user_name Heli Peltola
user_organisation University ofJoensuu
Faculty of Forestry
Joensuu
Finland
date 19th September 1996
model_name HWIND
description The mechanistic model for wind and snow damage of single trees attempts to
fully describe the mechanistic behaviour of trees under wind and snow
loading. The model takes site and stand information and predicts the canopy
top mean windspeeds at which the trees will uproot and break due to wind
and/or snow loading both at the stand edge and for various distances from
the stand edge. To provide a measure of total turning moment on tree, model
calculates first the mean wind loading and gravity based force (caused by
stem, crown and snow weight) at each height in the canopy using a predicted
wind profile at the stand edge and the vertical distribution of stem, crown
and snow weights. HWIND calculates then gust factor, which relates then
mean wind loading of one hour and extreme wind loading of 3 second gusts,
to distance from stand edge, stand density and tree height based on wind
tunnel studies (Gardiner and Stacey 1996, see Gardiner and Peltola 1996).
To calculate the resistance to uprooting model uses a prediction of
root-soil plate mass to derive a resistive moment. The prediction of stem
breakage relies on values of Modulus of Rupture determined for different
timbers. To date the model covers especially Scots pine, Norway spruce
and Birch sp growing on podzolic soils in Finnish conditions. However,
also other tree species and soil types for various geographical locations
can be used by changing the controlling parameters (and equations if needed)
to cover new species and soils.
software C++, and visual basic for graphics in Windows
operating_system PC in DOS and Windows, also UNIX
isumm Tree species and soil type a. Tree species b. Soil type Tree and stand characteristics a. One tree simulation Tree height Tree diameter at 1.3m above base (dbh) Stand density b. Rotation simulation If many years are simulated simultaneously, tree characteristics should
be available in existing file named *.inp (including age, height, dbh,
stand density) or the new file should be created.

Wind

a. Simulation windspeed (mean)
b. Gust factor

Snow load

a. Snow load kg/tree
b. Snow load kg/m2 of crown area
Simulation conditions (stand edge/within the stand)

a. Distance from stand edge in tree heights

Other inputs

a. Crown streamlining
b. Simulation without leaves

ispecfile Tree species and soil selected from menus

Tree height, diameter, stand density and other possible inputs
from the keyboard (to the input window) (see below):
Select Tree Species
Scots Pine (Spine1.par)
Norway Spruce (Nspruce1.par)
Birch sp (pbirch1.par)

Select Soil Type
Podzol(podzol.spr)

Tree Characteristics
Set Tree height to <20> metres
Set Tree Diameter at 1.3m above base to <20> cm
Set Stand Density to <690> trees/ha

Rotation Simulation

Same tree characteristics as for one year simulation should be available in existing file named *.inp (simulation year, height, dbh, stand density) or the new file should be created.

Wind

Set simulation windspeed (default is that the program seeks damaging windspeed)
Set gust factor (default is to let the program calculate it)

Snow load (defaults is no snow load)

Set Snow load kg/tree
Set snow load kg/m2 of crown area

Simulation conditions (stand edge/within the stand)

Set distance from stand edge in tree heights (default: stand edge)

Other Inputs:
Set Crown streamlining (default: model calculates it as a function of windspeed)
Set simulation without leaves (default is with leaves)

iexpspecfile This model is an interactive version of a model designed to read input
files and output critical windspeeds (mean of one hour) and mean turning
moments to cause uprooting and stem breakage of single trees.
csumm Various constants are used to calculate mean and extreme wind loading and
another loading due to gravity (crown, stem and snow mass), resistance to
uprooting and stem breakage. These constants are currently fixed but will
be improved if more proper information will be available (see references
for constants/parameters presented below in details from Peltola and
Kellomaki (1993), Peltola (1995), Peltola et al. (1996e), and Gardiner
and Peltola (1996b).
cspecfile Spine1.par

