亚高山针叶林土壤动物和土壤微生物对针叶分解的作用(英文)

RELATIVE ROLES OF MICROORGANISMS AND SOIL ANIMALS ON NEEDEL LITTER DECOMPOSITION IN A SUBALPINE CONIFEROUS FOREST

通过 8 0片亚高山针叶林土壤有机物层切片的显微观察和统计 ,并结合微生物 (CFU)的培养观察 ,对亚高山针叶林土壤有机物分解过程中土壤动物和土壤微生物的作用进行了研究。根据可见针叶数目和C/N比率在土壤有机物层的垂直分布变化将分解过程分为 3个阶段。真菌数量 (CFU)在第一阶段 (表层 0～ 2cm)明显高于第二和第三阶段 (深层 ) ;与此相反细菌的数量 (CFU)却表层少深层多。具有虫便的针叶在表层 (0～ 2cm)为最多 ,而深于 2cm后便急剧减少 ,至 4.5cm处为零。综合以上结果并结合微形态观察我们认为针叶的分解过程随着深度的增加而增加 ;真菌首先定着和破坏针叶表皮层使得内居性动物大量侵入针叶的内部 ;由于动物的取食可视针叶的数量从 2cm到 4.5cm逐渐消失 ;最后破损的针叶逐渐变成碎削和粪便 ,致使碎片的体积越来越小而有机物表面积却相对变大 ,微生物便很容易定着并分解这些碎片 ,在深层起主要作用的可能是细菌。

Eighty thin-sections of the subalpine coniferous organic layer were used for observing the effect of microorganisms and animals on the needle decomposition. The distribution patterns of fungal spores and bacteria along the upper 8 cm soil profile of the forest floor were counted using the plate culture method. The changes in needle number and C/N ratio of litter suggest that the decomposition of the needles could be divided into three stages. Colony forming units (CFU) of fungi were higher in the surface 0-2 cm layer (decomposition Stage 1) than in deeper layers. In contrast, the CFU of bacteria was lower in the surface 0-2 cm layer (Stage 1) than in deeper layers. The needles with faeces increased from 0 cm to 2 cm layer, decreased sharply from 2 cm to 4.5 cm layer (Stage 2) and slowly in deeper than 4.5 cm layer (Stage 3). Decomposition of needle litter was clearly apparent with increasing depth of the forest floor. Needles in the surface layer of soil were colonized and then destroyed by fungi resulting in the rupturing of needle epidermis. The destroyed epidermis led to the invasion by animals in the inner tissue. Thus, a large number of needles disappeared from the 2 cm to 4.5 cm layer due largely to the activity of animals. Faunal induced decomposition of the needles resulted in the needles changing into fragments and faeces. The size of residues decreased but the surface area of whole fragments increased. Microorganisms could easily colonize the debris and decay it. This may be a big contribution to the decomposition of litter by bacteria in later stages or in deeper layer of the forest floor.