Potential indicators of soil quality in temperate forest ecosystems: a case study in the Basque Country

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Table III

Particulate organic matter (mg C g^-1 soil), microbial, bacterial and fungal biomass (nmol PLFA g^-1 soil), Gram-negative (Gram–) and Gram-positive (Gram+) biomarkers (%mole PLFA) and Shannon diversity index H at 0–5 cm and 5–15 cm in the soil profile of semi-natural oak and beech stands, and cultivated 40-year-old, 16-year-old and 3-year-old pine stands.

	Oak	Beech	40 y Pine	16 y Pine	3 y Pine
0–5 cm
POM	6.52 (0.27)^a	6.43 (1.58)^a	3.25 (0.25)^b	5.40 (0.01)^a^b	1.63 (0.15)^b
Microbial biomass	210.59 (28.84)^a	221.12 (10.64)^a	239.21 (23.72)^a^c	304.06 (26.09)^c	136.51 (4.0)^b
Bacterial biomass	115.67 (16.12)^a^b	117.43 (3.83)^a^b	125.02 (14.11)^a^b	159.29 (13.43)^a	80.64 (1.08)^b
Gram+	23.95 (0.37)^a	25.47 (0.99)^a	23.59 (0.74)^a	23.00 (0.39)^a	34.49 (1.3)^b
Gram–	29.43 (0.93)^a	25.79 (0.34)^b	26.44 (1.58)^a^b	27.75 (0.58)^a^b	22.64 (0.35)^b^c
Gram+/Gram–	0.82 (0.04)^a	0.99 (0.03)^b	0.90 (0.04)^a^b	0.83 (0.03)^a^b	1.53 (0.08)^c
fungal	6.63 (1.0)^a^*	7.97 (1.21)^a^c	12.85 (2.53)^b	12.05 (1.13)^b^c	3.17 (0.84)^a
Shannon diversity H	2.50 (0.03)^a	2.58 (0.02)^b	2.65 (0.02)^b	2.65 (0.02)^b	2.61 (0.01)^b
5–15 cm
POM	1.64 (0.05)^a	1.43 (0.13)^a	3.24 (0.51)^b	1.95 (0.48)^a	1.54 (0.11)^a
Microbial biomass	168.34 (6.81)^a^b	147.03 (20.08)^a^b	185.51 (20.56)^a	203.71 (27.75)^a	90.13 (4.52)^b
Bacterial biomass	89.90 (3.36)^a	82.11 (9.11)^a^b	99.86 (7.09)^a	111.20 (14.47)^a	50.62 (2.86)^b
Gram+	27.08 (0.16)^a^b	28.08 (0.76)^a^b	25.68 (1.8)^a	24.41 (1.2)^a	30.91 (0.83)^b
Gram–	24.74 (0.67)^a	26.16 (1.12)^a^b	26.71 (0.72)^a^b	28.65 (0.91)^b	23.13 (0.44)^a^c
Gram+/Gram–	1.10 (0.02)^a	1.08 (0.04)^a	0.96 (0.04)^a^b	0.86 (0.06)^b	1.34 (0.06)^c
fungal	5.56 (0.84)^a	4.57 (0.83)^a	8.74 (3.47)^a	5.41 (0.42)^a	2.99 (0.44)^a^c
Shannon diversity H	2.55 (0.05)^a	2.64 (0.02)^a^b	2.60 (0.01)^a^b	2.66 (0.02)^a^b	2.71 (0.04)^b

Significance level, P < 0.1.

Values are the means of three replicates, with standard errors in parentheses. Different letters in the same row indicate significant differences at P< 0.05.