Fatigue is essential in mechanical pulping when producing flexible paper fibers energy efficiently from stiff wood fibers. Fatigue propagation depends mainly on strain variation. The objective of the study is to determine how compressive strain is distributed between earlywood and latewood. Uneven distribution of local strain variation is likely to cause different amount of fatigue for earlywood and latewood and thus affects the usability of these fibers in the paper products. To characterize the material's response to mechanical defibration at high strain rates a unique testing equipment was utilized. The ESHD (Encapsulated Split-Hopkinson Device) at Mid Sweden University allows generation of such high strain rate pulses. Combining this with high speed photography at 50 000 fps offered the possibility of quantitative strain field mapping by image analysis. Since both wood temperature and moisture content affect strain behavior, moisture content was in this study kept constant at 45 %. Testing temperature was varied between 20°C and 135°C. Additionally, four levels of compressive fatigue treatment in the radial direction, prior to the high strain rate tests, were used to investigate how different parts of the annual rings were changed due to the fatigue treatment. In the measurements, it was noted that the strain was concentrated in the softer earlywood layers and there were unexpectedly little strain in the latewood layers. The temperature and the fatigue level clearly affected the magnitude of the strains. Higher temperature and fatigue level increased the strain difference between earlywood and latewood in the sample.