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!*****************************************************************!
!*                                                               *!
!*                 ForeSee Simulation Model                      *!
!*                                                               *!
!*                                                               *!
!*            Declaration of species and cohort variables        *!
!*            data_stand                                         *!
!*            Subroutines:                                       *!
!*                del_cohort                                     *!
!*                test_cohort                                    *!
!*                list_cohort                                    *!
!*                                                               *!
!*                  Copyright (C) 1996-2018                      *!
!*     Potsdam Institute for Climate Impact Reserach (PIK)       *!
!*          Authors and contributors see AUTHOR file             *!
!*  This file is part of 4C and is licensed under BSD-2-Clause   *!
!*                   See LICENSE file or under:                  *!
!*     http://www.https://opensource.org/licenses/BSD-2-Clause   *!
!*                           Contact:                            *!
!*       https://gitlab.pik-potsdam.de/foresee/4C                *!
!*                                                               *!
!*****************************************************************!

MODULE data_stand

  INTEGER    :: anz_coh = 0         ! current amount of cohortes
  INTEGER    :: max_coh = 0         ! max. amount of cohortes
  REAL       :: kpatchsize = 200    ! patch size [m^2]
  REAL       :: dz = 50             ! thickness of a crown layer [cm]
  INTEGER    :: waldtyp             ! forest type

