Table 2.

Tree characteristics of the studied clusters in 1997 and 2010, for small trees (trees <30 mm at DBH and higher than 1.3 m), large trees (trees >30 mm at DBH) and all trees (all trees higher than 1.3 m)

	Small trees					Large trees					All trees
	1997		2010			1997		2010			1997		2010
	Mean	SD	Mean	SD	p	Mean	SD	Mean	SD	p	Meana	SD	Meana	SD	ta	p
Mountain birch
Mean diam. (mm)	5.4	7.2	4.6	6.2	0.23	27.3	33.8	29.2	35.7	0.005	16.5	24.3	15.7	26.2	−0.45	0.66
No. of trunks (ha−1)	826.6	1695.5	804.3	1364.1	0.86	252.7	429.7	300.7	496.4	0.008	1079.2	1069.8	1105.0	1081.3	0.21	0.83
Basal area (m2 ha−1)	0.15	0.33	0.13	0.22	0.39	0.79	1.26	0.99	1.54	<0.001	0.94	0.93	1.12	1.10	2.98	0.004
TDW (kg ha−1)	544	1216	461	808	0.39	2741	4384	3452	5330	<0.001	3285	5216	3914	5968	2.92	0.005
Willow
Mean diam. (mm)	1.7	5.8	0.3	2.7	0.038	11.4	18.0	11.1	19.4	0.83	10.3	16.4	10.9	19.2	0.35	0.73
No. of trunks (ha−1)	13.8	49.7	0.9	7.2	0.047	9.0	22.5	7.9	26.7	0.55	22.7	23.0	8.9	9.0	−2.20	0.032
Basal area (m2 ha−1)	<0.01	0.02	<0.01	<0.01	0.09	0.01	0.04	0.01	0.05	0.82	0.02	0.02	0.01	0.01	−0.91	0.37
TDW (kg ha−1)	15	64	1	9	0.09	49	142	51	173	0.83	64	174	52	173	−0.94	0.35
Alder
Mean diam. (mm)	0.4	3.2	0.2	1.0	0.45	2.0	11.3	2.3	12.6	0.19	2.0	11.1	1.3	7.0	−1.43	0.16
No. of trunks (ha−1)	0.5	3.8	9.31	65.5	0.27	9.4	67.4	11.4	83.4	0.32	9.9	10.0	20.7	21.0	1.09	0.28
Basal area (m2 ha−1)	<0.01	<0.01	<0.01	<0.01	0.30	0.04	0.32	0.06	0.45	0.30	0.04	0.04	0.06	0.06	1.03	0.30
TDW (kg ha−1)	0.9	6.8	1.7	13.2	0.30	148.7	1104	208.0	1553	0.30	150	1111	210	1566	1.03	0.30
Rowan
Mean diam. (mm)	1.0	4.5	0	–	0.09	2.7	13.7	1.2	6.5	0.40	3.7	14.3	1.2	6.5	−1.41	0.16
No. of trunks (ha−1)	7.9	53.8	0	–	0.26	0.2	0.7	0.2	1.4	0.68	8.0	8.1	0.23	0.24	−1.16	0.25
Basal area (m2 ha−1)	<0.01	0.01	0	–	0.22	<0.01	<0.01	<0.01	<0.01	0.62	<0.01	<0.01	<0.01	<0.01	−1.56	0.12
TDW (kg ha−1)	7	43	0	–	0.22	2	10	1	6	0.64	8	44	1	6	−1.54	0.13
Pine
Mean diam. (mm)	0.4	2.88	0	–	0.32	0	–	0	–	–	0.4	2.8	0	0	−1.00	0.32
No. of trunks (ha−1)	0.5	3.8	0	–	0.32	0	–	0	–	–	0.5	0.5	0	0	−1.00	0.32
Basal area (m2 ha−1)	<0.01	<0.01	0	–	0.32	0	–	0	–	–	<0.01	<0.01	0	0	−1.00	0.32
TDW (kg ha−1)	<1	5	0	–	0.32	0	–	0	–	–	<1	5	0	0	−1.00	0.32
Other Tree species
Mean diam. (mm)	0.1	1.0	0	–	0.32	0	–	0	–	–	0.1	1.0	0	0	−1.00	0.32
No. of trunks (ha−1)	0.5	3.8	0	–	0.32	0	–	0	–	–	0.5	0.5	0	0	−1.00	0.32
Basal area (m2 ha−1)	<0.01	<0.01	0	–	0.32	0	–	0	–	–	<0.01	<0.01	0	0	−1.00	0.32
TDW (kg ha−1)	<0.1	0.7	0	–	0.32	0	–	0	–	–	<0.1	0.7	0	0	−1.00	0.32
All Trees
Mean diam. (mm)	5.9	7.4	4.7	6.2	0.050	26.6	32.2	29.0	33.8	0.006	14.8	20.5	15.7	22.6	0.66	0.51
No. of trunks (ha−1)	849.6	1702.9	814.5	1374.8	0.78	271.1	448.7	320.3	514.9	0.009	1120.8	1112.0	1134.8	1111.6	0.11	0.91
Basal area (m2 ha−1)	0.15	0.34	0.13	0.22	0.29	0.84	1.35	1.07	1.69	<0.001	1.00	1.00	1.19	1.18	2.84	0.006
TDW (kg ha−1)	568	1235.9	464	812.4	0.29	2940	4701.5	3712	5862.6	<0.001	3507	5520	4176	6476	2.78	0.007

Paired t-tests were based on all 61 clusters, df = 60. Bold figures denote significant changes in tree variables between 1997 and 2010

^aThe mean diameter for all trees was weighted as small and large trees, respectively, were measured on different plot size

Number of trunks is the mean number of trunks based on all clusters

Basal area is the mean basal area based on all clusters

TDW is Total dry weight (kg ha⁻¹) and corresponds to mean tree biomass per hectare