Torkan 2018 och dess påverkan på skogsvegeationen i Skogaryd och Västra Tunhem, Västra Götaland. - En satellitbaserad fjärranalysstudie
Abstract
In the summer of 2018 Sweden was hit by a long-term drought that heavily affected the forest
with forest fires that lasted for several months. After the summer a lot of time and resources
were spent on forest fire prevention. However, knowledge is lacking regarding the direct
impact of the drought on forest vegetation. The aim of this study is to examine how the
drought affected different natural environments in a forest and mire mosaic in SW Sweden.
Satellite based remote sensing has been used to produce two Vegetation Indices (VI), namely
Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index
(NDWI), where NDVI measures the photosynthesis and NDWI measures the photosynthesis
and wetness of the vegetation. A time series of VI-values over the months of May to
September for the years 2017 and 2018 has been constructed over parts of Skogaryd and
Västra Tunhem. Climate data has been used for both years to examine the connection
between VI, air temperature and precipitation. The remote sensing indicates that the values of
both NDVI and NDWI were generally lower during the summer of 2018 in comparison to
2017. However, different trends are visible in different types of vegetation. Both VIs are
good indicators of the drought in the deciduous forest and on the mire. NDVI is a good
indicator of the drought over the coniferous forest with lower NDVI-values in July 2018.
NDWI did not show any clear trends over the coniferous forest. Neither of the VIs from the
clear cut show any clear trends. The results from this study indicate that NDVI should be
preferred over NDWI as a drought indicator. This is contrary to earlier research that has
argued that NDWI is a better indicator of drought than NDVI. The generally lower VI-values
for 2018 is most likely a result of the higher air temperatures and lower precipitation in 2018
compared to 2017.
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Date
2019-10-30Author
Flink, Erica
Stålnacke, Ville
Keywords
NDVI
NDWI
drought
Sentinel-2
hemiboreal forest
Series/Report no.
B
1058
Language
swe