Implementing forest thinning/insect mortality

Forest Thinning and Insect Mortality

There are a few options that can be used as tec events to force biomass pool changes that mimic forest thinning or insect mortality. Use the commands below in your tec file at a specified date similar to the way you implement a redefine, so you will need a corresponding redefine world file at the same specified date.

redefine_world_multiplier

Whatever value you put in the redefine file will be multiplied to the existing worldfile value. So, for example, if you have a 0.75 in the cs_leafc slot in the redefine file, the leaf carbon value in the worldfile will be multiplied by 0.75.

redefine_world_thin_remain

Only cover fraction, gap fraction, and the main carbon pool variables (cs_pool, cs_leafc, cs_dead_leafc, cs_live_stemc, cs_dead_stemc, cs_live_crootc, cs_dead_crootc, cs_frootc) will be read in from the redefine file (all other values will be ignored). For cover fraction and gap fraction, the value in the redefine file will become the value in the new worldfile (i.e., how the main "redefine_world" routine works... if you put a 0.3 in the redefine file the new worldfile value will be 0.3). For the C-pool values, the values in the redefine file should be the fraction of those pools you want "thinned", or removed from the live biomass pools. The corresponding N-pool values will be automatically removed and both the C and N removed fractions will be distributed to the appropriate litter and CWD pools. So, for example, you might want to run a thinning routine that "thins" all biomass by 0.25 and changes the gap fraction to 0.25. Your redefine file would have 0.25 for all the above listed variables except cover fraction, and the resulting new worldfile will show 75% of the pre-redefine C and N pools, with the missing 25% C and N moved to the litter and CWD pools. Of course, you can also vary what fraction of leaf versus stem versus root C (and corresponding N) you want to remove, and can change these fractions across space.

redefine_world_thin_harvest

Works the same as above, but the aboveground C and N fractions are "harvested" (e.g., removed from the live biomass pools but not added into the litter and CWD pools) while the belowground C and N fractions are removed and added to the litter and CWD pools as in the redefine_world_thin_remain option. The user sets the redefine file exactly as they would for the previous case.

redefine_world_thin_snags

This option should be used when you want to remove leaf biomass but leave standing dead (snags), for example to mimic insect defoliation or leaf drop from drought mortality. Leaf C and N pools are reduced based on the fraction specified (transferred to litter pools) and livestem C and N pools are transferred to deadwood based on the fraction specified.

Example tec event:

1997 7 2 1 redefine_world_thin_harvest

Example stratum section of a template file used to create a thinning redefine world:

_stratum patch.fullveg 1
	veg_default_ID      value -9999
	cover_fraction          value -9999 
	gap_fraction            mode gap
	root_depth              value -9999
	snow_stored             value -9999
	rain_stored             value -9999
        cs_pool                 mode thin
	cs_leafc		mode thin
	cs_dead_leafc		mode thin
	cs_leafc_store		value -9999
	cs_leafc_transfer	value -9999
	cs_live_stemc		mode thin
	cs_livestemc_store	value -9999
	cs_livestemc_transfer	value -9999
	cs_dead_stemc		mode thin
	cs_deadstemc_store	value -9999
	cs_deadstemc_transfer	value -9999
	cs_live_crootc		mode thin
	cs_livecrootc_store	value -9999
	cs_livecrootc_transfer	value -9999
	cs_dead_crootc		mode thin
	cs_deadcrootc_store	value -9999
	cs_deadcrootc_transfer	value -9999
	cs_frootc		mode thin
	cs_frootc_store		value -9999
	cs_frootc_transfer	value -9999
	cs_cwdc			value -9999
	epv.prev_leafcalloc	value -9999
	ns_pool			value -9999
	ns_leafn		value -9999
	ns_dead_leafn		value -9999
	ns_leafn_store		value -9999
	ns_leafn_transfer	value -9999
	ns_live_stemn		value -9999
	ns_livestemn_store	value -9999
	ns_livestemn_transfer	value -9999
	ns_dead_stemn		value -9999
	ns_deadstemn_store	value -9999
	ns_deadstemn_transfer	value -9999
	ns_live_crootn		value -9999
	ns_livecrootn_store	value -9999
	ns_livecrootn_transfer	value -9999
	ns_dead_crootn		value -9999
	ns_deadcrootn_store	value -9999
	ns_deadcrootn_transfer	value -9999
	ns_frootn		value -9999
	ns_frootn_store		value -9999
	ns_frootn_transfer	value -9999
	ns_cwdn                 value -9999
	ns_retransn		value -9999
	epv_wstress_days             value -9999
	epv_max_fparabs         value -9999
 	epv_min_vwc             value -9999
 	n_basestations          value -9999