# Scots pine
1000# green density of roots (kg/m**3)
473# basic density of roots (kg/m**3)
0.21# RSMean (m)
0.30# Arsw
1.33# conversion of dbh to stump diameter
39.1# modulus of rupture, MOR (MPa) (Lavers 1969)
7000# modulus_of_elasticity, E (MPa)
0.29# drag coefficient, Cd (dimensionless)
850# green density of stem (kg/m**3)
0.0# zero plane displacement d
0.06# roughness length Z0/h
0.42# crown ratio
0.30# crown stem mass ratio
0.5# crown center point
1.0# leafless crown area ratio
1.0# leafless crown mass ratio

# Scots pine
1# tree species
16 2.4 -0.023# maximum depth of roots
1.0# longest root
-4.9 0.044# dry mass of roots
1.0 0.6 0.094# longest branch
2.1288 -0.63157
-1.6082 2.4886
-2.4147 2.3619
-1.7539 1.0817		# taper curve par

Nspruce1.par

# Norway Spruce
1000# green density of roots (kg/m**3)
452# basic density of roots (kg/m**3)
0.21# RSMean (m)
0.20# Arsw
1.33# conversion of dbh to stump diameter
30.6# modulus of rupture, MOR (MPa) (Lavers 1969)
6300# modulus_of_elasticity, E (MPa)
0.35# drag coefficient, Cd (dimensionless)
800# green density of stem (kg/m**3)
0.0# zero plane displacement d
0.06# roughness length Z0/h
0.76# crown ratio
0.50# crown stem mass ratio
0.7# crown center point
1.0# leafless crown area ratio
1.0# leafless crown mass ratio

# Norway spruce
2# tree species
15.6 1.17 0.0# maximum depth of roots
1.0# longest root
-7.1 0.060# dry mass of roots
1.0 1.2 0.063# longest branch
2.3366 -3.2684
3.6513 -2.2608
0.0 2.1501
-2.7412 1.8876		# taper curve par

pBirch1.par

# Birch sp.
1000# green density of roots (kg/m**3)
445# basic density of roots (kg/m**3)
0.21# RSMean (m)
0.3# Arsw
1.33# conversion of dbh to stump diameter
53.6# modulus of rupture, MOR (MPa) (Lavers 1969)
9900.0# modulus_of_elasticity, E (MPa)
0.29# drag coefficient, Cd (dimensionless)
900# green density of stem (kg/m**3)
0.0# zero plane displacement d
0.06# roughness length Z0/h
0.50# crown ratio
0.30# crown stem mass ratio
0.5# crown center point
0.2# leafless crown area ratio
0.68# leafless crown mass ratio

# Birch sp.
3# tree species
16 2.4 -0.023# maximum depth of roots
1.0# longest root
-4.9 0.044# dry mass of roots
1.0 0.6 0.094# longest branch
0.93838 4.1060
-7.8517 7.8993
-7.5018 6.3863
-4.3918 2.1604 		# taper curve par

Podzol.spr

1 1500 # green density of soil (kg/m**3)

