Table 2. Soil physical factors of five natural secondary forest types.

	Natural secondary forest type
Chemical factor	Chinese pine	Sharptooth oak	Chinese pine+Sharptooth oak	Armand pine	Wilson spruce
Root content	++	+++	++	++	++
Sand (%)	19.70(0.77)a	32.96(1.40)b	18.80(1.56)a	14.61(0.36)c	28.84(0.38)d
Silt (%)	52.01(1.64)a	51.16(1.09)a	64.42(2.35)b	66.05(2.51)b	65.14(1.61)b
Clay (%)	28.29(1.82)a	15.88(1.77)b	16.78(2.06)bc	19.35(1.49)c	6.20(0.08)d
BD (g/cm3)	1.08(0.08)a	0.89(0.05)b	1.14(0.04)a	1.11(0.04)a	1.06(0.03)a
Porosity (%)	3.29(0.20)a	24.12(1.14)b	16.20(1.95)c	13.69(0.65)c	20.19(2.68)d
WHC (%)	22(1)a	20(2)a	21(1)a	17(1)b	16(1)b

BD, bulk density; WHC, water holding capacity. Values are means±SD and letters denote significant differences among forest types (P = 0.05).