樟子松固沙林土壤理化特性对林分密度的响应

Response of Soil Physiochemical Properties under Sand-Fixation Forest of Pinus sylvestris var. mongolica to Stand Density

为了研究樟子松人工固沙林林分密度对土壤理化特性的影响,在章古台地区选取林分密度分别为625(P1)、775(P2)、1 025(P3)、1 175(P4)株·hm^-2和1 250(P5)株·hm^-2的樟子松中龄林(林龄为23~27 a)为研究对象,对0~100 cm深度的樟子松林地土壤按0~10、10~20、20~40、40~60、60~80、80~100 cm进行分层,分析其理化特性。结果表明:0~10 cm土层全氮和20~40 cm土层土壤容重随密度增加呈上升趋势,P5显著高于P1(P <0. 05);0~80 cm土层全钾和0~60 cm土层pH随密度增加先升高后降低,P3最高,且P3样地全钾在10~60 cm土层显著高于P1(P <0. 05);pH在0~40 cm土层显著高于其他样地(P <0. 05);0~10 cm土层全磷随密度增加而减小,P1显著高于P3~P5(P <0. 05);P4或P5样地有效钾在0~40 cm土层显著高于P1、P2样地(P <0. 05),在40~100 cm土层显著高于P3样地(P <0. 05);P2~P4样地的土壤孔隙度在40~100 cm土层低于P1和P5样地。综合考虑林分密度对樟子松中龄林土壤理化特性的影响,章古台地区樟子松林的合理林分密度为1 025~1 175株·hm^-2,可采取间伐等营林管理措施调节林分密度,确保樟子松固沙林生长具有良好的土壤条件。

In this study,the 23-27-year aged forests with stand densities of 625 (P1),775 (P2),1 025 (P3),1 175 (P4) and 1 250 (P5) plants·hm^-2 in the Zhanggutai region were selected. The purpose of the study was to analyze the effect of stand density on soil physiochemical properties at 0-100 cm depth. The results showed that the total nitrogen content in 0-10-cm soil layer and the bulk density in 20-40-cm soil layer increased with the increase of stand density,and the total nitrogen content and bulk density in plot P5 were significantly higher than those in plot P1 (P < 0. 05). The total potassium content in 0-80-cm soil layer and the pH value in 0-60-cm soil layer increased at first and then decreased with the increase of stand density,and they were the highest in plot P3. The total potassium content in 10-60-cm soil layer in plot P3 was significantly higher than that in plot P1 (P < 0. 05),and the pH value in 0-40-cm soil layer was significantly higher than that in other plots (P <0. 05). The total phosphorus content in 0-10-cm soil layer decreased with the increase of stand density,and it in plot P1 was significantly higher than that in plots P3-P5 (P < 0. 05). The available potassium content in 0-40-cm soil layer in plot P4 or P5 was significantly higher than that in plots P1 and P2 (P < 0. 05),and also significantly higher than that in 40-100-cm soil layer in plot P3 (P < 0. 05). The porosity in 40-100-cm soil layer in plots P2-P4 was lower than that in plots P1 and P5. Considering the influence of stand density on soil physiochemical properties of middle-aged P. sylvestris var. mongolica plantation,the rational stand density of P. sylvestris var. mongolica plantation in the study area should be 1 025-1 175 plants·hm^-2. Intermediate cuttings and other forest management measures could be taken to regulate the stand density so as to ensure the good soil conditions for the growth of sand-fixing forests of P. sylvestris var. mongolica.