question: why do Orchard Growers periodically chop all their trees down?
comment: Fruit-bearing trees are at peak production and health for about 10 years after they start fruiting. After that, the tree is much more susceptible to disease and pests. Orchards are planted in rotation so there are always productive trees when others need to be culled. The lumber of aged trees is valuable as well, but it won't be valuable if it's in poor condition. Harvests are timed to consider all of these factors and end up with the highest quality product.
passages: Liberation cutting
  
  Liberation cutting has similar goals to cleaning, namely the allocation of resources to the most promising trees available on a site. What separates liberation cutting from cleaning is that the overtopping competitors are of a distinctly older age class. Need for liberation cutting often occurs when seedlings of a desired species have been regenerated by a logging operation, but that operation has left older, poor quality or undesired trees that are shading the regeneration and limiting its growth.
   There can be a vast difference between the techniques and practices of professional arborists and those of inadequately trained tree workers who simply "trim trees". Some commonly offered "services" are considered unacceptable by modern arboricultural standards and may seriously damage, disfigure, weaken, or even kill trees. One such example is tree topping, lopping, or "hat-racking", where entire tops of trees or main stems are removed, generally by cross-cutting the main stem(s) or leaders, leaving large unsightly stubs. Trees that manage to survive such treatment are left prone to a spectrum of detrimental effects, including vigorous but weakly attached regrowth, pest susceptibility, pathogen intrusion, and internal decay. 
   During harvest, pickers must climb ladders to carefully remove branches of fruit from longan trees. Longan fruit remain fresher when still attached to the branch, so efforts are made to prevent the fruit from detaching too early. Mechanical picking would damage the delicate skin of the fruit, so the preferred method is to harvest by hand. Knives and scissors are the most commonly used tools.
   "The relative permanence of an orchard demands far-sightedness. An ill-chosen variety can cost years of time and care before it is discarded as impractical or chronic diseases exact their toll. Failure to properly amend a soil before planting is not easily rectified after a tree is established. And a pruning, fertilization, and training regimen needs to be well-considered at the start and somewhat consistent through the years, or the orchardists are risking aggravating diseases, inducing biennial bearing, delaying the age of fruiting, or otherwise creating long-lasting problems for themselves and the plants.
  
  Section::::Challenges Faced by Community Orchardists.:Community Resistance.
   "Uneven-aged and even-aged methods differ in the scale and intensity of disturbance. Uneven-aged methods maintain a mix of tree sizes or ages within a habitat patch by periodically harvesting individual or small groups of trees, Even-aged methods harvest most or all of the overstory and create a fairly uniform habitat patch dominated by trees of the same age". Even-aged management systems have been the prime methods to use when studying the effects on birds.
  
  Section::::Mortality.
   Historical orchards have large, mature trees spaced for heavy equipment. Modern commercial apple orchards, by contrast and as one example, are often "high-density" (above 150 trees per acre) and in extreme cases have up to 9000 trees per acre. These plants are no longer trees in the traditional sense, but instead resemble vines on dwarf stock and require trellises to support them.
  
  Section::::Orchard conservation in the UK.
  
  BULLET::::- Natural England, through its Countryside Stewardship Scheme, Environmental Stewardship and Environmentally Sensitive Areas Scheme, gives grant aid and advice for the maintenance, enhancement or re-creation of historical orchards.
   In the early development of forest stand, density of trees remain high and there is competition among trees for nutrients.When natural regeneration or artificial seeding has resulted in dense, overstocked young stands, natural thinning will in most cases eventually reduce stocking to more silviculturally desirable levels. But by the time some trees reach merchantable size, others will be overmature and defective, and others will still be unmerchantable. To reduce this unbalance and to obtain more economic returns, in the early stage, one kind of cleaning is done which is known as precommercial thinning. Generally, one or two times precommercial thinning is done to facilitate the growth of the tree
   Section::::Challenges Faced by Community Orchardists.
  
  Section::::Challenges Faced by Community Orchardists.:Pest and Disease Problems.
  
  One of the problems faced by the community orchard movement is that many groups are planting fruit trees without knowing the complexities of how to care for them organically. Poor decisions early on and a lack of fruit tree care skills can lead to long-lasting problems.
  
  In an article "Community Orchards" by the National Sustainable Agriculture Information Service, author and NCAT Horticulture Specialist Guy K. Ames writes.
   Many promising plantations have failed through lack of tending. Young crop trees are often ill-equipped to fight it out with competition resurgent following initial site preparation and planting.
   This means that in shelterwood the trees will be removed at some time as part of the method, but with seed-tree methods there are so few that it is not necessary to make a cut just to remove them, they are more likely to be taken when performing a tending or thinning operation or other cut than a removal cut.
  
  Section::::Potential problems.
  
  Any silvicultural method is more prone to certain problems than another. Shelterwood has several particular problems.
  
  BULLET::::- Windthrow from poor selection of trees in relation to the local wind patterns and direction on a site.
   BULLET::::- clear-cutting involves removal of all trees from a tract of land within a 20-acre area followed by replanting if the new ingrowth of seedlings does not meet stocking levels outlined by the Forest Practice Rules. This can result in disturbances in the Sierra Nevada environment by creating patches of densely packed, single-species, same-aged, tree plantations.
  
