R/Andreassen_2003_ba_models_Norway.R

In Silviculturalist/forester: Forest Science and Forestry

#' Individual tree growth models of Norway spruce, Scots Pine, Birch and other broadleaves in Norway.
#'
#' @description OBSERVE! Quality control not complete.
#'
#' @source Andreassen, K., Tomter, S.M. (2003) Basal area growth models for
#' individual trees of Norway Spruce, Scots pine, birch and other broadleaves
#' in Norway. For. Ecol. Manage. 180:1-3. 11-24. ISSN 0378-1127. DOI:
#' \url{https://doi.org/10.1016/S0378-1127(02)00560-1}
#' @description Models based on 5.64 m radius plots (100 m^2).
#' Mean inventory period of 5.4 years.
#' @param BA_m2 Basal area of the tree, in m^2.
#' @param diameter_cm Diameter at breast height 1.3 m in cm.
#' @param BA_m2_ha Basal area of the plot, in m^2 / ha
#' @param BA_m2_ha_Spruce Basal area Spruce, in m^2 / ha
#' @param BA_m2_ha_Broadleaves Basal area Broadleaves, in m^2 / ha
#' @param HL Lorey's Mean Height for the plot.
#' @param QMD Basal area weighted mean diameter, in cm. (To do: Check with authors)
#' @param stems_ha Number of stems per hectare.
#' @param SI40_Spruce Site Index H40 for Spruce. (will override SI40_Pine if not NULL (default))
#' @param SI40_Pine Site Index H40 for Scots Pine.
#' @param latitude Latitude, decimal.
#' @param altitude Meters above sea level.
#' @param even_aged TRUE if even-aged stand (one-layered). FALSE if uneven-aged stand (multi-layered)
#'
#' @name andreassen_2003
#'

#' @rdname andreassen_2003
#' @export

Andreassen_2003_BA_increment_Norway_Norway_Spruce_SI <- function(
  BA_m2,
  diameter_cm,
  BA_m2_ha,
  BA_m2_ha_Spruce,
  #BA_m2_ha_Pine,
  BA_m2_ha_Broadleaves,
  HL,
  QMD,
  stems_ha,
  SI40_Spruce=NULL,
  SI40_Pine=NULL,
  #latitude,
  #altitude,
  even_aged=TRUE
  #spruce_presence,
  #pine_presence,
  #birch_presence
){

  if(!is.null(SI40_Spruce)) SI40_Pine <- NULL
  if(!is.null(SI40_Pine)) SI40_Spruce <- NULL
  if(is.null(SI40_Spruce) & is.null(SI40_Pine)) stop("Either SI40_Spruce or SI40_Pine must be given")
  #stopifnot(is.logical(c(spruce_presence,pine_presence,birch_presence)))
  stopifnot(is.logical(even_aged))


  #Multiply all proportions by 10 to ensure sum of proportions == 10.
  BA_quotient_Spruce <- (BA_m2_ha_Spruce / BA_m2_ha)*10
  #BA_quotient_Pine <- (BA_m2_ha_Pine / BA_m2_ha)*10
  BA_quotient_Broadleaves <- (BA_m2_ha_Broadleaves / BA_m2_ha)*10

  #Set missing vars to zero for simplicity with model components.
  latitude <- 0
  altitude <- 0
  BA_quotient_Pine <- 0
  pine_presence <- 0
  spruce_presence <- 0
  birch_presence <- 0


  #Follows order of table 4.
  a <- -0.8706
  b1 <- 0.7069
  b2 <- -0.0975 * 10^-3
  b3 <- 0.0405 * 10^-6
  c5 <- 0.2232
  c3 <- 0.302 * 10^-2
  c2 <- -0.750 * 10^-2
  c1 <- -0.0106
  c4 <- -0.123* 10^-3
  d1 <- 0.09337
  d2 <- 0.08841
  d3 <- 0
  d4 <- 0
  e4 <- -0.0122
  e5 <- 0
  e6 <- 0.0280
  e1 <- 0
  e2 <- 0
  e3 <- 0
  e7 <- 0.0043


  size <- b1 * log(BA_m2*10^4) + b2 * (BA_m2*10^4) + b3 * ((BA_m2*10^4)^2)
  competition <- c1 * BA_m2_ha + c2 * (HL * 10) + c3 * (QMD*10) + c4 * stems_ha + c5*(diameter_cm/QMD)
  #Latitude decimal, as opposed to in paper.
  site <- d1 * SI40_Spruce + d2 * SI40_Pine + d3 * (latitude*10) + d4 * altitude
  stand <- e1*spruce_presence + e2*pine_presence + e3*birch_presence + e4*BA_quotient_Spruce + e5*BA_quotient_Pine + e6*BA_quotient_Broadleaves + e7*even_aged

  return(
    exp(a + size + competition + site + stand)/10^4 # cm^2 to m^2
  )


