Soil–plant interactions in a pasture of the Italian Alps

Figures & data

Figure 1. Study area: (a) geographic position of the study area; (b) the doline; (c) the earth hummock vegetation; (d) locations of the sampling points.

Table 1. Investigated soil properties, environmental variables, vegetation, and their abbreviations.

Soil properties, environmental variables and vegetation	Unit	Abbreviation
Soil organic carbon content of the 0–10 cm mineral soil layer	%	SOC
Soil organic carbon stock of the 0–10 cm mineral soil layer	kg m^−2	SOCstock
C:N ratio of the 0–10 cm mineral soil layer		CN
pH in water of the 0–10 cm mineral soil layer		pHw
Available phosphorus content of the 0–10 cm mineral soil layer	mg kg^−1	avP
Bulk density of the 0–10 cm mineral soil layer	g cm^−3	BD
Soil porosity	%	totPor
Coarse sand content of the 0–10 cm mineral soil layer	g kg^−1	cSand
Silt content of the 0–10 cm mineral soil layer	g kg^−1
Clay content of the 0-10 cm mineral soil layer	g kg^−1
Water filled pore space at 0-8 cm depth	%	WFPS
Total, very fine and fine total root biomass	g dm^−3	totRoots, vfRoots, fRoots
Carbon and nitrogen content of fulvic acids	g kg^−1	CFA, NFA
Carbon and nitrogen content of humic acids	g kg^−1	CHA, NHA
Carbon and nitrogen content of humin	g kg^−1	CHUM, NHUM
Slope	%
Solar radiation	MJ m^−2 d^−1	Rad
Soil temperature at 5 cm depth	°C	T
Available water content	mm	AWC
Intensity of erosion		Eros
Rich pasture		RP
Earth hummocks		EH
Sesleria varia grassland		SV
Bentgrass		B
Nardus stricta pasture		N

Figure 2. Vegetation types of the investigated doline: (a) number of contacts; (b) number of species; and (c) aboveground biomass (2006–2018). SV: Sesleria varia grassland; RP: rich pasture; N: Nardus stricta pasture; EH: earth hummocks; B: bentgrass.

Table 2. Total root density (g dm⁻³) for each vegetation type in the three investigated layers.

	0–10 cm			10–20 cm			20–30 cm
Vegetation	N	Mean	Std. Err.	N	Mean	Std. Err.	N	Mean	Std. Err.
B - Bentgrass	9	5.17	0.80	3	1.56	1.26		-	-
RP - Rich pasture	10	5.35	0.70	4	0.99	0.60	4	0.93	0.30
SV - Sesleria varia grassland	5	8.16	1.97	3	1.56	1.26		-	-
EH - Earth hummock	4	8.04	2.17	4	3.83	1.42	4	1.46	0.30
N - Nardus stricta pasture	7	6.20	0.95	3	0.99	0.28	3	1.39	0.28

Figure 3. Functional profiling through Grime’s CSR model (R: ruderal strategy; C: competitive strategy; S: stress-tolerant strategy) for each sampling point of the investigated vegetation types (SV: Sesleria varia grassland; RP: rich pasture; N: Nardus stricta pasture; EH: earth hummocks; B: bentgrass).

Table 3. Main properties of representative soil profiles (taxonomy according to IUSS Working Group WRB, 2015).