cexpspecfile The above shows examples of input files for Scots pine, Norway spruce and
birch sp on podzolic soil (*1.par includes specific parameters for
individual species and parameters for tree characteristic
relationships, respectively *.spr includes soil parameters).
osumm Model outputs critical windspeed at canopy top and turning
moment at the stem base for uprooting and stem breakage of
tree caused by the wind and/or critical snow loading (at
the stand edge and within the stand). It also outputs the mean wind
profile and turning moment distribution, and the contributions
of wind and snow load, stem and crown mass for total turning
moment of trees for various heights above ground (i.e. 6 tables
and various figures).
ospecfile Output files (one tree simulation only)
Scots pine
6.dat
Simulation year1 years
Tree height20.00 m
Diameter at breast height20.00 cm
Crown height8.00 m
Crown mass74.49 kg
Crown width4.96 m
Projected crown area19.84 m**2
Projected stem area2.47 m**2
Stem mass248.32 kg
Green mass of roots63.78 kg
Length of longest root2.48m
Maximum root depth0.64 m
Root soil plate volume4.09m**3
Soil mass6045.47 kg
Anchorage moment26694.58
Modulus of Rupture39.10
Wind (uproot)13.00 m/s
Wind (stem breakage)16.30 m/s
Turning moment by wind (uproot) 6253.25 Nm
Turning moment by wind (stem bre)7682.66 Nm
Turning moment by weight (uproot) 1305.58 Nm
Turning moment by weight (stem b) 1614.28 Nm
Total turning moment (uproot) 7558.83 Nm
Total turning moment (stem break) 9296.94 Nm
Maximum x(z) (uproot) 1.31 m
Maximum x(z) (stem breakage) 1.62 m
Snow load0.0 kg
Gust factor3.55
n.b. For simulation of many years/rotation, the same information is
included in file 6.dat but printed out in horizontal format.

2.dat

yearstand densitydbhhgttapercrown ratiocrwn wdthrootplatedepthrplate width (longest root)stem Masscrown Massstem+crownMassrootMassrootsoilplateMassSnow mass
1120201.00.424.960.642.48248743236460450.00

3.dat 18.50
yearzsA(z)cA(z)cA'(z)sA+cA'sM(z)cM(z)Snow
119.500.010.740.740.750.093.6451.26
10.032.212.212.250.7510.91153.79
from left to right: simulation year, height above ground, stem projected area against wind, crown proj. area, streamlined crown area, stem mass, crown mass, snow mass.

4.dat

yearZu(z)x(z)F1(z)F2(z)TF1(z)TF2(z)TF1+TF2
119.5012.881.3112.6023.40245.7730.75276.52
118.5012.641.2237.1773.29687.6289.49777.11
from left to right: year, height above ground, windspeed, stem deflection,
force due to wind, force due to gravity, turning moment due to wind, turning
moment due to gravity and total turning moment due to wind and gravity.

