RD: Relative Density

In ryanmismith/inventoryfunctions: Forestry Inventory Functions

Relative Density

Description

This function computes the Relative Density Index for each plot in your inventory.

Usage

RD(SDIPlot, SDIMax)

Arguments

SDIPlot	The calculated SDI at each plot.
SDIMax	The calculated SDImax for each plot.

Details

Stand density is a quantitative measure of the degree of crowding and resulting level of competition existing within the stand.

Combined with the SDI.Plot (SDI using summation method) and SDI.Max functions (using either method in the package - Woodall or Weiskittel), this is a measure for examining and comparing competition within mixed and uneven aged stands.

Interpreting Relative Density

Based on the interpretation of RD proposed by Drew and Flewelling (1979), relative densities of 0.15, 0.40, and 0.55 correspond to the onset of competition, lower limit of full site occupancy, and the zone of imminent competition mortality, respectively. Curtis (2010) suggests that trees less than 4 cm DBH should be excluded from the computation of any relative density measure.

Inputs - Plot, Stand, and Tree Tables

This function can be used in three different ways. First, you can run a tibble or dataframe of tree level measurements where each tree has a corresponding SDI and SDImax based on its plot or stand location. Second, you can run a tibble or dataframe of plot level data that will provide you with the relative density ratios at each plot. Third, you can utilize this at the stand level, by running mean stand density and mean stand density max data for an entire stand.

The ratio is unitless so it can be used for both imperial and metric data sets.

Value

The return value will be a relative density which is a ratio of Stand Density and Maximum Stand Density.

Author(s)

Ryan Smith

References

Curtis, R.O. 2010. Effect of diameter limits and stand structure on relative density indices: A case study. Wes. J. Appl. For. 25(4): 169–175.

Drew, T.J. and J.W. Flewelling. 1979. Stand density management: An alternative approach and its application to Douglas-fir plantations. For. Sci. 25(3): 518–532.

Weiskittel, A.R., D.W. Hann, J.A. Kershaw Jr and J.K. Vanclay. 2011a. Forest growth and yield modeling. Wiley. Chichester, UK.

See Also

SDI.Plot

SDI.Max

Other Stand Density Index Functions: SDI.Max(), SDI.Plot()

Other Plot Level Functions: BA.Larger.Trees(), BAPH(), CCF.Larger(), CrownCompF(), DBHFuns(), HeightPredict(), SDI.Max(), SDI.Plot(), TPH(), TallestTrees(), Unique.ID()

Examples

SDIPlot  <- c(1200, 987, 1823)
SDIMax   <- c(2100, 2050, 2150)
RD(SDIPlot, SDIMax)

ryanmismith/inventoryfunctions documentation built on Aug. 5, 2022, 2:22 a.m.