Table 2 Classification of decay in the aged wood samples and sound sample
Damage level | Classification criteria | Samples |
|---|---|---|
I | No sign of degradation. All cell walls are smooth and intact | F-0 |
II | Sporadic signs of degradation. Ray and tracheid cell walls well-preserved and almost intact. Only smaller cracks exist on a few cell walls | F-1 |
III | Some border pits, vessel, and ray cell walls are cracked and squeezed, showing moderate degradation of secondary walls | F-2, F-5 |
IV | Majority of cell walls are distorted, and the lumen often disappears. Some cells are more or less cracked along the micro-fibril angle, transforming the wall itself to strips of fibers | F-3, F-4, F-6, F-7 |
V | The cell walls have completely disintegrated, showing evident and widespread decay. Cell walls are extremely distorted, leading to the collapses of all cells. The identification of morphology can be very difficult | F-8 |