5.dat

Turning moment %
yearzstemcrownsnowloadwindload
119.500.000.141.981.98
118.500.030.395.525.41
oexpspecfile see above
copyright
ivar1 tree species
ifile1 menu selection (Spine1.par, Nspruce1.par, pbirch1.par)
idescr1 descriptor selected from a menu Select Tree Species: Scots Pine Norway Spruce Birch sp
isensitiv1 Sensitive
isensdescr1 Comparisons are available for Scots Pine, Norway spruce and Birch sp for a variety of tree heights and stem diameters on podzolic soil (see Peltola et al. 1996b, e). Especially Birch sp without leaves differs a lot from Scots pine and Norway spruce.
ivar2 soil type
ifile2 menu selection (parameters in e.g. podzol.spr)
idescr2 description selected from menu
isensitiv2 Unknown
isensdescr2 None available yet
ivar3 tree height
ifile3 interactive input (*.inp for rotation simulations)
idescr3 tree height in metres inupt interactively
isensitiv3 Not Very Sensitive
isensdescr3 Comparisons are available for Scots pine, Norway spruce and birch sp. for a variety of tree heights on podzolic soil (see Peltola et al. 1996b, e). Comparisons cover critical windspeeds at canopy tops.
ivar4 tree diameter
ifile4 interactive input (*.inp for rotation simulations)
idescr4 diameter at breast height in centimetres
isensitiv4 Sensitive
isensdescr4 Comparisons are available for Scots pine, Norway spruce and birch sp. for a variety of stem diameters on podzolic soil(see Peltola et al 1996b,e).
ivar5 stand density
ifile5 interactive input (*.inp for rotation simulations)
idescr5 stand density in trees per hectare
isensitiv5 Sensitive
isensdescr5 not as sensitive at stand edge as within the stand comparisons are available for Scots pine, Norway spruce and birch sp. for a variety of stem diameters on podzolic soil (see Peltola et al. 1996b, e).
ivar6 distance from stand edge
ifile6 interactive input
idescr6 distance from stand edge measured in tree heights ??
isensitiv6 Very Sensitive
isensdescr6 Comparisons are available for Scots pine, Norway spruce and birch sp. for a variety of tree heights and stem diameters for various distances from stand edge on podzolic soil(see Peltola et al 1996b,e).
ivar7 Crown streamlining
ifile7 interactive input
idescr7 The crown area is assumed to streamline as a function of windspeed, i.e. the reduction of crown area being 20% for windspeeds of less than 10m/s and 60% for windspeeds of more than 20m/s, the value of streamline between these two points being interpolated (Raymer 1962, Walshe and Fraser 1963, see Peltola and Kellomaki, 1993). However, if snow loading exists the streamlining should not be used. Default: with leaves - model calculates it as a function of windspeed)
isensitiv7 Very Sensitive
isensdescr7 Computations available at the moment for Scots pine (see Gardiner and Peltola, 1996b).
ivar8 snow load
ifile8 interactive input
idescr8 the snowload (kg/m2) is assumed to correspond to snowfall (mm) accumulated in the crownbased on the projected corwn area against ground surface (e.g. Petty and Worrel, 1981).
isensitiv8 Not Very Sensitive
isensdescr8 Comparisons are available for Scots pine, Norway spruce and birch sp. for a variety of tree heights and stem diameters on podzolic soil(see Peltola et al 1996b,e). However, because no streamlining of crown should be expected due to snow loading, the overall effect of snow loading on critical windspeeds is much greater than that only due to change in snow loading.
ivar9 simulation without leaves
ifile9 interactive input
idescr9 If the tree is simulated without leaves, the projected crownarea is expected to be only 20% of that with leaves based on Halddin (1985). Respectively the leafless crown mass ratio is assumed to equal 68% of that with leaves based on Malkonen (1977). This alternative will be valid especially for Birch sp. (from late autumn up to early spring).
isensitiv9 Sensitive
isensdescr9 Some comparisons are available for Birch sp.
cpar1 air density (p)
cval1 1.2226
cfile1
