Methods of Yield Regulation with Limited Information

for natural tropical forests

Diagram of MYRLIN toolbox Stand tables tool Tree growth tool Harvest scheduling & sustainable yield tool

MYRLIN is an acronym for Methods of Yield Regulation with Limited Information.

MYRLIN is a set of three simple software tools designed to assist in yield regulation for natural tropical forest. The diagram at the right shows their interaction and data inputs and outputs. These tools are directed at the needs of organisations and enterprises which have only a limited research base of information on forest dynamics in their locality. This website provides technical information on their use. It assumes familiarity with forest management terminology and a knowledge of Microsoft Excel.

Yield regulation is the process of calculating a sustainable timber yield from a forest by species, location, and year, specifying it in forest management plans, and monitoring the actual harvest to ensure compliance. A common difficulty in developing yield regulation plans and procedures in tropical forestry is the lack of knowledge of tree growth rates from locally applicable permanent sample plots.

Although tropical forests are very diverse, actual tree growth rates fall into a narrow band of values and can be reasonably estimated from features of species ecology and wood properties. The MYRLIN tools and the information on this web site provide a basis for this estimation process. The three MYRLIN tools follow a logical sequence. MYRLIN#1 organizes forest inventory and stock survey data into stand tables useful for planning, and required for the growth modelling. MYRLIN#2 assists in the process of estimating increments and mortality rates for species. MYRLIN#3 is a model that uses the inventory and growth tables to estimate sustainable yield and give a detailed list of coupes and quantities by year. These outputs are designed to form the basis for a management plan and a monitoring and control system.

Each MYRLIN module comprises a Microsoft Excel workbook with embedded macros. The user will need to have MS Excel version 2000 or later fully installed on their computer in order to be able to use the tools. This website provides documentation on how to use them, and it is recommended that each section is worked through carefully in conjunction with the relevant MYRLIN module.

The software tools and documentation at this site have been developed under the project "Yield regulation for tropical moist forests with minimal data" at the Oxford Forestry Institute. An inaugural workshop for the project was held in Costa Rica in 1999. The papers from the workshop contain background information that can be viewed or downloaded here. A training workshop in the use of the MYRLIN tools was also held in Oxford in September 2001.

The project was supported through the Forest Research Programme of the UK Department for International Development. The software and information at this site are provided freely as a service towards improving the sustainable management of natural tropical forest. However, it is a condition of use that software is not incorporated in whole or in part into any commercial product that is subsequently re-sold; and that reports, plans or presentations of information acknowledge this website ( as the source.

The following citations should be given in formal publications:

Alder, D, Baker, N, Wright, HL (2002) MYRLIN: Methods of Yield Regulation with Limited Information. University of Oxford, Oxford Forestry Institute.

Wright, HL & Alder,D [Editors] (2000) Proceedings of a workshop on Humid and semi-humid tropical forest yield regulation with minimal data.University of Oxford, Department of Plant Sciences, Oxford Forestry Institute. OFI Occasional Papers 52. (ISBN 0 85074 152 1)