PHOLIAGE

Photosynthesis and Light Absorption Model

Details

PHOLIAGE is a 3D model that calculates light absorption and photosynthesis for trees in opened canopies (e.g. for enrichment planting). For a full description, see the model description and the program manual.

Figure 1: Schematic representation of a tree in a canopy as modelled in PHOLIAGE.

A related model for closed canopies is StratiPHOLIAGE.

Literature

Studies that have used the model:

Van Kuijk et al., 2014. Stimulating seedling growth in early stages of secondary forest succession: A modeling approach to guide tree liberation

Van Kuijk et al., 2008. The limited importance of size-asymmetric light competition and growth of pioneer species in early secondary forest succession in Vietnam

Implementation details

Lazarus / Delphi

The original version was written in Delphi. This is the version ported to Lazarus / FPC.

Main functional changes

• Supports multiple platforms (Linux, Windows, and macOS).
• Reads *.xls, *.xlsx, and *.ods files natively (previous version used Windows-only Excel OLE automation).
• Removed Windows/Delphi-specific multithreading code (too much work to port).
• Removed some initial code for a planned extension for lane-based simulations.

For further details, see the changelog.

Numerical differences between versions

Between versions 0.3 and 0.5 exist small differences in the results, for which the changelog does not give an explanation. Correlation (R²) between results from both versions is still almost 1, as tested with the example data.

Between versions 0.5 and 1.0.0 exist negligible differences (~1e-13), and the differences between the Win64 and Linux/Win32 versions are even smaller.

Model results can differ slightly between Linux/Win32 builds and Win64 builds, because on Win64 the 80-bit floating point Extended datatype is not supported. The Math unit therefore internally uses Double (64 bit) instead of Extended, leading to minute differences. This is not a problem, the loss in precision is negligible, and the PHOLIAGE model itself uses Double for all calculations anyway. For details see for example this forum post, and the source code of the Math unit.

Running

Binary releases are available under the releases tab.

For usage details see the program manual.

Compiling/Modifying

1. Install Lazarus
2. Install FPSpreadSheet
3. Check out the sources ('Clone or download' button above)
4. Open project file PHOLIAGE.lpi in Lazarus and press F9 to run.