cdescr1 One of 4 aerodynamic constants (Gardiner and Peltola, 1996)
cpar2 von Karman's constant (k)
cval2 0.41
cfile2
cdescr2 One of 4 aerodynamic constants (Gardiner and Peltola, 1996)
cpar3 zero plane displacement (d/h)
cval3 0.0
cfile3
cdescr3 one of 4 aerodynamic constants (Gardiner and Peltola, 1996)
cpar4 roughness length parameter (Zo/h)
cval4 0.06
cfile4
cdescr4 one of four aerodynamic constants (Gardiner and Peltola, 1996)
cpar5 drag coefficient (Cd)
cval5 Scots Pine 0.29, Norway spruce 0.35, Birch sp. 0.29 (using Spine)
cfile5 *1.par (spine1.par, etc)
cdescr5 Tree species dependent constant (Gardiner and Peltola 1996)
cpar6 Green density of stem
cval6 Scots pine 850, Norway spruce 800, Birch sp. 900
cfile6 *1.par (spine1.par, etc)
cdescr6 Tree species dependent constant (Gardiner and Peltola 1996)
cpar7 green density of roots
cval7 1000
cfile7 *1.par (e.g spine1.par, etc.)
cdescr7 Tree species dependent constant (Gardiner and Peltola 1996), same value used for all species.
cpar8 basic density of roots
cval8 Scots pine 473, Norway spruce 452, Birch sp. 445
cfile8 *1.par (e.g. spine1.par)
cdescr8 Tree species dependent constant (Gardiner and Peltola 1996)
cpar9 conversion of dbh to stump diameter
cval9 1.33
cfile9 *1.par (e.g. spine1.par)
cdescr9 Tree species dependent constant (Gardiner and Peltola 1996). The same value is used for all species.
cpar10 crown ratio
cval10 scots pine 0.42, Norway spruce 0.76, Birch sp. 0.50
cfile10 *1.par (e.g. spine1.par)
cdescr10 Tree species dependent constant (Gardiner and Peltola 1996)
cpar11 crown stem mass ratio
cval11 Scots pine 0.30, Norway spruce 0.50, Birch sp. 0.30
cfile11 *1.par (e.g. Spine1.par etc)
cdescr11 Tree species dependent constant (Gardiner and Peltola 1996)
cpar12 crown centre point
cval12 Pine 0.50, Spruce 0.70, Birch 0.50
cfile12 *1.par (e.g. spine1.par)
cdescr12 Tree species dependent constant (Gardiner and Peltola 1996)
cpar13 leafless crown area ratio
cval13 Birch sp. 0.20
cfile13 *1.par (e.g. spine1.par)
cdescr13 Tree species dependent constant (Gardiner and Peltola 1996)
cpar14 Soil density (fresh)
cval14 1500
cfile14 *.spr
cdescr14 Tree species dependent constant (Gardiner and Peltola 1996)
cpar15 RSmean
cval15 0.21
cfile15 *1.par (e.g. spine1.par)
cdescr15 Mean depth of the soil root plate anchorage of total root depth. Tree species dependent constant (Gardiner and Peltola 1996) The same value is used for all species.
cpar16 Arsw
cval16 Scots pine 0.30, Norway spruce 0.20, Birch sp. 0.30
cfile16 *1.par (e.g. spine1.par)
cdescr16 proportion of the root-soil plate weight of the total anchorage moment Tree species dependent constant (Gardiner and Peltola 1996)
cpar17 Modulus of Rupture (MOR)
cval17 Scots pine 39.1, Norway spruce 30.6, Birch sp. 53.6
cfile17 *1.par (e.g. spine1.par)
cdescr17 Modulus of Rupture Tree species dependent constant (Gardiner and Peltola 1996)
cpar18 Modulus of Elasticity (MOE)
cval18 Scots pine 7000, Norway spruce 6300, Birch sp. 9900
cfile18 *1.par (e.g. spine1.par)
cdescr18 Tree species dependent constant (Gardiner and Peltola 1996)
cpar19 maximum depth of roots
cval19 16 2.4 -0.023 for Scots pine
cfile19
cdescr19
cpar20 longest root
cval20 1.0
cfile20
cdescr20
cpar21 dry mass of roots
cval20 -4.9, 0.044
cfile20
cdescr20
cpar22 longest branch
cval20 1.0 0.6 0.094
cfile20
cdescr20
cpar23 taper curve parameter
cval20 2.1288 -0.63157 -1.6082 2.4886 -2.4147 2.3619 -1.7539 1.0817
cfile20
cdescr20
Parameter Constants Summary Pine Constants
1000 # green density of roots (kg/m**3)
473# basic density of roots (kg/m**3)
0.21# RSmean (m)
0.30#Arsw
1.33#conversion of dbh to stump diameter
39.1#modulus of rupture MOR (MPa)
7000.0#modulus of elasticity, E (MPa)
0.29#drag coefficient, Cd (dimensionless)
850#gree density of stem (kg/m**3)
0.0#zero plane displacement d/h
0.06#roughness length Zo/H
0.42#crown ratio
0.30#crown stem mass ratio
0.50#crown center point
1.0#leafless crown area ratio
1.0#leafless crown mass ratio