}



#' @rdname andreassen_2003
#' @export
#'

Andreassen_2003_BA_increment_Norway_Scots_Pine_SI <- function(
    BA_m2,
    diameter_cm,
    BA_m2_ha,
    BA_m2_ha_Spruce,
    #BA_m2_ha_Pine,
    BA_m2_ha_Broadleaves,
    HL,
    QMD,
    stems_ha,
    SI40_Spruce=NULL,
    SI40_Pine=NULL,
    #latitude,
    #altitude,
    even_aged=TRUE
    #spruce_presence,
    #pine_presence,
    #birch_presence
){

  if(!is.null(SI40_Spruce)) SI40_Pine <- NULL
  if(!is.null(SI40_Pine)) SI40_Spruce <- NULL
  if(is.null(SI40_Spruce) & is.null(SI40_Pine)) stop("Either SI40_Spruce or SI40_Pine must be given")
  #stopifnot(is.logical(c(spruce_presence,pine_presence,birch_presence)))
  stopifnot(is.logical(even_aged))


  #Multiply all proportions by 10 to ensure sum of proportions == 10.
  BA_quotient_Spruce <- (BA_m2_ha_Spruce / BA_m2_ha)*10
  #BA_quotient_Pine <- (BA_m2_ha_Pine / BA_m2_ha)*10
  BA_quotient_Broadleaves <- (BA_m2_ha_Broadleaves / BA_m2_ha)*10

  #Set missing vars to zero for simplicity with model components.
  latitude <- 0
  altitude <- 0
  BA_quotient_Pine <- 0
  pine_presence <- 0
  spruce_presence <- 0
  birch_presence <- 0


  #Follows order of table 4.
  a <- -0.8407
  b1 <- 0.7541
  b2 <- -0.3463 * 10^-3
  b3 <- 0.0564 * 10^-6
  c5 <- 0.0849
  c3 <- 0
  c2 <- -0.427 * 10^-2
  c1 <- -0.0115
  c4 <- -0.194* 10^-3
  d1 <- 0.08253
  d2 <- 0.08899
  d3 <- 0
  d4 <- 0
  e4 <- 0.0378
  e5 <- 0
  e6 <- 0.0451
  e1 <- 0
  e2 <- 0
  e3 <- 0
  e7 <- -0.0328


  size <- b1 * log(BA_m2*10^4) + b2 * (BA_m2*10^4) + b3 * ((BA_m2*10^4)^2)
  competition <- c1 * BA_m2_ha + c2 * (HL * 10) + c3 * (QMD*10) + c4 * stems_ha + c5*(diameter_cm/QMD)
  #Latitude decimal, as opposed to in paper.
  site <- d1 * SI40_Spruce + d2 * SI40_Pine + d3 * (latitude*10) + d4 * altitude
  stand <- e1*spruce_presence + e2*pine_presence + e3*birch_presence + e4*BA_quotient_Spruce + e5*BA_quotient_Pine + e6*BA_quotient_Broadleaves + e7*even_aged

  return(
    exp(a + size + competition + site + stand)/10^4 # cm^2 to m^2
  )


}


#' @rdname andreassen_2003
#' @export
#'

Andreassen_2003_BA_increment_Norway_Birch_SI <- function(
    BA_m2,
    diameter_cm,
    BA_m2_ha,
    BA_m2_ha_Spruce,
    #BA_m2_ha_Pine,
    BA_m2_ha_Broadleaves,
    #HL,
    QMD,
    #stems_ha,
    SI40_Spruce=NULL,
    SI40_Pine=NULL,
    #latitude,
    #altitude,
    even_aged=TRUE
    #spruce_presence,
    #pine_presence,
    #birch_presence
){

  if(!is.null(SI40_Spruce)) SI40_Pine <- NULL
  if(!is.null(SI40_Pine)) SI40_Spruce <- NULL
  if(is.null(SI40_Spruce) & is.null(SI40_Pine)) stop("Either SI40_Spruce or SI40_Pine must be given")
  #stopifnot(is.logical(c(spruce_presence,pine_presence,birch_presence)))
  stopifnot(is.logical(even_aged))


