2017 and 2018 Estate Crop • Located in Anjungan Dalam Village • Consist of palm oil plantation owned by individuals and corporations • Understory cover is often low due to intensive management; however, in some spots, we also found areas with dense understory cover. • Near crossroad • Canal blocking was built in 2018 Disturbed wet shrub • Located in three villages, i.e., Sungai Bakau Besar Darat, Sungai Rasau, and Antibar • Wet shrub in Antibar is actively managed for agriculture (pineapple and herb plantation) • Wet shrub in Sungai Bakau Besar Darat bordered with secondary peat forest • Wet shrub in Sungai Rasau is located near land clearing for oil palm plantations and has experienced repeated fires • Canal blocking was built in 2015, 2017, and 2018 Kubu Raya Less disturbed peat forest • Located in Permata Village

• The forest is community forest reserve. • Rarely entered by people • Experienced low disturbance since logging activity stopped approximately 10 years ago • Bordered with palm oil plantations • Canal blocking near the forest was established in 2021 https://doi.org/10.1371/journal.pone.0334014.t001