Spruce Constants
1000 # green density of roots (kg/m**3)
452# basic density of roots (kg/m**3)
0.21# RSmean (m)
0.20#Arsw
1.33#conversion of dbh to stump diameter
30.6#modulus of rupture MOR (MPa)
6300.0#modulus of elasticity, E (MPa)
0.35#drag coefficient, Cd (dimensionless)
800#gree density of stem (kg/m**3)
0.0#zero plane displacement d/h
0.06#roughness length Zo/H
0.76#crown ratio
0.50#crown stem mass ratio
0.70#crown center point
1.0#leafless crown area ratio
1.0#leafless crown mass ratio

Birch constants
1000 # green density of roots (kg/m**3)
445# basic density of roots (kg/m**3)
0.21# RSmean (m)
0.30#Arsw
1.33#conversion of dbh to stump diameter
53.6#modulus of rupture MOR (MPa)
9900.0#modulus of elasticity, E (MPa)
0.29#drag coefficient, Cd (dimensionless)
900#gree density of stem (kg/m**3)
0.0#zero plane displacement d/h
0.06#roughness length Zo/H
0.50#crown ratio
0.30#crown stem mass ratio
0.50#crown center point
0.2#leafless crown area ratio
0.68#leafless crown mass ratio

pine constants
1#tree species
16 2.4 -0.023#maximum depth of roots
1.0#longest root
-4.9 0.044#dry mass of roots
1.0 0.6 0.094#longest branch
2.1288 -0.63157 -1.6082 2.4886 -2.4147 2.3619 -1.7539 1.0817

spruce constants
2#tree species
15.6 1.17 0#maximum depth of roots
1.0#longest root
-7.1 0.060#dry mass of roots
1.0 1.2 0.063#longest branch
2.3366 -3.2684 3.6513 -2.2608 0.0 2.1501 -2.7412 1.8876#taper curve par

birch constants
3#tree species
16 2.4 -0.023#maximum depth of roots
1.0#longest root
-4.9 0.044#dry mass of roots
1.0 0.6 0.094#longest branch
0.93838 4.1060 -7.8517 7.8993 -7.5018 6.3863 -4.3918 2.1604#taper curve par

Podzol.spr
1 1500# green density of soil (kg/m**3)

ovar1 critical wind speed (uproot)
ofile1 6.dat
odescr1 Critical wind speed required to uproot the tree in metres per second. filename 6.dat contains all of the model output parameters and a summary of the key input parameters.
ovar2 critical wind speed (stem breakage)
ofile2 6.dat
odescr2 Critical wind speed required to break the tree stem in metres per second filename 6.dat contains all of the model output parameters and a summary of the key input parameters.
ovar3 Turning moment by wind(uproot)
ofile3 6.dat
odescr3 Critical turning moment produced by wind speed required to uproot the tree in Newton Metres (Nm) filename 6.dat contains all of the model output parameters and a summary of the key input parameters.
ovar4 diameter at breast height (dbh)
ofile4 6.dat
odescr4 Critical turning modment produced by wind speed required to break the tree stem (Nm) filename 6.dat contains all of the model output parameters and a summary of the key input parameters.
ovar5 Turning moment by weight (uproot)
ofile5 6.dat
odescr5 Critical turning moment produced by tree weight (Nm) filename 6.dat contains all of the model output parameters and a summary of the key input parameters.
ovar6 Turning moment by weight (stem breakage)
ofile6 6.dat
odescr6 Critical turning moment produced by tree weight(Nm)
ovar7 Total turning moment (uproot)
ofile7 6.dat
odescr7 Total turning moment required to uproot the tree (Nm)
ovar8 Turning moment required to break the stem of the tree
ofile8 6.dat
odescr8 Total turning moment required to break the stem of the tree.
ovar9 Snow load
ofile9 6.dat
odescr9 kg/tree
ovar10 Gust factor
ofile10 6.dat
stat_meth Tree stem weight calculation is based on empirical relationships presented
by Laasasenaho (1982) as a function of tree species and tree height and
breast height diameter, and on green density of stem wood (e.g. Tamminen
1962). The canopy width, which is needed for calculation of the crown
projected area against wind as well as snow load accumulation on the
crown is also based on empirical relationship calculated by Hakkila
(1971) between the longest branch in the crown and breast height diameter
of the tree. Also rooting characteristics (root-soil plate width and depth)
as a function of stump diameter (and respectively dbh) are based on empirical relationship presented by Hakkila (1972). However, for Norway spruce, the
equation for depth of the root-soil plate has been modified using Finnish
tree pulling data; and thus having 1.30 as a multiplyer for Hakkila's (1972)
relationship, which does not take into account roots having diameter less
than 5 cm (this is a problem especially for Norway spruce and birch sp).
Respectively, based on Finnish tree pullings, Hakkila's (1972) equation
for Scots pine's rooting depth is used also for Birch sp. (see in details
Peltola et al. 1996e, Gardiner and Peltola 1996).