  #Multiply all proportions by 10 to ensure sum of proportions == 10.
  BA_quotient_Spruce <- (BA_m2_ha_Spruce / BA_m2_ha)*10
  #BA_quotient_Pine <- (BA_m2_ha_Pine / BA_m2_ha)*10
  BA_quotient_Broadleaves <- (BA_m2_ha_Broadleaves / BA_m2_ha)*10

  #Set missing vars to zero for simplicity with model components.
  latitude <- 0
  altitude <- 0
  BA_quotient_Pine <- 0
  stems_ha <- 0
  HL <- 0
  pine_presence <- 0
  spruce_presence <- 0
  birch_presence <- 0


  #Follows order of table 4.
  a  <-  -0.5651
  b1 <-  0.4889
  b2 <-  0.365 *10^-3
  b3 <-  0 *10^-6
  c5 <-  0.3798
  c3 <-  0
  c2 <-  0 *10^-2
  c1 <-  -0.0110
  c4 <-  0 *10^-3
  d1 <-  0.03473
  d2 <-  0.03332
  d3 <-  0
  d4 <-  0
  e4 <-  -0.0094
  e5 <-  0
  e6 <-  -0.0088
  e1 <-  0
  e2 <-  0
  e3 <-  0
  e7 <-  0.0595



  size <- b1 * log(BA_m2*10^4) + b2 * (BA_m2*10^4) + b3 * ((BA_m2*10^4)^2)
  competition <- c1 * BA_m2_ha + c2 * (HL * 10) + c3 * (QMD*10) + c4 * stems_ha + c5*(diameter_cm/QMD)
  #Latitude decimal, as opposed to in paper.
  site <- d1 * SI40_Spruce + d2 * SI40_Pine + d3 * (latitude*10) + d4 * altitude
  stand <- e1*spruce_presence + e2*pine_presence + e3*birch_presence + e4*BA_quotient_Spruce + e5*BA_quotient_Pine + e6*BA_quotient_Broadleaves + e7*even_aged

  return(
    exp(a + size + competition + site + stand)/10^4 # cm^2 to m^2
  )


}


#' @rdname andreassen_2003
#' @export
#'

Andreassen_2003_BA_increment_Norway_Broadleaves_SI <- function(
    BA_m2,
    diameter_cm,
    BA_m2_ha,
    #BA_m2_ha_Spruce,
    #BA_m2_ha_Pine,
    BA_m2_ha_Broadleaves,
    #HL,
    QMD,
    #stems_ha,
    SI40_Spruce=NULL,
    SI40_Pine=NULL,
    #latitude,
    #altitude,
    even_aged=TRUE
    #spruce_presence,
    #pine_presence,
    #birch_presence
){

  if(!is.null(SI40_Spruce)) SI40_Pine <- NULL
  if(!is.null(SI40_Pine)) SI40_Spruce <- NULL
  if(is.null(SI40_Spruce) & is.null(SI40_Pine)) stop("Either SI40_Spruce or SI40_Pine must be given")
  #stopifnot(is.logical(c(spruce_presence,pine_presence,birch_presence)))
  stopifnot(is.logical(even_aged))


  #Multiply all proportions by 10 to ensure sum of proportions == 10.
  #BA_quotient_Spruce <- (BA_m2_ha_Spruce / BA_m2_ha)*10
  #BA_quotient_Pine <- (BA_m2_ha_Pine / BA_m2_ha)*10
  BA_quotient_Broadleaves <- (BA_m2_ha_Broadleaves / BA_m2_ha)*10

  #Set missing vars to zero for simplicity with model components.
  latitude <- 0
  altitude <- 0
  BA_quotient_Pine <- 0
  BA_quotient_Spruce <- 0
  stems_ha <- 0
  HL <- 0
  pine_presence <- 0
  spruce_presence <- 0
  birch_presence <- 0


