Natural Disturbance
In the Natural Disturbance Module of ALCES®, the average annual proportion of each forest type and selected non-forest cover types disturbed by fire and other natural disturbances are specified, along with the potential change in the area burned due to fire suppression efforts. Future trends in natural disturbance rates can be modelled stochastically for simulations involving “range of natural variability” and deterministically (constant) for both backcast and forecast scenarios. Stochastic fire regimes can reflect a random draw from either a lognormal or exponential distribution. Additional inputs include fire size class distribution, the percent of aboveground vegetation combusted by fire, and the relationship between forest stand age and the probability that a stand might be burned.
It is possible to specify the average area of each forest type and selected non-forest cover types disturbed by fire, insect outbreaks, and avalanches in the land base, along with the potential change in the area burned due to fire suppression efforts. Future trends in fire and insect outbreaks may be modelled as constant or random variables. The effects of climate change on the rates of disturbance by fire and insect outbreaks can also be specified. More detailed information related to fire that can also be specified includes fire size class distribution, the percent of aboveground vegetation combusted by fire, the number of acreages and agricultural residences lost to fire, and the relationship between forest stand age and the probability that a stand might be burned. It is also possible to specify the probability that forest stands change from one cover type to another following fire. The effects of beavers, an additional disturbance agent in some regions, can be simulated by identifying the landscape types in which beavers occur, and defining selected measures defining the number, size, and life span of beaver dams.
Table inputs
Table 1. Average natural and prescribed fire rate x landscape type
The average pre-suppression annual burn rate may be specified for each forest trajectory and selected non-forest plant communities in the study area. Examples of published burn rates for selected plant communities in Alberta are available in the ALCES Technical Manual.
Table 2. Desired or expected fire suppression level
It is possible to specify the effectiveness of fire suppression for each forest trajectory and selected non-forest landscape types. Values can range between 0 and 100% (0 - 1). If a desired level of fire suppression above 0% is entered, then it is also possible to specify the general relationship between fire suppression costs and the level of fire suppression realized.
Table 3. Average insect mortality rate and crop loss
Enter the average annual losses to insect outbreaks in each forest trajectory and crop type in the study area.
Table 4. Average avalanche rate x FLB
Enter the average annual losses to avalanches in each forest trajectory in the study area.
Table 5. Fire size distribution and edge metrics
Enter the size class distribution of fire events. Fire size intervals (in hectares) are (0 - 10), (11 - 100), (101 - 1,000), (1,001 - 10,000), and (10,001 - 100,000). Values in this table must sum to 100% (1.0). Default values in the model are applicable to Alberta boreal forest regions based on analyses conducted by Stelfox on the 1961-1995 Government of Alberta LFS fire dataset. The proportion of area burned by fire were as follows: 0 - 10 ha (0.01), 10 - 100 ha (0.02), 100 - 1,000 ha (0.04), 1,000 -10,000 ha (0.1) and 10,000-100,000 ha (0.83). These values may be different from those in other regions and should be modified where necessary. The patch edges caused by fire are transitional and will eventually merge into adjoining patches. "Average Lifespan of Transitional Edge" refers to the average number of years required for pyrogenic edge to become undetectable.
Table 6. Percent of aboveground phytomass combusted in fire
Enter the percent of aboveground phytomass combusted in fire for each landscape type.
Table 7. Acreages & agricultural residences lost to fires
Enter the percent of acreages and agricultural residences saved from fire in each landscape type.
Table 8. Fire rate x seral stage modifier
The concept of "cooling the forest landscape to fire risk" can be explored by relating fire rates to landscape age class structure. This is done by entering seral stage modifier for burn rate that specifies specify fire rates that differ among seral stages in a forest trajectory. Enter a value for each seral stage that modifies its burn rate relative to that of the overall forest trajectory. For example, hardwood forest may have an overall burn rate of 0.01 (100 year fire cycle) but it may be desirable to specify that the burn rate of hardwood forests between 0 and 20 years is 0.005 (200 year fire cycle). In this case the user would enter a HW burn rate of 0.01 in the HW row of Table 1 (Panel 6) and a value of 0.5 in the HW(SS1) row of Table 8 (Panel 6). A burn rate of 0.005 (0.01*0.5=0.005) would then be applied to all hardwood forests between 0 and 20 years of age.
Table 9 Fire and insect induced forest trajectory conversions
It is possible that fire or insect outbreaks may alter the successional trajectory of forests they affect. This potential scenario may be simulated by specifying the percent of all forests affected by fire or insect outbreaks that remain in their current trajectory or move to another forest trajectory. These values must sum to 100% (1.0).