HWIND uses also existing empirical relationships derived by Gardiner and
Stacey (1996) from wind tunnel studies to calculate the gust factor, which
relates mean and extreme wind loading to distance from stand edge, stand
density and tree height. (see in details Peltola et al. 1996e, Gardiner
and Peltola 1996).

mech_meth There are mechanistic relationships used to calculate the mean wind loading
and gravity based loading on the tree based on tree height, dbh, stand
density, canopy depth and width. This involves calculating the mean wind
loading on the tree (e.g. Oliver and Mayhead 1974) and the force due to
gravity (caused by stem, crown and snow weight) at each height in the
canopy (e.g. Grace 1977, Jones 1983) using a predicted wind profile at
stand edge and the vertical distribution of stem, crown and snow weights
(Peltola and Kellomki 1993, see Peltola et al. 1996e, Gardiner and Peltola
1996).

The crown area is also assumed to streamline as a function of
windspeed, i.e. the reduction of crown area being 20% for windspeeds of
less than 10 m/s and 60% for windspeeds of more than 20 m/s, the value of
streamline between these two points being interpolated (Raymer 1962,
Walshe and Fraser 1963, see Peltola and Kellomaki 1993)

To calculate the resistance to uprooting model uses a prediction of
root-soil plate mass to derive a resistive moment (Coutts 1986, see
Peltola and Kellomki 1993).

The prediction of stem breakage is based on engineering principles and
relies on values of Modulus of Rupture determined for different timbers
(see Lavers 1969, Peltola and Kellomki 1993)

log_meth
scope
other The empirical relationships used for various tree characteristics are
based currently on data of Scots pine, Norway spruce and Birch sp growing
on podzolic soil in Finland. Trees growing in other countries may have
different relationships for various tree characteristics (e.g. due to
different weather and soil conditions) and also different relationships
between resistance to uprooting (e.g. different rooting characteristics
even in same soil type) and different MOR values (depending e.g. on wood
density). To date, the sensitivity tests have been conducted for
HWIND-model to determine critical parameters involved and the reliability
that can be placed on the critical windspeed predictions (see Peltola
et al. 1996e, Gardiner and Peltola 1996). More information will be added
in the future, i.e. another tree species and soil types.

This model is based on the preliminary mechanistic wind damage model
already developed for Scots pine along the stand edge by Peltola and Kellomaki 1993

Gardiner, B.A. and Peltola, H. 1997 The development and testing
of models for predicting the critical wind speed to damage
trees. To be submitted to Ecological Modelling

Peltola, H. and Kellomaki, S. 1993 A mechanistic model for
calculating windthrow and stem breakage of scots pines at stand
edge. Silva Fennica 27 (2):99-11

Peltola, H., Nykanen, M-L. and Kellomaki, S. 1997a. Model
computations on the critical combination of snow loading and
windspeed for snow damage of Scots pine, Norway spruce
and birch sp. at stand edge. Submitted to Forest Ecology and
management.

Peltola, H., Kellomaki, S. and Nykanen, M-L. 1997b Model computations on the
critical windspeed for wind damage of Scots pine, Norway
spruce and birch sp along the margins of clear-cut areas for
various distances to stand edge. Manuscript in preparation.

contact Heli Peltola
University of Joensuu
Email: heli.peltola@forest.joensuu.fi