Laser scanning of fine scale pattern along a hydrological gradient in a peatland ecosystem

Abstract

Lowland ombrotrophic (rain-fed) peatlands are a declining ecological resource in Europe. Peatlands display characteristic patterns in vegetation and surface topography, linked to ecological function, hydrology, biodiversity and carbon sequestration. Laser scanning provides a means of precisely measuring vegetation pattern in peatlands, and thus holds promise as a tool for monitoring peatland condition. Terrestrial laser scanning (TLS) was used for measurement of vegetation pattern along an eco-hydrological gradient at a UK peatland (Wedholme Flow, Cumbria) at fine grain sizes (<1 cm spatial resolution over 10 m spatial extent). Seven sites were investigated—each showed varying water table and ecological characteristics. TLS data were analysed using semi-variogram analysis which enabled the scale of spatial dependence in vegetation structures to be measured. In addition ecological, hydrological and positional surveys were conducted to elucidate interpretation of spatial patterns. Results show that TLS was able to rapidly measure vegetation patterns associated with eco-hydrological condition classes. Intact sites with hummock-hollow topography showed an isotropic pattern with a grain size or length-scale of 1 m or less (indicated by semi-variogram range). Degraded sites with high shrub cover showed increased sill variance values at larger range distances—typically around 3–4 m. The work presented shows the advantages of TLS methodologies for rapid measurement of 3-D vegetation canopy structure and surface microtopography, at fine spatial scales, in short vegetation. The paper considers how these approaches may be extended to monitoring peatland structure over larger spatial extents from airborne LiDAR systems.