Tegnhammar_1992_adjusted_SI_by_stand_variables: Calculate Tegnhammar's adjusted Site Index from stand...

In Silviculturalist/forester: Forest Science and Forestry

Calculate Tegnhammar's adjusted Site Index from stand variables

Description

Stand variables were regressed to estimate Tegnhammar's adjusted site index SIHjust.

SIHjust corrects height development functions by Hägglund (1972, 1973) for the 'apparent' trend, an age bias, wherein the functions would indicate higher SIH in young forests as compared to older forests, even if the site index is the same.

Tegnhammar's dissertation investigated a trend in the site index curves for spruce in Sweden, possibly caused by stem sectioning of elderly trees that were suppressed in their youth; young planted forests are composed of better plant material; young forests have recieved a better start as a result of methods introduced during the 1920-1950's; older stands which were not suitable for SI estimation by height were measured in such a manner nonetheless; The risk of including hidden top breakages is larger for older trees; & the productivity has increased with time due to nitrogen deposition - younger trees have been affected for a longer period of their lifetime.

Usage

Tegnhammar_1992_adjusted_SI_by_stand_variables(
  latitude,
  longitude,
  altitude,
  vegetation,
  ground_layer,
  aspect_main,
  soil_moisture,
  soil_depth,
  soil_texture,
  humidity,
  ditched,
  lateral_water,
  peat_humification = "Medium",
  epsg = "EPSG:4326"
)

Arguments

latitude	decimal degrees. By default WGS84, see parameter 'epsg'.
longitude	decimal degrees. By default WGS84, see parameter 'epsg'.
altitude	metres above sea level
vegetation	Vegetation type according to follows Swedish National forest inventory FALTSKIKT: Code Vegetation 1 Rich-herb without shrubs 2 Rich-herb with shrubs/bilberry 3 Rich-herb with shrubs/lingonberry 4 Low-herb without shrubs 5 Low-herb with shrubs/bilberry 6 Low-herb with shrubs/lingonberry 7 No field layer 8 Broadleaved grass 9 Thinleaved grass 10 Sedge, high 11 Sedge, low 12 Horsetail, Equisetum ssp. 13 Bilberry 14 Lingonberry 15 Crowberry 16 Poor shrub 17 Lichen, frequent occurrence 18 Lichen, dominating
ground_layer	According to Swedish NFI, roughly: Code Ground layer 1 Lichen type (>50% of existing ground layer) 2 Lichen-rich bogmoss type (>25% lichen + >50% Sphagnum of existing ground layer) 3 Lichen rich (>25% lichen, & not >50% Sphagnum of existing ground layer) 4 Bogmoss type (Sphagnum > 50% of existing ground layer) 5 Swamp moss type (Polytrichum commune, P. gracile, P. strictum, Sphagnum, Depranocladus, Scorpidium, Paludella, Calliergon, Tomentypnum, Campylium.) 6 Fresh moss type (Hylocomium splendens, Ptilium crista-castrensis, Dicranum ssp.)
aspect_main	If more than 1:20 (5%), one of the following, otherwise 0. 1 North 2 North-East 3 East 4 South-East 5 South 6 South-West 7 West 8 North-West
soil_moisture	Type 1="Dry/torr",2="Mesic/frisk",3="Mesic-moist/frisk-fuktig",4="Moist/fuktig",5="Wet/Blöt"
soil_depth	Type 1="Deep, >70cm",2="Rather shallow, 20-70cm",3="Shallow <20cm", 4= "Varying".
soil_texture	Code Short 1 Boulder 2 Gravel 3 Coarse sand 4 Medium sand 5 Fine sand 6 Coarse silt 7 Fine silt 8 Clay 9 Peat
humidity	Humidity during the vegetation period. mm. If not provided, will be calculated from latitude, longitude with [forester::Eriksson_1986_humidity()] from Eriksson, B. (1986) fig.34. Available online (26/10/2021) https://www.smhi.se/polopoly_fs/1.166663!/RMK_46%20Nederbörds-%20och%20humiditetsklimat%20i%20Sverige%20under%20vegetationsperioden..pdf
ditched	TRUE/FALSE if affected by ditching.
lateral_water	Type 1="Missing",Type 2="Seldom",3="shorter periods",4="longer periods", 5="slope".
peat_humification	"Low", if organic remnants clearly visible: squeezing sample gives somewhat cloudy water; "Medium", if with some difficulty organic remnants can be distinguished, if sample is squeezed the water is cloudy; or "High", if no organic remnants can be distinguished. Water and humus cannot be separated by squeezing. Humus is porridge-like.
epsg	Default is WGS84 'EPSG:4326'. For SWEREF-99TM - 'EPSG:3006'.

Details

N.B. Not for use on Öland / Gotland, or soil moisture types 'Wet'/'Blöt'. No underlying material for these sites. The material was too small to determine the exact size of the error, but indicate that estimates are much too high for these sites.

s = 30.71662 R^2 = 0.7045

Value

Tegnhammars adjusted SI, meters.

Source

Tegnhammar, L. (1992) "Om skattningen av ståndortsindex för gran", eng:"On the estimation of site index for Norway spruce". Report 53. Dept. of Forest Survey. Swedish University of Agricultural Sciences. Umeå. p.80. ISSN 0348-0496

Silviculturalist/forester documentation built on April 20, 2024, 2:13 p.m.