In trees, heart rot is a

fungal A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as one of the tradit ...

disease that causes the decay of wood at the center of the trunk and

branch A branch, also called a ramus in botany, is a stem that grows off from another stem, or when structures like veins in leaves are divided into smaller veins. History and etymology In Old English, there are numerous words for branch, includ ...

es. Fungi enter the tree through wounds in the bark and decay the

heartwood Wood is a structural tissue/material found as xylem in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulosic fibers that are strong in tension and embedded in a matrix of lignin t ...

. The diseased heartwood softens, making trees structurally weaker and prone to breakage. Heart rot is a major factor in the economics of

logging Logging is the process of cutting, processing, and moving trees to a location for transport. It may include skidder, skidding, on-site processing, and loading of trees or trunk (botany), logs onto logging truck, truckshardwood Hardwood is wood from Flowering plant, angiosperm trees. These are usually found in broad-leaved temperate and tropical forests. In temperate and boreal ecosystem, boreal latitudes they are mostly deciduous, but in tropics and subtropics mostl ...

trees and can be very difficult to prevent. A good indication of heart rot is the presence of

mushroom A mushroom or toadstool is the fleshy, spore-bearing Sporocarp (fungi), fruiting body of a fungus, typically produced above ground on soil or another food source. ''Toadstool'' generally refers to a poisonous mushroom. The standard for the n ...

s or fungus conks on the tree.

Biological cause

300px, The bracket fungus '' Fistulina hepatica'' is one of many that cause heart rot. Heart rot is caused by

fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

entering the trunk of the tree through wounds in the

bark Bark may refer to: Common meanings * Bark (botany), an outer layer of a woody plant such as a tree or stick * Bark (sound), a vocalization of some animals (which is commonly the dog) Arts and entertainment * ''Bark'' (Jefferson Airplane album), ...

. These wounds are areas of the tree where bare

wood Wood is a structural tissue/material found as xylem in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulosic fibers that are strong in tension and embedded in a matrix of lignin t ...

is exposed and usually, a result of improper

pruning Pruning is the selective removal of certain parts of a plant, such as branches, buds, or roots. It is practiced in horticulture (especially fruit tree pruning), arboriculture, and silviculture. The practice entails the targeted removal of di ...

fire Fire is the rapid oxidation of a fuel in the exothermic chemical process of combustion, releasing heat, light, and various reaction Product (chemistry), products. Flames, the most visible portion of the fire, are produced in the combustion re ...

damage, dead

es,

insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...

s, or even

animal Animals are multicellular, eukaryotic organisms in the Biology, biological Kingdom (biology), kingdom Animalia (). With few exceptions, animals heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, ...

damage. The fungal

spore In biology, a spore is a unit of sexual reproduction, sexual (in fungi) or asexual reproduction that may be adapted for biological dispersal, dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores fo ...

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 advance in the heartwood by 6–8 centimeters per year, and extensive development in the wood tissue is needed before mushrooms or conks are produced.

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 Wood is a structural tissue/material found as xylem in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulosic fibers that are strong in tension and embedded in a matrix of lignin that ...

. 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 trunks.

Logging

Heart rot causes huge profit loss in the

logging Logging is the process of cutting, processing, and moving trees to a location for transport. It may include skidder, skidding, on-site processing, and loading of trees or trunk (botany), logs onto logging truck, truckstimber Lumber is wood that has been processed into uniform and useful sizes (dimensional lumber), including beams and planks or boards. Lumber is mainly used for construction framing, as well as finishing (floors, wall panels, window frames). ...

. 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 are 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 An old-growth forest or primary forest is a forest that has developed over a long period of time without Disturbance (ecology), disturbance. Due to this, old-growth forests exhibit unique ecological features. The Food and Agriculture Organizati ...

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 and

tree hollow A tree hollow or tree hole is a semi-enclosed cavity which has naturally formed in the trunk or branch of a tree. They are found mainly in old trees, whether living or not. Hollows form in many species of trees. They are a prominent feature of n ...

s also provide shelter to animals as well as

microorganism A microorganism, or microbe, is an organism of microscopic scale, microscopic size, which may exist in its unicellular organism, single-celled form or as a Colony (biology)#Microbial colonies, colony of cells. The possible existence of unseen ...

s. Through this process of dynamic change, heart rot contributes to biologically diverse

habitat In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...

Prevention and 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 compartmentalization. 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

Pruning Pruning is the selective removal of certain parts of a plant, such as branches, buds, or roots. It is practiced in horticulture (especially fruit tree pruning), arboriculture, and silviculture. The practice entails the targeted removal of di ...

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 A branch collar is the "shoulder" between the branch and trunk of woody plants; the inflammation formed at the base of the branch is caused by annually overlapping Trunk (botany), trunk tissue. The shape of the branch collar is due to two separat ...

. While the branch itself may 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 damage it while pruning. Make clean cuts at the base of the 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.^ Hickman, G.W.. "Wood Decay Fungi in Landscape Trees Management Guidelines--UC IPM." UC Statewide Integrated Pest Management Program. http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74109.html#IDENTIFICATION (accessed January 25, 2010).

Examples

The following are some trees susceptible to heart rot: *

Alder Alders are trees of the genus ''Alnus'' in the birch family Betulaceae. The genus includes about 35 species of monoecious trees and shrubs, a few reaching a large size, distributed throughout the north temperate zone with a few species ex ...

* Aspen trunk rot *

Spirostachys africana ''Spirostachys africana'' is a medium-sized (about tall) deciduous tree with a straight, clear trunk, occurring in the warmer parts of Southern Africa. Its wood is known as tamboti, tambotie, tambootie or tambuti. It prefers growing in single-s ...

References

External links

{{Portal, Trees
Picture of a tree with heart rotThe heart rot fungus
Fungal tree pathogens and diseases