Red oak leaves in the autumn park by Silva Wischeropp

These bright, autumnal leaves of the oak tree were taken on 18 October 2019 in the late midday hours in a park in the Berlin district of Pankow.
The photo was taken with the NIKON D800 (lens: NIKKOR 20.0 mm f/2.8).

Autumn, one of the four meteorological and astronomical seasons, is the time of year between summer and winter. In the temperate zones it is the time of harvest and leaf fall. In autumn in the northern hemisphere, the sun appears to move from the celestial equator to the Tropic of Capricorn. Astronomically, autumn begins here with the equinox on 22 or 23 September; meteorologically and biologically, it is usually at the beginning of September. For the southern hemisphere, the astronomical start is on 20/21 March. Autumn ends astronomically on 21 or 22 December in the northern hemisphere and on 21 June in the southern hemisphere (winter solstice). The months of September, October and November in the northern hemisphere and March, April and May in the southern hemisphere are considered to be autumn. In autumn, the leaves on the trees change colour before they fall off. This is due to the slow withdrawal of plant sap into the trunk or roots. The chlorophyll is broken down and other leaf pigments provide the colour. These pigments are, for example, carotenoids and anthocyanins. Some of them are already present in the leaf, others are newly formed, such as anthocyanins. The colouring agents have a protective function against sunlight, so that the juices present in the leaf can be transferred to the stem before it finally falls off (see leaf fall).