Heart rot
Encyclopedia
Trunk (botany)
In botany, trunk refers to the main wooden axis of a tree that supports the branches and is supported by and directly attached to the roots. The trunk is covered by the bark, which is an important diagnostic feature in tree identification, and which often differs markedly from the bottom of the...
and branches. Fungi enter the tree through wounds in the bark and decay the heartwood. The diseased heartwood softens resulting in trees that structurally weaker and prone to breakage. Heart rot is a major factor in the economics of logging and the natural growth dynamic of many older forests. Heart rot is prevalent throughout the world affecting all hardwood trees and can be very difficult to prevent. A good indication of heart rot is the presence of mushrooms or fungus conks on the tree.
Biological cause
Heart rot is caused by fungiFungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
entering the trunk of the tree through wounds in the bark
Bark
Bark is the outermost layers of stems and roots of woody plants. Plants with bark include trees, woody vines and shrubs. Bark refers to all the tissues outside of the vascular cambium and is a nontechnical term. It overlays the wood and consists of the inner bark and the outer bark. The inner...
. These wounds are areas of the tree where bare wood
Wood
Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...
is exposed and usually a result of improper pruning
Pruning
Pruning is a horticultural practice involving the selective removal of parts of a plant, such as branches, buds, or roots. Reasons to prune plants include deadwood removal, shaping , improving or maintaining health, reducing risk from falling branches, preparing nursery specimens for...
, fire
Fire
Fire is the rapid oxidation of a material in the chemical process of combustion, releasing heat, light, and various reaction products. Slower oxidative processes like rusting or digestion are not included by this definition....
damage, dead branches, insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s or even animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...
damage. The fungal spore
Spore
In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...
s enter the exposed wounds, germinate within the wood tissues and slowly ingest the heartwood. The infection is a very slow process and can take from months to years, depending on conditions and tree health. An average fungus will grow 6–8 centimeters per year, and extensive development in the wood tissue is needed to produce mushrooms or conks.
Impact
Heart rot fungi have both a huge economic and environmental impact. The fungi only target the nonliving wood tissue of the heartwood and do not affect the living sapwood. Initially, infected heartwood is discolored but not structurally compromised. As the fungi grow they decay more wood and the tissue becomes increasingly soft and weak. The tree can still grow around the decayed heartwood because the live wood tissue is not affected. The growth around decayed areas of heartwood creates structural weaknesses in the tree. Trees with extensive decay are more susceptible to broken branches and trunksTrunk (botany)
In botany, trunk refers to the main wooden axis of a tree that supports the branches and is supported by and directly attached to the roots. The trunk is covered by the bark, which is an important diagnostic feature in tree identification, and which often differs markedly from the bottom of the...
.
Logging
Heart rot causes huge profit loss in the loggingLogging
Logging is the cutting, skidding, on-site processing, and loading of trees or logs onto trucks.In forestry, the term logging is sometimes used in a narrow sense concerning the logistics of moving wood from the stump to somewhere outside the forest, usually a sawmill or a lumber yard...
industry every year due to damaged and decayed timber
Timber
Timber may refer to:* Timber, a term common in the United Kingdom and Australia for wood materials * Timber, Oregon, an unincorporated community in the U.S...
. It is estimated that about one third of annual timber (20 billion board feet) harvest is lost due to some form of rot. Trees wounded from machinery or other falling trees and are then more susceptible to heart rot. It results in trees that cannot be sold due to substantial decay and introducing ideal rot conditions into younger forests that would normally not be as susceptible.
Environmental
Heart rot and other tree disease serve as factors of environmental change. This is magnified in areas that are not prone to large scale dynamic disturbances like wildfires or are dominated by old growth timber. In older growth forests, trees are unable to combat heart rot effectively because they grow at a much slower pace. Extensive rot causes these trees to be more susceptible to high winds and trunk fracture. As the old growth dies out, it allows new growth to take its place, altering the dynamic of the environment. Decaying trees also provide shelter to animals as well as microorganisms. Through this process of dynamic change, heart rot contributes to biologically diverse habitatHabitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
s.
Prevention/control
The prevention of heart rot can be a very difficult task but, there are effective measures to minimize damage. These methods include facilitating healthy growth, minimizing wounds and proper pruning of branches. A healthy tree naturally combats heart rot through a process called compartmentalizationCellular compartment
Cellular compartments in cell biology comprise all closed parts within a cell, usually surrounded by a single or double lipid layer membrane. Most organelles are compartments like mitochondria, chloroplasts , peroxisomes, lysosomes, the endoplasmic reticulum, the cell nucleus or the Golgi apparatus...
. The tree grows around the decayed wood tissue and prevents the fungus from spreading to a larger area of the trunk. Providing a tree with the necessary nutrients, water and growing conditions will promote healthy growth and minimize rot. The bark is the tree's main defense against disease; reducing the amount of large wounds and bare wood, especially in older trees, helps prevent rot.
Pruning techniques
PruningPruning
Pruning is a horticultural practice involving the selective removal of parts of a plant, such as branches, buds, or roots. Reasons to prune plants include deadwood removal, shaping , improving or maintaining health, reducing risk from falling branches, preparing nursery specimens for...
focuses on removing dead or diseased branches with minimal damage done to the tree. Branches connect to the trunk and grow from the branch collar
Branch collar
A branch collar is the attachment structure in woody plants that connects a branch to its parent branch or to the trunk. The branch collar consists of overlapping wood fibers....
. While the branch itself maybe be dead, the branch collar is still healthy and resistant to disease. It is from the branch collar that a new limb will generate and grow so, it is important not to damaged it while pruning. Make clean cuts at the base of branch adjacent to the branch collar. Small branch stubs(larger than three inches) will inhibit the growth process and provide fungi with ideal growth environments.