  BULLET::::- Single Tree Selection involves removal of individual trees in a prescribed fashion. Usually this is done across the size distribution of trees in a stand and mimics to some degree the natural mortality pattern and rate within a stand.
   Section::::Season of planting.:Conventional fall planting with fresh-lifted stock.
   BULLET::::- The production centers, i.e. the leaves, are sources, the storage organs, growth tips or other destinations for the photosynthetic production are sinks. The lack of sinks can be a limiting factor for production too, as happens e.g. in apple orchards where insects or night frost have destroyed the blossoms and the produced assimilates cannot be converted into apples. Biennial and perennial plants employ the stored starch and fats in their storage organs to produce new leaves and shoots the next year.
   BULLET::::- As supporting tree breeding make advances, new seed orchards will be genetically better than old ones. This is a relevant factor for the economic lifetime of a seed orchard. Considerations for Swedish Scots pine suggested an economic lifetime of 30 years, which is less than the current lifetime.
   Section::::Season of planting.:Summer planting with fresh-lifted stock.
   The dearth of seed and a deficiency of receptive seedbeds were recognized as major reasons for the lack of success of clearcut harvesting. One remedy attempted in British Columbia and Alberta has been alternate strip cutting. The greater seed source from uncut trees between the cut strips, and the disturbance to the forest floor within the cut strips could be expected to increase the amount of natural regeneration. Trees were cut to a diameter limit in the cut strips, but large trees in the leave strips often proved too much of a temptation and were cut too, thus removing those trees that would otherwise have been the major source of seed.
   Of course the owner could set a condition that none team could leave a tree that until it is fully harvested. That would help in some way to break the escalation archetype unless workers realize they are not punished for some other undesirable behaviour, for example being careless of tree condition after the harvest.
  
  As can be seen in this example, the escalation archetype might bring positive results (faster harvesting) but it is necessary to monitor behaviour of the affected system to ensure long-term prosperity.
  
  Section::::Examples.:The attention fight.
   Section::::Common methods of harvesting.:Shelterwood systems.
  
  Shelterwood systems involve 2, 3, or exceptionally more partial cuttings. A final cut is made once adequate natural regeneration has been obtained. The shelterwood system is most commonly applied as a 2-cut uniform shelterwood, first an initial regeneration (seed) cut, the second a final harvest cut. In stands less than 100 years old, a light preparatory cut can be useful. A series of intermediate cuts at intervals of 10–20 years has been recommended for intensively managed stands.
   The best time to harvest leaves varies, although most locals seem to agree that one should harvest when the moon is in "menguante" (after the full moon), usually anywhere from 3 to 15 days. Most also agree that this is because natural pesticides found in the "Manicaria saccifera" are released at this time and prevent insects from damaging the roofing.
   BULLET::::- Cleaning: Release of select saplings from competition by overtopping trees of a comparable age. The treatment favors trees of a desired species and stem quality.
  
  BULLET::::- Liberation cutting: A treatment that releases tree seedling or saplings by removing older overtopping trees.
  
  Section::::Tending.:Spacing.
   Difficulties in harvesting are the major barriers of orchard production and development of the plant's potential as a cash crop. Harvesting the fruit is problematic because the fruit does not easily release from the stem. Different mechanical harvest methods have been developed, such as shaking, vacuum and quick freezing, but most have the disadvantages of fruit and bark damage and low efficiency. 
   Quite often, tree planting contractors will deduct some of the cost associated with the operation of the contract directly from the tree planter's daily earned wages. These imposed fees typically vary from $10 to $30 per day, and are referred to as "camp costs". In "some" cases, rookie tree planters end up owing their employer money for the first few pay periods.
   BULLET::::- Regulatory pruning: This is carried out on the tree as a whole, and is aimed at keeping the tree and its environment healthy, e.g., by keeping the centre open so that air can circulate; removing dead or diseased wood; preventing branches from becoming overcrowded (branches should be roughly 50 cm apart and spurs not less than 25 cm apart along the branch framework); and preventing any branches from crossing.
  
  Section::::Pruning of tip bearers.
   Fruit harvest is made during September, October, December, January and June. Since the fruits are dehiscent, it is recommended to harvest the fruits directly from the trees before they open to release the seeds when they are still green, but opening lines can be seeing. 
   BULLET::::- Restrictive policies:Stipulated in the agreements made between YISEDA and the government, “YISEDA can only cut down trees from plantation areas measuring at least 30 centimetres in diameter”. For this reason it is only recently that the trees planted in the early 1990s by YISEDA could be harvested and sold on the market. Before this the YISEDA had very little income on which to maintain their livelihoods, and were strongly relying on the uncertain future success of the CBFM.
  
raw_presuppositions: Orchard trees are always productive.
raw_corrections: Orchard trees are at peak production for about 10 years after they start fruiting, after that the tree is much more susceptible to disease and pests.