CTFS.abundance {CTFS} | R Documentation |
Provides an overview for the analysis of abundance and change in population size by a variety of categories. This overview includes functions that are available, supporting functions and ways for using the options of the main functions.
FUNCTIONS TO COMPUTE ABUNDANCE AND CHANGE IN POPULATION SIZE RATE
abundance | Abundance of Tree by Categories (User Defined Groups) |
abundance.spp | Abundance of Trees by Species and DBH Classes, DBH determined separately for each year |
abundance.quad | Abundance of Trees by Species and User Defined Quadrates |
abundance.change | Annual Change in Population Size by Categories (User Defined Groups |
FUNCTIONS FOR FORMATTING RESULTS
assemble.demography | Reformat the Output from Demographic Functions from List to Dataframe |
COMPUTATION OF ABUNDANCE AND CHANGE IN ABUNDANCE
Abundance is the number of individuals alive at a given census.
Trees that are broken at the point of dbh measurement are not
included. By convention, the first census is referred to as N0
and the second census as N1
, as in an initial and any subsequent
census. Censuses do NOT have to be in immediate order though they must
be in the order of “earlier, more recent”. The change in
abundance can be computed for any two censuses no matter how many years
apart they are.
The annual population rate is calculated as
p = (logN1-logN0) / (time1-time0)
where N0
is the number of live individuals at the first census,
where N1
is the number of live individuals at the second census
which includes recruits at that census,
where time1
and time0
are expressed in years.
The probabiilty that N0 = N1 (test of hypothesis) is computed as
the combined probability of the observed mortality and recruitment.
Probabilities for mortality are computed using a binomial distribution
and a poisson distribution is used for recruitment. The number of
survivors, S
, is computed based N0
.
DETERMINATION OF WHETHER TO INCLUDE A TREE IN THE COMPUTATION
By default, trees are included in the computation of abundance for a
single census if their status
= “A” and if their
mindbh
>= 10 mm for the census being used. The user can alter these
values.
For computation of changes in abundance, the inclusion of a tree is
determined independently for each census. The user can only define
status
and mindbh
once. These values are used for
assessing a tree for inclusion for each census.
Survivors are trees that were alive in census 1 and are also alive in census 2.
Rick Condit and Pamela Hall