The MYRLIN growth estimation tool

The MYRLIN growth estimation tool is an Excel workbook with facilities designed to help in estimating growth and mortality rates for natural forest species. It is intended for cases where no direct information is available from permanent sample plots or research records.

It links to and reads the options, species and inventory data from the MYRLIN stand table module. It is necessary therefore to set up the stand table module correctly before using the growth estimation tool.

The growth estimation tool is based on the premise that for a large, broadly based sample of tree increment measurements, there is a relationship between typical size, expressed as the 95% point on the cumulative diameter distribution, and mean species increment. This relationship depends also on other indicators of growth rate, such as ecological guild and wood properties. It is also influenced by site characteristics such as soil fertility. The Reference section discusses the empirical basis for this proposition.

The workbook comprises three sheets and two macros,as follows:

{Table} worksheet Contains a list of species groups extracted from MYRLIN#1, with their mean number per ha, 95% cumulative diameter, mean basal area per ha, and an initial estimate of diameter increment and annual mortality rate based on a pan-tropical regression of increment on typical size.
{Fig1} chart Plots species group typical size on mean increment. Has background lines indicating size-increment relation for ecological guild/wood property groups. Allows initial estimates of increment to be adjusted manually according to knowledge of ecology or wood properties. Has handle to adjust overall graph scaling for site indicators.
{Model} worksheet Provides summary data of increment-size groupings based on ecological/wood property characters, as noted in the Reference section. Used to provide background lines, site scaling, and increment-size regression on {Fig1}. The worksheet is protected as it should not normally be edited.
MakeD95List macro This macro updates the {Table} worksheet from a selected MYRLIN#1 wortkbook, using the current Options, species list and data settings in that workbook.
UpdateLabels macro If the groups are re-sorted or group labels are amended manually, this macro must be run to reflect changes in the data labels on the chart {Fig1}. This is not done automatically by Excel. It can also be used to limit the number of groups displayed on the graph, for greater clarity.

The procedure for using this workbook is as follows: