Silva Fennica

Fig. 1. Geographical layout of the forest districts where the test plots were located (Lachowicz 2015).

Table 1. The basic density of birch wood [kg m^–3] with respect to location and tree age.
Location – Forest district	Tree age	Number of samples (N)	Average	Minimum	Maximum
1 Płońsk FBF	30	80	516	417	616
	50	89	544	438	637
	70	96	550	482	615
	Total	265	538	417	637
2 Sokołów FBF	30	93	545	450	647
	50	96	557	461	620
	70	96	544	445	616
	Total	285	549	445	647
3 Biała Podlaska FBF	30	87	511	433	577
	50	96	548	470	652
	70	90	547	489	607
	Total	273	536	433	652
4 Płaska FBF	30	93	517	447	585
	50	96	501	435	592
	70	96	518	450	577
	Total	285	512	435	592
5 Giżycko FBF	30	96	520	443	574
	50	55	514	443	639
	70	96	548	476	617
	Total	247	530	443	639
6 Giżycko FMBF	30	96	527	442	636
	50	96	555	456	630
	70	96	564	510	629
	Total	288	548	442	636
7 Górowo Iławeckie FBF	30	96	506	441	567
	50	96	523	414	609
	70	94	545	460	624
	Total	286	525	414	624
8 Elbląg FBF	30	96	518	413	616
	50	96	520	475	585
	70	96	527	439	625
	Total	288	522	413	625
9 Mircze FBF	30	96	527	457	585
	50	96	542	444	617
	70	96	532	487	625
	Total	288	534	444	625
10 Bobolice FBF	30	95	507	407	569
	50	96	518	456	590
	70	96	533	490	586
	Total	287	519	407	590
11 Bobolice FMBF	30	90	519	459	576
	50	95	495	400	574
	70	95	532	432	593
	Total	280	515	400	593
12 Łobez FBF	30	87	477	404	562
	50	96	547	462	608
	70	96	561	504	634
	Total	279	530	404	634
13 Łobez FMBF	30	91	487	425	552
	50	96	511	469	565
	70	96	540	499	592
	Total	283	513	425	592
14 Lipinki FBF	30	89	501	427	565
	50	96	526	469	608
	70	96	536	490	611
	Total	281	521	427	611
15 Lipinki FMBF	30	95	501	405	558
	50	96	534	450	596
	70	96	551	489	603
	Total	287	528	405	603
16 Rudziniec FBF	30	96	500	447	601
	50	96	526	435	602
	70	96	537	504	589
	Total	288	521	435	602
17 Rudziniec FMBF	30	95	537	450	618
	50	96	526	423	606
	70	96	554	491	642
	Total	287	539	423	642
FBF		3352	528	404	652
FMBF		1425	529	400	642
Age 30		1571	513	404	647
Age 50		1583	529	400	652
Age 70		1623	542	432	642
Total		4777	528	400	652
FBF – fresh broadleaved forest FMBF – fresh mixed broadleaved forest

Table 2. Influence of location and tree age and the interaction of those properties on the basic density of wood (two-factor analysis of variance).
Source of variance	F empirical	p-value
Intercept	1148482	< 0.0001 *
Location	31	< 0.0001 *
Age	301	< 0.0001 *
Location-Age (interaction)	16	< 0.0001 *
* statistically significant at the 0.05 level

Table 3. Groups of homogeneous locations in terms of the mean values of basic density of wood.
Location	Mean	1	2	3	4	5	6
Płaska - FBF	512	****
Łobez - FMBF	513	****
Bobolice - FMBF	515	****	****
Bobolice - FBF	519	****	****	****
Rudziniec - FBF	521	****	****	****
Lipinki - FBF	521	****	****	****
Elbląg - FBF	522	****	****	****
Górowo Iławeckie - FBF	525		****	****	****
Lipinki - FMBF	528			****	****	****
Giżycko - FBF	530			****	****	****
Łobez - FBF	530			****	****	****
Mircze - FBF	534				****	****
Biała Podlaska - FBF	536					****
Płońsk - FBF	538					****	****
Rudziniec - FMBF	539					****	****
Giżycko - FMBF	548						****
Sokołów - FBF	549						****
FBF – fresh broadleaved forest FMBF – fresh mixed broadleaved forest

Fig. 2. Average values of basic density of wood and their standard errors, with respect to location and tree age.

Table 4. Influence of tree age and thickness class and the interaction of those properties on the basic density of wood (two-factor analysis of variance).
Source of variance	F empirical	p-value
Intercept	980706.861	< 0.0001 *
Age	252.457743	< 0.0001 *
Thickness class	12.4152923	< 0.0001 *
Age-Thickness class (interaction)	16.426154	< 0.0001 *
* statistically significant at the 0.05 level

Table 5. Properties of the basic density of wood for different tree age and thickness classes.
Age	Thickness class	Mean	Number of samples (N)
30	1	512	484
	2	513	544
	3	514	543
50	1	531	526
	2	521	523
	3	534	534
70	1	551	537
	2	541	544
	3	535	542
Total		528	4777

Table 6. Influence of location and the forest habitat type and the interaction of those properties on the basic density of wood (two-factor analysis of variance).
Source of variance	F empirical	p-value
Intercept	604983.0	< 0.0001 *
Location	30.0	< 0.0001 *
FHT	11.8	0.0006 *
Location-FHT (interaction)	24.6	< 0.0001 *
* statistically significant at the 0.05 level FHT – forest habitat type

Fig. 3. Average values of basic density of wood from selected locations in different forest habitat types.