Tending Operations Shrinivas N Sabale Tending Operations Operations

Tending Operations Shrinivas N. Sabale

Tending Operations • Operations carried out for the benefits of forest crop at any stage of its life. • It essentially covers operation on the crop itself and competing for vegetation and include weeding, cleaning, thinning, felling, pruning, climber cutting, girdling but exclude soil working, drainage, irrigation, and burning, etc. • For the establishment of the regeneration and subsequent development of the forest crop up to harvesting, several operations are carried out. • These operations are carried out in the forest crop at different stages of growth in order to provide a healthy environment for their development.

NEED FOR TENDING OPERATIONS Two major needs: • 1. Sanitation: • 2. To provide growing space for trees. – The act of reducing the chanced of insects and other diseases in sanitation. The trees which are susceptible, injured, broken, weak, diseased, or infected by insects are removed. – Looking for space in which trees extend their masses, lastly tending operations are essential for providing, the tree with more light water nutrients, etc. – Tending operations result in the achievement of a form which confirms the human sense of liking.

Weeding • Any unwanted plant that interferes or tends to interfere with the growth of the individuals of favoured species’ is called a weed. Weeding is defined as ‘a tending operation done in the seedling stage in the nursery or in a forest crop, that involves the removal or cutting back of all weeds.

Objectives of Weeding • To protect the crops from suppression • To reduce root competition for moisture and nutrients available in the soil • To reduce transpirational water loss • To improve light conditions

Methods of Weeding • Weeds may be controlled by the following methods: • a) Mechanical Methods • b) Biological Methods • c) Chemical Methods

When Weeding is done? • It is done at the seedling stage. A common practice for weeding is that it must be done before weeds start suppressing the seedling crops and when seedlings have stopped growing in the season. • Weeding should be carried out when the weeds have tender roots and shoots, otherwise, it will be difficult to uproot. In plantation, weeding is done during and after the monsoon. • Number of weeding depends upon the intensity of weed growth and the rate of growth of seedlings of the favoured species, three weddings are usually done in the first year, two in the second year and one in the third year, whereas fastgrowing species require weeding for one or two years.

Where Weeding is done? • Areas where weeds are tall and dense. • Where light cannot reach the ground easily, which not only affect the regeneration but also obstructs the growth of species, because weeds grow at a faster rate than the crop species. • It can be done in nurseries, natural or artificial regeneration.

How Weeding is done? • It is customary to weed in a circle of 60 cm in diameter around the plants, but this should be regarded as an absolute minimum. • Increasing the diameter of the circle of one metre would be very desirable. • In parts of the Terai and Bhabar Terai Zones, where there is a dense growth of perennial grasses, weeding 60 cm around the plants is certainly inadequate. Weeds should be pulled to come with the roots. • During the winter, seedlings need protection from frost. Therefore, weeding should be stopped by the end of September until the start of spring. • The intensity of weed growth and rate of growth of crop species determine the number of weeding.

Weeding Limitations • Despite weeding removes all plants that compete with the crop species. • Some crop species, by nature, love to have shade-partial or complete while some others are shade tolerant.

Weeding Important Points to Note • The removal or cutting back of any sort of weed growth that is interfering with the growth of the crop is called weeding. • Removal means uprooting the entire weed even Morus alba if not required. • Cutting back is meant by cutting the upper portion but this does not control weeding. • When plants are 3 feet high or less, the stage is seedling. In the seedling stage usually, the side branches have yet to come out and light frequently falls upon open interplant spaces and then weeds become active, start competing and start sucking food, hence they are removed.

• Weeds mainly appear from seeds, others from coppice and still others form suckers. • In natural forests, Viburnum spp creates a problem by appearing again and again. • Weeding should be at early ages because seedlings have to suffer when the weeds surpass them in height. • For shisham plantation, weeding is done twice in the first year. • In addition, weeding continues with cleaning as well.

CLEANING: • Cleaning is carried out in a crop which has not crossed the sapling stage • It is defined as the cutting made in order to face the best individuals from undesirable one of the same age which interfere or are likely to interfere with the growth of the desired individuals. • Advantage offered by cleaning is the proper regulation of the composition of the crop, particularly in mixed crops.

Methods of Cleaning • Methods of cleaning may be mechanical, biological and chemical as described under weeding. • Tending operations done in sapling crop particularly just before or with the first thinning are involving the removal or cutting back of all inferior growth, climbers, etc” including an excess of coppice shoots and sapling if interfering with better one. • Sometimes cleaning and the first thinning is done simultaneously or sometimes separate. • After sapling branches shade up the ground then weaker type of seedlings may appear, they are undesired and removable. • Bela plantations of Shisham raised from root suckers and coppices demands cleaning. Here hundreds of coppice shoots are reduced. Diseased shisham will also be removed.

