Photo by Pixabay on Pexels.com[/caption]The objective of Seed Processing is to produce good quality seeds for sowing. The Processes are Pre-cleaning, Pre-curing, Cleaning.
Pre-cleaning involves cleaning of twigs, barks, leaf litter and other impurities before they are sent for extraction. It can be done by hand and by flotation and fruits be separated by blowing and winnowing.
Pre-curing involves the deliberate storage for ripening of seeds and slow air drying of seeds/fruits.
Cleaning of sound seeds from impurities can be done by screening and sieving,sorting,winnowing,flotation. Screening and sieving remove almost all impurities which have different size than the hole in sieve or screen. Sorting according to length may remove longer and shorter impurities. Cleaning by winnowing is a common practice.Likewise, Flotation method can be used to separate out impurities having different specific gravity than that of seed.
BAMBOOS are tall, perennial, arborescent grasses, belonging to Poaceae family. There are 50 genera and approximately 1326 species generally inhibiting the humid tropical, sub-tropical and mild temperate regions of the world. It is found in over 18 million hectares of land, of which 75% lies only in Asia.The rhizomes of the Bamboo may be short and thick and clustered together and produce Bamboo in well defined clumps. Mature Bamboo clumps produced new shoots every year throughout the rainy season. The shoots develop then rapidly within 2-3 months and reach their full height and diameter.
RATTANS belong to the family Palmae/Arecaceae. 600 species of Rattans belonging to 13 genera are reported to be distributed worldwide concentrated in Africa and South East Asia.Rattan is an ideal raw material for cottage industries. Its industrial use is in furniture, walking sticks, polo sticks, umbrella handles, basket making, mats, ropes, and various other articles.Cutch and Katha are obtained by boiling in water, chips of heartwood of Acacia catechu (khair) as the chief constituent of heartwood are Catechin (katha) and catechu-tannic acid (cutch). The manufacturing process is essentially extraction rather than distillation as the chips are boiled in water and not treated with stream.
The manufacture of Cutch and Katha is done by Country method as well as by Factory method. But the country method is wasteful. In Factory Method, wood is chipped by disintegrators and boiled chipped in copper vessels with hot water under slight pressure. The extract is concentrated in vacuum and cooled in a refrigerator tank for about a week, when Katha crystallizes out. It is separated by filter presses cut into slabs and further sliced into square tablets which are then dried. The yield of Katha by this method is about 4 to 5 % by weight of the wood. To obtain Cutch, the liquor is further concentrated in evaporators to a consistency at which it is solidified on cooling. The Cutch yield is about 10 to 12% by weight of the wood.
Katha is mainly used in Pan but sometimes also used in medicine. Cutch is an important commercial product which is used as dyeing and preservative agent. It is used in dyeing cotton and silk and in calico-printing.
The age of trees is either determined by their general appearance or from existing record. The size and taper in stem, size and shape of the crown, and the color and condition of the bark. But this method requires a great practice and experience and to estimate the age of tree within responsible limits of accuracy.
Some trees shows distinct annual rings on their cross section. So the age of the trees when standing can be determined by pressler’s borer. This instrument is used to take out a narrow cylinder of the about 2cm in length from a standing tree at both ends of the diameter. The number of the rings on the cylinders are counted. Then by ratio proportion method, the number of rings on the whole diameter are estimated.
Age of the trees which do not show annual rings is determined by measuring of trees of various sizes at fixed intervals. The measurement of a particular year are then classified by diameter classes and the average diameter of each diameter class is found. The same procedure is followed at subsequent measurements taken after a fixed interval. The difference between the two averages gives the periodic diameter increment which is then plotted against DBH and a smooth curve drawn. The increment curve is transformed into diameter age curve. From this curve, age of any tree of known DBH can be read.
The age of felled tree can be determined if the stump shows the annual rings. The rings are counted after levelling the stump by a chisel along the diameter on which the rings are to be counted. Then age to stump height is added to determine the age of the tree at the time it was felled.
The age of trees is either determined by their general appearance or from existing record. The size and taper in stem, size and shape of the crown, and the colour and condition of the bark. But this method requires a great practice and experience and to estimate the age of tree within responsible limits of accuracy.
Some trees shows distinct annual rings on their cross section. So the age of the trees when standing can be determined by pressler’s borer. This instrument is used to take out a narrow cylinder of the about 2cm in length from a standing tree at both ends of the diameter. The number of the rings on the cylinders are counted. Then by ratio proportion method, the number of rings on the whole diameter are estimated.
Age of the trees which do not show annual rings is determined by measuring of trees of various sizes at fixed intervals. The measurement of a particular year are then classified by diameter classes and the average diameter of each diameter class is found. The same procedure is followed at subsequent measurements taken after a fixed interval. The difference between the two averages gives the periodic diameter increment which is then plotted against DBH and a smooth curve drawn. The increment curve is transformed into diameter age curve. From this curve, age of any tree of known DBH can be read.
The age of felled tree can be determined if the stump shows the annual rings. The rings are counted after leveling the stump by a chisel along the diameter on which the rings are to be counted. Then age to stump height is added to determine the age of the tree at the time it was felled.
Afforestation- It may be defined as the establishment of a forest by artificial means on an area from which forest vegetation has always or long been absent.
Advance Growth/Advanced Regeneration/ Advanced Reproduction- The seedlings, saplings and poles of specie of the overwood that establishes naturally in a forest before regeneration felling started.
Broad-leaved Tree- Tree with hardwood and belonging to botanical group Dicotyledons.
Budding- It is the method of vegetative reproduction in which a bud with some portion of the bark of a genetically superior plant is grafted on an inferior plant so that it may produce shoot when the old shoot of the stock is cut off.
Clone- All cuttings and grafts derived from one tree by asexual reproduction are collectively called a clone.
Cover Crop- The subsidiary crop of low plants introduced in a plantation to afford soil cover between or below the main crop.
Conifer- Tree bearing cones and generally needle shaped or scale like leaves, usually evergreen and belonging to the order Coniferales of the botanical group, Gymnospermae.
Coppice- It is the method of vegetative reproduction in which the trees, plants or the seedlings of a species when cut from near the ground level, produce coppice shoots. The coppice shoots are the shoots arising from an adventitious bud at the base of a woody plant that has been cut near the ground or burnt back.
Damping off- The killing of the young seedling by certain fungi that causes the decay of the stem or roots.
Die-back- The progressive dying, usually backwards from the tip, of any portion of the plant. It is caused by the adverse climatic and edaphic factors as well as adverse weed conditions.
Frost Hardy Species- The species which possess power to withstand frost without being damaged are called frost-hardy.
Frost Tender- The species which are killed back by the frost are called Frost-tender species.
Germinative Capacity- It is defined as the percentage, by number of seeds in a given sample that actually germinate irrespective of time.
Germinative Energy- It is defined as the percentage by number of seeds in a given sample that have germinated up to the time when the rate of germination reaches its peak.
Girdling- It may be defined as the cutting through the bark and outer living layers of wood in a continuous incision all- around the bole of the tree.
Lopping- The cutting of a branch of a tree.
Mulch- Plant residues and other materials used as a covering for the soil.
Reforestation- The restocking of a felled or otherwise cleared woodland by artificial means. It is the raising of a forest artificially in an area which had forest vegetation before.
Regeneration- It may be defined as “the renewal of the forest crop by natural or artificial means.”
Seed Dormancy- It is a condition of mature viable seed in which germination is considerably delayed even though external conditions favors germination.
Shelterbelt- It is a wide belt of trees, shrubs, grasses, planted in rows which go right across the land at right angles to the direction of prevailing winds to deflect air current, to reduce wind velocity and to give general protection to cultivated areas against wind erosion and desiccating effect of hot winds.
Weeding- The tending operation done in the seedling stage in nursery or in a forest crop that involves the removal or cutting back of all the weeds.
Thinning- The felling made in an immature stand for the purpose of improving the growth and form of the trees that remain, without permanent breaking of the canopy.
Viability- It is defined as the potential capacity of a seed to germinate.
Nepal has diverse climatic and topographical features which results in the contribution of different forest types in Nepal.Adapted from J.k. Jackson, here is the list of different forest types of Nepal.
i.Shorea robusta Forest – The dominant species is Sal and other associates are Terminalia alata, Anogeissus latifolia, Syzyzium cumini,etc.
ii.Acacia catechu- Dalbergia Sissoo Forest- It is mostly found along streams and rivers in deposited alluvium and often gravelly and will be eventually be succeeded by Sal or other types of forest.
iii. Other Riverain forest- This types of forest is not large and extends far from the stream banks. Jamun is dominant in western Nepal.
iv.Grassland- This type is usually found on poorly drained clays. Grass species such as Saccharam spontaneum, Eulaliopsis bipinata, Phragmites Karka.etc are found.
v.Terminalia- Anogeissus deciduous hill forest- It is confined to dry south facing slopes in the larger river valleys and up to 1200m in Western Nepal.
i.Pinus roxburghii forest- It is found in the west of Nepal extensively. In the east, it is found in large river valleys. It is almost pure. In the far west at higher altitude, it may be associated with Olea ferruginea, Pistacia spps, etc. In transitional areas, it may be mixed with Schima wallichi or Shorea robusta.
ii.Schima-castanopsis forest – This Schima- castanopsis forest covers very large areas of the mid-hills, but much of it has been cleared for cultivation and very small passages are left.
iii.Alnus nepalensis forest- Alnus nepalensis is dominant and almost pure and associated in some places with Lyonia ovalifolia.
iv.Riverain forest with Toona and Albezia species- It is confined to narrow strips along streams and is very mixed in composition.
i.Lower temperate forest ( 2000m- 2700m)
a.Quercus leucotricophora and Quercus lanata
b.Quercus floribunda forest
c.Quercus lamellose forest
d.Lower temperate mixed broad leaved forest with abundant lauraceae
e.Pinus wallichiana forest
ii.Upper temperate forest (2700m – 3100m)
a.Quercus semecarpifolia forest
b.Upper temperate mixed broadleaved forest
c.Rhododendron Forest
d.Upper temperate coniferous forest
i.Abies spectabilis forest
ii.Betula utilis forest
iii.Rhododendron forest
iv.Juniperous indica steppe
v.Caragana steppe
It has no trees, but shrubby Rhodendrons and Junipers and some other shrubby species are found at lower elevations up to about 4500m.
CAI is the increment which a tree puts on in a single year. The CAI varies from year to year being affected by seasonal conditions and treatments.
MAI is the mean volume of a tree or crop put on from origin up to the desired age i.e. the total increment up to a given age divided by that age.
If when the curves of Current and Mean annual increments are plotted over tree age, the two do not coincide with each other through out the life of the tree except at two periods one at the end of first year and the other at the culmination of MAI.The CAI rises to maximum and then gradually fall off.The MAI also increases to a maximum at a later age but with much lower rate.The MAI continues to rise towards maximum even after the CAI has started falling.
When the CAI falls to such an extent it is equal to MAI, the MAI reaches its highest points. This is the year of culmination of the MAI. At later stage, the CAI is less than the MAI, and MAI also beings to drop but not as rapid as that of CAI. THE CAI will be zero and also negative when there is rot or other damages resulting in negative CAI. But the MAI value is never Zero and negative like CAI.
