How does a tree live?
Trees are anchored into the soil by their roots. The roots also take up water containing dissolved minerals, which then travels up the tree via special vessels called xylem within the wood of the tree. This upward passage of water and nutrients is caused by 2 phenomena; transpirational pull which is created by the evaporation of water from the surface of leaves which then pulls the sap up the xylem vessels and root pressure which is created by osmosis of water into the roots causing a positive pressure that forces water up the trunk of the tree. Damage to roots or soil compaction above roots, such as from vehicles or construction traffic can therefore seriously affect the health of a tree.
The leaves of a tree are important in capturing sunlight energy which is converted into sugar by the process of photosynthesis. This chemical
reaction also uses carbon dioxide which is absorbed by the tree from the atmosphere and releases oxygen and so is a very important process to maintain a healthy balance of gases in our surroundings. This also explains how an unprofessional prune of a tree canopy can seriously damage the tree’s health.
The sugars that are created by photosynthesis are then transported around the tree in vessels called phloem. The sugars are either used to feed the cells of the tree or either stored for future use. The phloem vessels are found in the innermost layers of the bark, hence a tree will
normally die if a ring of bark is removed right around the tree.
During winter when deciduous trees lose their leaves, the tree survives on stored sugars produced earlier in the year. The process of leaf drop conserves water and helps some trees better survive harsh winter conditions. The most stressful times in the tree’s yearly cycle are when it is coming into leaf and when it is shedding leaves. Pruning operations should not take place during these times.