Forest dynamics helps to understand several succession methods and to know about stand structure and development with forest based models like FORMIND, FORMIX, GRASMIND etc.,

2. Introduction
• Forest dynamics : Forest models and tree models (Shugart and west 1980)
• The study of change in forest stand structure with time, including stand behaviour
during and after disturbance (human-caused or natural) - every management
action (Willson, 2014)
• Studied through Compositional change - relay floristics (the classical successional
model) (Johnstone et al. 2010)
• Stand dynamics is the study of changes in forest stand structure over time,
including stand behavior during and after disturbances (Smith et al. 1997)

3. What are the Foundations - Forest Stand
Dynamics? / need
 Observation
 Ecology, physiology, morphology, anatomy, environmental
factors
 Facilitates study of Interactions –i.e., tree-tree, species-
species, tree-site.
 Enables understanding of Stand Growth and Succession

4. Why is Forest Stand Dynamics important
for foresters?
• Aids understanding of forest development and responses to natural disturbance
• Basis for understanding the interactions and responses to planned interventions
– Predicting productivity and future yield
– Predicting future structure and composition
– Controlling silvicultural costs
– Habitat and conservation values
– Enhancing landscape-scale values
• Forests are complex systems and need to be managed to be both resilient (to minimise
effects of climate change, pests and diseases) and sustainable (social, economic, ecological
and environmental factors)
• Principles of forest stand dynamics apply to all forest types and forest biomes

6. Succession - "Relay floristics" - Balsam fir
is replacing trembling aspen
• Composition of forest does
not changes so completely
or in a singular direction
• Mode of replacement is
strongly dependent on the
composition of the stand
and site type
Change through "gap replacement"

7. Canopy gap replacement
• If a stand is a mixture of mid- tolerant
(e.g., red oak white ash) and tolerant
(e.g., sugar maple) species, and
occurs on a rich mesic site, any
canopy gaps that occur through
death of single trees are likely to be
"captured" by tolerant species.
• This is because tolerant species are
likely to be better represented in the
reproduction layer and their growth
rates are optimal on such sites.
• If a similar stand develops on a drier,
less fertile site, the mid-tolerant
species have a greater chance to fill
gaps because on these sites their
growth rates exceed those of the
more moisture and nutrient
demanding tolerant species
Canopy gap replacement as a function of chance occurrence of seedlings in the gap area
and differential growth rate of species on a dry-mesic site.
SM=sugar maple
WA=white ash
RO=red oak

8. Resilience and response dynamics - ecosystem
feedbacks (Kilchenmann, 2013)

9. Alternate successional cycles - Black
spruce domain

10. Alternate successional cycles –
Broadleaf forest domain

11. Forest dynamics models- schematic diagram illustrates
assumptions that are associated with model classification
(Shugart,1984)
Mode of classification Phenomena
schematic
Category
Agestructure
Diversity
space
Regeneration
Growth
Geometric
competition
Resource
competition
Mortality
Tree Mixed Mono Spatial ** *
Tree Mixed Mono Nonspatial **
Tree Mixed Mono Nonspatial * **
Tree Mixed Mono Spatial ** *
Tree Mixed Mono Nonspatial ** * * **
Tree Mixed Mono Spatial * ** ** * **
Tree Mixed Mono Nonspatial ** ** **
Gap Mixed Mono Nonspatial ** **
Gap Mixed Mono Spatial ** ** * * *
** strong emphasis, * some emphasis and a blank no or little emphasis

12. Mixed aged, Mixed-species non spatial tree model - Principal
subroutines in the FOREST model
• MAIN
• INPUT
• STANGN
• HOWFAR
• COMPE
• YIELD
• STAT
• CUT
• OUTPUT
• REPRO
• PSEED
• SEEDYR
• DSTRIB
• GRAMIN8
• GROW

13. MAIN Determines height, diameter, and crown development of over story trees
INPUT Accepts parameter values for each species primarily for over story development
STANGN Accepts real tree input data or generates spatial patterns and tree characteristics for each species
HOWFAR
Determines the distance between points on main plot and buffer zone that are needed for evaluation of competition and seed and
sprout distribution
COMPE Evaluates the tree competition
YIELD Calculates the timber product yields based on individual tree dimensions, specific gravity and bark characteristics
STAT Computes parameters of distribution of tree and stand characteristics for summary output
CUT
Orders tres by size or increment for pruning or harvest treatments and implements these treatments on individual trees by species.
Harvest includes row thinning, selection according to specified criteria, spacing rules, cuts to basal area levels and combinations above.
The timing and degree of cutting may be set by the user or allowed to vary as dictated by stand development
OUTPUT Prepare table, stem map, and graphic output that describe stand development
REPRO
Accepts input of initial reproduction status, reproduction parameters for each species, and specifications for degree and timing of any
changes in reproduction parameters to be implemented during the run
PSEED Determines seed and sprout production for each over story tree as a function of species, size and threshold stage
SEEDYR Generates seed year multiplier for each species (i.e., frequency of good, moderate and poor seed years)
DSTRIB Distributes seeds and sprouts (root suckers and basal sprouts) from each overstory tree to subplots within main plot
GRMIN8 Calculates seed germination as a function of microsite and over story cover conditions
GROW
Controls growth and mortality of reproduction until surviving individual reproduction stems reach overstory status - then MAIN
assumes control of stem development
Contd.,

