关键词: 关键词：人工林近自然化, 水曲柳, 落叶松, 土壤理化性质

Abstract: Abstract: To investigate the effect of various level of close-to-nature cultivated forests on the soil physicochemical properties, a close-to-nature gradient was established with 20-year-old larch ( Larix olgensis ), ash ( Fraxinus mandshurica ) monoculture and mixture plantation forests and a 50-year-old secondary forest. Soil samples were collected from two horizons (0～10 cm, 10～20 cm) in the four stands and the physicochemical properties were analyzed. No significant variances were detected in soil physical properties among the four stands, but significant differences were found in some of the chemical properties. The soil physical properties in the ash monoculture stand tended to be better than that in any other stand, with the bulk density 10.4% lower than that in the secondary forest the saturated moisture capacity and capillary water holding capacity 21.2% and 18.2% greater than that in the natural forest. The physical properties of soil in the mixture forest and the secondary forest were second to the ash stand. The least ideal soil physical properties were found within the larch monoculture stands. The soil pH of plantation stands was slightly lower than second growth (pH=5.32), with the lowest found in larch monoculture stand, but no significant differences were detected among the stands ( P <0.05 ). The concentration of organic matter, total N, P in the lower soil horizon in larch stand were significantly lower than that in the other stand; while the concentration of available P was significantly greater than that in other stands (15.92 and 7.42 mg kg^-1, respectively). The concentration of hydrolysable N in both soil horizons and available K in the lower horizon were significantly lower than that in other stands. No significant variances in nutrients concentration in soils under ash monoculture, the mixture and the secondary forest were found ( P >0.05). The soil physicochemical properties in the close-to-nature plantation forest of ash and larch mixture and the ash monoculture were relatively more close to that in the secondary forest in comparison with that in the monoculture stands of the larch.

Key words: Key words: close-to-nature plantation forests, Fraxinus mandshurica, Larix olgensis, soil physicochemical properties