Package 'dfoliatR'

Cast data frame to list-like defol object

Description

Cast data frame to list-like defol object

Usage

as_defol(x)

Arguments

x	A data frame or list-like object to cast. Must have named elements for "year", "series", "gsi", "ngsi", and "defol_status".

Value

x cast to a defol object

Examples

data(dmj_defol)
example_data <- as.data.frame(dmj_defol)
is.defol(example_data)
back_to_defol <- as_defol(example_data)
is.defol(back_to_defol)

---

Cast data frame to list-like obr object

Description

Cast data frame to list-like obr object

Usage

as_obr(x)

Arguments

x	A data frame or list-like object to cast. Must have named elements for "year", "samp_depth", "num_defol", "perc_defol", "num_max_defol", "perc_max_defol", "mean_gsi", "mean_ngsi", "outbreak_status".

Value

x cast to an obr object

Examples

data(dmj_obr)
example_data <- as.data.frame(dmj_obr)
is.obr(example_data)
back_to_obr <- as_obr(example_data)
is.obr(back_to_obr)

---

Alias to as_defol()

Description

Alias to as_defol()

Usage

as.defol(x)

Arguments

x	A data frame or list-like object to cast. Must have named elements for "year", "series", "gsi", "ngsi", and "defol_status".

Value

x cast to a defol object

Examples

data(dmj_defol)
example_data <- as.data.frame(dmj_defol)
is.defol(example_data)
back_to_defol <- as_defol(example_data)
is.defol(back_to_defol)

---

Alias to as_obr()

Description

Alias to as_obr()

Usage

as.obr(x)

Arguments

x	A data frame or list-like object to cast. Must have named elements for "year", "samp_depth", "num_defol", "perc_defol", "num_max_defol", "perc_max_defol", "mean_gsi", "mean_ngsi", "outbreak_status".

Value

x cast to an obr object

Examples

data(dmj_obr)
example_data <- as.data.frame(dmj_obr)
is.obr(example_data)
back_to_obr <- as_obr(example_data)
is.obr(back_to_obr)

---

Constructor for S3 defol class

Description

Constructor for S3 defol class

Usage

defol(year, series, gsi, ngsi, defol_status)

Arguments

year	An n-length integer vector of observation years
series	An n-length factor or character vector of series names
gsi	An n-length numeric vector of growth suppression index, such as calculated by gsi()
ngsi	An n-length numeric vector of normalized gsi, such as calculated by gsi().
defol_status	An n-length factor or character vector denoting the defoliation event status of each year. This uses a controlled vocabulary, see dfoliatR:::make_defol_status for possible values.

Value

a tree-level defol object

---

Descriptive statistics for defoliation trees

Description

Descriptive statistics for defoliation trees

Usage

defol_stats(x)

Arguments

x	A defol object after running defoliate_trees().

Value

A data frame containing tree/series-level statistics.

Note

If series-end-events are present, they are omitted from calculations of total event years and mean duration.

Examples

data("dmj_defol")
defol_stats(dmj_defol)

---

Identify defoliation events in host trees

Description

defoliate_trees() is the starting point for most analyses of insect defoliation signals preserved in the growth patterns of trees. It requires individual-tree standardized measurements from potential host trees and a tree-ring chronology from a nearby non-host species. First, defoliate_trees() combines these tree-ring indices by calling gsi() to perform a "correction" of the host-tree indices to remove the climatic influences on tree growth as represented by the non-host chronology. This should isolate a disturbance-related signal. Second, defoliate_trees(), runs id_defoliation(), which completes a runs analyses to evaluate sequences of negative departures in the host tree growth series (ngsi) for potential defoliation events.

Usage

defoliate_trees(
  host_tree,
  nonhost_chron = NULL,
  duration_years = 8,
  max_reduction = -1.28,
  bridge_events = FALSE,
  series_end_event = FALSE,
  list_output = FALSE
)

