## 3 Results
### Review of Thematic Foci on Extreme Weather Events and Climate Change
#### 3.6.1 Drought
With seven study areas in each country, this proportion is distinctly higher than the overall distribution. The focus of the research with plots in Germany was on the influence of several other forest variables on the effects of drought in the forest. The extent to which a forest is damaged by drought does not depend solely on the characteristics of the drought. For example, in pine forests, the outer areas of the forest are more affected [105]. Soil type, soil texture, stoniness, effective rooting depth, and available water capacity (AWC) also determine the effects of drought. The proportion of dead spruce correlates with AWC [131]. Tree species play a role, e.g., beoch is more sensitive to drought than oak. According to [PERSON] et al. [129], this can be measured using spaceborne NDVI during severe droughs, as was the case in Germany in 2003. [PERSON] et al. [127] compared different NDVI values of four years before, during, and after a drought, and analyzed their relationship with forest structure type, soil moisture, and climate variables. They showed that different years show different relationships between the RS signal and other variables. [PERSON] et al. [128] came also to an unexpected conclusion when they compared the influence of drought in forests with different tree species densities. By employing airborne hyperspectral sensors, they discovered that plots with greater species richness were not less affected by drought-induced NDVI decreases. [PERSON] et al. [139] came to a comparable assumption, emphasizing that the location of the forest, rather than the tree species composition, is the critical factor influencing drought-induced forest damage. Studies in the USA have focused on the Sierra Nevada region [133; 134; 135; 137]. Again, several variables were shown to influence vulnerability to drought. The comprehensive study by [PERSON] et al. [135] used AHS and ALS data to show that mortality risk increases with tree height, forest density, and distance to the nearest river. The US studies also showed that tree species are particularly important. By accounting for tree species, [PERSON] et al. [133] were able to improve their mortality risk models. A method rarely used in this context is that of [PERSON] et al. [132], who implemented a spectral unmixing method to assess partial cover of pinon and juniper, as well as dead pinon. Using Landsat multispectral imagery from 2009 to 2016, they found increasing areas of dead pinon, especially during severe 2011-2014 drought. Studies with Chinese study areas are also well represented. The three studies by first author [PERSON] [140; 141; 142] on the importance of canopy height showed that taller trees had the highest damage rate, that shorter trees were more likely to recover after drought than taller trees, and that the resilience of taller trees decreased more during particularly severe drought. Age is closely related to size, which, according to [PERSON] et al. [143], is positively correlated with mortality in the southern taiga. In addition to tree size, forest type also plays a role in drought resilience. Using MODIS timeseries, [PERSON] et al. [144] showed that deciduous broadleaf forests were better adapted during the 2002 drought in China. A total of 11 drought studies were not assigned to a forest response category [145; 146; 147; 148; 149; 150; 151; 152; 153; 154; 155]. Most of these studies used MODIS timeseries and compared them with climate timeseries, in particular with the Standardized Precipitation Evapotranspiration Index (SPEI), which is often used in the context of drought. Studies on all continents with temperate forests were able to demonstrate the relationship between SPEI and MODIS timeseries. In summary, it can be concluded that relationships between drought events and forest dieback can be identified using various methods of relationship analysis between the remote sensing signal and one or more weather/climate variables.