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fgr – the ForestGALES R package

A version of the ForestGALES wind risk model is available for use by forestry and land-use change scientists and specialists, ecologists and meteorologists, in a format that is flexible and fully customisable. This is designed to meet the needs of users for application in any forested landscape, and to encourage international collaboration on forest wind risk research.

Since the release of ForestGALES version 2.5, the tree stability team at Forest Research have used the R programming language for all further model development. The model fgr, the ForestGALES R package, is the product of the latest research and development.

R is widely used in the forestry and land-use change research sectors in Britain and throughout the rest of the world. Many models and utilities are available as R packages, thus providing the opportunity for relatively straightforward integration between tools within a common platform. R packages can also be used as a plugin within the QGIS software, as we have done with fgr in the FOSPREF-Wind project.  

What’s new in fgr?

This latest version of ForestGALES, fgr, features a series of modifications and improvements from ForestGALES 2.5, and as such fgr represents the cutting edge of forest wind risk modelling.  Two sets of changes have been made:

  • Firstly, improvements have been made to the ‘roughness’ method which underpins calculations of wind loading in uniform forest stands.
  • Secondly, we have introduced the “’turning moment coefficient’ (TMC) method for calculating risk to individual trees in mixed forest stands.

These changes are described in more detail:

Stand-level calculations

fgr represents an improvement on the traditional stand-level approach used in previous ForestGALES releases.  Several scientific advances have been incorporated into the calculations of critical wind speed in uniform stands:

  • We use new equations for more precise calculation of stem volume, based on the work of Fonweban et al. (2012);
  • The calculations of the effects of wind gusts, upwind gaps, and newly formed (brown) edges have been improved;
  • We have revised the method of calculating the contribution of the mass of canopy to the critical bending moment of the tree;
  • We have improved how the distribution of drag across the forest canopy is represented;
  • We have added more species to the ForestGALES parameterisation, including alternative conifers species (jack pine, white spruce, black spruce, balsam fir, maritime pine, radiata pine) and some broadleaves species (beech, birch, oak, and Eucalyptus globulus).

Individual-tree calculations

The traditional roughness method of ForestGALES calculates vulnerability and risk of the average tree in a stand.  Based on the innovative work published in Hale et al. (2012) and Hale et al. (2015), fgr allows the calculation of individual-tree vulnerability, and the associated risk of wind damage, in stands of mixed-species and irregular structure. This allows easier and more confident risk and vulnerability assessments in complex stands. The effect of complex stand dynamics on wind risk can be accounted for with the TMC method if tree-level competition indices are available. While still in a developmental stage, provisional tests have shown that results are consistent with observed damage.

Where can I download fgr?

The first release of fgr can only be downloaded from the Forest Research website.

This online form will capture your contact details. Terms and conditions must be accepted.

Once the form is complete, an email with four attachments will be sent to the email provided in the form. All personal data are treated in compliance with GDPR regulations.

What’s in the package

Once the form has been submitted, you will receive an email with four attachments:

  1. The Windows binary fgr package in a compressed archive (in .zip format)
  2. The fgr package User Manual in a PDF file
  3. A PDF file containing a copy of the fgr package Licence terms
  4. A text file with simple instructions to install the fgr package within your R library.

The fgr package is built in a modular way, so that not only wrapper functions for the two methods (‘roughness’ and ‘TMC’) are available for standard use, but all the individual functions are also available for advanced users. The simulations are fully customisable: all species parameters can be changed (including mechanical properties of wood, wood density, etc.), parameter sets for new species can be added and stored, and the values of physical constants (e.g. air density, snow density amongst many others) can be changed and stored for future use.

Model outputs can be produced in a compact form that is suitable for most standard use and contains calculated vulnerabilities and risks of uprooting and stem breakage, or in an extended format reporting the outputs of all advanced calculations. Example datasets are provided to help users familiarise with the functionality of fgr. All functions and datasets are documented. Working in batch mode in fgr is easy, since it takes advantage of all standard R practices for vectorised functions.

The fgr manual is a PDF document that details and explains the functionalities of the package and provides extensive background to the numerous aspects of wind damage risk research that went into the creation of fgr. Worked examples based on the provided datasets are included in the manual to provide further assistance, together with an extensive bibliography.

DAMS scores: a measure of windiness for the UK

As a hybrid-mechanistic model, fgr is designed to be able to simulate most forestry conditions, anywhere in the world. The windiness of a site is typically described with the scale and shape parameters of a Weibull distribution of mean wind speeds, as per standard meteorological practice.

In the UK, information on the wind climate throughout Britain is classified in the DAMS scoring system. DAMS scores in raster format (as GeoTiff) are available to download in a coordinate reference system (CRS) compatible with Ordnance Survey data (EPSG: 27700), or alternatively in a CRS compatible with Google Maps, OpenStreetMap, etc. (EPSG: 3857).

Assistance with fgr

For technical support and enquiries relating to fgr, please contact Forest Research at: forestgales.support@forestresearch.gov.uk

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