Sunday, July 1, 2018

What is DBH ?

DBH is defined as the average stem diameter outside bark at the point of 1.3m or 1.37m (FAO) above the ground as measured.

  • It is a convenient height for taking measurement as it does not require bending down or stretching up to reach a lower or higher point.

  • It is a place on a tree stem, which is free from obstructions from thorny shrubs  and abnormalities like root swell, etc.

  • It gives uniform point of measurement and therefore standardizes measurement.

  • It shows strong correlation to the volume or weight of the stem for most tree species.

Rules of the DBH Measurement

  • Loose barks, mosses, lichens that are found on the tree must be removed before measuring the diameter over bark.

  • Breast Height (BH) should be measured by means of a measuring stick on standing trees at 1.3m or 1.37m (FAO)  above the ground level.

  • BH should be marked by intersecting vertical and horizontal lines 12 cm long painted with white paint.

  • On sloping land, the diameter at BH should be measured on uphill side.

  • In case of the tree is leaning, DBH is measured along the tree stem and not vertically, on the side of the lean for trees growing on flat ground and on uphill side, for trees growing on sloping ground.

  • BH should be taken at the lowest point above which the buttress formation is not likely to extend.

  • When the tree is forked above the BH, it is counted as one tree, but when it is forked below BH, each fork should be treated as though it were a separate tree.

Instruments used in Diameter measurement of trees

1. Diameter Tape

  The Diameter of a tree cross section  may be obtained with a flexible tape by measuring the circumference of the tree. A diameter tape is a measuring tape that has scale on both sides: one side is specially marked to show the diameter of a tree, and the other is a normal scale.


2. Calipers

Calipers are often used to measure tree DBHor when diameters are less than about 60cm. A Caliper may be constructed of metal, plastic or wood, consists of a graduated beam with two perpendicular arms. One arm  is fixed at the origin of the scale and the other arm slides.When the beam is pressed against the tree and the arms closed, the beam of the Caliper can be read on the scale.


3. Wooden Scale

It is generally a two feet folding scale used to measure diameters of logs at their end cross sections.


Saturday, June 30, 2018

Silviculture and Silvicultural systems

Silviculture is defined as the art an science of cultivating forest crops. In other words, Silviculture  includes both Silvics and its practical application. Silvics is defined as the study of life history and general characteristics of forest crops with particular reference to environmental factors, as the basis for practice of the silviculture. 

Objectives of the Study of Silviculture

  1. Increasing the productivity of the forest

  2. To fulfill the multifarious requirements of the people with the cultivation of more valuable and useful species of trees

  3. Improvement of deteriorating natural forest and creating new man-made forest

  4. Maintaining the good forest condition of both natural and man-made forests by proper tending

A Silvicultural System is defined as a method of silvicultural procedure worked out in accordance with accepted sets of silvicultural principles by which crops constituting forests are tended, harvested and replaced by new crops of distinctive forms.

Silvicultural systems are primarily classified on the basis of the mode of regeneration and this is further classified according to the pattern of felling.

  1. High Forest Systems- These are the systems in which the regeneration is normally of seedling origin, either natural or artificial or a combination of the both and where the rotation is generally long.

          a.Clear -felling System

   b. Shelterwood System

          c. Selection System

          d. High Forest with reserve

          e.Two Storeyed High Forest

          f .Improvement Felling

2. Coppice Systems- These are those Silvicultural Systems in which the crop originates  mainly from coppice and where the rotation of the Coppice is short. These systems are further classified into several Silvicultural systems on the pattern of felling.

a. Simple Coppice system

b.Coppice with Standards system

c. Coppice with reserve System

d. The Coppice of two Rotation system

e.The Coppice Selection system

f.The Shelter wood Coppice System

g. The pollarding