CLIMBER CONTROL: • A plant that attaches itself to other plants or objects such as posts and walls as it grows is a Climber. • This difficulty is faced in nurseries usually seedlings are twined by climbers. Afterwards, the internode increases in length. The climber pulls the head of the seedling. Since this host climber can’t be extended, shoot of the seedling is broken. • Sometimes it completely girdles the shoots and plants die of suffocation. • Removal of climbers is necessary.

THINNING • Thinning is defined as a felling made in an immature stand for the purpose of improving the growth and form of the trees that remain without permanently breaking the canopy. – 1. It is a treatment of forest crops whereby the number of trees growing in a stand is reduced. – 2. Thinning consists of a series of successive felling operation for a number of times before the crop matures. – 3. The interval between two succession felling may be fixed but it is dependent on the time required for canopy closure. – 4. Thinning is carried out in a crop after it reaches the sapling stage and continued up to the beginning of the regeneration period. – 5. The thinning principles are applicable to pure and even-aged or nearly even-aged crop or even-aged groups of the trees in a crop. – 6. Thinning always increases spacing and decreases the number of trees per unit area.

– 7. Most of the trees species are raised at a close spacing i. e. i. 2 m x 2 m or, ii. 3 m x 2 m or, iii. 3 m x 1 m – 8. After five or ten years depending upon species and site conditions the canopy closes or root competition is so heavy that the plants are not able to grow unless they are thinned out. – 9. They are quite spaced for the crown as well as root development. – 10. Thinning is based on the principle of natural development of crop after each thinning number of trees/hectare decreases but this is compensated by its diameter and height growth.

OBJECTIVES OF THINNING 1. 2. 3. 4. 5. 6. 7. To improve the hygienic condition. To create best conditions of growth. Salvage the anticipated losses of the merchantable volume. To obtain a desirable composition of crops. Retaining seed beares. Improvement in wood quality. To obtain intermediate yield and increase net yield and financial out-turn. 8. Decomposition of raw hummus. 9. To reduce the risk of diseases and pests.

Purpose/aims of thinning • • • To reduce competition in root and crown Discourage weed growth Improve quality of wood Regulation of rate of growth Thinning controls rotation. Closer the trees, smaller is the rate of growth longer is the rotation and vice versa. So thinning is done to increase rate of growth and reduce rotation. • Trees on ridges are exposed to hazards, so they are heavily thinned. Greater snow will be accumulated in dense crop and smaller amount in open crop. Bigger the crown, larger is the production of resin. Wider the crown, greater is seed/fruit production.

• Thinning is also a determinant of quality. Wider space provided give wider annual rings. • To increase seed production • Reduction in the net cost of growing • Whatever spending is done on growing stock, thinning pays some of it back as fuel wood, etc. • Reducing the risk of fire and diseases • Encouraging the advanced growth • Fulfilling the market demands

METHODS OF THINNING • For regular crop the following methods are used for thinning: • 1. Mechanical thinning • 2. Ordinary or low thinning • 3. Crown Thinning • 4. Free thinning • 5. Advance thinning • 6. Maximum/ Numerical thinning

MECHANICAL THINNING • In this type of thinning the trees are removed by some thumb rule – e. g. Removal or alternate rows, – or Removal of alternate diagonals – or Removal of every second third, fourth line etc. – or where the spacing is irregular the minimum spacing is maintained by using “STANDARD STICK” method. • This type of thinning is applied to young plantations in which canopy differentiation has not taken place.

Types of mechanical thinning • i. Row thinning – trees are removed in lines or rows. • Ii. Space thinning – Trees at fixed intervals of distance are selected by using “STICK” for retention end all others are cut. – This method is well suited to plantations having uniforms productivity but in case of high mortality plantation, this is difficult to apply.

– The formula evolved for some species to carry out thinnings are: i. GLOVER’S formula for Deodar D = d ii. WARREN’S formula for Deodar D = 1*1/2 d =3/2 d = 1. 5 d iii. HOWARD’S formula for Dalbergia sissoo D = 2 d where D = Spacing of trees in feet and d = Average diameter of trees inches – This method may be good for an area having uniform productivity but the disadvantage that many good trees which fall in diagonals or row are removed.

Low or ordinary thinning • This is known as “GERMAN THINNING” or “THINNING FROM THE BLOW” and consists of the removal of inferior individuals starting from the suppressed class, then taking the dominated class and ultimately some of the dominant class. • It is a very common form of selective thinning in regular crops. • It has been devised to be in line with nature because only those trees which have been unsuccessful in the struggle for growth are removed first.

ADVANTAGES OF ORDINARY THINNING • It is useful in areas where the demand for small timber is more and has a market for selling. • It is most suited for light demander species e. g. chir pine, sissoo, semal etc. • It is simple to apply and even a less trained staff can mark the trees for felling. • This thinning practice improves the HYGENIC condition because several diseased and insect infected trees are removed.

