Teak (Tectona grandis Linn. f) and Edaphic Factors Affecting the Regeneration of Woody Species and Their Functional Traits in Economic Forest Plantation, Northern Thailand

Table 4

Mean ± standard deviation (SD) of soil variables including sand, silt, clay, organic matter (OM), nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) contents.

Soil	10-year-old	20-year-old	30-year-old	40-year-old	Old-growth forest	Sig
Sand (%)	47.43 ± 19.11^a	29.63 ± 6.15^bc	42.53 ± 9.73^ab	27.73 ± 4.30^c	45.93 ± 6.19^a
Silt (%)	21.15 ± 5.84	24.95 ± 2.37	23.95 ± 7.25	23.15 ± 1.68	21.85 ± 1.47	NS
Clay (%)	31.42 ± 13.43^b	45.42 ± 5.87^a	33.52 ± 5.53^b	49.12 ± 4.07^a	32.22 ± 5.32^b
pH	5.89 ± 0.42^b	5.97 ± 0.28^b	5.78 ± 0.22^b	6.57 ± 0.23^a	5.89 ± 0.23^b
OM (%)	3.21 ± 1.19^b	4.97 ± 0.83^a	3.55 ± 0.72^b	6.02 ± 0.85^a	4.91 ± 1.44^a
N (%)	0.13 ± 0.04^c	0.23 ± 0.04^b	0.16 ± 0.03^c	0.29 ± 0.03^a	0.24 ± 0.05^b
P (mg kg^−1)	4.33 ± 1.58	4.79 ± 1.50	4.48 ± 1.60	8.73 ± 8.90	3.54 ± 1.16	NS
K (mg kg^−1)	80.57 ± 37.12^b	77.83 ± 13.33^b	117.01 ± 38.79^ab	101.82 ± 27.08^ab	144.39 ± 47.82^a
Ca (mg kg^−1)	570.79 ± 393.55^b	867.96 ± 266.09^b	520.24 ± 165.98^b	1476.6 ± 498.46^a	642.86 ± 191.59^b
Mg (mg kg^−1)	170.3 ± 80.82^c	289.16 ± 81.36^b	196.86 ± 70.11^c	473.28 ± 71.01^a	194.27 ± 41.95^c

Measurements in teak plantations and old-growth forest sites in Khun Mae Khum Mee plantation. Different lowercase letters within a row indicate significantly different means by Tukey’s test (one-way ANOVA test, ; n = 50). ; NS = nonsignificant.