Description Usage Arguments Details Value Author(s) References Examples
The function calculates resilience components on a data.frame
of tree-ring series after Lloret et al. (2011), useful to analyze growth of individual trees prior, during and after extreme events / disturbances. The component 'resistance' is conceptually identical to 'abrupt growth changes' as described in Schweingruber et al. (1990). To identify negative event and pointer years, thresholds can be set as for the function pointer.rgc
. 'Recovery' is the ability of tree growth to recover after disturbance, whereas 'resilience' reflects the ability of trees to reach pre-disturbance growth levels. Weighting of the resilience by the experienced growth reduction results in 'relative resilience'.
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data |
a |
nb.yrs |
an |
post |
an |
res.thresh.neg |
a |
series.thresh |
a |
The function calculates the resilience components resistance, recovery, resilience and relative resilience as described in Lloret et al. (2011). A threshold on resistance can be set to identify negative event years for trees (cf. rgc.thresh.neg
in function pointer.rgc
), which are used to define negative pointer years for the site.
If nb.yrs
, res.thresh.neg
and series.thresh
are set to 4, 40 and 75 respectively, a negative pointer year will be defined when at least 75% of the tree-ring series display an event year with resistance values indicating a growth decrease of at least 40%, relative to the average growth in the 4 preceding years. The output provides the resilience components for all possible years, as well as for the selected pointer years separately.
Note that the resulting time series are truncated at both ends by the number of years specified in nb.yrs
(and post
), inherent to the calculation methods.
#' The function returns a list
containing the following components:
resist |
a |
EYvalues |
a |
recov |
a |
resil |
a |
rel.resil |
a |
out |
a |
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out.select |
a |
spec.param |
a |
Marieke van der Maaten-Theunissen and Ernst van der Maaten.
Lloret, F., Keeling, E.G. and Sala, A. (2011) Components of tree resilience: effects of successive low-growth episodes in old ponderosa pine forests. Oikos 120: 1909-1920.
Schweingruber, F.H., Eckstein, D., Serre-Bachet, F. and Br<c3><a4>ker, O.U. (1990) Identification, presentation and interpretation of event years and pointer years in dendrochronology. Dendrochronologia 8: 9-38.
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