  #Follows order of table 4.
  a  <- -0.6194
  b1 <- 0.6695
  b2 <- -0.3145   *10^-3
  b3 <- 0         *10^-6
  c5 <- 0.407
  c3 <- 0
  c2 <- 0         *10^-2
  c1 <- -0.0155
  c4 <- 0         *10^-3
  d1 <- 0.02478
  d2 <- 0.02285
  d3 <- 0
  d4 <- 0
  e4 <- 0
  e5 <- 0
  e6 <- -0.0079
  e1 <- 0
  e2 <- 0
  e3 <- 0
  e7 <- 0.0569

  size <- b1 * log(BA_m2*10^4) + b2 * (BA_m2*10^4) + b3 * ((BA_m2*10^4)^2)
  competition <- c1 * BA_m2_ha + c2 * (HL * 10) + c3 * (QMD*10) + c4 * stems_ha + c5*(diameter_cm/QMD)
  #Latitude decimal, as opposed to in paper.
  site <- d1 * SI40_Spruce + d2 * SI40_Pine + d3 * (latitude*10) + d4 * altitude
  stand <- e1*spruce_presence + e2*pine_presence + e3*birch_presence + e4*BA_quotient_Spruce + e5*BA_quotient_Pine + e6*BA_quotient_Broadleaves + e7*even_aged

  return(
    exp(a + size + competition + site + stand)/10^4 # cm^2 to m^2
  )


}

#' @rdname andreassen_2003
#' @export

Andreassen_2003_BA_increment_Norway_Norway_Spruce_topographic<- function(
    BA_m2,
    diameter_cm,
    BA_m2_ha,
    BA_m2_ha_Spruce,
    #BA_m2_ha_Pine,
    BA_m2_ha_Broadleaves,
    #HL,
    QMD,
    #stems_ha,
    #SI40_Spruce=NULL,
    #SI40_Pine=NULL,
    latitude,
    altitude,
    even_aged=TRUE
    #spruce_presence,
    #pine_presence,
    #birch_presence
){

  #if(!is.null(SI40_Spruce)) SI40_Pine <- NULL
  #if(!is.null(SI40_Pine)) SI40_Spruce <- NULL
  #if(is.null(SI40_Spruce) & is.null(SI40_Pine)) stop("Either SI40_Spruce or SI40_Pine must be given")
  #stopifnot(is.logical(c(spruce_presence,pine_presence,birch_presence)))
  stopifnot(is.logical(even_aged))


  #Multiply all proportions by 10 to ensure sum of proportions == 10.
  BA_quotient_Spruce <- (BA_m2_ha_Spruce / BA_m2_ha)*10
  #BA_quotient_Pine <- (BA_m2_ha_Pine / BA_m2_ha)*10
  BA_quotient_Broadleaves <- (BA_m2_ha_Broadleaves / BA_m2_ha)*10

  #Set missing vars to zero for simplicity with model components.
  SI40_Pine <- 0
  SI40_Spruce <- 0
  HL <- 0
  stems_ha <- 0
  BA_quotient_Pine <- 0
  pine_presence <- 0
  spruce_presence <- 0
  birch_presence <- 0


  #Follows order of table 4.
  a  <- 2.2388
  b1 <- 0.7263
  b2 <- -0.0792  *10^-3
  b3 <- 0.0533   *10^-6
  c5 <- 0.1676
  c3 <- 0
  c2 <- 0        *10^-2
  c1 <- -0.0118
  c4 <- 0        *10^-3
  d1 <- 0
  d2 <- 0
  d3 <- -4.311
  d4 <- -0.7422
  e4 <- 0.0236
  e5 <- 0
  e6 <- 0.0594
  e1 <- 0
  e2 <- 0
  e3 <- 0
  e7 <- 0.062


  size <- b1 * log(BA_m2*10^4) + b2 * (BA_m2*10^4) + b3 * ((BA_m2*10^4)^2)
  competition <- c1 * BA_m2_ha + c2 * (HL * 10) + c3 * (QMD*10) + c4 * stems_ha + c5*(diameter_cm/QMD)
  #Latitude decimal, as opposed to in paper.
  site <- d1 * SI40_Spruce + d2 * SI40_Pine + d3 * (latitude*10) + d4 * altitude
  stand <- e1*spruce_presence + e2*pine_presence + e3*birch_presence + e4*BA_quotient_Spruce + e5*BA_quotient_Pine + e6*BA_quotient_Broadleaves + e7*even_aged

  return(
    exp(a + size + competition + site + stand)/10^4 # cm^2 to m^2
  )


}

#' @rdname andreassen_2003
#' @export

Andreassen_2003_BA_increment_Norway_Scots_Pine_topographic<- function(
    BA_m2,
    diameter_cm,
    BA_m2_ha,
    #BA_m2_ha_Spruce,
    #BA_m2_ha_Pine,
    BA_m2_ha_Broadleaves,
    #HL,
    QMD,
    #stems_ha,
    #SI40_Spruce=NULL,
    #SI40_Pine=NULL,
    latitude,
    altitude,
    even_aged=TRUE
    #spruce_presence,
    #pine_presence,
    #birch_presence
){