Arguments

host_tree	A dplR::rwl object containing the tree-level growth series for all host trees to be compared to the non-host chronology.
nonhost_chron	A dplR::rwl object containing a single non-host chronology. If blank, defoliation events will be inferred on the host_tree series as provided. It is incumbent on the user to ensure the host_tree series are properly prepared for analyses when there is no nonhost_chron provided.
duration_years	The minimum length of time in which the tree is considered to be in defoliation.
max_reduction	The minimum value of ngsi required to be considered a defoliation event. If a sequence of negative ngsi values does not reach this threshold, the potential event is rejected. Defaults to -1.28.
bridge_events	Binary, defaults to FALSE. This option allows for successive events that are separated by a single year to be bridged and become one event. It should be used cautiously and closely evaluated to ensure the likelihood that the two (or more) events are actually one long event.
series_end_event	Binary, defaults to FALSE. This option allows the user to identify an event occurring at the time of sampling as a defoliation event, regardless of duration. Including it will help to quantify periodicity and extent of an outbreak. This should only be used if the user has direct knowledge of an ongoing defoliation event when the trees were sampled.
list_output	Defaults to FALSE. This option is to output a long list object containing a separate data.frame for each series in host_tree that includes the input series and the nonhost_chron, the corrected series, and the character string identifying the defoliation events.

Value

By default this returns a long-form data frame of tree-level growth suppression indices and identified defoliation events. If list_output = TRUE, it returns a list object with each element containing a data.frame rwl object of the host and non-host series, plus the outputs from gsi(). The list object is useful for assessing the effects of running gsi() on the host and nonhost data.

Note

Other functions in dfoliatR, like outbreak() and plot_defol(), require a long-form data frame identifiable as a defol() object. Selecting list_output = TRUE will trigger errors in running other functions.

Examples

# Load host and non-host data
data("dmj_h") # Host trees
data("dmj_nh") # Non-host chronology

dmj_defol <- defoliate_trees(dmj_h, dmj_nh)

---

Demi John dfol object

Description

Produced by running defoliate_trees(dmj_h, dmj_nh, series_end_events=TRUE)

Usage

dmj_defol

Format

A defol object with 4267 rows and 5 columns

---

Demi John Douglas-fir

Description

Western spruce budworm host series

Usage

dmj_h

Format

An rwl object with 17 tree-level series, standardized in ARSTAN. Dates range from 1620-1997.

---

Demi John area ponderosa pine

Description

Non-host pair to Demi John Douglas-fir dmj_h

Usage

dmj_nh

Format

An rwl object with 1 series, 1675-1997.

---

Demi John outbreak object

Description

Produced by running outbreak(dmj_defol)

Usage

dmj_obr

Format

An object of class obr (inherits from data.frame) with 323 rows and 9 columns.

Details

@format An outbreak object with 323 rows and 9 columns

---

East Fork defol object

Description

Produced by running defoliate_trees(efk_h, efk_nh, series_end_event = TRUE)

Usage

efk_defol

Format

A defol object with 5142 rows and 5 columns

---

East Fork Jemez River Douglas-fir

Description

Western spruce budworm host series

Usage

efk_h

Format

An rwl object with 37 tree-level series, standardized in ARSTAN. Dates range from 1776-1987.

References

Swetnam, T.W., Lynch, A.M., 1993. Multicentury, Regional-Scale Patterns of Western Spruce Budworm Outbreaks. Ecological Monographs 63, 399–424. https://doi.org/10.2307/2937153

---

Baca ponderosa pine chronology

Description

Non-host pair chronology for East Fork Douglas-fir efk_h

Usage

efk_nh

Format

An rwl chronology object with 1 series, 1612-1987. Standardized in ARSTAN.

Source

https://www.ncei.noaa.gov/access/paleo-search/study/5068

References

Swetnam, T.W., Lynch, A.M., 1993. Multicentury, Regional-Scale Patterns of Western Spruce Budworm Outbreaks. Ecological Monographs 63, 399–424. https://doi.org/10.2307/2937153

---

East Fork outbreak object

Description

Produced by running outbreak(efk_defol)

Usage

efk_obr

Format

An outbreak object with 221 rows and 9 columns

---

Defoliation event list

Description

Defoliation event list

Usage

get_defol_events(x)

Arguments

x	a defol object

---

Calculate the growth suppression index

Description

This function removes the nonhost growth signal from a host tree-ring series.

Usage

gsi(input_series)

Arguments

input_series

A dplr::rwl object with the host tree series as the first column and the non-host chronology as the second. Years should be the row names. This is specifically created by defoliate_trees() and passed to gsi().