  ! variables for the whole stand
  INTEGER,allocatable,save,dimension(:):: nrspec  ! actual kind numbers of species
  REAL,dimension(0:300) :: Irelpool ! relative light intensitiy of the crown space which is not
                                    ! occupied by trees (pool). This is the light intensitiy
                                    ! at the top of each layer. Irelpool(0)=light unto ground
  REAL,dimension(1:301) :: BGpool   ! fraction of patch covered by 'free crown space' for
                                    ! the next layer respectivley.
  REAL,dimension(0:300) :: precpool ! relative precipitation intensitiy of the crown space which is not
                                    ! occupied by trees (pool). This is the precipitation intensitiy
                                    ! at the top of each layer
  REAL    :: Irelpool_ll            ! relative light intensitiy at the lowest layer
  REAL    :: bgpool_ll              ! fraction of patch covered by 'free crown space'
  REAL    :: totFPARsum             ! fraction of absorbed light for the whole patch
  REAL    :: totFPARcan             ! fraction of absorbed light for the whole canopy
  REAL    :: LAI                    ! leaf area index of the patch [m^2/m^2]
  REAL    :: LAI_can                ! leaf area index of the canopy [m^2/m^2]
  REAL    :: LAI_sveg               ! leaf area index of the ground vegetation [m^2/m^2]
  REAL    :: LAImax                 ! leaf area index of the patch in period when all trees carry leaves [m^2/m^2]
  REAL    :: LAI_in                 ! leaf area index of new trees [m^2/m^2]
  REAL    :: LAI_out                ! leaf area index of removed trees [m^2/m^2]
  REAL    :: crown_area             ! projected crown area [m**2] for the whole canopy,
  REAL    :: gp_tot                 ! unstressed stomatal conductance of the total vegetation (canopy + ground vegetation) [mol/(m2*d)]
  REAL    :: gp_can                 ! unstressed stomatal conductance of the canopy [mol/(m2*d)]
  REAL    :: gp_can_mean            ! yearly mean of unstressed stomatal conductance of the canopy [mol/(m2*d)]
  REAL    :: gp_can_min             ! yearly minimum of unstressed stomatal conductance of the canopy [mol/(m2*d)]
  REAL    :: gp_can_max             ! yearly maximum of unstressed stomatal conductance of the canopy [mol/(m2*d)]
  REAL    :: drIndd                 ! daily drought index for the whole stand [-], weighted by ntree
  REAL    :: drIndAl                ! drought index for allocation calculation (cum.) for the whole stand [-],
                                    ! weighted by NPP
  REAL    :: mean_drIndAl           ! mean drought index for allocation calculation (cum.) for the whole stand [-],
  REAL    :: RedN_mean              ! mean RedN of all species
  INTEGER :: anz_RedN               ! number of RedN for calculation of RedN_mean  
  REAL    :: sumbio                 ! biomass of all cohorts and all tree-species [kg DW/ha]
  REAL    :: sumbio_sv              ! biomass of all cohorts and all ground-vegetation-species [kg DW/ha]
  REAL    :: sumbio_in              ! biomass of new trees [kg DW/ha]
  REAL    :: sumbio_out             ! biomass of removed trees [kg DW/ha]
  REAL    :: cumsteminc             ! total cumulated sum of all stem increments [kg/ha]
  REAL    :: cumsumvsab             ! cumulated total sum of volume of removed stems by management [kg/ha]
  REAL    :: cumsumvsdead           ! cumulated total sum of volume of dead stems  [kg/ha]
  REAL    :: sumvsab                ! total sum of volume of removed stems by management [kg/ha]
  REAL    :: sumvsab_m3             ! total sum of volume of removed stems by management [m³/ha]
  REAL    :: sumvsdead              ! total sum of volume of dead stems  [kg/ha]
  REAL    :: sumvsdead_m3           ! total sum of volume of dead stems  [m³/ha]
  REAL    :: totfol                 ! total biomass of foliage [kg DW/ha]
  REAL    :: totfol_in              ! total biomass of foliage of new trees [kg DW/ha]
  REAL    :: totfol_out             ! total biomass of foliage of removed trees [kg DW/ha]
  REAL    :: totsap                 ! total biomass of sapwood  [kg DW/ha]
  REAL    :: totfrt                 ! total fine root biomass of all cohorts and all species [kg DW/ha]
  REAL    :: totfrt_p               ! total fine root biomass of all cohorts and all species per patch [kg DW/patchsize]
  REAL    :: totfrt_1               ! reciprocal of total fine root biomass of all cohorts and all species per patch [kg DW/patchsize]
  REAL    :: tottb                  ! total twigs, branches biomass of all cohorts and all species [kg DW/ha]
  REAL    :: totcrt                 ! total coarse root biomass of all cohorts and all species [kg DW/ha]
  REAL    :: seedlfrt               ! total fine root biomass of all cohorts with height < thr_height [kg DW]
  REAL    :: tothrt                 ! total biomass of heartwood  [kg DW/ha]
  REAL    :: sumNPP                 ! total NPP of all cohorts and species
  REAL    :: cum_sumNPP             ! cumulative total NPP of all cohorts and species
  REAL    :: sumGPP                 ! total GPP of all cohorts and species [g C/m2 --> t C/ha]
  REAL    :: totfol_lit             ! total foliage litter [kg DW / ha / year]
  REAL    :: totfol_lit_tree        ! total foliage litter of trees [kg DW / ha / year]
  REAL    :: totfrt_lit             ! total fine root litter [kg DW / ha / year]
  REAL    :: totfrt_lit_tree        ! total fine root litter of trees [kg DW / ha / year]
  REAL    :: tottb_lit              ! total litter of twigs, and branches [kg DW / ha / year]
  REAL    :: totcrt_lit             ! total litter of coarse roots [kg DW / ha / year]
  REAL    :: totstem_lit            ! total dead biomass of stems [kg DW / ha / year]
  REAL    :: totsteminc             ! total stem increment of patch  [kg DW/ha]
  REAL    :: totsteminc_m3          ! total stem increment of patch in m3
  REAL    :: totstem_m3             ! total stem volume [m3/ha]
  REAL    :: Ndem                   ! total N demand of the stand per year [g/m2]
  REAL    :: autresp                ! total autotroph resp of all cohorts and species
  REAL    :: autresp_m              ! mean total autotroph resp of all cohorts and species (mean over all years)
  REAL    :: sumTER                 ! total ecosystem respiration of all cohorts and species [g C/m2 --> t C/ha]
  INTEGER :: coh_ident_max          ! actual maximum ident number of cohorts
  INTEGER :: anz_coh_in             ! number of new cohorts
  INTEGER :: anz_coh_out            ! number of removed cohorts
  INTEGER :: anz_coh_act            ! number of cohorts of the actual year
  INTEGER :: anz_spec               ! number of current existing tree species
  INTEGER :: anrspec                ! number of all current existing species
  INTEGER :: anz_spec_in            ! number of new tree species 
  INTEGER :: anz_spec_out           ! number of removed tree species 
  INTEGER :: anz_tree_dbh           ! number of trees with dbh
  INTEGER :: anz_tree               ! total number of trees /patch
  INTEGER :: anz_tree_ha            ! total number of trees /ha
  INTEGER :: anz_tree_in            ! number of new trees /ha
  INTEGER :: anz_tree_out           ! number of removed trees /ha
  INTEGER :: anz_sveg               ! total number of soil vegetation cohorts
  REAL    :: med_diam               ! medium diameter of stand (Dg)
  REAL    :: med_diam_in            ! medium diameter of new trees (Dg)
  REAL    :: med_diam_out           ! medium diameter of removed trees (Dg)
  REAL    :: hdom                   ! medium height of 2 dominant trees
  REAL    :: hmean_in               ! mean height of all new trees
  REAL    :: hmean_out              ! mean height of all removed trees
  REAL    :: mean_height            ! mean height of stand [cm]
  REAL    :: mean_diam              ! mean diameter of stand [cm]
  REAL    :: basal_area             ! basal area [m²]
  INTEGER :: highest_layer          ! highest foliage layer of the stand
  INTEGER :: lowest_layer           ! lowest foliage layer of the stand.
                                    ! lowest_layer=0: bare ground
  INTEGER :: lm3layer               ! light model 4: layer from that on light model 3 is used
    
