CIRCULAR No. 333 JANUARY 1935 



UNITED STATES DEPARTMENT OF AGRICULTURE 



WASHINGTON, D.C. 



SAMPLE PLOTS IN SILVICULTURAL RESEARCH 



By the Division of Silvics, Branch of Research, Forest Service 1 



CONTENTS 



Page 



Introduction 1 



Types of sample plots 4 



Preliminary considerations 4 



Qualifications of the investigator 4 



Planofwork 5 



Need of care in recording plot establish- 

 ment 7 



Crew organization 7 



Number and distribution of plots and sub- 

 plots 7 



Size and shape of plots and subplots 9 



Isolation strips 11 



Plot establishment 11 



Selecting the stand 11 



Agreements with forest managers and 



owners 13 



Locating plots within the stand 13 



Surveying and demarcating plots 14 



Numbering plots, subplots, and plot sec- 

 tions 20 



Location survey 21 



Plot maps 22 



Individual tree control 22 



Numbering trees and marking the measure- 

 ment point 22 



Numbering reproduction 28 



Plots in plantations 29 



Protection of plots 31 



Plot treatment 32 



Collection of plot data 34 



Field notes and forms 34 



Tree measurements 34 



Collection of plot data— Continued. Page 



Tree description and classification 46 



Reproduction measurements 48 



Stem and crown maps 50 



Plot description 52 



Photographs 53 



Remeasurements 56 



Reports and office records 57 



Report on plot establishment 57 



Progress reports 59 



Field record 59 



Plot index 60 



Preservation and filing of field records 60 



Plot abandonment 60 



Literature cited 62 



Appendix 66 



Typical field forms used in sample-plot 



work by the "United States Forest Service. 66 

 Instruments, accessories, tools, and sta- 

 tionery used in sample-plot work 72 



Abbreviations and numerical code for use 



in sample-plot work 73 



Symbols used in sample-plot mapping 76 



Description of ponderosa pine tree classes 



as developed by Dunning 76 



Swedish tree classification 78 



Methods of preparing volume and yield 



tables 79 



Forest Service policy regarding experi- 

 mental forests, natural areas, and primi- 

 tive areas 86 



Specimen agreement providing for experi- 

 mental use of private area 89 



INTRODUCTION 



Successful production of forest crops, as of other crops, depends in 

 very large measure upon detailed knowledge of the crops' growth 

 requirements and growth characteristics. For American forests and 

 forest species, information of this kind is very incomplete. In the 

 past quarter century, foresters and others have by observation 

 acquired certain data on the growth and behavior of our forest 



1 Acknowledgment is made of cooperation in the preparation of this manual by a 

 committee representing the Society of American Foresters, including O. A. Alderman, 

 F. S. Baker, F. W. Beslev, A. C. Cline, F. C. Craighead, Duncan Dunning, J. A. Ferguson, 

 Carl Hartley, W. R. Hine, G. A. Pearson, Edmund Secrest, J. N. Spaeth, and E. N. 

 Munns. chairman. So many of the silviculturists in the various Federal forest experiment 

 stations have contributed to the manual that it is impossible to mention them all. 

 Especially helpful has been the work of J. H. Buell, Perkins Coville, F. H. Eyre, and 

 I. T. Haig. The textual presentation is to a considerable extent the work of E. N. 

 Munns. 



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