| Popis: |
The breakdown of fresh willow, Salix pedicellata, and oleander, Nerium oleander, leaves in mesh bags was investigated over one year in Oued Cherraa, a temporary river. The three investigation stations were: a permanent pool, and, in the temporary river, a more sheltered upstream station with a sharper gradient and a more open downstream station with a lower gradient. The water was stagnant in the permanent pool, except during high water in March and April when it flowed with the rest of the river. The two river stations were dry for the first 4 months, they were submerged for 7 and 5 months, and dry again for 1 and 3 months, respectively. Leaf breakdown over the whole investigation period was faster in the pool (exponential breakdown coefficient k.day -1 = -0.009 for willow and -0.007 for oleander) than in the intermittently-flowing river (k between -0.003 and -0.005). Breakdown was much faster during submersion than during emersion; at each station it was faster in flowing than in standing water. The terrestrial fauna in the bags was scarce and consisted mostly of predators. During submersion in the river, scrapers and collectors developed in the bags, but shredders were scarce. They were more numerous in the pool and this may explain the faster breakdown. |