Table 10. Fire rate modifier for sensitivity analyses
Enter the fire rate modifier for sensitivity analyses.
Table 11. Beaver dam metrics
For each landscape type, a value of 0 means that beaver dams are not to occur; a value of 1 means that beaver dams do occur. Other inputs in this table include:
- percent of lotic systems available to beavers
- average distance (km) between beaver dams
- average beaver dam length (m)
- average beaver dam lifespan (yr)
- standard deviation of beaver dam lifespan (yr)
Graphic inputs
Precipitation x fire rate
The effects of a change in average regional precipitation on annual fire rate can be explored using this graphic input device. Specified changes in average annual precipitation (the x axis) may vary from -20 to 20 cm below or above the initial precipitation levels specified in the meteorological module. The Y axis describes the specified change in fire rate. For example, a value of 0 indicates a 0% change in fire rate; a value of 0.2 is equivalent to a 20% increase in fire rate and a value of -0.3 indicates a 30% decline in fire rate. Specified changes in average precipitation are defined in the meteorological module.
Temperature x fire rate
The effects of a change in average regional temperature on annual fire rate can be explored using this graphic input device. The maximum range in future changes in average ambient temperatures (the x axis) vary from -5 to +5 degrees C below or above the initial temperatures specified in the meteorological module. The Y axis describes specified change in fire rate. For example, a value of 0 indicates a 0% change in fire rate; a value of 0.2 is equivalent to a 20% increase in fire rate and a value of -0.3 indicates a 30% decline in fire rate. Specified changes in average ambient precipitation are defined in the meteorological module.
Human density x fire rate
It is possible to explore the effects of changing human population density (#/km2) on fire rate. For example, a value of 1.00 indicates no change in fire rate relative to the background pre-suppression fire rate defined in Table 1 (Panel 6). A value of 1.5 indicates a 50% increase in fire rate relative to the presuppression level. In contrast, a value of 0.4 indicates a 60% reduction in fire rate.
Precipitation x insect rate
The effects of a change in average regional precipitation on annual insect outbreak rate can be explored using this graphic input device. Specified changes in average annual precipitation (the x axis) may vary from -20 to 20 cm below or above the initial precipitation levels specified in the meteorological module. The Y axis describes the specified change in insect outbreak rate. For example, a value of 0 indicates a 0% change in insect outbreak rate; a value of 0.2 is equivalent to a 20% increase in insect outbreak rate and a value of -0.3 indicates a 30% decline in insect outbreak rate. Specified changes in average ambient precipitation are defined in the meteorological module.
Temperature x insect rate
The effects of a change in average regional temperature on annual insect outbreak rate can be explored using this graphic input device. The maximum range in future changes in average ambient temperatures (the x axis) vary from -5 to +5 degrees C below or above the initial temperatures specified in the meteorological module. The Y axis describes specified change in insect outbreak rate. For example, a value of 0 indicates a 0% change in insect outbreak rate; a value of 0.2 is equivalent to a 20% increase in insect outbreak rate and a value of -0.3 indicates a 30% decline in insect outbreak rate. Specified changes in average ambient precipitation are defined in the meteorological module.
Fire suppression $ x effectiveness
It is possible to explore the cost of fire suppression programs by applying a general relationship that relates suppression effectiveness to suppression cost ($/ha/year). If the User elects to define a desired level of fire suppression in Table 2 (Panel 6), then annual annual fire suppression costs are calculated and fire rate is adjusted accordingly.
Beaver habitat saturation
This graphic input device makes it possible to specify the proportion of creeks that are inhabited by beaver throughout the simulation period.
Met x dam failure
This graphic input device makes it possible to define the relationship between annual precipitation level and the probability that beaver dams will fail.
Switches
Fire induced forest conversion
Clicking this switch on (up) activates the inputs specified in Table 9 (Panel 6).
Fire x climate change
The effects of global warming on annual fire rate can be explored by activating this switch (up position).
Insects x climate change
The effects of global warming on annual insect outbreak rate can be explored by activating this switch (up position).
Fire / insect regimes: Random or constant?
Fires and insect outbreaks can be simulated as a constant perturbation event (down) or as a stochastic process (up). Stochastic (random) fires and insect outbreaks can be drawn from either an exponential or lognormal function whose mean is defined by average disturbance rate.
Fire distribution: Lognormal or exponential
Fire regimes in forest ecosystems can be generated randomly from either an exponential or lognormal distribution. Clicking this switch up selects the lognormal distribution; the down position selects the exponential distribution.