14. Gap model - 450 years change on a single simulated plot
(BRIND model) for alpine ash zone of the Brindabela mountains
(Shugart 1984)
The species are drawn to scale by height, and the width
of plot in 32 m

15. Die back regeneration cycle shown in simplified form
for Metrosiderous polymorpha on hawaiian islands
(Shugart, 1984)
Severely declining stand of ohia
Stand of mature healthy ohia

16. Forest Gap models - importance
1. Forests are represented as a collection of small patches. The
forest successional stage and age vary across patches.
2. Patches are independent of their neighborhoods and do not
interact with other patches. Thus, dynamic processes such as tree
recruitment, growth and mortality are calculated separately for
each patch.
3. All patches are homogeneous in size and resource level (i.e., light
reaching the upper canopy). The size of one patch is usually
chosen according to the extent of the largest possible tree crown
(e.g., 20 m x 20 m). Intra- or interspecific interactions are
simulated for all trees in a patch rather than tree-by-tree, as tree
positions are not included.
4. Leaves are modeled as thin disks on top of each tree. Trees
standing within one patch compete for light due to asymmetric
shading

17. Forest based models – Forest dynamics
(Fischer et al., 2016)
FORMIX
FORMIND
GRASSMIND

18. FORMIX
• Applied to tropical forests in South-East Asia. FORMIX
accounts for biomass and tree numbers in five distinct
canopy layers (each layer has some representative trees
similar to size class models). (Huth et al., 2001)

19. FORMIND
• Is the process- and individual-based successor of the FORMIX
model, in which the concept of distinct layers was discarded.
FORMIND was developed in the late 1990’s to simulate
tropical forest dynamics more realistically than before.
(Fischer et al., 2016)

20. MAIN PROCESSES OF FORMIND
• Establishment
• Growth
• Mortality
• Competition and environmental limitations
• Disturbances
• Carbon cycle

21. Simulation of species-rich forests with the
growth model FORMIND (Fischer et al., 2016)
Individual-based means that growth is calculated for each tree individually. Trees in
high diversity forests are aggregated into different plant functional types in order to
facilitate the parameter definition of similar-behaving species and to reduce
computing time.
Output - Allows to simulate forests of high
heterogeneity
The model area (1 to 50 ha) is divided into
20m x 20m patches. Forest gaps are
implemented to simulate forest structure and
dynamics. Gaps occur- dying trees or external
disturbances – leads to establishment of LD
spp.

22. • This image shows a visualization of a mountainous tropical forest in
Ecuador.
• Tree species are aggregated into seven plant functional types.
• Trees colored in red are of late successional stage (shade-tolerant
species), trees colored in green are of early successional stage (light-
demanding species) and trees in blue are of intermediate successional
stage.

24. GRASSMIND - Simulation of species-rich grasslands
with GRASSMIND
• The individual-based approach of forest gap models offer a high degree of
flexibility to be adapted to different environments (e.g., temperate
forests) or even other ecosystem types (e.g., temperate grassland
• GRASSMIND designed for simulating the structure and dynamcis of
herbaceous communities including:
– competition between individual plants for light, space, soil water and
nitrogen
– different management regimes (mowing, irrigation, fertilization)
– climatic changes (drought events, increased temperatures, etc.)
individual plants compete for light and space
aboveground and for soil water and nitrogen
belowground. So, the GRASSMIND is coupled
with the soil model CANDY.

25. Studying practically the forest
stand dynamics concept

26. Facilitating learning in forest stand
dynamics
• Part 1 : field (site inspection and data collection)
• Part 2 : data collection, presentation, analysis and
interpretation

28. Basic measurements
• Complete measurements in
100m2 or 200 m2 plots (trees and
ground vegetation)

29. Session 2 : Analysis and Interpretation
• Introduction
– Outline the learning goals, objectives and structure of the session
– review and reflect on key aspects of session 1
• Fast facts lecture
– Theory and terminology
• Explain the task
– Distribute handout and data sheets
– Explain steps required to complete the exercise
• Student activity
– Summarise and collate data
– Present results in graphical format
– Creat a stand profile diagram
• Review and reflect
– Group and class discussion
– Reviw of learning outcomes and reflect on application of knowledge to forestry
practice

33. References
• http://harvardforest.fas.harvard.edu/blog/forest-
dynamics-former-plantations
• http://www.ufz.de/index.php?en=36279
• http://formind.org/mode
• http://dialog.ua.edu/2014/11/seeing-both-the-
forest-and-the-trees/
• http://baloun.entu.cas.cz/png/wanang/forest-
dynamics-plot
• http://www.ctfs.si.edu/site/Mudumalai