Regional Net Primary Production (NPP) Derivation Using Imaging Spectroscopy for Vegetation Modelling

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14 Jun 2006 09:00 - 14 Jun 2006 09:30
Unit: Laboratory of Geo-Information Science and Remote Sensing
Location: Gaia 1
Organisation: Wageningen University

 By Uchenna Aduaka   

Abstract: 

Monitoring terrestrial net primary production (NPP) is relevant for understanding the carbon cycle and evaluating effects of interannual climate variation on food and fiber production. With the advent of specialized sensors, remote sensing has provided the opportunity for vegetation related mapping to be carried out at varying spatial and spectral resolution at almost near road-level granularity. The study investigates the potential of imaging spectroscopy for mapping spatially explicit NPP of a river floodplain.
Two strategic above-ground net primary production (ANPP), namely light-use efficiency (LUE) and climate dependent ANPP derivation approaches were adopted in this study in line with the general NPP research strategies adopted by past researchers. While the LUE-based approach is often used in both regional and global ANPP studies, the climate dependent approach is strictly tied to global based NPP studies. The climate dependent (global approach) NPP derivation approach was important in this research since it also aimed to investigate if ecosystems specific global-based NPP methods are applicable at regional scale. The LUE-based ANPP was found to be advantageous over the climate dependent approach. The climate dependent approach shows low variability of ANPP values for the vegetation types in the Millingerwaard study area.
The ANPP variability within the dominant species in the Millingerwaard was also investigated within this study. High ANPP values were obtained for agricultural crops compared to the other vegetation types, probably due to the use of fertilizers and highly productive vegetation species. In terms of the ANPP variation per specie, it was also noticed that the dominant species yield the same ranges of ANPP. The results show that an ecosystem equation that uses a biome-dependent LUE value yields similar ANPP values.
The result of this study was validated using the Moderate-resolution Imaging Spectroradiometer 8-day Net photosynthesis (MOD17A2) product and SMART-SUMO modelled ANPP values. An analysis on the effect of spatial aggregation of the HyMap ANPP results to the MOD17A2 supported a correlation between the two products but a weak correlation was achieved unlike the SMART-SUMO product which showed a strong correlation.
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