Species-specific, pan-European diameter increment models based on data of 2.3 million trees

Schelhaas, Mart-Jan; Hengeveld, Geerten M; Heidema, Nanny; Thürig, Esther; Rohner, Brigitte; Vacchiano, Giorgio; Vayreda, Jordi; Redmond, John; Socha, Jarosław; Fridman, Jonas; Tomter, Stein; Polley, Heino; Barreiro, Susana; Nabuurs, Gert-Jan

doi:10.1186/s40663-018-0133-3

Forest Ecosystems

Table 5 List of potential explanatory variables included. When two variables are correlated, the one with the highest score is discarded

From: Species-specific, pan-European diameter increment models based on data of 2.3 million trees

Type	Source / time span / resolution	Variable name	Explanation	Unit	Preference score
Forest structure	NFI / at first year of inventory	F-BA	basal area of the plot	m2/ha
		F-lnBA	Ln(F-BA)	–
		F-rDiffDq	proxy for tree social position	–
Weather	Agri4Cast / during observed growth period / 25 km	W-MaT	mean annual temperature	°C	111,111
		W-SDmT	standard deviation of monthly mean temperature	°C	122,111
		W-MAXmT	maximum monthly temperature	°C	123,111
		W-MINmT	minimum monthly temperature	°C	123,121
		W-MaDR	mean diurnal range	°C	112,141
		W-aTR	annual temperature range	°C	112,121
		W-ISO	isothermality	index	112,131
		W-DD0	degree days above 0 degrees Celsius	°C	111,511
		W-DD5	degree days above 5 degrees Celsius	°C	111,521
		W-DD10	degree days above 10 degrees Celsius	°C	111,531
		W-TaP	total annual precipitation	mm	111,211
		W-SDmP	standard deviation of monthly precipitation	mm	122,211
		W-MAXmP	maximum monthly precipitation	mm	123,211
		W-MINmP	minimum monthly precipitation	mm	123,221
		W-TaPET	total annual potential evapotranspiration	mm	111,411
		W-SDmPET	standard deviation of monthly PET	mm	122,411
		W-MAXmPET	maximum monthly PET	mm	123,411
		W-MINmPET	minimum monthly PET	mm	123,421
		W-TaR	total annual radiation	GJ∙m⁻²	111,311
		W-SDmR	standard deviation of monthly radiation	GJ∙m⁻²	122,311
		W-MAXmR	maximum monthly radiation	GJ∙m⁻²	123,311
		W-MINmR	minimum monthly radiation	GJ∙m⁻²	123,321
		W-MwaqT	mean warmest quarter temperature	°C	131,111
		W-McoqT	mean coldest quarter temperature	°C	131,131
		W-MweqT	mean wettest quarter temperature	°C	131,121
		W-MdrqT	mean driest quarter temperature	°C	131,141
		W-MwaqP	mean warmest quarter precipitation	mm	131,211
		W-McoqP	mean coldest quarter precipitation	mm	131,231
		W-MweqP	mean wettest quarter precipitation	mm	131,221
		W-MdrqP	mean driest quarter precipitation	mm	131,241
		W-MwaqR	mean warmest quarter radiation	GJ∙m⁻²	131,311
		W-McoqR	mean coldest quarter radiation	GJ∙m⁻²	131,331
		W-MweqR	mean wettest quarter radiation	GJ∙m⁻²	131,321
		W-MdrqR	mean driest quarter radiation	GJ∙m⁻²	131,341
		W-MwaqPET	mean warmest quarter PET	mm	131,411
		W-McoqPET	mean coldest quarter PET	mm	131,431
		W-MweqPET	mean wettest quarter PET	mm	131,421
		W-MdrqPET	mean driest quarter PET	mm	131,441
		W-ARi	aridity index	index	114,411
		W-ThHUi	thorntwaite 1948 humidity index	index	114,421
		W-ThARi	thorntwaite 1948 aridity index	index	114,431
Deposition	EMEP / average 1990–2010 / 50 km	D-DepOxN	deposition of oxidised nitrogen	mg(N)∙m⁻²	411,411
		D-DepOxS	deposition of oxidised sulphur	mg(S)∙m⁻²	412,411
		D-DepRedN	deposition of reduced nitrogen	mg(N)∙m⁻²	411,421
Soil	SoilGrids / NA / 1 km	S-BDRICM	depth to bedrock (R horizon) up to maximum 240 cm	cm	311,411
		S-BLD	bulk density of the fine earth fraction	kg∙m⁻³	311,321
		S-CEC	cation exchange capacity	cmol∙kg⁻¹	311,211
		S-CLYPPT	clay content mass fraction	%	311,111
		S-CRFVOL	coarse fragments (> 2 mm fraction) volumetric	%	311,331
		S-ORCDRC	soil organic carbon	%	311,311
		S-PHIHOX	pH in H₂O × 10		311,221
		S-SLTPPT	silt content mass fraction	%	311,121
		S-SNDPPT	sand content mass fraction	%	311,131
	European Soil Data Centre	S-comp	natural susceptibility to soil compaction	6 categories	311,341
	GENS / average 1950–2000 / 1 km	C-wemP (bio13)	precipitation of wettest month	mm	221,223
		C-drmP (bio14)	precipitation of driest month	mm	221,243
		C-MaT (var1)	annual mean temperature	K	211,112
		C-MaDR (var2)	mean diurnal range	K	212,142
		C-ISO (var3)	isothermality	K	212,132
		C-seaT (var4)	temperature seasonality	K	212,112
		C-MAXwamT (var5)	maximum temperature of the warmest month	K	223,113
		C-MINcomT (var6)	minimum temperature of the coldest month	K	223,133
		C-aTR (var7)	annual temperature range	K	212,123
		C-MweqT (var8)	mean temperature of wettest quarter	K	231,123
		C-MdrqT (var9)	mean temperature of driest quarter	K	231,143
		C-MwaqT (var10)	mean temperature of warmest quarter	K	231,112
		C-McoqT (var11)	mean temperature of coldest quarter	K	231,132
		C-DD0 (var12)	degree days above 0 degrees Celsius	°C	211,512
		C-DD5 (var13)	degree days above 5 degrees Celsius	°C	211,522
		C-McomT (var14)	mean temperature of the coldest month	K	221,132
		C-MwamT (var15)	mean temperature of the warmest month	K	221,112
		C-MAXcomT (var16)	maximum temperature of the coldest month	K	223,112
		C-MINwamT (var17)	minimum temperature of the warmest month	K	223,122
		C-NM10 (var18)	number of months with mean temperature > 10		221,512
		C-Ti (var19)	thermicity index		214,112
		C-TaP (var20)	total annual precipitation	mm	211,212
		C-MwemP (var21)	precipitation of the wettest month	mm	221,222
		C-MdrmP (var22)	precipitation of the driest month	mm	221,242
		C-seaP (var23)	precipitation seasonality	mm	212,212
		C-TweqP (var24)	precipitation of the wettest quarter	mm	231,222
		C-TdrqP (var25)	precipitation of the driest quarter	mm	231,242
		C-TwaqP (var26)	precipitation of the warmest quarter	mm	231,212
		C-TcoqP (var27)	precipitation of the coldest quarter	mm	231,232
		C-MINjjaP (var28)	minimum June July August precipitation	mm	233,221
		C-MAXjjaP (var29)	maximum June July August precipitation	mm	233,211
		C-MINdjbP (var30)	min Dec Jan Feb precipitation	mm	233,222
		C-MAXdjfP (var31)	max Dec Jan Feb precipitation	mm	233,212
		C-Tmm0P (var32)	total precipitation for months with mean monthly temperature above 0	mm	211,612
		C-TaAET (var33)	annual actual evapotranspiration	mm	211,442
		C-TaPET (var34)	annual potential evapotranspiration	mm	211,432
		C-coefmoist (var35)	coefficient of annual moisture availability		214,442
		C-Ari (var36)	aridity index		214,412
		C-seaPET (var37)	PET seasonality		212,412
		C-ThHUi (var38)	thorntwaite 1948 humidity index		214,422
		C-ThARi (var39)	thorntwaite 1948 aridity index		214,432
		C-EmPQ (var40)	embergers pluviothermic quotient		214,452
		C-TaR (var41)	total annual radiation		211,312

