重庆酸雨区人工木荷林对土壤化学性质的影响

 在属于酸雨区的重庆市铁山坪林场，选择在马尾松（Pinus massoniana）纯林火烧迹地上人工营造的木荷（Schima superba）纯林，采用钻取 土芯法调查木荷对土壤化学性质的影响，并与毗邻的同时造林但未遭受火烧的马尾松纯林比较。结果表明，木荷纯林0～20和20～60 cm土层的 pH值分别为3.61和3.77，盐基饱和度分别为4.68％和7.92％，而马尾松纯林的pH值分别为3.78和3.88，盐基饱和度分别为9.25%和16.32%。与马 尾松纯林相比，木荷纯林土壤的交换性盐基离子（K⁺ 、Na⁺ 、Ca ²⁺和Mg ²⁺ ）和全磷含量普遍低，而酸性阳离子Al ³⁺ 、Fe ³⁺和H⁺含量明显偏高 （p<0.05）。结果说明，并非木荷作为阔叶林对酸化土壤的改良作用就好于作为针叶林的马尾松，木荷纯林导致了土壤酸化加剧，养分非常缺 乏。因此，在酸雨区土壤酸化条件下，如果采用木荷营造防火林带或者进行马尾松纯林改造时，不宜集中大片营造木荷纯林，以避免对土壤环 境产生不利影响。

EFFECTS OF SCHIMA SUPERBA PLANTATIONS ON SOIL CHEMICAL PROPERTIES IN THE ACID RAIN REGION OF CHONGQING, SOUTHWESTERN CHINA

Aims In recent decades, frequent fires have destroyed large areas of coniferous Pinus massoniana forests in Chongqing, Southwestern China. Schima superba, a fire-resistant broadleaved tree species, has been widely planted on the burned areas. S. superba is thought to improve soil properties; however, little information is available from plantations exposed to acid deposition. Our objective was to examine the effects of S. superba plantations on soil chemical properties in the acid rain region. Methods We investigated soil chemical properties of a pure S. superba plantation planted on a burned area of a former pure P. massoniana plantation in the Tieshanping Forest Farm of Chongqing City using a soil core method. Results were com pared with those from an adjacent unburned pureP. massoniana plantation, which was planted at the same time as the burned pure P. massoniana plantation. Important findings For 0-20 and 20-60 cm soil layers in the S. superba plantation, average pH values were 3.61 and 3.77 and average base saturation (BS) values were 4.68% and 7.92％, respectively. For these two soil layers in the P. massoniana plantation, average pH values were 3.78 and 3.88 and average BS values were 9.25% and 16.32%, respectively. Compared with the P. massoniana plantation, contents of exchangeable basecations (K⁺ , Na⁺ , Ca²⁺ and Mg²⁺ ) and total P were generally lower in the soil of the S. superba plantation, but contents of exchangeable Al³⁺ , Fe³⁺ and H⁺ were significantly higher (p<0.05). This study suggested that the S. superba plantation accelerated soil acidification. Therefore, in the acid rain region of Chongqing, large areas of pure S. superba plantations should be avoided when using S. superba for establishment of fire- resistant forest belts or for regeneration and transformation of pure P. massoniana plantations.