diff --git a/biogeochem/EDPatchDynamicsMod.F90 b/biogeochem/EDPatchDynamicsMod.F90
index ffbf8da915..501ffba6cd 100755
--- a/biogeochem/EDPatchDynamicsMod.F90
+++ b/biogeochem/EDPatchDynamicsMod.F90
@@ -23,6 +23,7 @@ module EDPatchDynamicsMod
   use FatesConstantsMod    , only : r8 => fates_r8
   use FatesPlantHydraulicsMod, only : InitHydrCohort
   use FatesPlantHydraulicsMod, only : DeallocateHydrCohort
+  use EDParamsMod          , only : fates_mortality_disturbance_fraction
 
   ! CIME globals
   use shr_infnan_mod       , only : nan => shr_infnan_nan, assignment(=)
@@ -86,7 +87,7 @@ subroutine disturbance_rates( site_in)
           currentCohort%patchptr => currentPatch
 
           call mortality_rates(currentCohort,cmort,hmort,bmort)
-	  currentCohort%dmort  = cmort+hmort+bmort	
+          currentCohort%dmort  = cmort+hmort+bmort
           currentCohort%c_area = c_area(currentCohort)
 
           ! Initialize diagnostic mortality rates
@@ -99,6 +100,7 @@ subroutine disturbance_rates( site_in)
           if(currentCohort%canopy_layer == 1)then
 
              currentPatch%disturbance_rates(1) = currentPatch%disturbance_rates(1) + &
+                  fates_mortality_disturbance_fraction * &
                   min(1.0_r8,currentCohort%dmort)*hlm_freq_day*currentCohort%c_area/currentPatch%area
 
           endif
@@ -289,7 +291,8 @@ subroutine spawn_patches( currentSite, bc_in)
                    ! because this is the part of the original patch where no trees have actually fallen
                    ! The diagnostic cmort,bmort and hmort rates have already been saved         
 
-                   currentCohort%n = currentCohort%n * (1.0_r8 - min(1.0_r8,currentCohort%dmort * hlm_freq_day))
+                   currentCohort%n = currentCohort%n * (1.0_r8 - fates_mortality_disturbance_fraction * &
+                        min(1.0_r8,currentCohort%dmort * hlm_freq_day))
 
                    nc%n = 0.0_r8      ! kill all of the trees who caused the disturbance.         
                    nc%cmort = nan     ! The mortality diagnostics are set to nan because the cohort should dissappear
diff --git a/biogeochem/EDPhysiologyMod.F90 b/biogeochem/EDPhysiologyMod.F90
index a8aab76137..b147372260 100755
--- a/biogeochem/EDPhysiologyMod.F90
+++ b/biogeochem/EDPhysiologyMod.F90
@@ -31,7 +31,7 @@ module EDPhysiologyMod
   use shr_log_mod           , only : errMsg => shr_log_errMsg
   use FatesGlobals          , only : fates_log
   use FatesGlobals          , only : endrun => fates_endrun
-
+  use EDParamsMod           , only : fates_mortality_disturbance_fraction
 
   implicit none
   private
@@ -788,11 +788,12 @@ subroutine Growth_Derivatives( currentSite, currentCohort, bc_in)
 
     ! Mortality for trees in the understorey. 
     !if trees are in the canopy, then their death is 'disturbance'. This probably needs a different terminology
+    call mortality_rates(currentCohort,cmort,hmort,bmort)
     if (currentCohort%canopy_layer > 1)then 
-       call mortality_rates(currentCohort,cmort,hmort,bmort)
        currentCohort%dndt = -1.0_r8 * (cmort+hmort+bmort) * currentCohort%n
     else
-       currentCohort%dndt = 0._r8
+       currentCohort%dndt = -(1.0_r8 - fates_mortality_disturbance_fraction) &
+            * (cmort+hmort+bmort) * currentCohort%n
     endif
 
     ! Height
diff --git a/main/EDParamsMod.F90 b/main/EDParamsMod.F90
index 8bc4e9f908..eb99476625 100644
--- a/main/EDParamsMod.F90
+++ b/main/EDParamsMod.F90
@@ -72,6 +72,8 @@ module EDParamsMod
    public :: FatesParamsInit
    public :: FatesRegisterParams
    public :: FatesReceiveParams
+
+  real(r8), protected :: fates_mortality_disturbance_fraction  = 1.0_r8 ! the fraction of canopy mortality that results in disturbance (i.e. transfer of area from new to old patch)                                                              
   
 contains