Use ifmp and fmp indicies in veg%froot calculation (#462)

Currently veg%rootbeta may be partially initialised over the range
ifmp:fmp when calculating veg%froot. This is the case for offline MPI
configurations. This change avoids accessing uninitialised memory when
calculating veg%froot.

Fixes #395

## Type of change

Please delete options that are not relevant.

- [x] Bug fix

## Checklist

- [x] I have checked my code/text and corrected any misspellings


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src/offline/cable_parameters.F90

@@ -1171,7 +1171,6 @@ SUBROUTINE write_default_params(met,  air,    ssnow, veg, bgc,               &
     INTEGER :: e,f,h,i,klev  ! do loop counter
     INTEGER :: is     ! YP oct07
     INTEGER :: ir     ! BP sep2010
-    REAL :: totdepth  ! YP oct07
     REAL :: tmp       ! BP sep2010
 
     !    The following is for the alternate method to calculate froot by Zeng 2001
@@ -1261,18 +1260,6 @@ SUBROUTINE write_default_params(met,  air,    ssnow, veg, bgc,               &
 
     veg%meth = 1 ! canopy turbulence parameterisation method: 0 or 1
 
-    ! I brought this in with manual merge of #199 BUT Am i bringing this back in ?
-    ! calculate vegin%froot from using rootbeta and soil depth
-    ! (Jackson et al. 1996, Oceologica, 108:389-411)
-    !totdepth = 0.0
-    !DO is = 1, ms
-    !   totdepth = totdepth + soil%zse(is) * 100.0  ! unit in centimetres
-    !   vegin%froot(is, :) = MIN(1.0, 1.0-vegin%rootbeta(:)**totdepth)
-    !END DO
-    !DO is = ms, 2, -1
-    !   vegin%froot(is, :) = vegin%froot(is, :)-vegin%froot(is-1, :)
-    !END DO
-
     ALLOCATE(defaultLAI(mp, 12))
 
     DO e = 1, mland ! over all land grid points
@@ -3339,12 +3326,12 @@ SUBROUTINE init_veg_from_vegin(ifmp,fmp, veg, soil_zse )
     ! (Jackson et al. 1996, Oceologica, 108:389-411)
     totdepth = 0.0
     DO is = 1, ms-1
-       totdepth = totdepth + soil_zse(is) * 100.0  ! unit in centimetres
-       veg%froot(:, is) = MIN( 1.0, 1.0-veg%rootbeta(:)**totdepth )
+      totdepth = totdepth + soil_zse(is) * 100.0  ! unit in centimetres
+      veg%froot(ifmp:fmp, is) = MIN( 1.0, 1.0-veg%rootbeta(ifmp:fmp)**totdepth )
     END DO
-    veg%froot(:, ms) = 1.0 - veg%froot(:, ms-1)
+    veg%froot(ifmp:fmp, ms) = 1.0 - veg%froot(ifmp:fmp, ms-1)
     DO is = ms-1, 2, -1
-       veg%froot(:, is) = veg%froot(:, is)-veg%froot(:,is-1)
+      veg%froot(ifmp:fmp, is) = veg%froot(ifmp:fmp, is)-veg%froot(ifmp:fmp,is-1)
     END DO
 
   END SUBROUTINE init_veg_from_vegin