Horizon	Depth (cm)	Colour (moist)	Rock fragments	Structure	Roots	pH H2O	SOC (g kg^−1)	C:N ratio	Textural class	Notes
Soil profile #1 – Leptic Umbrisol (Siltic) (representative of bentgrass vegetation)
A1	0–11	10YR 2/1	Few, f	Granular, f	Common, vf-f	4.1	116	10.3	Silty loam
A2	11–27	10YR 3/3	many, m-f	Sub. blocky, f-m	very few, vf-f	5.0	54	8.9	Silty loam
R	27+									Fractured marble
Soil profile #2 – Dystric Leptic Cambisol (Humic) (representative of Nardus stricta pasture)
A	0–7	10YR 2/1	Absent	Granular, f	Common, vf-f	4.9	126	11.6	Loamy sand
BAw1	7–15	10YR 3/2.5	Common, vf-f	Sub. blocky, f	Few, vf-m	4.7	40	10.4	Silty loam
BAw2	15–42	10YR 3.5/4	Common, vf-f	Sub. blocky, f	Few, f	5.3	27	11.5	Sandy loam
R	42–60		Abundant, vf-f	Single grain	Very few, vf					Fractured marble
Soil profile #3 – Eutric Cambisol (Humic, Loamic) (representative of rich pasture vegetation)
Ah	0–5	10YR 2/1	Absent	Granular, f	Common, vf-f	5.7	82	10.5	Loam	Earthworms
A	5–15	10YR 3.5/3	Few, vf-f	Granular, m	Very few, mf-f	5.5	31	9.2	Loam
Bw1	15–26	10YR 4/4	Few, vf-f	Sub. blocky, f-m	Very few, vf	5.7	15	10.0	Loam
Bw2	26–34	2.5Y 4.5/4	Few, vf-f	Sub. blocky, f-m	Very few, vf	6.0	14	9.8	Loam
C1	34–55	2.5Y 5/4	Common, vf-m	Massive	Very few, vf	5.9	3		Loam
C2	55–95	2.5Y 5/3	Common, vf-m	Massive	Absent	6.0	2		Loam
Soil profile #4 – Rendzic Leptosol (Humic) (representative of Sesleria varia grassland)
A1	0–3	10YR 2/1	Common, vf-f	Granular, f	Many, vf	6.3	114	9.8	Sandy loam
A2	3–10	10YR 2/1	Frequent, vf-m	Granular, f	Few, vf	6.7	70	9.3	Sandy loam	Total carbonates: 3 g kg^−1
R/A	10–40	10YR 2/3	Abundant, f-vc			7.2	62	9.1		Fractured marble; total carbonates: 420 g kg^−1
Soil profile #5 – Dystric Cambisol (Humic, Siltic, Relictiturbic, Protospodic) (representative of earth hummocks vegetation)
A	0–5	10YR 3/3	Absent	Granular, m	Common, vf-m	4.5	43	10.2	Silty loam
AB	5–11	10YR 3.5/4	Absent	Granular, m	Few, vf-m	4.3	29	10.2	Silty loam
Bw (Bs)	11–30	10YR 5/5	Few, vf	Sub. blocky, m	Few, vf-m	4.4	11	8.5	Silty loam
CB1	30–55	10YR 5/6	Few, vf	Platy (lithogenic)	Very few, vf-f	4.7	1		Silty loam
CB2	55–80	1Y 5/6	Common, vf	Platy (lithogenic)	Very few, vf	5.9	0		Silty loam
C	80–120	2.5Y 5.5/6	Many, vf-m	Massive	Absent	7.6	0		Sandy loam	Total carbonates: 351 g kg^−1

Legend for rock fragments, structure and roots: vf: very fine; f: fine; m: medium; c: coarse; vc: very coarse. Textural classes according to Soil Survey Division Staff (1993).

Table 4. Main statistics of soil properties in the 0–10 cm layer. For abbreviations and units of variables, see Table 1.

	N	Mean	Median	Minimum	Maximum	Std. Dev.	Std. Error	Coeff. Var.(%)
Slope	35	22.31	25.00	0.00	51.00	18.11	3.06	81
BD	35	0.71	0.70	0.41	1.02	0.14	0.02	20
totPor	35	70.06	70.66	60.29	81.14	5.09	0.86	7
pHw	35	5.1	4.8	4.3	7.1	0.7	0.1	14
SOC	35	8.0	7.8	2.2	13.6	2.7	0.4	34
totN	35	0.8	0.8	0.2	1.2	0.3	0.1	36
CN	35	10.9	10.9	8.7	14.2	1.1	0.2	10
CFA	35	11.56	11.45	4.85	17.51	2.86	0.48	25
CHA	35	20.95	21.18	5.11	32.36	6.91	1.17	33
CHUM	35	41.19	40.34	12.51	80.76	16.06	2.71	39
NFA	35	1.14	1.07	0.48	1.69	0.32	0.05	28
NHA	35	2.00	1.99	0.27	3.25	0.72	0.12	36
NHUM	35	3.35	3.14	0.76	6.77	1.52	0.26	45
avP	35	23.57	20.41	2.86	67.48	17.36	2.93	74
Sand	35	556	582	355	781	89.09	15.06	16
Silt	35	372	363	178	554	81.42	13.76	22
Clay	35	72	72	41	106	15.41	2.61	21
T	35	16.1	15.9	12.7	19.3	1.9	0.32	12
WFPS	34	42.6	42.5	24.3	59.9	9.2	1.58	22

