Introduction

Allometric models relate attributes of trees, such as diameter, height, and crown size, to other attributes, such as biomass and volume. These models form the basis of forest inventory systems worldwide, and many statistical products quantifying forest health necessarily rely on them. The number of allometric models is vast, and they are often tucked away in obscure reports or other resources. The allometric project is a platform for archiving and using these models in a robust and interoperable format. Models are declared using publication YAML files, which are easy to read and write. For example, a hypothetical model for estimating tree biomass from diameter and height might be

- name: example_biomass_model
  type: fixed_effects
  response: { bt: "m3" }
  covariates: { dsob: "cm" }
  taxa:
    - family: Pinaceae
      genus: Pinus
      species: ponderosa
  parameters:
    a: 22.6
    b: 0.014482
    c: 0.001162
  prediction_function: "4.5 + a * exp((b - c * log(atb)) * (hst - 4.5))"
  description: |
    This model estimates tree biomass (bt) in cubic meters from diameter at
    breast height (dsob) in centimeters and tree height (hst) in meters for
    ponderosa pine trees.

Here, we declare a hypothetical biomass model for ponderosa pine trees, define some information about its usage, and provide a prediction function for estimating biomass from tree diameter and height. This approach yields a clear, standardized format for allometric storage that can be ingested into other processes.

Accessing Models

Models stored within the system are viewable at the models page. Each model is associated with a publication, and publication rednerings can be viewed at the publications page. Users can also programmatically access the models through the allometric R package, which provides a suite of tools for working with allometric models and their outputs. This website provides extensive documentation for the package here.

Contributing Models

The allometric project is entirely open-source and contributing models is as simple as writing a text file. All models are stored in the models repository, allowing for transparent version control and collaboration. We encourage users to contribute models to the repository, and we provide a contribution guide to help users get started.

The allometric Ecosystem

The allometric project is wide ranging, and relies on a suite of components to properly store, validate, and use models. Most of these systems are not necessary for routine use of models, but they are essential for contributing new models to the repository. These components include:

1. The models repository, which stores allometric in highly structured YAML files.
2. The orc validator, which ensures models are properly specified with a uniform schema.
3. The allometric R Package, which provides analysis tools for working with allometric models and their outputs.
4. The allometric website, which provides a user interface for exploring models and publications, as well as documentation for the above software.