Class: DeadTreeList

The DeadTreeList class represents a list of dead trees (snags or downed dead wood) that can be queried and analyzed.

Overview

Initializing the list

The object can be created as a standalone object. Populating the dead tree list is done using functions such as loadFromStand() or loadFromRU().

Example

 var deadTrees = new DeadTreeList(); // create a DeadTreeList object
 deadTrees.loadFromStand(123, DeadTreeList.Snags); // load all snags from stand 123
 var totalVolume = deadTrees.sum('volume');
 console.log('Total volume of snags in stand 123: ' + totalVolume);

Querying the content of the list

The list of dead trees can be filtered using filter(). Aggregate values can be calculated using functions like sum() and mean().

DeadTreeType

When loading dead trees, you need to specify the type: - DeadTreeList.Snags (or 0): Standing dead trees. - DeadTreeList.DWD (or 1): Downed dead wood (lying on the ground). - DeadTreeList.Both (or 2): Both snags and DWD.

Variables

A list of available variables for dead trees would typically be found in the iLand documentation (analogous to sapling variables). (Assuming a similar pattern to FMSaplingList regarding where variable lists are documented, e.g., https://iland-model.org/dead+tree+variables)

General notes

The dead tree list heavily uses the expression engine of iLand (see https://iland-model.org/Expression). Expressions are provided as strings to the respective Javascript functions (e.g., filter, sum, mean) and evaluated by iLand.

Example

 var dtl = new DeadTreeList();
 // Load all DWD from resource unit with index 0
 dtl.loadFromRU(0, DeadTreeList.DWD);
 console.log("Number of DWD pieces: " + dtl.count);

 // Filter for DWD with a diameter greater than 20cm
 dtl.filter('dbh > 20');
 console.log("Number of large DWD pieces: " + dtl.count);

 // Calculate the mean decay status of these large DWD pieces
 var meanDecay = dtl.mean('decayClass');
 console.log("Mean decay status: " + meanDecay);

 // Load snags from stand 42, appending them to the current list,
 // only including those of species 'pisy' (Pinus sylvestris)
 dtl.loadFromStand(42, DeadTreeList.Snags, 'species=pisy', true);
 console.log("Total dead tree elements after appending: " + dtl.count);

Properties Overview

Name	Type	Description
count	Integer (read-only)	The number of dead tree elements (snags or DWD pieces) currently loaded in the list.

Methods Overview

Method	Return Type	Description
filter(filter)	Integer	Applies a filter to the current list of dead trees. Only elements for which the
loadFromRU(ru_index, loadWhat)	Integer	Loads dead trees from a specific resource unit (RU) into the list.
loadFromStand(stand_id, loadWhat)	Integer	Loads dead trees from a specific stand into the list.
mean(expression)	Number	Calculates the mean value of a given expression for all dead tree elements in the list.
sum(expression)	Number	Calculates the sum of a given expression for all dead tree elements in the list.

Properties Details

count

Integer ReadOnly

The number of dead tree elements (snags or DWD pieces) currently loaded in the list.

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Methods Details

filter(filter)

Returns: Integer

Applies a filter to the current list of dead trees. Only elements for which the filter expression evaluates to true remain in the list.

Parameters:

• filter (String): A valid filter expression (see iLand expression engine documentation).

Return Value Description: The number of dead tree elements remaining in the list after applying the filter.

Example:

// Assume deadwood list is already populated
     // Keep only snags with volume > 0.5 m^3
     var remaining = deadwood.filter("snag=true and volume > 0.5");
     console.log(remaining + " large snags remain in the list.");

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loadFromRU(ru_index, loadWhat)

Returns: Integer

Loads dead trees from a specific resource unit (RU) into the list.

Parameters:

• ru_index (Integer): The index of the resource unit from which to load dead trees.
• loadWhat (enum): Specifies the type of dead wood to load. Possible values are:
  • DeadTreeList.Snags: Load only standing dead trees.
  • DeadTreeList.DWD: Load only downed dead wood.
  • DeadTreeList.Both: Load both snags and DWD.

Return Value Description: The number of dead tree elements loaded into the list.

Example:

var deadwood = new DeadTreeList();
     // Load all snags from RU with index 5
     var numLoaded = deadwood.loadFromRU(5, DeadTreeList.Snags);
     console.log(numLoaded + " snags loaded.");

     // Load DWD from RU 10 and append to the list
     deadwood.loadFromRU(10, DeadTreeList.DWD, true);
     console.log("Total deadwood count: " + deadwood.count);

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loadFromStand(stand_id, loadWhat)

Returns: Integer

Loads dead trees from a specific stand into the list.

Parameters:

• stand_id (Integer): The ID of the stand from which to load dead trees.
• loadWhat (enum): Specifies the type of dead wood to load. Possible values are:
  • DeadTreeList.Snags: Load only standing dead trees.
  • DeadTreeList.DWD: Load only downed dead wood.
  • DeadTreeList.Both: Load both snags and DWD.

Return Value Description: The number of dead tree elements loaded into the list.

Example:

var deadwood = new DeadTreeList();
     // Load all DWD from stand 77, with dbh > 10
     var numLoaded = deadwood.loadFromStand(77, DeadTreeList.DWD, "dbh > 10");
     console.log(numLoaded + " DWD pieces loaded from stand 77.");

     // Load all snags from stand 88 (implicitly clears previous DWD)
     deadwood.loadFromStand(88, DeadTreeList.Snags);
     console.log("Snags count from stand 88: " + deadwood.count);

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mean(expression)

Returns: Number

Calculates the mean value of a given expression for all dead tree elements in the list. An optional filter can be applied to include only specific elements in the calculation.

Parameters:

• expression (String): A valid expression (e.g., a dead tree variable name) for which to calculate the mean.

Return Value Description: The mean value of the expression for the (filtered) dead tree elements. Returns NaN if the list (after filtering) is empty.

Example:

// Calculate the mean DBH of all DWD pieces
     var meanDbhDWD = deadwood.mean("dbh", "snag = false");
     console.log("Mean DBH of DWD: " + meanDbhDWD);

     // Calculate the mean age of all snags
     var meanAgeSnags = deadwood.mean("age", "snag = true");
     console.log("Mean age of snags: " + meanAgeSnags);

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sum(expression)

Returns: Number

Calculates the sum of a given expression for all dead tree elements in the list. An optional filter can be applied to include only specific elements in the calculation.

Note: Counting elements that fulfill the filter expression can be expressed as: sum('1', '<filter-expr>').

Parameters:

• expression (String): A valid expression (e.g., a dead tree variable name or ‘1’ for counting) for which to calculate the sum.

Return Value Description: The sum of the expression for the (filtered) dead tree elements.

Example:

// Calculate the total carbon content of all snags
     var totalCarbonSnags = deadwood.sum("carbon", "snag=true");
     console.log("Total carbon in snags: " + totalCarbonSnags);

     // Count the number of DWD pieces with decay class > 2
     var countAdvancedDecayDWD = deadwood.sum("1", "snag=false and decayClass > 2");
     console.log("Number of DWD pieces in advanced decay: " + countAdvancedDecayDWD);

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