The iLand Javascript API
DeadTreeList Class
ABE\deadtreelist_doc.js:2
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, "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:
"Snags": Standing dead trees."DWD": Downed dead wood (lying on the ground)."Both": 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, "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, "Snags", 'species=pisy', true);
console.log("Total dead tree elements after appending: " + dtl.count);Constructor
DeadTreeList
()
Methods
filter
-
filter
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:
-
filterStringA valid filter expression (see iLand expression engine documentation).
Returns:
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.");loadFromRU
-
ru_index -
loadWhat -
[append=false]
Loads dead trees from a specific resource unit (RU) into the list.
Parameters:
-
ru_indexIntegerThe index of the resource unit from which to load dead trees.
-
loadWhatStringSpecifies the type of dead wood to load. Possible values are: -
"Snags": Load only standing dead trees. -"DWD": Load only downed dead wood. -"Both": Load both snags and DWD. -
[append=false]Boolean optionalIf
true, the newly loaded dead trees are appended to the existing list. Iffalse(default), the list is cleared before loading.
Returns:
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, "Snags");
console.log(numLoaded + " snags loaded.");
// Load DWD from RU 10 and append to the list
deadwood.loadFromRU(10, "DWD", true);
console.log("Total deadwood count: " + deadwood.count);loadFromStand
-
stand_id -
loadWhat -
[filter=""]
Loads dead trees from a specific stand into the list.
Parameters:
-
stand_idIntegerThe ID of the stand from which to load dead trees.
-
loadWhatStringSpecifies the type of dead wood to load. Possible values are: -
"Snags": Load only standing dead trees. -"DWD": Load only downed dead wood. -"Both": Load both snags and DWD. -
[filter=""]String optionalAn optional filter expression. Only dead trees for which this expression evaluates to true will be loaded. The list is cleared before loading new trees.
Returns:
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, "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, "Snags");
console.log("Snags count from stand 88: " + deadwood.count);mean
-
expression -
[filter=""]
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:
-
expressionStringA valid expression (e.g., a dead tree variable name) for which to calculate the mean.
-
[filter=""]String optionalAn optional filter expression. Only elements for which this expression evaluates to true will be included in the mean calculation.
Returns:
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);sum
-
expression -
[filter=""]
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:
-
expressionStringA valid expression (e.g., a dead tree variable name or '1' for counting) for which to calculate the sum.
-
[filter=""]String optionalAn optional filter expression. Only elements for which this expression evaluates to true will be included in the sum.
Returns:
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);Properties
count
Integer
The number of dead tree elements (snags or DWD pieces) currently loaded in the list.