  REAL                :: GRASS_day
  REAL                :: NETASS_day
  REAL                :: GPP_day      ! daily GPP of all cohorts and species after scaling by temperature
  REAL, dimension(12) :: GPP_mon      ! monthly GPP of all cohorts and species
  REAL, dimension(53) :: GPP_week     ! weekly GPP of all cohorts and species
  REAL                :: GPP_dec      ! sum of GPP of all cohorts and species of last december
  REAL, dimension(12) :: NEE_mon      ! monthly NEE of all cohorts and species
  REAL                :: NEE_dec      ! sum of NEE of all cohorts and species of last december
  REAL                :: NPP_day      ! daily NPP of all cohorts and species after scaling by temperature
  REAL, dimension(12) :: NPP_mon      ! monthly NPP of all cohorts and species
  REAL, dimension(53) :: NPP_week     ! weekly NPP of all cohorts and species
  REAL                :: NPP_dec      ! sum of NPP of all cohorts and species of last december
  REAL                :: TER_day      ! daily TER of all cohorts and species after scaling by temperature
  REAL, dimension(12) :: TER_mon      ! monthly total ecosystem respiration of all cohorts and species
  REAL, dimension(53) :: TER_week     ! weekly total ecosystem respiration of all cohorts and species
  REAL                :: TER_dec      ! sum of TER of all cohorts and species of last december
  REAL                :: respr_day    ! daily root respiration of all cohorts and species after scaling by temperature
  REAL, dimension(12) :: respr_mon    ! monthly total root respiration of all cohorts and species (fine and coarse roots)
  REAL, dimension(53) :: respr_week   ! weekly total root respiration of all cohorts and species
  REAL,allocatable, save, dimension(:) :: dayfract     ! daily fraction of fluxes (depending on temperature)
  REAL    :: dailyNPP_C,        &   ! daily net production [gC/m2]
             dailypotNPP_C,     &   ! daily potential (= no water and nutrient limitation) net primary production [gC/m2]
			 dailyautresp_C,    &   ! daily autotrophic respiration [gC/m2]
			 dailygrass_C,      &   ! daily gross assimilation [gC/m2]
			 dailynetass_C,     &   ! daily net assimilation [gC/m2]
			 dailyrespfol_C,    &   ! daily maintenance leaf respiration [gC/m2]
             phot_C,            &   ! daily gross photosynthesis [gC/m2]
             precsum
  REAL    :: ceppot_can             ! pot. intercept. whole canopy
  REAL    :: ceppot_sveg            ! pot. intercept. whole ground vegetation
  INTEGER :: phen_flag=0            ! phenology flag, =1 if canopy changes due to
                                    ! phenological events
  REAL    :: basal_area_tot         ! basal area of the whole stand [cm²]

! variables  used in sum-output
  REAL    :: photsum,nppsum,    &
             npppotsum,resosum, &
             lightsum,          &
             abslightsum,nee,   &
			 gppsum,            &
			 tersum,            &   ! total ecosystem respiration
			 resautsum,         &   ! autotrophe respiratiom
			 aet_sum, pet_sum,  &
			 tempmean, tempmeanh     !summation variable for output *_sum

 ! variables for representation index calculation
   REAL    :: rindex1,          &
              rindex2
 
