| survival_weibull {care4cmodel} | R Documentation |
Weibull-Based Estimates of Stand Survival
Description
Estimates the probability of a forest stand to survive a period t after its establishment, based on the Weibull-Method published by Staupendahl (2011) Forstarchiv 82, 10-19.
Usage
survival_weibull(t, alpha, s_100)
Arguments
t |
Time in years after stand establishment |
alpha |
Shape parameter. According to Staupendahl, Values < 1 indicate a high risk at young ages, alpha = 1 indicates an indifference of the risk to t (exponential distribution), values > 1 indicate high risk at old ages, where 1 < alpha < 2 means a degressively increasing, alpha = 2 a constantly increasing, and alpha > 2 a progressively increasing risk. |
s_100 |
Survival probability up to t = 100 |
Details
The parameter s_100 represents the survival probability after t = 100
years, and alpha is the shape parameter, indicating the risk profile
of the stand (type) of interest.
Value
The probability to survive up to t = 100
Examples
# Calculations for Common oak, European beech, Norway spruce, Douglas fir,
# and Scots pine with parameters after Staupendahl and Zucchini (AFJZ 2011)
t <- seq(0, 120, 5)
survival_weibull(t, alpha = 2.75, s_100 = 0.971) # oak
survival_weibull(t, alpha = 1.76, s_100 = 0.967) # beech
survival_weibull(t, alpha = 2.78, s_100 = 0.726) # spruce
survival_weibull(t, alpha = 3.11, s_100 = 0.916) # Douglas
survival_weibull(t, alpha = 2.45, s_100 = 0.923) # pine