ADVANTAGES OF ORDINARY THINNING • This thinning is preferred where climber infestation is a problem but should not be carried out where there is a danger of soil erosion. • In this method, smaller and less vigorous trees are removed and vigorous trees are retained for fast growth. • Removal of lower crown classes helps in the Natural Regeneration of the species.

DEMERITS OF ORDINARY THINNING • There is always a danger of exposure to the soil • Increases the fire hazards • The removal of lower crown classes is troublesome and expensive due to thorny bushes, undesirable trees and climber infestation is heavy. • The surplus of the nutrients store is utilized by lower crown classes and remains in cycling.

CROWN THINNING • This is also known as “THINNING FROM ABOVE”. • This is a kind of selective thinning in which thinning is primarily directed to the dominant trees in a regular crop, the less promising ones being removed in the interest of the best available individuals: – The dominated and suppressed stems are retained unless they are dead, dying or diseased. • The crown thinning favours the crown development of the selected potential final crop, trees; – Retaining trees of lower crown classes can help in the natural pruning of the dominant trees which are to make the final crop.

• The selection of ELITES or ALPHA stems is necessary, – evenly spaced over the ground, – which are retained upto maturity or till the last thinning or two, – and thinning operations may accordingly be directed primarily to the removal of other stem hindering their optimum development. • Efforts are made on freeing the selection of most promising stems called “ELITE or ALPHA STEMS” from the competition of their less promising neighbors. • The number of future stems to be required at the rotation are first selected and retained evenly distributed over the area. • After selecting and marking the elite tree, if considered necessary, they are cut otherwise left for the protection of the site. • The crop after free thinning do not differ much in appearance from those subject to crown thinning, but the attention is concentrated on the trees to be retained rather than on the trees to be removed, just as in seeding felling.

Types of crown thinning • i. Light Crown Thinning (L. C. Grade) – This consists in the removal of dead, dying, diseased and wolf trees with such of the defective and after them the better dominants as are necessary to leave room for further development of the best available trees evenly distributed over the area. – The trees belong to classes V, VI, I (d), I (c), many of I (b) and a few of I (a) but not III and II are removed.

• ii. Heavy Crown Thinning (H. C. Thinning) – This grade of thinning pays even more attention to favouring the selected best times by removing all the remaining I (b), which can be taken without creating permanent gaps and more of I (a) i. e. classes V, I (d), I (c) most or I (b), some of I (a); but not III and II. – The final crop is target to achieve certain stocking e. g. 500 to 600 trees per hectare. – The dominated and suppressed trees are removed.

THE ADVANTAGES OF CROWN THINNING • This method checks soil erosion and damage due to frost, snow, wind etc. • Shade bearing trees are also protected. • The lower classes help in controlling weed and shrubs growth. • The side branches are pruned in a better way.

DISADVANTAGES OF CROWN THINNING ARE • The dominants are adversely affected. • The lower tree classes make difficult various operations. – e. g. marking, felling, logging and extraction of the thinned material. • It requires experience and skill.

FREE THINNING • This is also called HECK’S free thinning and is a modification of crown thinning. • It is also called “ELITE THINNING” or “SINGLE STEM SILVICULTURE”.

ADVANCE THINNING • This method was developed by CRAIB (1939) and O, CONNER for wattle and pine plantations in South Africa. • Advance thinning was tried for chir pine, but this method is not suitable for light demanding species under tropical conditions. • The rapid extension of the crown and quick closure of the canopy after felling does not take place in South Africa but rather grass and other weed growth are encouraged increasing fire hazard.

FACTORS AFFECTING THINNING PRACTICE • 1. Site Factors • 2. Nature of species • 3. Age

1. Site Factors • The site quality influence on thinning practice is that a relatively close canopy on the poorer sites should be maintained. • On low quality sites heavy openings should not be made. • The spacing out widely in earlier stages should not be carried out on hot, dry, slopes, on poor soils and on all sites where grass and other weed invasion is likely to occur. • A poor site will usually support less stems per hectare than a good one.

2. Nature of Species • The shade-bearers are more tolerant of crown than the light demanders therefore more frequent thinnings is needed for light demanders species. • Light demanders usually show good response to ordinary thinning where as shade-bearers to crown thinning. • Chir pine and sissoo, being light demanders require heavier grades of ordinary thinning. • For Deodar advance thinning is suitable as the site is not likely to degrade even after expose.

3. Age • The crown formation depends on age and in young ages when the crown formation is not completed mechanical thinning or stick thinning may e done with succession. • The light demander species require heavier grade of thinning at frequent intervals in younger crops. • On the other hand some species in middle age or maturity require crown thinning.