关键词: 林窗, 干扰状况, 丽江云杉林, 玉龙雪山自然保护区

Abstract: Litter fall mass and its decomposition plays a key role in nutrient cycling, especially in carbon cycling. This paper compared the litter fall mass and its decomposition characteristics in three primary forests (Platycarya longipes, Distylium macrophyllum, and Pteroceltis tatarinowi; Abbr. P1, P2, and P3) and three secondary forests (Sapium rotundifolium, Alangium chinense and Vitex negundo; Abbr. S1, S2, S3) in karst area of Northwest Guangxi. In all of the forests, leaf litter occupied about 80% of the total litter fall, and was negatively correlated with rainfall, with a peak in dry season. A decomposition experiment was conducted by using litter bags filled with the litter fall from all six forests. The litter bags were re-weighed at 90-day intervals after placed on the floor, and the results showed that the mass loss in primary forest P2 was the least, with 87.6% of the mass remaining un-decomposed after 90-day incubation. The total litter fall mass and the nutrient return were larger in secondary forests than in primary forests except P2 which had the largest litter fall mass and the slowest decomposition rate. The litter fall in secondary forest S1 had the highest N content and the fastest decomposition rate, and thus, the S1 could be a better choice for vegetation restoration and nutrient recovery in degraded lands in karst area of Northwest Guangxi.

Key words: Forest gap, Disturbance regimes, Picea likiangensis forest, Yulong Snow Mountain Natural Reserve