Details

The growth suppression index (GSI) is referred to as the "corrected" series in OUTBREAK. It is calculated as:

$GSI(i) = H(i) - (NH(i) - mean(NH)) sd(H)/sd(NH)$

where H and NH are the host and nonhost tree-ring series as standardized index values; i is the year, and the functions mean() and sd() are applied to the common period.

gsi() will rarely be run directly by a user. It is called from defoliate_trees().

Value

A data frame with the two input columns (host and nonhost series) and 3 added columns:

1. The mean/sd adjusted non-host chronology,

2. The growth suppression index ("gsi") of the host series after subtraction of the adjusted nonhost chronology,

3. The normalized growth suppression index ("ngsi") generated by applying scale() to the gsi.

---

Identify defoliation events in a host series

Description

After calculating the growth suppression index in gsi(), id_defoliation() performs a runs analysis on the normalized growth suppression index, or ngsi, in which sequences of negative departures are assessed as possible defoliation events. id_defoliation() is the workhorse for defoliate_trees(), performing much of the necessary criteria evaluation used in OUTBREAK. The defaults for most parameters originate from OUTBREAK. Two new features distinguish the dfoliatR version: bridging events that occur in close sequence and allowing for the recent end of a series to be evaluated for defoliation regardless of the event duration. See parameter specifics for details.

Usage

id_defoliation(
  input_series,
  duration_years = 8,
  max_reduction = -1.28,
  bridge_events = FALSE,
  series_end_event = FALSE
)

Arguments

input_series	A data frame with 5 columns, as generated by gsi().
duration_years	The minimum length of time in which the tree is considered to be in defoliation.
max_reduction	The minimum value of ngsi required to be considered a defoliation event. If a sequence of negative ngsi values does not reach this threshold, the potential event is rejected. Defaults to -1.28.
bridge_events	Binary, defaults to FALSE. This option allows for successive events that are separated by a single year to be bridged and become one event. It should be used cautiously and closely evaluated to ensure the likelihood that the two (or more) events are actually one long event.
series_end_event	Binary, defaults to FALSE. This option allows the user to identify an event occurring at the time of sampling as a defoliation event, regardless of duration. Including it will help to quantify periodicity and extent of an outbreak. This should only be used if the user has direct knowledge of an ongoing defoliation event when the trees were sampled.

Value

After performing runs analyses, the function adds a column to the input data frame that distinguishes years of defoliation and the maximum defoliation year (ie. the year the greatest negative growth departure within the event).

Note

id_defoliation() is called by defoliate_trees(). It might only be used by the user for troubleshooting.

---

Check if object is tree-level defoliation object: defol

Description

Check if object is tree-level defoliation object: defol

Usage

is.defol(x)

Arguments

x	Any R object.

Value

Boolean indicating whether x is a defol object.

---

Check if object is outbreak, meaning site-level outbreak object

Description

Check if object is outbreak, meaning site-level outbreak object

Usage

is.obr(x)

Arguments

x	Any R object.

Value

Boolean indicating whether x is an outbreak object.

---

Constructor for an obr object.

Description

Constructor for an obr object.

Usage

obr(
  year,
  samp_depth,
  num_defol,
  perc_defol,
  num_max_defol,
  perc_max_defol,
  mean_gsi,
  mean_ngsi,
  outbreak_status
)

Arguments

year	An n-length numeric vector of observed years.
samp_depth	An n-length numeric vector of the number of trees.
num_defol	An n-length numeric vector of the number of trees experiencing defoliation.
perc_defol	An n-length numeric vector of the percent of trees experiencing defoliation.
num_max_defol	An n-length numeric vector of the number of trees experiencing their maximum level of defoliation (i.e., their most extreme negative growth departure).
perc_max_defol	An n-length numeric vector of the percent of trees experiencing their maximum level of defoliation (i.e., their most extreme negative growth departure).
mean_gsi	An n-length numeric vector of the average growth suppression index across all observed trees.
mean_ngsi	An n-length numeric vector of the average normalized (scaled) growth suppression index.
outbreak_status	An n-length factor or character vector that identified whether that year surpasses the designated thresholds for an "outbreak event". Threshold criteria are provided in outbreak().

Value

An obr object with columns matching the input variables.

---

Composite defoliation series to determine outbreak events

Description

outbreak() takes a defol object from defoliate_trees() and composites it into a site-level object. Function parameters allow the user to filter the tree-level series in various ways to optimize thresholds of what constitutes an "outbreak" level event recorded by the host trees.