 ! variable for ground-vegetation
   REAL    :: M_avail               ! mass available for allocation to organs in soil veg. initialisation [kg DM m-2]
   REAL    :: NPP_est               ! NPP estimated for soil veg. initialisation [g DM m-2]  
   
 ! Variables for disturbances
   REAL    :: phlo_feed             ! Percentage loss of carbon due to phloem feeders 
   REAL    :: stem_rot              ! Percentage loss of stems due to stem rot 

  ! variables for classification of trees
  INTEGER    :: num_class=29         ! number of diameter and height classes
  INTEGER,allocatable, save, dimension(:,:)   :: diam_class,  diam_classm, diam_class_t, diam_class_age 
  REAL ,allocatable, save, dimension(:,:)   ::   diam_class_h, diam_classm_h, diam_class_mvol
  INTEGER,allocatable, save, dimension(:)   :: height_class

!  ! variables per species
  INTEGER,allocatable,save,dimension(:) :: height_rank ! number of trees per species
  INTEGER,allocatable,save,dimension(:) :: dbh_rank ! number of trees per species

  type species_var
  ! variables per species
   INTEGER  :: daybb            ! day of bud burst per species [julian day of year]
   INTEGER  :: ext_daybb        ! externally prescribed day of bud burst per species [julian day of year]
   INTEGER  :: sum_nTreeA       ! number of trees per species [per ha]
   INTEGER  :: sum_nTreeD       ! number of all dead trees per species [per ha]
   INTEGER  :: anz_coh          ! number of cohorts per species
   REAL     :: RedN             ! photosynthesis nitrogen reduction factor [-]
   REAL     :: RedNm            ! mean annual photosynthesis nitrogen reduction factor [-]
   REAL     :: med_diam         ! medium diameter per species (squared average) [cm]
   REAL     :: mean_diam        ! average diameter per species [cm]
   REAL     :: mean_jrb         ! average year ring width [mm]
   REAL     :: dom_height       ! dominant height per species [cm]
   REAL     :: mean_height      ! average height per species [cm]
   REAL     :: basal_area       ! basal area per species [m²] 
   REAL     :: drIndAl          ! drought index for allocation calculation (cum.) per species [-]
                                ! weighted by NPP
   REAL     :: sumNPP           ! total NPP of all cohorts per species
   REAL     :: sum_bio          ! total biomass per species  [kg DW/ha]
   REAL     :: sum_lai          ! maximum annual LAI per species
   REAL     :: act_sum_lai      ! LAI per species
   REAL     :: fol              ! total foliage mass per species  [kg DW/ha]
   REAL     :: hrt              ! total heartwood mass per species  [kg DW/ha]
   REAL     :: sap              ! totalsapwood mass per species  [kg DW/ha]
   REAL     :: frt              ! total fine root mass per species  [kg DW/ha]
   REAL     :: totsteminc       ! total stem increment per species  [kg DW/ha]
   REAL     :: totsteminc_m3    ! total stem increment per species  [m3/ha]
   REAL     :: totstem_m3       ! total stem volume per species [m³/ha]
   REAL     :: sumvsab          ! total sum of volume of harvested stem mass of species [kg/ha]
   REAL     :: sumvsdead        ! total sum of volume of dead stems  [kg/ha]
   REAL     :: sumvsdead_m3     ! total sum of volume of dead stems  [m3/ha]
   REAL     :: crown_area       ! species specific crown area
   REAL     :: Ndem             ! total N demand per species and year [g/m2]
   REAL     :: Nupt             ! total N uptake per species and year [g/m2]
   REAL     :: Ndemp            ! total N demand per species and potosynthesis period [g/m2]
   REAL     :: Nuptp            ! total N uptake per species and potosynthesis period [g/m2]
    
  ! Phenology parameters
    REAL     :: Pro           ! Depending on phenomodel: Promotor or Temperature sum
    REAL     :: Inh           ! Depending on phenomodel: Inhibitor or chill days
    REAL     :: Tcrit         ! Critical temperature sum for Cannel-Smith model [°C]

