The influence of structure on spectral reflectance of four tropical rainforest types in Amazonia.
Authors: Hill, R.A., Boyd, D.S. and Hopkinson, C.
Conference: RSPSoc 2010: From The Sea-bed to the Cloud-tops (Remote Sensing and Photogrammetry Society)
Dates: 1-3 September 2010
Abstract:This paper investigates the influence of within-pixel variation of forest canopy height on the spectral response recorded in Landsat ETM+ data for tropical rainforest. Forest canopy height is derived from airborne, small-footprint LiDAR data acquired using a Leica ALS50 II system. The field site is in the Tambopata National Reserve, in Peruvian Amazonia, where forest types include regenerating, swamp, floodplain and terra firme. Previous work at this site, mapping forest types and investigating spectral response in relation to field plot data, was successful but limited by the difficulties of coupling ground and satellite data which were compromised by their comparative scale. This study benefits from extensive forest structure data derived from airborne LiDAR data, processed into a 2m Canopy Height Model.
For regenerating, floodplain and terra firme forest, spectral reflectance in ETM+ Bands 4, 5 and 7 (near and middle infrared) was negatively correlated with the mean and maximum canopy height per 30m pixel. In all cases, the strongest relationships occurred for Band 4, whilst Bands 1, 2 and 3 showed only weak or insignificant relationships. For swamp forest, only Bands 5 and 7 had a statistically significant (negative) relationship with mean and maximum canopy height per pixel. Stronger correlations occurred with canopy height for normalised difference band indices. For regenerating, floodplain and terra firme forest, the strongest correlations with mean and max. canopy height occurred for ND43 (i.e. the NDVI) and ND42 respectively, whilst for swamp forest the strongest correlations occurred for ND54.
Many papers have identified middle infrared bands as being most sensitive to tropical rainforest structure, although these have often focussed on young regenerative forests. By focussing on older regenerative forest and mature rainforest types, this work has shown that there is considerable variation with how structure may influence spectral reflectance.
http://www.rspsoc.org/events/info/rpsoc-annual-conference-2010/
Source: Manual
Preferred by: Ross Hill