
Inventory Practice for Managed Forests C.J. Goulding M.E. Lawrence FRI BULLETIN NO . 171 !!!f.·- FRI BULLETIN NO. 171 FORESTRY !{MA NATO NGAHfi{H[tf INVENTORY PRACTICE FOR MANAGED FORESTS by C.J. Goulding M.E. Lawrence 1992 Published by the Forest Research Institute Private Bag 3020 Rotorua New Zealand Telephone (07) 347-5899 Facsimile (07) 347-9380 ISSN 0111-8129 ODC 524.6 2 TABLE OF CONTENTS CHAPTER 1- INTRODUCTION ............................................................... 5 1.1 Preamble ...................................................................................................... 5 1.2 Management inventory .............................................................................. 6 1.3 Preharvest inventory ................................................................................. 6 CHAPTER 2- BASIC STATISTICS . ....................................................... 8 2.1 Sa1npling ...................................................................................................... 8 2.2 So1ne tenninology ...................................................................................... 8 2.3 Variance, standard error, and covariance ............................................... 9 2.4 Confidence lin1its ...................................................................................... 14 2.5 Variances of products and sums ............................................................ 15 2.6 Sampling methods .................................................................................... 18 CHAPTER 3- PLANNING AN ASSESSMENT ..................................... 20 3.1 Definition of the inventory ...................................................................... 20 3.2 Calculating the size of the sample .......................................................... 20 3.3 Locating and demarcating plots ............................................................. 25 3.4 Size and shape of bounded plots ............................................................ 27 3.5 Angle gauge or point sampling .............................................................. 29 3.6 Horizontal line sampling ......................................................................... 30 CHAPTER 4- FIELD PROCEDURE ...................................................... 32 4.1 Transects I grid lines ................................................................................. 32 4.2 Bounded plots ........................................................................................... 32 4.3 Angle gauge points ................................................................................... 34 4.4 Horizontal line plots ................................................................................. 37 4.5 Field equipment ........................................................................................ 38 4.6 Sampling for total height ......................................................................... 39 3 REFERENCES ......................................................................................... 41 APPENDICES .......................................................................................... 42 Table 1-Random numbers ............................................................................. 42 Table 2- Student's "t" values for probability of 95% .................................. 43 Table 3- Conversion of true distance to slope distance ............................. 44 Table 4- Half diagonal length for diamond-shaped plots ........................ 45 Table 5- Radii of circular plots ..................................................................... 46 Table 6- Horizontal marginal distances for BAFs ..................................... 47 Table 7- Height formulae ............................................................................... 48 Table 8- Height tables- method 1 (degrees) .............................................. 49 Table 9- Height tables- method 2 (percent) .............................................. 50 FIGURES Figure 1-Example of a map used for inventory planning ........................ 28 Figure 2- Use of a prism ................................................................................. 35 Figure 3- Use of a relaskop ............................................................................ 35 Figure 4- Prism placed on a Suunto ............................................................. 36 4 CHAPTER 1 INTRODUCTION 1.1 Preamble This is a manual on the elementary and practical aspects of planning and conducting inventories in forests managed primarily for timber production. A managed forest for the purposes of this manual is one in which stands of trees may be established either by planting or natural regeneration and one or more silvicultural operations take place in addition to felling. It is assumed that forest maps exist and stocked areas are known reasonably accurately. Most of the experience used in compiling this manual has been obtained in fast-grown, intensively-managed coniferous forests comprising stands which contain one or at most three species. The special problems of multi-species, tropical hardwood, or extensive unmanaged boreal forests are not described. National forest inventory is a subject on its own, and is also not covered. The manual should be useful to operational staff who are called upon to provide stand information for management planning and control, for marketing and sale purposes, and for the assessment of merchantable volume. The chapter on basic statistics is limited to those practical aspects of sampling likely to be of day-to-day use to inventory personnel. No theory is given, but formulae are, even though nowadays staff may have access to computer programs which will perform the necessary calculations. A more thorough description of elementary forest sampling is given by Freese (1962), of forest inventory by Loestch and Hailer (1973), and of forest mensuration by Husch et al. (1982) or Philip (1983). The other chapters and appendices are designed to assist inventory staff firstly in planning and defining their procedures, and secondly in compiling their own detailed manual, specific to their needs. For managed forests, inventory can be divided into two basic types: 1. Management inventory, which estimates the basic stand parameters used to control silvicultural operations, to provide stand records and as input for growth models. 2. Preharvest inventory, which provides marketing and logging personnel with information on the likely product volume yield shortly before harvesting. 5 1.2 Management inventory Inventories associated with silvicultural operations such as pruning and thinning are classified as management inventories. Rate-setting inventories are used to collect information about the stand in order to formulate a prescription for a forest operation and to set a work target or contract rate for the job. Quality control inventories ensure that the work is performed in an acceptable manner, and the information on the residual stand may also be stored in stand records to be used for projecting the stand's subsequent growth and yield. When a stand is untended or the information stored in the records about the stand is regarded as suspect, an inventory may be carried out to update the records and provide the data needed by the growth prediction system. The parameters assessed are usually confined to numbers of stems per hectare, basal area per hectare, total height, and possibly some indication of future merchantability. Management inventory procedures can provide broad-based estimates of standing volume and are adequate where there is little differential in the value of products. They are inadequate where merchantable reduction factors cannot be obtained from past experience or where it is required to differentiate between the merchantability of individual stands destined for diverse markets. 1.3 Preharvest inventory Preharvest inventory methods provide information for the planning and administration of harvest operations and for forest valuation. They assist in marketing and logging planning by estimating the crop yield by different log types and by defining the quantity and location of high value products such as peeler logs. As an aid in allocating logging equipment and setting bonus targets, they provide information on total recoverable volume, on average merchantable sizes for hauls, and on numbers and sizes of individual logs. They can also be used to provide merchantability factors as a control for long­ term yield forecasting. The MARVL inventory procedure typifies such a system. MARVL stands for Method of Assessment of the Recoverable Volume by Log-types, and is implemented on IBM compatible personal computers as MicroMARVL (Deadman 1990). MARVL recognises the potential of stands to yield different products when subjected to different stem cross-cutting ("bucking") patterns. The approach used is to observe and record stem quality and size on a sample of standing trees and then to predict the results of cross-cutting these trees under the influence of a variety of log specifications and requirements, as 6 specified by the inventory officer. No merchantability factors are required. However, because of the cruising involved, the field crew must be competent in measuring or estimating by eye upper diameters and heights, and more importantly, in recognising the changes in stem quality that determine log grade. 7 CHAPTER 2 BASIC STATISTICS 2.1 Sampling When every tree in a stand is measured
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