   REAL,pointer,dimension(:) :: BDmax       ! species specific maximum bulk density for root growth in soil layers
   REAL,pointer,dimension(:) :: tstress     ! species specific temperature stress for root growth in soil layers
   REAL,pointer,dimension(:) :: sstr        ! species specific soil strength stress for root growth in soil layers
   REAL,pointer,dimension(:) :: BDstr       ! species specific bulk density stress for root growth in soil layers
   REAL,pointer,dimension(:) :: porcrit     ! species specific critical pore space for root growth in soil layers
   REAL,pointer,dimension(:) :: airstr      ! species specific aeration stress for root growth in soil layers
   REAL,pointer,dimension(:) :: phstr       ! species specific pH stress for root growth in soil layers
   REAL,pointer,dimension(:) :: Rstress     ! species specific total daily stress for root growth in soil layers
   REAL,pointer,dimension(:) :: Smean       ! species specific total yearly stress for root growth in soil layers  
  end type species_var

  type(species_var),allocatable,dimension(:),target :: svar
  
  type cohort
    INTEGER  :: ident     ! identification of cohort
    INTEGER  :: species   ! number of species parameter set in spar (type)

    ! state variables for population dynamics
    REAL     :: nTreeA    ! number of alive trees (output) integer [-]
    REAL     :: nTreeD    ! number of dead trees integer [-]
    REAL     :: nTreeM    ! number of trees harvested by Management
    REAL     :: nTreet    ! number of trees tended by Management
    REAL     :: nta       ! number of alive trees (internal) REAL [-]
    INTEGER  :: mistletoe ! cohort has / has no mistletoe infection

    ! all variables are values of single trees !!!
    ! tree state variables; DW = dry weight (i.e., dry biomass)
    INTEGER  :: x_age     ! tree age [yr]
    REAL     :: x_fol     ! foliage biomass [kg DW / tree]
    REAL     :: x_fol_loss     ! loss of foliage biomass [kg DW / tree] by disturbance (flag_dis=1)
    REAL     :: x_sap     ! sapwood biomass [kg DW / tree]
    REAL     :: x_frt     ! fine root biomass [kg DW / tree]
    REAL     :: x_frt_loss     ! loss of fine root biomass [kg DW / tree] by disturbance (flag_dis=1)
    REAL     :: x_hrt     ! heartwood biomass [kg DW / tree]
    REAL	 :: x_rdpt	  ! rooting depth  [cm]
	REAL     :: x_crt     ! coarse root biomass [kg DW / tree]
    REAL     :: x_tb      ! twigs and branches biomass [kg DW / tree]
    REAL     :: x_hsap    ! sapwood height [cm]
    REAL     :: x_hbole   ! bole height [cm]
    REAL     :: x_Ahb     ! cross sectional area of heart wood at stem base [cm**2]
    INTEGER  :: x_stress  ! number of stress years [-]
    INTEGER  :: x_health  ! number of years without stress [-]
	REAL     :: x_nsc_sap ! sapwood nsc-pool [kg C / tree]
    REAL     :: x_nsc_tb  ! twigs and branch nsc-pool [kg C / tree]
    REAL     :: x_nsc_crt ! coarse root nsc-pool [kg C / tree]
    REAL     :: x_nsc_sap_max !maximum amount sapwood nsc-pool [kg C / tree]
    REAL     :: x_nsc_tb_max  !maximum amount twigs and branch nsc-pool [kg C / tree]
    REAL     :: x_nsc_crt_max !maximum amount coarse root nsc-pool [kg C / tree]
    REAL     :: biocost_all !biosynthesis costs for refilling process [kg DW / tree]

