Copyright 2002 Silvi-Crew Ltd.
SILVI-CREW LTD. SPACING SAW TRAINING PROGRAM: MODULE 7
CROP TREE SELECTION AND SPACING
OBJECTIVES: This module is designed to provide the student with the knowledge required to select individual trees as crop trees and how to space these trees to obtain proper post treatment density. Emphasis in this module will be placed on achieving certain minimum standards of productivity and job quality, with quality being most important.
STUDENT PERFORMANCE EVALUATION:
The student must demonstrate competent identification of native New Brunswick trees. This will be done through on site inspection of crown shapes and classroom twig tests. The students will also be tested on the important characteristics of crop trees, and the variable requirements with respect to their post treatment densities. Finally from this module, the student must discuss aspects and demonstrate satisfactory work technique, both in terms of the quantitative stem density and the qualitative parameters of precommercial thinning.
CROP TREE SELECTION AND SPACING
1.) Tree Identification There are two groups of forest trees in our region worth considering as crop trees. These are the conifers, commonly called the softwoods and the deciduous trees, commonly called the hardwoods or broad¬leaved trees. These two groups have quite different characteristics and may be compared as follows: Conifers (softwoods) Ex.: Spruce, fir, pine, larch, et al. Leaves: Needle-like; remain on the tree for years (except for larch).
2 types: needles bundled needles unbundled Twigs & Buds: Partly or completely surrounded by needles (except larch). Buds randomly arranged, and cannot be readily seen even in winter. Wood: Gummy and composed of longer fibres. Usually soft and easily worked.Fruit: Cone-like with scales; each cone contains many seeds.
Deciduous (hardwoods) Ex.: Maple, birch, poplar, et al.
Leaves leaf-like, broad, flat and thin; leaves drop off in the fall of each year. 2 types: simple,one-piece; compound,many-parts. Twigs & Buds many colors, rough or smooth, zig-zag or straight. Buds with single or many overlapping scales, alternating or opposite.Wood:- Not gummy. Shorter fibres. Usually hard and difficult to work with, although a few are rather soft and easily worked.Fruit:- Of various forms; nut-like (acorns), or ╠with wings (maple), or often berry-like (pin cherry)
6.) TAMARACK (LARCH)
Twig test from collected specimens
2.) Characteristics of Crop Trees
3.) Spacing Requirements
Post treatment density is the quantitative assessment in precommercial thinning. It is deemed satisfactory in New Brunswick, and other jurisdictions when the average total is within a range between 800 to 1200 trees per acre. 800 to 1200 trees/acre = 2000 to 3000 trees/ha Average spacing = 6.5 ft x 6.5 ft = 1000 trees/acre This is obtainable by strictly enforcing thinners to undertake daily 40 sq. metre check plots (1/100 of an acre). Post treatment density is measured by constructing a circle with a 3.57m radius. one plot is 1/250 of a hectare or 1/100 of an acre 8 to 12 trees per plot.
Counting the leave trees, arrives at a density value which, multiplied by the sample area, gives the density of crop trees per acre. This must be done firstly to provide the thinner with a "feel" for the proper spacing. The count ensures that the quantitative aspects of post assessment, namely the density parameter has been achieved by the treatment. Secondly, the check plot allows the thinner to evaluate the qualitative aspects of job quality (see below).
New thinners (trainees) must do at least two per day.
Below is a table illustrating the between tree spacing and its effect on total number of trees/Ac, and trees per circular check plot.
trees/ac 1742 1440 1210 1031 888 774 680 between tree spacing (ft) 5.0 5.5 6.0 6.5 7.0 7.5 8.0 trees per checkplot 17 14 12 10 8(c)9 7(c)8 6(c)7 Handy : # of crop formula: trees/ac =43560/(between tree spacing squared) =43560/6.5x6.5 =43560/42.25 # of crop =1031 trees/ac. Quality control parameters of P.C.T.
Qualitative assessments are made during the daily check plot to obtain post treatment density. The checks plots allow the thinner to survey his work close up. These quality control items are discussed in order of importance below. They all are essential to maintain high standards of thinning expertise and subsequent job quality:
Last Updated 02/18/2004