Lecerf Antoine, Dobson Michael, Dang Christian K, Chauvet Eric
Laboratoire Dynamique de la Biodiversité, UMR 5172 CNRS-UPS, 29 rue Jeanne Marvig, 31055 Toulouse, France.
Oecologia. 2005 Dec;146(3):432-42. doi: 10.1007/s00442-005-0212-3. Epub 2005 Oct 27.
Riparian vegetation is closely connected to stream food webs through input of leaf detritus as a primary energy supply, and therefore, any alteration of plant diversity may influence aquatic ecosystem functioning. We measured leaf litter breakdown rate and associated biological parameters in mesh bags in eight headwater streams bordered either with mixed deciduous forest or with beech forest. The variety of leaf litter types in mixed forest results in higher food quality for large-particle invertebrate detritivores ('shredders') than in beech forest, which is dominated by a single leaf species of low quality. Breakdown rate of low quality (oak) leaf litter in coarse mesh bags was lower in beech forest streams than in mixed forest streams, a consequence of lower shredder biomass. In contrast, high quality (alder) leaf litter broke down at similar rates in both stream categories as a result of similar shredder biomass in coarse mesh bags. Microbial breakdown rate of oak and alder leaves, determined in fine mesh bags, did not differ between the stream categories. We found however aquatic hyphomycete species richness on leaf litter to positively co-vary with riparian plant species richness. Fungal species richness may enhance leaf litter breakdown rate through positive effects on resource quality for shredders. A feeding experiment established a positive relationship between fungal species richness per se and leaf litter consumption rate by an amphipod shredder (Gammarus fossarum). Our results show therefore that plant species richness may indirectly govern ecosystem functioning through complex trophic interactions. Integrating microbial diversity and trophic dynamics would considerably improve the prediction of the consequences of species loss.
河岸植被通过输入作为主要能量来源的落叶碎屑与溪流食物网紧密相连，因此，植物多样性的任何改变都可能影响水生生态系统的功能。我们在八条源头溪流的网袋中测量了落叶分解速率及相关生物学参数，这些溪流一侧为混交落叶林，另一侧为山毛榉林。与以单一低质量叶片物种为主的山毛榉林相比，混交林中落叶类型的多样性为大型颗粒无脊椎动物碎屑食性动物（“碎食者”）提供了更高质量的食物。在粗网袋中，山毛榉林溪流中低质量（橡木）落叶的分解速率低于混交林溪流，这是碎食者生物量较低的结果。相比之下，高质量（桤木）落叶在两种溪流类型中的分解速率相似，这是因为粗网袋中碎食者生物量相似。在细网袋中测定的橡木和桤木叶的微生物分解速率在不同溪流类型之间没有差异。然而，我们发现落叶上水生丝状真菌的物种丰富度与河岸植物物种丰富度呈正相关。真菌物种丰富度可能通过对碎食者资源质量的积极影响来提高落叶分解速率。一项摄食实验确定了丝状真菌物种丰富度本身与一种双足类碎食者（河蚬）的落叶消耗速率之间存在正相关关系。因此，我们的研究结果表明，植物物种丰富度可能通过复杂的营养相互作用间接控制生态系统功能。整合微生物多样性和营养动态将大大改善对物种丧失后果的预测。