    ! auxiliary variables
    REAL     :: bes       ! avarage beset or press of cohort
    REAL     :: med_sla   ! average cohort specific leaf area [m²/kg]
    REAL     :: Fmax      ! maximum foliage biomass [kg DW]
    REAL     :: totBio    ! total tree biomass [kg DW]
    REAL     :: Dbio      ! total dead biomass per cohort [kg DW]
    REAL     :: height    ! total tree height [cm]
    REAL     :: deltaB    ! change in bole height [cm]
    REAL     :: Ahc       ! cross sectional area of heart wood  at crown base [cm**2]
    REAL     :: dcrb      ! trunc diameter at crown base [cm]
    REAL     :: diam      ! diameter at breast height [cm]
    real     :: jrb       ! year ring width [mm]
    REAL     :: assi      ! optimum gross assimilation rate [kg DW/d/patch] !!! not a tree variable
    REAL     :: LUE       ! light use efficiency [gC/micromole]
    REAL     :: resp      ! leaf respiration rate [kg DW/d/patch] !!! not a tree variable
    REAL     :: netAss    ! realized net assimilation rate [kg DW/d]
    REAL     :: NPP       ! NPP [kg DW/yr]
    REAL     :: weekNPP   ! weekly NPP [kg DW/yr]
    REAL     :: NPPpool
    REAL     :: t_leaf    ! leaf area per tree [m2]
    REAL     :: geff      ! growth efficiency  [kg stem DM/(yr*m2)]
    REAL     :: Asapw     ! tree sapwood cross sectional area in bole space [cm2]
    REAL     :: crown_area ! projected crown area [m**2],
                           ! is the same in each layer; maximal proj. crown area,
                           ! when enough space available crown_area
    REAL,dimension(301) :: BG ! fraction of the patch covered by the
                              ! tree in each layer, may change through the layers.
    REAL,dimension(0:300) :: leafArea  ! leaf area per layer [m2]
    REAL,dimension(0:300) :: sleafArea  ! leaf area per layer [m2], stocked
    REAL,dimension(0:300) :: FPAR  ! light version 1-3 : fraction of PAR
                                 ! absorbed by each layer per crown coverage area [-]
                                 ! light version 4 : fraction of PAR absorbed until(!)
                                 ! each layer per patch [-]
    REAL,dimension(0:300) :: antFPAR  ! fraction of totFPAR per crown layer
    REAL,dimension(0:300) :: Irel  ! relative incident radiation
                                 ! intensitiy at the top of a given layer
    REAL     :: totFPAR   ! total fraction of PAR absorbed [-],
                          ! per m² patch area!
    REAL     :: IrelCan   ! the relative light regime in the
                          ! middle of the cohort's canopy
    INTEGER  :: botLayer  ! number of bottom layer of crown [-]
    INTEGER  :: topLayer  ! number of top layer of crown [-]
    REAL     :: survp     ! survival probability first 5 years of simulation
    REAL     :: rel_fol   ! relative part foliage of cohort
    REAL     :: gfol      ! gross growth rate foliage
    REAL     :: gfrt      ! gross growth rate fine root
    REAL     :: gsap      ! gross growth rate sap wood
    REAL     :: sfol      ! senescence rate foliage
    REAL     :: sfrt      ! senescence rate fine root
    REAL     :: ssap      ! senescence rate sap wood
    REAL     :: grossass  ! gross assimilation rate [kg DW/yr]
    REAL     :: maintres  ! cumulative maintenance respiration (sap + frt) [kg DW/yr]
    REAL     :: respsap   ! daily respiration rate sapwood [kg DW/d]
    REAL     :: respfrt   ! daily respiration rate fine root [kg DW/d]
    REAL     :: respfol   ! maintenance daily leaf respiration [kg DW/d]
    REAL     :: respbr    ! daily respiration rate branches, c. roots .... [kg DW/d]
    REAL     :: respaut   ! daily autotrophic respiration rate of tree .... [kg DW/d]
    REAL     :: resphet   ! daily hetrotrophic respiration rate of tree .... [kg DW/d]
                          ! 
!  aux. variables for calculation of crown_area of new established trees
   REAL      :: height_ini   ! initial value of height of a new established tree cohort by ingrowth [cm]
   REAL      :: ca_ini       ! initial value of crown area of a new established tree cohort by ingrowth [m2]

   ! new aux. variables for mAustrian management by relative diamter class
   INTEGER     :: rel_dbh_cl  ! relative DBH class
   INTEGER     :: underst     ! 0 = overstorey, 1 =  seedling cohort, 2 = understorey
   INTEGER     :: sprout      ! 0 = tree is no sprout, 1 = sprout
   INTEGER     :: fl_sap      ! sapling = 0, tree = 1

! growth-mortality coupling variables
    REAL     :: fol_inc       ! foliage increment [kg DW/yr]
    REAL     :: fol_inc_old   ! foliage increment of last year[kg DW/yr]
    REAL     :: bio_inc       ! net biomass increment [kg DW/yr]
    REAL     :: stem_inc      ! stem wood increment [kg DW/yr]
    REAL     :: frt_inc       ! fine root wood increment [kg DW/yr]
    logical  :: notViable     ! .TRUE. if non-biological tree dimensions occur
    integer  :: flag_vegend=0
    
