University of Twente Student Theses


Assessment of carbon assimilation in a tropical forest of Western Ghats, India

Shijo, Joseph (2009) Assessment of carbon assimilation in a tropical forest of Western Ghats, India.

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Abstract:Terrestrial vegetation plays a significant role in climate balance and biogeochemical cycling. The feedback interactions between the biosphere and atmosphere and the identification of mechanisms which maintains these interactions is one of today’s scientific priorities in view of the climate change debate. However, the methods to assess these interactions operationally are widely criticized. The present attempts to validate the algorithms are biased towards temperate and neotropical areas. In this context, the present study assesses the implementation of an alternative algorithm in an old world tropical biodiversity hotspot. The model is formulated by taking into consideration of the local environmental conditions. The maximum light use efficiency of vegetation types (e0), and the controlling factors which limits e0, the amount of incident PAR and fraction of PAR that canopy absorbs are combined together to estimate the carbon assimilation. The result is compared with the existing operational algorithm (MODIS GPP product) and the difference is analysed in terms of structure of algorithm and resolution of input datasets. The results indicated that the lower elevation tropical wet evergreen forest assimilates the highest amount of carbon whereas montane grasslands assimilate lowest level of carbon. Tropical deciduous forests showed an assimilation rate which was almost equal to evergreen forest during wet season. The comparison with globally derived estimate (MODIS GPP product) showed that both the estimates are significantly different. The change in magnitude of estimate was not because of algorithm difference, but it was due to the resolution of the input datasets. The estimates using global datasets of 10 resolution was almost three times higher than the estimates using ground measurements. The study leads to several ecological insights and practical implications in the carbon assimilation monitoring. Daily data at 500 m resolution by MODIS is quite reasonable to understand the spatial and temporal dimensions of vegetative surfaces. Advanced vegetation index such as EVI can outperform conventional index like NDVI. Soil moisture condition could be adequately represented by MODIS shortwave infrared indices. Physical constraints can limit carbon assimilation capacity of vegetation types. GPP estimation in heterogeneous mountain areas needs high resolution temperature and IPAR datasets. Resolution of the input datasets plays a major role rather than algorithm in carbon assimilation estimation.
Item Type:Essay (Master)
Faculty:ITC: Faculty of Geo-information Science and Earth Observation
Programme:Geoinformation Science and Earth Observation MSc (75014)
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