Silva Fennica

Fig. 1. Location of study area and study sites.

Table 1. Average characteristics of the investigated stands.
Site No.	Soil type	Forest site type	Composition of trees	No. of trees per hectare	Age, yr	Site quality index	Canopy cover	Height, m	Breast height diameter, cm	Density of understory
1	Haplic Podzol	Rhodococcum	100 Ps	149	180	IV	0.45	24	37	Low
2	Haplic Podzol	Cladonia	100 Ps	191	190	IV	0.54	24	36	Low
3	Haplic Podzol	Cladonia	100 Ps	98	200	IV	0.62	21	44	Low
4	Haplic Podzol	Cladonia	100 Ps	143	210	IV	0.60	23	38	Low
Ps = Pinus sylvestris

Fig. 2. Venn diagram showing the overlapping and individuality of vascular plant species at different sites.

Table 2. The results of multiple response permutation procedure (MRPP) tests for the comparison of species composition on different dunes.
Test pair	Site 1 vs. Site 2	Site 1 vs. Site 3	Site 1 vs. Site 4	Site 2 vs. Site 3	Site 2 vs. Site 4	Site 3 vs. Site 4
p-value	<0.001	<0.001	<0.001	0.002	<0.001	0.011
Bold values are significant after the Bonferroni correction

Fig. 3. Venn diagram showing the overlapping and individuality of vascular plant species at different locations on dunes.

Table 3. Vascular plant indicator species with indicator values (IV) for different zones (bottom, slope and top) on dunes according to the indicator species analysis (ISA).
	Bottom			Slope			Top
		IV	p-value		IV	p-value		IV	p-value
Site 1	Rubu ida	28	0.011	Empe nig	36	0.016	Call vul	32	0.05
	Oxal ace	25	0.041
	Mela pra	50	0.042
Site 2	Empe nig	53	0.0002				Hier umb	26	0.001
	Fest pol	50	0.0004				Call vul	50	0.001
	Conv maj	13	0.035				Mela pra	52	0.002
							Soli vir	26	0.002
							Fest rub	35	0.006
							Trie eur	21	0.021
Site 3	Vacc myr	73	0.0002	Trie eur	61	0.001	Fest rub	41	0.05
	Vacc vit	69	0.0002
	Ledu pal	43	0.012
Site 4	Vacc uli	38	0.012	Fest pol	48	0.025	Empe nig	52	0.002
Site 4							Call vul	59	0.008
Rubu ida = Rubus idaeus; Oxal ace = Oxalis acetosella; Mela pra = Melampyrum pratense; Empe nig = Empetrum nigrum; Fest pol = Festuca polesica; Conv maj = Convallaria majalis; Vacc myr = Vaccinium myrtillus; Vacc vit = Vaccinium vitis-idaea; Ledu pal = Ledum palustre; Vacc uli = Vaccinium uliginosum; Trie eur = Trientalis europaea; Call vul = Calluna vulgaris; Hier umb = Hieracium umbellatum; Soli vir = Solidago virgaurea; Fest rub = Festuca rubra

Table 4. Average values of soil and light characteristics from different sites and locations on the dunes. View in new window/tab.

Table 5. Significance (p-values, type 3 effects) of factors contributing to species richness and the coverage of vascular plants according to a linear mixed model.
Species richness of vascular plants	DF	F-value	p-value
Location on dune (zone)	215.97	15.43	<0.001
Aspect of the quadrat	7.87	16.67	<0.001
Absolute height	183.53	0.17	0.685^a
Cover of bryophyte and lichen layers	215.42	0.003	0.960^a
PAR	215.18	15.46	<0.001^a
VWC	216.36	26.54	<0.001
pH	216.54	10.70	0.001
N_total	215.46	29.22	<0.001^a
P	216.92	0.002	0.969
K	216.85	4.98	0.027
O horizon	215.50	1.97	0.162
Total cover of vascular plant species	DF	F-value	p-value
Location on dune	102.68	13.46	<0.001
Aspect of the quadrat	3.29	1.53	0.356
Absolute height	2.31	22.06	0.032
Cover of bryophyte and lichen layers	199.17	1.86	0.174^a
PAR	216.78	0.04	0.844
VWC	205.64	22.96	<0.001
pH	124.85	4.78	0.031^a
N_total	217.00	27.28	<0.001^a
P	32.27	0.12	0.727
K	139.17	24.43	<0.001
O horizon	174.46	6.61	0.011
^a – indicates a negative effect
PAR = below-canopy photosynthetically active radiation (μmol m^–2 s^–1); VWC = average soil volumetric water content (%); pH = average pH_H2O; O = soil litter horizon thickness (cm); N_total = nitrogen content (%); P = phosphorus content (mg kg^–1); K = potassium content (mg kg^–1)

Fig. 4. Non-metric multidimensional scaling (NMDS) ordination graph with fitted environmental variables. Arrows represent environmental variables that were most significantly (p ≤ 0.005) related to ordination. View larger in new window/tab.

Table 6. Relationships between species composition (non-metric multidimensional scaling (NMDS) ordination, Fig. 4) and environmental variables on dunes. Bold values are variables presented as arrows in Fig. 4.
Variable	r²	p-value	Level of significance
H_abs	0.2541	0.001	***
CC	0.2486	0.001	***
Cov_bryolich	0.2054	0.001	***
Site	0.2949	0.001	***
N_total	0.2259	0.002	**
Asp	0.1552	0.003	**
K	0.2067	0.004	**
P	0.1634	0.005	**
Mg	0.1826	0.007	**
VWC_aver	0.1553	0.008	**
pH	0.1248	0.022	*
Ca	0.1180	0.030	*
H_rel	0.0942	0.062	.
EC	0.0809	0.073	.
Degr	0.0622	0.158
Loc	0.0497	0.225
O	0.0150	0.655
A	0.0103	0.744
PAR	0.0026	0.914
Significance codes: 0 ‘*’ 0.001 ‘’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
H_abs = absolute height of the quadrat location (m); CC = average canopy cover; Cov_bryolich = total coverage of bryophytes and lichens (%); N_total = average total nitrogen content (%); Asp = aspect of the quadrat; K = average potassium content (mg kg^–1); P = average phosphorus content (mg kg^–1); Mg = average magnesium content (mg kg^–1); VWC_aver = average soil water content (%); pH = average soil pH_H2O; Ca = average soil calcium content (mg kg^–1); H_rel = relative height (m); EC = electrical conductivity (µS); Degr = degree of inclination or ascent; Loc = location on dune (bottom, slope, top); O = average litter horizon thickness (cm); A = average humus horizon thickness (cm); PAR = average photosynthetically active radiation (μmol m^–2 s^–1)