ObjectiveThis paper aims to evaluate the effects of converting time from cropland to forestland on soil physical properties, and provide a basis for the construction of soil and water conservation forests in the region.
MethodThe 23 years positioning continuous monitoring was taken on soil physical properties under five typical forests, including one natural restoration Populus davidiana plantation, two mixed plantations of Platycladus orientalis and Robinia pseudoacacia, Pinus tabuliformis and Robinia pseudoacacia, two pure plantations of Robinia pseudoacacia and Pinus tabuliform, and taking the corn farmland as control.
Result(1) With the increase of converted years, the soil bulk density (BD) under the four plantations increased first and then decreased to a stable value, which was lower than initial value at about 10−15 years. In the natural restoration forest (NF), BD showed a downward tendency with the highest decreasing range of 11.21% at 0−20 cm soil depth. (2) The soil total porosity (TP) under the 4 plantations decreased first and then increased to a stable value, which was higher than initial value at about 10−15 years. The cumulative changing rates of TP at the soil depths of 0−20 cm and 20−40 cm were 1.4% and 0.6%, respectively under NF. (3) The capillary porosity (CP) under the five typical forests all showed an increasing trend with the increase of converting time. The CP at 0−20 cm changed more than at 20−40 cm in the plantations; the cumulative changing rates of CP at 0−20 cm and 20−40 cm were 2.5% and 1.5%, respectively under NF.
Conclution The converted years showed a significant effects on soil physical properties (P < 0.05) under the typical forests, while for the plantations, the change of BD and TP mostly occurred in the first 10−15 years. The mixed forests of Pinus tabuliformis and Robinia pseudoacacia should be the prioritized for the artificial vegetation restoration in the research area based on its remarkable improvement effects on soil physical properties.
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