天然林及坡耕地转变为巨桉林后土壤养分含量变化

以川西低山区天然林及其人工更新形成的1年生(Ⅰ1)、2年生(Ⅰ2)和3年生(Ⅰ3)巨桉林,坡耕地及其退耕形成的1年生(Ⅱ1)、2年生(Ⅱ2)和3年生(Ⅱ3)巨桉林为对象,研究天然林及坡耕地转变为巨桉人工林后土壤有机质、全氮、碱解氮、有效磷和速效钾含量变化。结果表明:各土壤养分含量均呈现出天然林>Ⅰ1>Ⅰ3>Ⅰ2,坡耕地<Ⅱ1<Ⅱ2<Ⅱ3,0~20 cm土层高于20~40 cm土层。说明天然林转变为巨桉林会造成土壤养分降低,但这种情况可能随着栽种年限的增加有所缓解;同时,坡耕地转变为巨桉林后土壤养分含量随栽种年限的增加而增加。

Effects of Conversion of Natural Forest and Slope Farmland to Eucalyptus grandis Plantation on Soil Nutrients

With the natural forest and its regenerated 1(Ⅰ1)-2(Ⅰ2)-and-3(Ⅰ3)-year-old Eucalyptus grandis plantation, the slope farmland and its converted 1(Ⅱ1)-2(Ⅱ2)-and-3(Ⅱ3) year-old Eucalyptus grandis plantation in low mountains of western Sichuan province as subjects, the paper made a study on the change of the content of such soil nutrients as soil organic matter, total N, hydrolysis N, available P and available K after the natural forests and slope farmlands were converted to Eucalyptus grandis plantation.The results showed that the content of soil organic matter, total N, hydrolysis N, available P and available K was observed higher at 0～20 cm than that at 20～40 cm, and a trend was shown as natural forest ＞Ⅰ1＞Ⅰ3＞Ⅰ2, and slope farmland ＜Ⅱ1＜Ⅱ2＜Ⅱ3.This indicated that soil nutrient content could be decreased in initial conversion of natural forest to Eucalyptus grandis plantation;however, this trend would be delayed with the increase of plantation years.Meanwhile, conversion of slope farmland to forestland could improve soil nutrient content with the plantation year increasing.