About two months ago my marine science class went for a tour behind our school. It has been a week since we revisited the sites after summer has passed. There were some dramatic changes near the lake and in the forest. Seems like the water level has rises. The surroundings are more moist, yet the trees are drying out. Their leaves have start to fall.
In the forest, the sun is lower in the sky causes shade area to shifted. The good old Douglas-fern tree looks like it is thirst for water. There are also maple leaves all over the forest. Vegetation of mushrooms also increases.
During autumn or winter, there are less sunlight and water for plants to use in photosynthesis. After they had shut down their food-making factories, they will use the energy that they have stored in summer. Tress need to ‘sweat’ constantly in order to survive through cold weather. Loosing their leaves decrease the amount of space for them to ‘sweat.’
Therefore, hormones in tress trigger the process of abscission where their leaves are being cut-off by specialized cells. The green chlorophyll start to disappear as the pigments are broken down for nutrients. This is one of the reason why the colour yellow, orange, red and gold start to show. When the leaves has been shed at the end of abscission progress, a protective layer of cells grows over the exposed area.