Usage

outbreak(x, filter_perc = 25, filter_min_series = 3, filter_min_defol = 1)

Arguments

x	a defol object
filter_perc	the minimum percentage of defoliated trees to be considered an outbreak. Default is 25 percent.
filter_min_series	The minimum number of trees required for an outbreak event. Default is 3 trees.
filter_min_defol	The minimum number of trees recording a defoliation event. Default is 1 tree.

Value

A data.frame obr object for the site that includes all trees in the host defol object. Columns in the obr include:

1. year for every year in the set of host trees,

2. num_defol the number of trees recording a defoliation event,

3. percent_defol the percent of trees recording a defoliation,

4. num_max_defol the number of trees recording a maximum growth suppression (or peak of that event on that tree),

5. perc_max_defol the percent of trees at maximum defoliation,

6. mean_gsi the average of all trees growth suppression index (gsi),

7. mean_ngsi the average of all trees normalized growth suppression index (ngsi),

8. outbreak_status whether that year constitutes an outbreak based on the filters applied to the function.

Examples

data("dmj_defol")
head(outbreak(dmj_defol))

---

Outbreak statistics

Description

Summary statistics for inferred outbreaks

Usage

outbreak_stats(x)

Arguments

x	An obr object after running outbreak()

Value

A data frame with descriptive statistics for each outbreak event determined by outbreak(), including:

• "start" – first year of outbreak

• "end" – last year of outbreak

• "duration" – length of outbreak (in years)

• "n_df_start" – number of trees defoliated at the start

• "perc_df_start" – percent of trees defoliated at the start

• "max_df_obr" – maximum number of trees in the outbreak during a single year

• "yr_max_df" – year with the maximum number of trees defoliated

• "yr_min_ngsi" – year with the lowest mean normalized growth suppression index (NGSI)

• "min_gsi" – minimum growth suppression index

• "min_ngsi" – minimum normalized gsi

Note

Certain statistics will be set to NA for the final outbreak event if there was an ongoing defoliation event (in which series_end_event = TRUE in defoliate_trees()). This is because the end of the outbreak remains unknown, so statistics such as duration cannot be calculated. Statistics pertaining to the start of the event are provided.

Examples

data("dmj_obr")
outbreak_stats(dmj_obr)

---

Produce a Gantt plot of individual tree-ring series to show defoliation events in time

Description

Produce a Gantt plot of individual tree-ring series to show defoliation events in time

Usage

plot_defol(x, breaks)

Arguments

x	a defol object produced by defoliate_trees().
breaks	a vector length two providing threshold (negative) ngsi values to separate minor, moderate, and severe defoliation events. If blank, the mean and 1st quartile are used.

Examples

data("dmj_defol")
plot_defol(dmj_defol)

## Change the values severity classes
plot_defol(dmj_defol, breaks = c(-1.0, -0.5))

---

Produce a stacked plot to present composited, site-level insect outbreak chronologies

Description

Produce a stacked plot to present composited, site-level insect outbreak chronologies

Usage

plot_outbreak(x, disp_index = c("GSI", "NGSI"), label_defol = "% defoliated")

Arguments

x	an 'obr' object produced by outbreak()
disp_index	Identify the timeseries index to plot. Defaults to NGSI, the average normalized growth suppression index for the site. The only other option is GSI, the average growth suppression index.
label_defol	Allows users to change the bottom tile of the printed ouput to read what they'd like. Defaults to "% defoliated"

Examples

data(dmj_obr)
plot_outbreak(dmj_obr)

# Change middle panel display from the default "NGSI" to "GSI"
plot_outbreak(dmj_obr, disp_index = "GSI")

---

Plot a defol object

Description

Plot a defol object

Usage

## S3 method for class 'defol'
plot(...)

Arguments

...	arguments passed to plot_defol()

---

Calculate the sample depth of a defol object

Description

Calculate the sample depth of a defol object

Usage

sample_depth(x)

Arguments

x	A defol object.

Value

A data.frame containing the years and number of trees

Examples

data("dmj_defol")
head(sample_depth(dmj_defol))

---

Extract series names from a defol object

Description

Extract series names from a defol object

Usage

series_names(x)

Arguments

x	a defol object

---

Stack a defoliation list

Description

Stack a defoliation list

Usage

stack_defoliation(x)

Arguments

x	a list object created by defoliate_trees()

Value

a defol object (long-format data frame)

---