Tuesday, 07. February 2017

Photosynthesis and the Beech

Photosynthesis is the most important energy conversion process on earth, through which all vascular plants, ferns, mosses, most algae and some bacteria are capable of converting light energy into chemical energy.

The foliage of a common European beech, which is populating around 19% of the Ger-man forests, contains about a million leaves – assuming a 100 years old and 35 meters high specimen. Each of these leaves encloses the green pigment chlorophyll. It absorbs mainly light from the blue, red and violet spectrum and then reflects green light, which is why chlorophyll-containing parts of the plants appear green. In fall the tree slowly looses these colour molecules, so that other pigments dominate and give us an almost golden impression.

But in summer, when the midday sun in Central Europe is at an angle of 60° to 65° and under ideal weather conditions shines with an irradiance of about 700 watts per square meter on the broad, sweeping crown of the beech, the small power plants in the leaves are running at full steam.

Because during the complex biochemical process, which derives from the two Greek words "photos" for light and "synthesis" for composition, the chlorophyll is responsible for ensuring that the leaves produce nutrients from the carbon dioxide of the air and the water of the soil. The green pigment is stored in the pigment carriers of the leaves: the so-called chloroplasts. This is where the photosynthesis takes place.

On the undersides of the leaves, there are the so-called stomata: pores, through which air passes into the interior of the leaves and flows through the voids between the plant cells. By using solar energy, the chlorophyll molecules succeed in extracting the carbon dioxide from the air. Thereupon a complicated production process initiates:

The carbon dioxide reacts with the water flowing through the tree and from this proce-dure glucose, also known as dextrose or grape sugar, is produced. On this energy-rich material the tree feeds and lives. In addition to glucose, another chemical compound is released: oxygen - on which all life on our planet depends.

For example, the stomata of our 100-year-old beech, releases about 1.7 kilogram of oxygen per hour. This is as much oxygen as 50 people on average need to breathe for an hour. The more radiation the leave is met by and the more chlorophyll it encloses, the higher the photosynthetic activity. Furthermore, humidity and temperature play an important role. At high humidity and 86 °F the stomata are fully opened and the gas exchange of carbon dioxide and oxygen is best ensured. In view of these facts, it is not surprising that the tropics are called the planets "green lungs".

After the common European beech was driven out of Central Europe during the last ice age, it survived in the Mediterranean region and began its re-conquest of the continent about 10000 years ago. From sunrise to sunset it has been producing oxygen and glu-cose for itself and its environment ever since then.

On 25 June 2011 the UNESCO World Heritage Committee has received five old German beech forests into the World Heritage List. Accordingly these join the cross-border World Heritage "Beech forests", which originally only forests in Ukraine and Slovakia belonged to. The World Heritage Site is now named "Primeval beech forests in the Car-pathians and ancient beech forests of Germany". These are the National Park Kellerwald-Edersee in Hesse, the Grumsiner Forst in Brandenburg, the Müritz National Park in Mecklenburg-West Pomerania, the National Park Jasmund and the National Park Hainich in Thuringia. In these forests one can find specimen, which are impressive 260 years old – so they represent the most venerable remnants of a large, wild beech population in Germany.