DISTURBANCES
Logging
Different logging strategies can be simulated with the FORMIND forest model. Trees with specifi c attributes can be removed from the forest plot, simulating logging preferences. At the same time, surrounding trees are damaged based on the chosen logging strategy, logging intensity, logging cycle, cutting limits and resulting damage.
In FORMIND, logging can be simulated through two different strategies: Reduced impact logging (RIL), where trees are directed to fall towards the closest gap, and conventional logging (CON), with a random direction for falling trees.
Development of bole volume by ecological groups applying different cutting cycles under fragmentation scenario. (a) 10-yr cutting cycle (3–8 stems removed); (b) 10-yr cutting cycle (8–20 stems removed); (c) 30-yr cutting cycle; (d) 60-yr cutting cycle (Kammerscheidt et al. 2002).
The fire module ForFire
Fire is an important disturbance process affecting the terrestrial vegetation. In forests it can lead to a decrease of carbon storage and result in the emission of greenhouse gases.
We developed a simple forest fire module ForFire which combines elements of well-established fire models (Gardner et al., 1999; Keane et al., 2004; Thonicke et al., 2001). External inputs to the ForFire module are: the fire frequency per hectare and year, the mean fire size related to the investigated forest area and the fire severity.
Visualization of two randomly chosen fire events. The simulated area is nine hectare. The green scale indicates the amount of standing biomass. The red colour shows burnt areas.
The landslide module
In montane forests landslides are an important natural disturbance regime. Disturbances by landslides differ from disturbances by falling trees or logging. When a landslide occurs, not only vegetation is destroyed. In addition, soil layers and seed banks are removed from the disturbed patch. Therefore, in the landslide module, forest regeneration underlies particular environmental conditions.
For instance, solar radiation on recent landslide sites is high and nutrient levels are low. Due to this changed environmental and habitat conditions establishment rates of trees as well as tree mortality and tree growth rates might deviate from pre-disturbance levels.
The external input variables to the landslide module are the landslide frequency per hectare and year and the distribution of landslide sizes.
The fragmentation module
In human modified landscapes, remnants of original forests exist as scattered patches called forest fragments. Plant and animal communities left in these areas suffer from isolation to other populations, and from microclimatic alterations (such as excess light and drier conditions) on the border of the fragments called “edge effects” (Laurance et al. 2011). These processes can pose difficulties for human modified landscapes to support similar biodiversity levels as the original area.
FORMIND simulates the edge effects of fragmented forests by increasing the mortality in the plots located up to 100 meters from the edge of the simulating area. The mortality of large trees, and lower seed input can be further raised optionally.
Four Hectare simulation area showing a larger occurrence of lower biomass plots along the border.
References
Gardner, R.H., Romme, W.H., Turner, M.G., 1999. Predicting forest fire e ffects at landscape scales, in: Mladeno ff , D.J., Baker, W.L. (Eds.), Spatial Modeling of Forest Landscape Change: Approaches and Applications., Cambridge University Press, Cambridge. 163-185.
Kammesheidt, L., Köhler, P., Huth, A. 2002. “Simulating logging scenarios in secondary forest embedded in a fragmented neotropical landscape” Forest Ecology and Management, Volume 170, Pages 89–105
Keane, R.E., Cary, G.J., Davies, I.D., Flannigan, M.D., Gardner, R.H., Lavorel, S., Lenihan, J.M., Li, C., Rupp, T.S., 2004. A classi cation of landscape fi re succession models: spatial simulations of fi re and vegetation dynamics. Ecological Modelling 179, 3-27.
Laurance et al. 2011. The fate of Amazonian forest fragments: A 32-year investigation. Biological Conservation 144, 56–67.
Pfeiff er, M., Spessa, A., Kaplan, J.O., 2013. A model for global biomass burning in preindustrial time: Lpj-lmfi re (v1.0). Geoscienti c Model Development 6, 643-685.
Thonicke, K., Venevsky, S., Sitch, S., Cramer, W., 2001. The role of fire disturbance for global vegetation dynamics: coupling re into a dynamic global vegetation model. Global Ecology and Biogeography 10, 661-677.
Wilcke, W., Valladarez, H., Stoyan, R., Yasin, S., Valarezo, C., Zech, W., 2003. Soil properties on a chronosequence of landslides in montane rain forest, Ecuador. CATENA 53, 79-95.