trim.growth {CTFS} | R Documentation

## Determines if the Growth Rate of a Tree is Within Defined Limits

### Description

Growth rates of trees is computed as the annual change in DBH between censuses (mm / year). Some of these rates are unreasonably high or low, due to errors in measurement or data entry. Unreasonable values are identified by this function with user defined maximum and a predetermined minimum. This is a core function as all valid growth rates and DBHs are assessed using the parameters of this function. It is usually called within other functions. The function returns a logical vector of which trees have valid growth rates.

### Usage

    trim.growth(dbh1,dbh2,pom1,pom2,status1,status2,timeint,
       slope=0.006214,intercept=.9036,err.limit=4,maxgrow=75)

### Arguments

`dbh1` | DBH (mm) of tree at census 1
`dbh2` | DBH (mm) of tree at census 2
`pom1` | Point of measurement of tree at census 1
`pom2` | Point of measurement of tree at census 2
`status1` | Status of tree at census 1
`status2` | Status of tree at census 2
`timeint` | time (years) between censuses
`slope` | slope of error of measurement line
`intercept` | intercept of error of measurement line
`err.limit` | number of standard deviations for allowed for limit of negative growth rate
`maxgrow` | mm per year for maximum allowable growth rate

### Details

This function is NOT normally invoked directly by a user. It is designed to be called from within other functions that compute growth rates. Therefore, the other functions should provide for adjustment of the acceptable limits of growth. At this time, we recommend that only the maximum limit be adjusted by the user. The minimum limit is based on empirical data from a single CTFS site (BCI, 1995 and repeated in 2000) and until this same data is collected at other sites, then the BCI data will serve to set the minimum allowable growth rate.

See `CTFS.datafiles` for more information on arguments.

Only trees that have measured DBHs, a status code of “A” in both censuses and no change in the point of measurement between censuses, are assessed for whether their growth rate is reasonable using this function.

This means that trees that are missing a dbh, have a change in point of measurement, have a dbh < 10 mm in either census or where the growth computes to NA are not assessed for reasonable growth rates. In these cases, a growth rate cannot be calculated.

The maximum allowable growth rate is just an absolute value in mm per year that can (usually) be set by the user, provided that the calling function supports it (which it should).

The minimum allowable growth rate (usually negative) is based on a linear model estimating the standard deviation of dbh measures due to measurement error; the parameters slope and intercept define the linear relationship between this error deviation and dbh. The lower limit of growth is where the second dbh measure is more than 4 standard deviations below the first. The default values of slope and intercept are based on dbh remeasure tests done in both 1995 and 2000 at BCI. A line was fitted through the absolute dbh errors as a function of dbh in both years; the average slope and intercept is used here.

### Value

The function returns a logical vector indicating which trees (rows) have valid growth rates. No estimation of growth rates is done.

### Author(s)

Rick Condit

### See Also

`CTFS.datafiles`, `CTFS.growth`, `CTFS.biomass`

### Examples

    ## Not run:

    dbh1 <- tst.bci90.full$dbh
    dbh2 <- tst.bci95.full$dbh
    pom1 <- tst.bci90.full$pom
    pom2 <- tst.bci95.full$pom
    status1 <- tst.bci90.full$status
    status2 <- tst.bci95.full$status
    time <- (tst.bci95.full$date-tst.bci90.full$date)/365.25

    trim.out <- trim.growth(dbh1,dbh2,pom1,pom2,status1,status2,time,
                         slope=0.006214,intercept=.9036,err.limit=4,maxgrow=75)

    ## End(Not run)

[Package CTFS version 1.00 Index]