Changes in plant development - monitored on the individual plant over geographical area
2007
Bruegger, R.,Universitaet Bern, Bern (Switzerland). Geographisches Institut | Studer, S. | Stoeckli, R.
The phenological development of plants provides information about the influence of weather on vegetation and may be assessed on both the individual plant level and on a global level. Since 2000, Switzerland has had a phenological monitoring network for forest trees which records the seasonality and is complementary to the ICP-Forests Assessments (International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests). A comparison of leaf discoloration at the monitoring plot Kaiseraugst has shown that beech, oak and ash trees have all been affected differently as a result of the summer drought of 2003. In 2004, a digital picture data base was developed for the research project 'Phenophot' at the Geographical Institute Berne which allows the phenological observations to become objective and reproducible. A Phenological Growing Index (PGI) is being derived from the red-green-blue channel data of the digital sensor, which complements the information of satellite based vegetation indices. These indices include the Normalized Differenced Vegetation Index (NDVI) on a sub-pixel level which provides improved accuracy for the information on the character and beginning and ending of the vegetation period. The first comparison of the phenological spring index from the satellite based NDVI revealed that the annual start of spring is reproduced most accurately by determining a threshold of the NDVI.
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