  #if(!is.null(SI40_Spruce)) SI40_Pine <- NULL
  #if(!is.null(SI40_Pine)) SI40_Spruce <- NULL
  #if(is.null(SI40_Spruce) & is.null(SI40_Pine)) stop("Either SI40_Spruce or SI40_Pine must be given")
  #stopifnot(is.logical(c(spruce_presence,pine_presence,birch_presence)))
  stopifnot(is.logical(even_aged))


  #Multiply all proportions by 10 to ensure sum of proportions == 10.
  #BA_quotient_Spruce <- (BA_m2_ha_Spruce / BA_m2_ha)*10
  #BA_quotient_Pine <- (BA_m2_ha_Pine / BA_m2_ha)*10
  BA_quotient_Broadleaves <- (BA_m2_ha_Broadleaves / BA_m2_ha)*10

  #Set missing vars to zero for simplicity with model components.
  SI40_Spruce <- 0
  SI40_Pine <- 0
  BA_quotient_Pine <- 0
  BA_quotient_Spruce <- 0
  HL <- 0
  stems_ha <- 0
  pine_presence <- 0
  spruce_presence <- 0
  birch_presence <- 0


  #Follows order of table 4.
  a  <- 0.4391
  b1 <- 0.7155
  b2 <- -0.4691      *10^-3
  b3 <- 0.1173       *10^-6
  c5 <- 0.1863
  c3 <- 0
  c2 <- 0            *10^-2
  c1 <- -0.0161
  c4 <- 0            *10^-3
  d1 <- 0
  d2 <- 0
  d3 <- -0.974
  d4 <- -0.3893
  e4 <- 0
  e5 <- 0
  e6 <- 0.0337
  e1 <- 0
  e2 <- 0
  e3 <- 0
  e7 <- -0.0376



  size <- b1 * log(BA_m2*10^4) + b2 * (BA_m2*10^4) + b3 * ((BA_m2*10^4)^2)
  competition <- c1 * BA_m2_ha + c2 * (HL * 10) + c3 * (QMD*10) + c4 * stems_ha + c5*(diameter_cm/QMD)
  #Latitude decimal, as opposed to in paper.
  site <- d1 * SI40_Spruce + d2 * SI40_Pine + d3 * (latitude*10) + d4 * altitude
  stand <- e1*spruce_presence + e2*pine_presence + e3*birch_presence + e4*BA_quotient_Spruce + e5*BA_quotient_Pine + e6*BA_quotient_Broadleaves + e7*even_aged

  return(
    exp(a + size + competition + site + stand)/10^4 # cm^2 to m^2
  )


}

#' @rdname andreassen_2003
#' @export

Andreassen_2003_BA_increment_Norway_Birch_topographic<- function(
    BA_m2,
    diameter_cm,
    BA_m2_ha,
    #BA_m2_ha_Spruce,
    #BA_m2_ha_Pine,
    #BA_m2_ha_Broadleaves,
    #HL,
    QMD,
    #stems_ha,
    #SI40_Spruce=NULL,
    #SI40_Pine=NULL,
    latitude,
    altitude,
    even_aged=TRUE
    #spruce_presence,
    #pine_presence,
    #birch_presence
){

  #if(!is.null(SI40_Spruce)) SI40_Pine <- NULL
  #if(!is.null(SI40_Pine)) SI40_Spruce <- NULL
  #if(is.null(SI40_Spruce) & is.null(SI40_Pine)) stop("Either SI40_Spruce or SI40_Pine must be given")
  #stopifnot(is.logical(c(spruce_presence,pine_presence,birch_presence)))
  stopifnot(is.logical(even_aged))


  #Multiply all proportions by 10 to ensure sum of proportions == 10.
  #BA_quotient_Spruce <- (BA_m2_ha_Spruce / BA_m2_ha)*10
  #BA_quotient_Pine <- (BA_m2_ha_Pine / BA_m2_ha)*10
  #BA_quotient_Broadleaves <- (BA_m2_ha_Broadleaves / BA_m2_ha)*10

  #Set missing vars to zero for simplicity with model components.
  SI40_Spruce <- 0
  SI40_Pine <- 0
  stems_ha <- 0
  BA_quotient_Pine <- 0
  BA_quotient_Spruce <- 0
  BA_quotient_Broadleaves <- 0
  HL <- 0
  pine_presence <- 0
  spruce_presence <- 0
  birch_presence <- 0