! plant-soil water coupling variables
    REAL,dimension(0:300):: intcap   ! precipitation absorbed by
                          ! each layer per  m² patch area [mm]
    REAL,dimension(0:300):: prel  ! precipitation
                          ! at the top of a given layer [mm] per  m² patch area
    REAL     :: interc    ! total intercepted precipitation [mm],
                          ! per m² patch area!
    REAL     :: prelCan   ! the relative precipitaion regime
                          ! in the middle of the cohort's canopy
    REAL     :: interc_st ! interception storage [mm/m2]
    REAL     :: aev_i     ! actual evaporation of intercepted water [mm]
    REAL     :: demand    ! daily demand for soil water of cohort [mm/day]
    REAL     :: supply    ! daily uptake of soil water by roots of cohort [mm/day]
    REAL     :: watuptc   ! yearly total uptake of soil water by roots [mm/day]
    REAL     :: watleft   ! yearly total water left in soil layer next to last rooted soil layer [mm]
	REAL     :: gp        ! unstressed stomatal conductance [mol/(m2*d)]
    REAL     :: drIndd    ! daily drought index [-]
    REAL     :: drIndPS   ! drought index for photosynthesis calculation (cum.) [-]
    REAL     :: nDaysPS   ! number of growing season days per time step of PS model [-]
    REAL     :: drIndAl   ! drought index for allocation calculation (cum.) [-]
    INTEGER  :: nDaysGr   ! number of growing season days per year [#]
    logical  :: isGrSDay  ! is the current day a growing season day?

    ! plant-soil C/N coupling variables in kg per cohort
    REAL     :: litC_fol  ! foliage litter C pool [kg/cohort]
    REAL     :: litC_fold ! foliage litter C pool [kg/cohort]  of dead trees
    REAL     :: litN_fol  ! foliage litter N pool [kg/cohort]
    REAL     :: litN_fold ! foliage litter N pool [kg/cohort] of dead trees
    REAL     :: litC_frt  ! fine root litter C pool [kg/cohort]
    REAL     :: litC_frtd ! fine root litter C pool [kg/cohort] of dead trees
    REAL     :: litN_frt  ! fine root litter N pool [kg/cohort]
    REAL     :: litN_frtd ! fine root litter N pool [kg/cohort] of dead trees
    REAL     :: litC_stem ! stemwood litter C pool [kg/cohort]
    REAL     :: litN_stem ! stemwood litter N pool [kg/cohort]
    REAL     :: litC_tb   ! twig, and branch litter C pool [kg/cohort]
    REAL     :: litC_crt  ! coarse root litter C pool [kg/cohort]
    REAL     :: litC_tbcd ! twigs, branches, and coarse root litter C pool [kg/cohort] of dead trees
    REAL     :: litN_tb   ! twig, and branch litter N pool [kg/cohort]
    REAL     :: litN_crt  ! coarse root litter N pool [kg/cohort]
    REAL     :: litN_tbcd ! twigs, branches, and coarse root litter N pool [kg/cohort] of dead trees
    REAL     :: Nuptc_c   ! N uptake per tree and year [g/yr]
    REAL     :: Ndemc_c   ! N demand per tree and year [g/yr]
    REAL     :: Nuptc_d   ! daily N uptake per tree [g/d]
    REAL     :: Ndemc_d   ! daily N demand per tree [g/d]
    REAL     :: RedNc     ! tree specific RedN (photosynthesis nitrogen reduction factor) [-]
    REAL     :: N_pool    ! N pool per tree [g]
    REAL     :: N_fol     ! N content of foliage per tree [g]
	REAL     :: wat_mg    ! cohort water uptake (flag_wred=9)

    ! root distribution
    REAL,pointer,dimension(:) :: frtrel  ! relative part of fine root mass of tree per soil layer
    REAL,pointer,dimension(:) :: frtrelc ! relative part of fine root mass of cohort of total layer fine root mass per soil layer
	REAL,pointer,dimension(:) :: rld     ! root length [cm per cm3]
	REAL,pointer,dimension(:) :: rooteff ! root uptake efficiency per soil layer

    INTEGER   :: nroot    ! nroot soil layer with max. root depth

    ! pseudo parameter (used as an index for field spar with species-specific parameters)
    INTEGER  :: shelter   ! Überhaelter

