作 者 ：李志勇,王彦辉,于澎涛,张治军
期 刊 ：生态学报 2007年 27卷 12期 页码：5245~5253
Keywords:acidified soil, Pinus massoniana, Cinnamomum camphora, fine roots, growth, distribution,
摘 要 ：采用钻取土芯法对土壤和根系取样，分析比较了在相似立地条件下的酸化土壤上生长的马尾松（Pinus massoniana）纯林和香樟（Cinnamomum camphora）纯林的抗酸能力及细根生长与垂直分布。研究结果表明，与马尾松纯林相比，香樟纯林在腐殖质层和0～60 cm土层中的盐基离子（Ca2+和Mg2+）含量、盐基饱和度和pH值较高，而Al3+、H+含量较低，香樟纯林具有较强的减缓土壤酸化能力；在腐殖质层和0～20 cm土层，香樟纯林单位面积的各项细根生长指标均显著高于马尾松纯林（p < 005），其中，在0～20 cm土层，香樟纯林单位面积的细根干重、长度、表面积、体积和根尖数分别是马尾松纯林的1.40、2.91、255、2.27倍和3.48倍；在腐殖质层，香樟纯林和马尾松纯林单位土体的细根干重、长度、表面积、体积和根尖数达最大值，而且香樟纯林分别是马尾松纯林的3.30、7.55、6.16、4.89倍和6.89倍，二者各项细根密度指标的垂直分布均随土层加深而减少，但香樟纯林递减速度快于马尾松纯林，就细根而言，香樟属于浅根性树种，马尾松属于深根性树种。对两树种0～20 cm土层的土壤酸化程度和细根生长的分析表明，香樟细根的抗土壤酸化能力较强。因此，利用香樟混交来改良酸沉降区马尾松纯林的酸化土壤和林木生长具有重要意义。
Abstract:The high levels of acid deposition experienced in recent decades have caused a decline in health of forest tree species in the south and southwest of China, but differences in the extent of decline exist among the tree species. For Pinus massoniana and Cinnamomum camphora, the two indigenous tree species exposed to frequent acid rain and acid fogs, the former shows more visible injury symptoms of defoliation and twig death than the latter due to its higher sensitivity to acid deposition. Ecologists have focused on the chemical properties of acidified soils in Pinus massoniana forests for a long period and made a great progress. However, the information on difference in resistance to soil acidification between the two tree species, especially on fine root (≤2 mm in diameter) characteristics under field conditions exposed to long-term acid deposition, is still scarce. Therefore, we investigated the pure stands of the two tree species that grow on acidified soil under similar site conditions in Chongqing, southwestern China. The fine roots were collected according to the layers of humus, 0-20 cm, 20-40 cm and 40-60 cm by a soil core method. Contents of the exchangeable cations (K+, Na+, Ca2+, Mg2+, Al3+ and H+) and pH values in each layer were also analyzed at the same time.
The results showed that the pure Cinnamomum camphora stand had greater ability to slow down soil acidification than the pure Pinus massoniana stand due to its more exchangeable base cations (Ca2+ and Mg2+), higher base saturation (BS) and pH values and fewer exchangeable Al3+ and H+ ions in the humus layer and 0-60 cm soil layer. In the humus layer and top soil, growth indexes of fine roots of the pure Cinnamomum camphora stand were significantly higher than those of the pure Pinus massoniana stand (p < 0.05). For example, in the 0-20 cm soil layer, dry weight, length, surface area, volume and the tip number of fine roots per unit area of soil of the pure Cinnamomum camphora stand was 1.40, 291, 2.55, 2.27 and 3.48 times as much as that of the pure Pinus massoniana stand, respectively. For the two pure stands, maximum values of density indexes of fine roots were found in the humus layer, where dry weight, length, surface area, volume and the tip number of fine roots per unit volume of humus of the pure Cinnamomum camphora stand was 330, 7.55, 6.16, 4.89 and 6.89 times as much as that of the pure Pinus massoniana stand, respectively. Density indexes of fine roots of the two pure stands decreased with the increasing soil depth with the Cinnamomum camphora stand decreasing more rapidly than the Pinus massoniana stand. Analyses on the soil acidity and growth indexes of fine roots in the 0-20 cm soil layer for the two pure stands showed that fine roots of Cinnamomum camphora possess higher resistance to soil acidification. Consequently, Cinnamomum camphora can be used to improve the acidified soil and growth of Pinus massoniana forests on acidified soil.
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