在中国黄土高原地区的“退耕还林”地区,人工种植的树木很难成林。在目前的研究中,经过10年自然恢复的废弃耕地作为对照(CK),而处理包括2、4、6、8和10年的造林期。从不同深度收集土壤样品:0-20、20-40、40-60、60-80至80-100厘米。研究结果表明,随着人工造林年限的增加,土壤pH值逐渐升高,在黄土高原的马刺山地区,0-20cm层的土壤水分含量上升,而在较深层(20-100cm)的土壤水分含量下降。此外,总碳,氮,磷,随着人工造林的持续时间,钾含量先增加后减少,8年后达到峰值。有机物含量,铵态氮,硝酸盐氮,有效磷,同一土层中的速效钾随造林年而增加。然而,人工造林达到10年后,60-80和80-100厘米土壤层的有效养分含量下降。不同造林年限的综合生育力指数(FI)排序为:8年>6年>10年>4年>2年,但均显著小于自然恢复区CK(P<0.05)。总的来说,黄土高原马刺山地区的土壤肥力随着人工造林的增加而增加。然而,当人工造林期为10年时,土壤肥力下降,标志着从增强到下降的转变。
In the area of \"returning farmland to forest\" on the Loess Plateau in China, it is difficult to cultivate artificially planted trees into forests. In the current study, abandoned cultivated land after 10 years of natural restoration served as controls (CK), while the treatments included
afforestation periods of 2, 4, 6, 8, and 10 years. Soil samples were collected from various depths: 0-20, 20-40, 40-60, 60-80, to 80-100 cm. The findings revealed that with increasing years of artificial
afforestation, soil pH gradually increased, and soil moisture content rose in the 0-20 cm layer while declining in deeper layers (20-100 cm) in the Maxian Mountain region of the Loess Plateau. Moreover, the total carbon, nitrogen, phosphorus, and potassium content initially increased and then decreased with the duration of artificial afforestation, reaching peak values after 8 years. Contents of organic matter, ammonium nitrogen, nitrate nitrogen, available phosphorus, and available potassium in the same soil layer increased with each year of afforestation. However, upon reaching 10 years of artificial
afforestation, the effective nutrient content in the 60-80 and 80-100 cm soil layers exhibited a decrease. The values of Integrated Fertility Index (IFI) in different
afforestation years were ranked as follows: 8 years > 6 years > 10 years > 4 years > 2 year, but all of them were significantly smaller than those of natural restoration plot CK (P < 0.05). Overall, soil fertility in the Maxian Mountain area of the Loess Plateau increases with each additional year of artificial afforestation. However, when the artificial
afforestation period is 10 years, soil fertility decreases and marking a shift from enhancement to decline beyond this duration.