Figure 4. Schematic representation of soil–plant relationships along a topographic transect in the investigated doline. The dotted line approximately represents the depth of the substrate. B: bentgrass; RP: rich pasture; SV: Sesleria varia grassland; EH: earth hummocks; N: Nardus stricta pasture.

Figure 5. Box plots for the comparison of soil properties among vegetation types (B: bentgrass; RP: rich pasture; SV: Sesleria varia grassland; EH: earth hummocks; N: Nardus stricta pasture). Different letters indicate statistically significant differences (p < 0.05) in the response variable among vegetation types in the mixed model. For abbreviations of variables, see Table 1.

Figure 6. CCA analysis of plant species in relation to the considered soil and environmental variables. Significant variables (at p < 0.05) are reported within rectangles. Species abbreviations: Agrostis schraderiana: Agr_schr; Alchemilla vulgaris: Alch_vul; Carex caryophyllaea: Car_car; Festuca nigrescens: Fest_nig; Heliantemum oleandicum: Hel_olea; Hippocrepis comosa: Hipp_com; Nardus stricta: Nard_str; Phleum alpinum: Phl_alp; Phleum pratense: Phl_prat; Poa alpina: Poa_alp; Sesleria varia: Sesl_var; Trifolium alpinum: Trif_alp; Vaccinum uliginosum: Vacc_uli. For abbreviations of variables, see Table 1.

Table 5. Canonical correlation analysis (CCA) for the 14 most abundant plant species in relation to the considered environmental variables (soil properties of the 0–10 cm layer).

	Axis 1	Axis 2	Axis 3	Axis 4
Eigenvalues:	0.484	0.358	0.193	0.111
Species-environment correlation:	0.965	0.880	0.778	0.808
Cumulative percentage variance of species data and species-environment relation:	34.9	60.7	74.6	82.7
Variable	Lambda1	LambdaA	P	F
pHw	0.42	0.42	**	8.62
CN	0.23	0.24	**	5.74
Eros	0.41	0.14	**	3.79
Silt	0.21	0.11	*	2.95
WFPS	0.12	0.07	+	2.00
Rad	0.11	0.07	*	2.07
T	0.17	0.06	+	1.88
SOCstock	0.18	0.06	ns	1.66
CHUM	0.3	0.04	ns	1.33
avP	0.23	0.04	ns	1.27
Slope	0.19	0.04	ns	1.14
Clay	0.13	0.03	ns	1.13
CFA	0.17	0.03	ns	0.89
AWC	0.12	0.02	ns	0.65
BD	0.2	0.02	ns	0.44

Marginal (Lambda1) and conditional (LambdaA) effect scores (variance partitioning) are reported. P: ** < 0.01; * < 0.05; + < 0.1; ns = not significant. For abbreviations of variables, see table 1.

Figure 7. PCA analysis. Plot of CSR components, considered soil and environmental variables, and vegetation types. For abbreviations of variables, see Table 1.

IUSS Working Group WRB. 2015. World reference base for soil resources 2014 - Update 2015. Roma: [publisher unknown] (World Soil Resources Reports; vol. 106).

 Google Scholar

Soil Survey Division Staff. 1993. Soil survey manual. Washington, DC: U.S. Gov Print Office (U.S. Department of Agriculture Handbook; vol. 18).

 Google Scholar

Data availability

The datasets generated and analyzed during the current study are available in the Pangaea repository: Ferré, Chiara; Comolli, Roberto (2019): Soil and plant data of a pasture of the Italian Alps (Andossi, SO). PANGAEA, https://doi.org/10.1594/PANGAEA.910055.