    ! Phenology parameters
    INTEGER  :: day_bb    ! day_bb day of bud burst [julian day of year]
                          ! day_bb
    REAL     :: P       ! Depending on phenomodel: Promotor or Temperature sum
    REAL     :: I       ! Depending on phenomodel: Inhibitor or chill days
    REAL     :: Tcrit   ! Critical temperature sum for Cannel-Smith model [°C]

  end type cohort

 type coh_obj
   type(cohort)   :: coh      ! cohort data structure
   type(coh_obj), pointer :: next     ! pointer to next cohort
 end type coh_obj

 type coh_list
   type(coh_obj), pointer :: first    ! List of cohorts
 end type coh_list

 type(coh_list)       :: pt       ! variable for whole stand, all cohorts
 type(cohort), pointer, dimension(:) :: coh_save  ! pointer to variables for saving intialisation of all cohorts

 type(coh_obj), pointer   :: zeig     ! pointer variable for manipulating cohorts

 INTEGER               :: anz_coh_save

 type vert_struct
   REAL      :: LA        ! leaf area in a given layer [m²]
   REAL      :: cumLAI    ! cumulative leaf area index at the bottom of a given layer [m²/m²]
   REAL      :: radFrac   ! fraction of total radiation absorbed in a given layer [-]
   REAL      :: sumBG     ! sum of all crown areas in a layer [m²]
   REAL      :: Irel      ! light version 1,2 : relative incident radiation at the top of a given layer [-]
                          ! light version 3,4 : average relative incident radiation at the bottom of a given layer [-]. For test reasons only

 end type vert_struct

 type(vert_struct),dimension(0:300)  :: vStruct  ! field with vertical patch structure

  ! variables for litter retention
  type dead_litter
    INTEGER   ::  specnr     ! species number 
    ! arrays of dead stem and twigs/branches
    REAL,pointer,dimension(:) ::  C_tb  
    REAL,pointer,dimension(:) ::  N_tb  
    REAL,pointer,dimension(:) ::  C_stem  
    REAL,pointer,dimension(:) ::  N_stem  
  
  end type dead_litter

  INTEGER :: lit_year = 5  ! number of years of retention
  type(dead_litter),allocatable,dimension(:),target :: dead_wood                                                                     ! delay over 5 years []   

!----------------------------------------------------------------------------------------

contains

function neu() result (stand_neu)     ! Create a new pointer list = new stand without any cohort

  implicit none

  type(coh_list) :: stand_neu

  nullify(stand_neu%first)

end function neu

!----------------------------------------------------------------------------------------

subroutine del_cohort
  use data_species
  use data_simul
  implicit none
  type(coh_obj), pointer :: nachlauf

  zeig => pt%first

    do while (associated(zeig))
       if (zeig%coh%nTreeA < 0.1.or. (zeig%coh%species.gt.nspec_tree.and.zeig%coh%x_fol.le. 1.E-6)) then
	      pt%first => zeig%next
          deallocate(zeig%coh%frtrel)
          deallocate(zeig%coh%frtrelc)
          deallocate(zeig%coh%rooteff)
          if (flag_wred .eq. 9) deallocate(zeig%coh%rld)
          deallocate(zeig)
          zeig => pt%first
          anz_coh=anz_coh-1
       else
          nachlauf => zeig
          zeig => zeig%next
          exit
       end if
    end do

    do while (associated(zeig))
     if (zeig%coh%nTreeA < 0.1.or. (zeig%coh%species.gt.nspec_tree.and.zeig%coh%x_fol.le. 1.E-6)) then
         nachlauf%next => zeig%next
          deallocate(zeig%coh%frtrel)
          deallocate(zeig%coh%frtrelc)
          deallocate(zeig%coh%rooteff)
          if (flag_wred .eq. 9) deallocate(zeig%coh%rld)
          deallocate(zeig)
         zeig => nachlauf%next
         anz_coh=anz_coh-1
      else
         nachlauf => zeig
         zeig => zeig%next
      end if
    end do
end subroutine del_cohort

!----------------------------------------------------------------------------------------

subroutine list_cohort ! Output of cohort list
  implicit none
  INTEGER :: i

  zeig => pt%first
  i = 0
  do while (associated(zeig))
    i = i + 1
    zeig => zeig%next
  end do

end subroutine list_cohort

!----------------------------------------------------------------------------------------

subroutine test_cohort(ts)
  implicit none

  INTEGER, intent(out):: ts

  zeig => pt%first
   if (.not. associated(zeig)) then
   print *,'  No existing cohort!'
   ts = 1
   else
   ts = 0
   end if
end subroutine test_cohort

end module data_stand