Image measurements of leaf scorches on landscape trees subjected to extreme meteorological events

Trees grow in changing environments and are usually injured by many external factors including both abiotic and biotic. Leaf scorch is a main symptom for many landscape trees when they are stricken by meteorological extreme events, such as summer drought, strong typhoon and winter freezing and so on. In the study, the internal angle of injured area (IAIA) was defined in relation to vein lines and measured non-destructively for some landscape tree species. Meanwhile, the leaf scorch area percent (LSAP) and percent of scorched central vein (PSCV) were also determined from RGB images. Positive relationships between IAIA and LSAP and between PSCV and LSAP were found. The larger IAIA values for scorched leaves and smaller IAIA values for spot/anthracnose diseased leaves of the studied trees indicated that IAIA may be used as a diagnosing index of leaf scorch symptoms.

► Leaf scorch is an evident symptom for many landscape trees.
► The internal angle of injured area (IAIA) measured by using the image measurement.
► The leaf scorch area percent (LSAP) and percent of scorched central vein (PSCV) were also determined.
► Positive relationships between IAIA and LSAP and between PSCV and LSAP were found.
► The larger IAIA values for scorched leaves supported the partial withering hypothesis of landscape trees.