Each explanatory variable X_i was given a score on six different levels (S_AX_i–S_FX_i). The final score S was calculated as:
\( {\mathit{\mathsf{S}\mathsf{X}}}_{\mathit{\mathsf{i}}}={\mathit{\mathsf{S}}}_{\mathit{\mathsf{A}}}{\mathit{\mathsf{X}}}_{\mathit{\mathsf{i}}}\times \mathsf{10}\mathsf{0}\mathsf{0}\mathsf{0}\mathsf{0}+{\mathit{\mathsf{S}}}_{\mathit{\mathsf{B}}}{\mathit{\mathsf{X}}}_{\mathit{\mathsf{i}}}\times \mathsf{10}\mathsf{0}\mathsf{0}\mathsf{0}+{\mathit{\mathsf{S}}}_{\mathit{\mathsf{C}}}{\mathit{\mathsf{X}}}_{\mathit{\mathsf{i}}}\times \mathsf{10}\mathsf{0}\mathsf{0}+{\mathit{\mathsf{S}}}_{\mathit{\mathsf{D}}}{\mathit{\mathsf{X}}}_{\mathit{\mathsf{i}}}\times \mathsf{10}\mathsf{0}+{\mathit{\mathsf{S}}}_{\mathit{\mathsf{E}}}{\mathit{\mathsf{X}}}_{\mathit{\mathsf{i}}}\times \mathsf{10}+{\mathit{\mathsf{S}}}_{\mathit{\mathsf{F}}}{\mathit{\mathsf{X}}}_{\mathit{\mathsf{i}}} \)
where S₁ is the score at level A, relating to the variable group (weather, climate, soil, nutrient deposition), S₂ the score at level B, relating to the aggregation level of weather-and climate related variables, etc. Scores per level are listed in Table 6 and final score per variable is included in Table 5

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