  #Follows order of table 4.
  a  <- -0.00043
  b1 <- 0.5123
  b2 <- 0.3469       *10^-3
  b3 <- 0            *10^-6
  c5 <- 0.3637
  c3 <- 0
  c2 <- 0            *10^-2
  c1 <- -0.0080
  c4 <- 0            *10^-3
  d1 <- 0
  d2 <- 0
  d3 <- -0.398
  d4 <- -0.3373
  e4 <- 0
  e5 <- 0
  e6 <- 0
  e1 <- 0
  e2 <- 0
  e3 <- 0
  e7 <- 0.0797



  size <- b1 * log(BA_m2*10^4) + b2 * (BA_m2*10^4) + b3 * ((BA_m2*10^4)^2)
  competition <- c1 * BA_m2_ha + c2 * (HL * 10) + c3 * (QMD*10) + c4 * stems_ha + c5*(diameter_cm/QMD)
  #Latitude decimal, as opposed to in paper.
  site <- d1 * SI40_Spruce + d2 * SI40_Pine + d3 * (latitude*10) + d4 * altitude
  stand <- e1*spruce_presence + e2*pine_presence + e3*birch_presence + e4*BA_quotient_Spruce + e5*BA_quotient_Pine + e6*BA_quotient_Broadleaves + e7*even_aged

  return(
    exp(a + size + competition + site + stand)/10^4 # cm^2 to m^2
  )


}


#' @rdname andreassen_2003
#' @export


Andreassen_2003_BA_increment_Norway_Broadleaves_topographic<- function(
    BA_m2,
    diameter_cm,
    BA_m2_ha,
    BA_m2_ha_Spruce,
    #BA_m2_ha_Pine,
    #BA_m2_ha_Broadleaves,
    #HL,
    QMD,
    #stems_ha,
    #SI40_Spruce=NULL,
    #SI40_Pine=NULL,
    latitude,
    altitude,
    even_aged=TRUE
    #spruce_presence,
    #pine_presence,
    #birch_presence
){

  #if(!is.null(SI40_Spruce)) SI40_Pine <- NULL
  #if(!is.null(SI40_Pine)) SI40_Spruce <- NULL
  #if(is.null(SI40_Spruce) & is.null(SI40_Pine)) stop("Either SI40_Spruce or SI40_Pine must be given")
  #stopifnot(is.logical(c(spruce_presence,pine_presence,birch_presence)))
  stopifnot(is.logical(even_aged))


  #Multiply all proportions by 10 to ensure sum of proportions == 10.
  BA_quotient_Spruce <- (BA_m2_ha_Spruce / BA_m2_ha)*10
  #BA_quotient_Pine <- (BA_m2_ha_Pine / BA_m2_ha)*10
  #BA_quotient_Broadleaves <- (BA_m2_ha_Broadleaves / BA_m2_ha)*10

  #Set missing vars to zero for simplicity with model components.
  SI40_Spruce <- 0
  SI40_Pine <- 0
  HL <- 0
  stems_ha <- 0
  BA_quotient_Pine <- 0
  BA_quotient_Broadleaves <- 0
  pine_presence <- 0
  spruce_presence <- 0
  birch_presence <- 0


  #Follows order of table 4.
  a  <- -0.1527
  b1 <- 0.645
  b2 <- -0.2169      *10^-3
  b3 <- 0            *10^-6
  c5 <- 0.3927
  c3 <- 0
  c2 <- 0            *10^-2
  c1 <- -0.0131
  c4 <- 0            *10^-3
  d1 <- 0
  d2 <- 0
  d3 <- 0
  d4 <- -0.3115
  e4 <- -0.0121
  e5 <- 0
  e6 <- 0
  e1 <- 0
  e2 <- 0
  e3 <- 0
  e7 <- 0.0713

  size <- b1 * log(BA_m2*10^4) + b2 * (BA_m2*10^4) + b3 * ((BA_m2*10^4)^2)
  competition <- c1 * BA_m2_ha + c2 * (HL * 10) + c3 * (QMD*10) + c4 * stems_ha + c5*(diameter_cm/QMD)
  #Latitude decimal, as opposed to in paper.
  site <- d1 * SI40_Spruce + d2 * SI40_Pine + d3 * (latitude*10) + d4 * altitude
  stand <- e1*spruce_presence + e2*pine_presence + e3*birch_presence + e4*BA_quotient_Spruce + e5*BA_quotient_Pine + e6*BA_quotient_Broadleaves + e7*even_aged

  return(
    exp(a + size + competition + site + stand)/10^4 # cm^2 to m^2
  )


}