* Green Inside (Cambium): The green layer you see is the cambium. This is a thin layer of living tissue that produces new wood cells (xylem) on the inside and new bark cells (phloem) on the outside. The cambium contains chlorophyll, the pigment that allows plants to photosynthesize, giving it that green color.
* Brown Outside (Bark): The brown outer layer is the bark. This is dead tissue that primarily protects the living tree from injury, disease, and weather. The bark can vary in thickness and color depending on the tree species.
Here's a simplified breakdown:
* Living: Cambium (green) - actively growing
* Dead: Bark (brown) - protective outer layer
Why does the cambium turn brown?
* Aging: As the cambium produces new layers of xylem, the older wood gets pushed further inward. Eventually, these older xylem cells die and become part of the heartwood, which is darker and denser than the living sapwood.
* Injury/Disease: If the bark is damaged, the cambium can be exposed and die, resulting in a brown spot.
It's important to remember that not all trees have a green cambium layer. Some trees have a more cream or light-colored cambium, but it's still the living layer that produces new wood.
