广西主要人工林凋落物分解过程及其对淋溶水质的影响

Litter decomposition of dominant plantations in Guangxi and its effects on leachate quality

为探讨不同人工林各组分凋落物分解过程特征及其释放物质对淋溶水质的影响,恒温(28℃)培养条件下,在室内人工定期淋水模拟自然环境中凋落物的淋溶过程,对1年生和4年生尾巨桉、7年生杂交相思、13年生马尾松以及软阔林5种人工林的凋落叶、凋落枝、凋落皮进行255d的模拟淋溶.结果表明:1年生和4年生尾巨桉各组分凋落物分解0～105d的淋溶液色度和化学需氧量(COD)、总N和总P含量显著高于杂交相思、马尾松、软阔林,淋溶液pH值显著低于其他3种林分人工林;至255d,1年生和4年生尾巨桉凋落叶淋溶液的COD累积量(193.9和212.8g·kg-1)分别是杂交相思、马尾松、软阔林的4.2、4.0、4.3倍和5.3、4.4、4.7倍;1年生尾巨桉凋落叶质量损失率、N和P淋失率显著大于杂交相思、马尾松和软阔林,凋落皮显著大于马尾松,而凋落枝与后三者基本相当.1年生尾巨桉凋落叶和凋落皮比4年生尾巨桉更易被分解淋溶,但凋落枝差异不显著.5种林分凋落物不同组分间,凋落叶最易被分解淋溶,凋落枝难于被分解淋溶.尾巨桉凋落物淋溶液pH值与色度、COD含量呈显著负相关,COD与色度、总N和总P呈显著正相关.

To understand the decomposition characteristics of the litters in different forest plantations and the effects of released substances during litter decomposition on the leachate quality, litter samples （leaf, shoot, and cortices） were collected from five forest plantations （1 year-old Eucalyptus urophylla × E. grandis, EU1; 4 year-old Eucalyptus urophylla × E. grandis, EU4; 7 year-old Acacia mangium × A. auriculaef, AM; 13 year-old Pinus massoniana Lamb, PL; and mixed broadleaved softwood, BL）, and incubated at 28 ℃, using water leached for 255 days. In the first 105 days, the litter leachates of EU1 and EU4 had significantly higher coloration and N and P contents and lower pH than those of AM, PL, and BL. On the 255th day, the cumulative chemical oxygen demand （COD） in the leaf litters leachates of EU1 and EU4 was 193.9 and 212.8 g·kg-1, being 4.2, 4.0, and 4.3 times and 5.3, 4.4, and 4.7 times higher than that of AM, PL, and BL, respectively. The mass loss rate and the N and P leaching rate of the leaf litter of EU1 were significantly higher than those of AM, PL, and BL. The mass loss rate of cortices of EU1 was significantly higher than that of PL. No significant difference was observed for the leaching rate of the shoot litters between AM, PL, and BL. Among the litter samples, leaf litter was easiest to be decomposed, while shoot litter was most difficult to be decomposed. The pH value of the litter leachates of Eucalyptus plantations was significantly negatively correlated with leachate chroma and COD, and the COD had significant positive correlations with the concentrations of total N and P in the leachates.