3 results on '"Vernimmen, Ronald"'
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2. A New Method for Rapid Measurement of Canal Water Table Depth Using Airborne LiDAR, with Application to Drained Peatlands in Indonesia.
- Author
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Vernimmen, Ronald, Hooijer, Aljosja, Mulyadi, Dedi, Setiawan, Iwan, Pronk, Maarten, and Yuherdha, Angga T.
- Subjects
WATER depth ,LIDAR ,BODIES of water ,DIGITAL elevation models ,PEATLANDS ,WATER table - Abstract
Water management in lowland areas usually aims to keep water tables within a narrow range to avoid flooding and drought conditions. A common water management target parameter is the depth of the canal water table below the surrounding soil surface. We demonstrated a method that rapidly determines canal water table depth (CWD) from airborne LiDAR data. The water table elevation was measured as the minimum value determined in a grid of 100 m × 100 m applied to a 1 m × 1 m digital terrain model (DTM), and the soil surface was calculated as the median value of values in each grid cell. Results for areas in eastern Sumatra and West Kalimantan, Indonesia, were validated against 145 field measurements at the time of LiDAR data collection. LiDAR-derived CWD was found to be accurate within 0.25 m and 0.5 m for 86% and 99% of field measurements, respectively, with an R
2 value of 0.74. We demonstrated the method for CWD conditions in a drained peatland area in Central Kalimantan, where we found CWD in the dry season of 2011 to be generally below −1.5 and often below −2.5 m indicating severely overdrained conditions. We concluded that airborne LiDAR can provide an efficient and rapid mapping tool of CWD at the time of LiDAR data collection, which can be cost-effective especially where LiDAR data or derived DTMs are already available. The method can be applied to any LiDAR-based DTM that represents a flat landscape that has open water bodies. [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
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3. Distance to forest, mammal and bird dispersal drive natural regeneration on degraded tropical peatland.
- Author
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Wijedasa, Lahiru S., Vernimmen, Ronald, Page, Susan E., Mulyadi, Dedi, Bahri, Samsul, Randi, Agusti, Evans, Theodore A., Lasmito, Priatna, Dolly, Jensen, Rolf M., and Hooijer, Aljosja
- Subjects
FOREST birds ,CLEARCUTTING ,FOREST regeneration ,RESTORATION ecology ,PEATLAND restoration ,LAND use ,FOREST degradation ,SPECIES diversity - Abstract
• Natural regeneration of peatswamp forest on degraded peatlands is driven by distance to forest, mammal and bird dispersal. • Regeneration occurred in clusters of young trees at distances up to 2 km from the forest. • Forest burnt in 1997 had higher species diversity and trees per plot than intact forest. • Natural regeneration could restore degraded peatlands surrounding remnant forest patches up to 500 m from natural forest. Restoration of peat swamp forest (PSF) on degraded Southeast Asian peatlands could reduce global carbon emissions and biodiversity loss. However, multiple ecological barriers are believed to hinder natural regeneration of native trees on degraded peatland and make restoration expensive. We evaluated if natural PSF regeneration occurs and what factors may influence it on eight different land use and land cover (LULC) classes with different types of disturbance, including drainage and fire, in a retired Acacia crassicarpa Benth. (Acacia) plantation landscape. The study involved 42 plots inside five PSF LULCs – intact, logged, burnt (1997, 2015), remnant and 212 plots at distances up to 2 km from the PSF edge in three Acacia plantation LULCs – unharvested, harvested, and burnt. The number of species per plot were similar between intact PSF (25 ± 6 (SD) per 20 m × 10 m plot), logged forest (30 ± 6) and 1997 burnt forest (30 ± 13) but lower in 2015 burnt forest (11 ± 10) and remnant forest (18 ± 11). Regeneration away from the PSF across all degraded LULCs varied from fern dominated areas with no regeneration to clusters with high stem densities. The plantation LULCs, unharvested (94 species) and harvested Acacia (71 species), had similar overall species diversity after 3–4 years of regeneration to the intact and logged PSF (90 species). In unharvested Acacia , total species diversity, species per plot and stem density decreased with distance from forest edge (1–300 m – 87 species; 9 ± 6 (SD) species per 20 m × 10 m plot; 1,056 stems/ha; 301–500 m – 33; 5 ± 2; 511 and >500 m – 38; 6 ± 3; 683). In harvested Acacia , there was low plot species diversity irrespective of distance from the forest (1–300 m – 51; 4 ± 2; 578; 301–500 m – 17; 4 ± 2; 1,100; >500 m – 48; 4 ± 2; 780). Factors which may influence regeneration differed between different LULCs, but there was a clear influence of distance from forest edge and dispersal mechanism – i.e. whether a tree was bird or mammal dispersed and the interaction between these two factors. While our study suggests that if not further disturbed by logging, drainage and/or fire, degraded PSF could regenerate naturally to a similar species diversity as intact PSF, the lower levels of natural regeneration further away from the forest may warrant selective planting of species which do not disperse over long distances. More study is needed on the factors facilitating natural regeneration, whether it leads to restoration of PSF ecosystem functioning and the role of Acacia as a potential regeneration catalyst. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
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