沙质草地营造樟子松林后土壤容重的变化及其影响因子

采用野外调查和室内试验相结合,以辽宁省章古台地区不同生长阶段(包括幼龄林、中龄林、成熟林和过熟林)的20块樟子松人工固沙林样地(以临近的7块天然草地为对照)为研究对象,研究了沙质草地营造樟子松人工林后不同生长阶段0—100 cm土层土壤容重的变化及其影响因子。结果表明:天然沙质草地营造樟子松人工固沙林后,不同生长阶段樟子松林在0—10 cm土层土壤容重变化的变异系数为78%,其他土层变异系数范围为1.08%—4.35%。随着樟子松人工林林龄的增加,土壤容重变化量在0—20 cm和60—100 cm层逐渐降低,在20—60 cm层先降低,到37年左右后逐渐升高,过熟林较成熟林显著增大。林龄对不同土层容重变化的决定系数由大到小依次为40—60、60—80、20—40、10—20、0—10、80—100 cm层。土壤容重变化在60—80 cm层与土壤粗颗粒(粒径0.05 mm)含量、在0—10、20—40 cm和60—80 cm层与土壤全氮含量、在0—10、20—60 cm和80—100 cm层与土壤全磷含量、在20—40 cm和80—100 cm层与土壤全钾含量显著负相关,且土壤全氮和全磷含量对土壤容重的影响效果随土层深度的增加逐渐降低,土壤容重变化在10—20 cm层与土壤含水率、在20—40 cm层与土壤有机碳含量呈显著的正相关。总体上,沙质草地营造樟子松人工林可以改善土壤结构,提高土壤质量,建议采取封育禁牧等营林措施增加樟子松林下枯落物积累,提高土壤养分含量,同时对37年樟子松人工林逐渐进行更新。

Changes in soil bulk density and its influencing factors after sandy grassland afforestation with Pinus sylvestris var. mongolica

Using a combination of field surveys and laboratory analysis, in the Zhanggutai area of Liaoning province, 20 forest plantations of Pinus sylvestris var. mongolica in different growth stages (including young forests, mid-aged forests, mature forests, and over-mature forests) and 7 neighboring control grasslands were selected. In this paper, the changes in soil bulk density and its influencing factors were studied in the 0-100 cm soil layer of different growth stages after sandy grassland afforestation with P. sylvestris var. mongolica. The results showed that after sandy grassland afforestation, the variance coefficient of soil bulk density was 78% in the 0-10 cm soil layer and the variance coefficient in other soil layers ranged from 1.08% to 4.35%. As the stand age increased, the magnitude of soil bulk density decreased gradually in 0-20 and 60-100 cm soil layers, however, the magnitude decreased firstly and then increased after 37 years in 20-60 cm soil layers, and the magnitude in over-mature forests was significantly higher than that in mature forests. In different soil layers, the coefficients of determination of stand ages for the magnitude of soil bulk density in decreasing order were 40-60, 60-80, 20-40, 10-20, 0-10, and 80-100 cm soil layers. The coarse-textured soil (particle size>0.05 mm) in the 60-80 cm soil layer; soil total nitrogen content in 0-10, 20-40, and 60-80 cm soil layers; soil total phosphorus content in 0-10, 20-60, and 80-100 cm soil layers; and soil total potassium content in 20-40 and 80-100 cm soil layers were significantly negatively correlated with soil bulk density, and the impact of soil total nitrogen and soil total phosphorus content on soil bulk density changes gradually decreased as the soil layer depth increased. However, soil moisture in the 10-20 cm soil layer and soil organic carbon content in the 20-40 cm soil layer were significantly positively correlated with soil bulk density. On the whole, sandy grassland afforestation with P. sylvestris var. mongolica can improve soil structure and quality. It is suggested that enclosure and grazing prohibition are effective to increase leaf litter accumulation and improve soil nutrient content in P. sylvestris var. mongolica plantations. In addition, 37 year old P. sylvestris var. mongolica plantations need to be regenerated gradually.