Resource quality and stoichiometric constraints on stream ecosystem functioning
Resource quality and stoichiometric constraints on stream ecosystem functioning
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DOI：
10.1111/j.1365-2427.2008.02138.x
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发表时间：
2009-05-01
影响因子：
2.7
通讯作者：
Woodward, Guy
中科院分区：
文献类型：
--
作者：
Hladyz, Sally;Gessner, Mark O.;Woodward, Guy
1.消费者和资源之间的碳营养物比例的资源质量和化学计量不平衡可以影响关键的生态系统过程。在许多溪流中，这对主要基于利用陆地落叶的食物网具有重要意义，而落叶作为食草动物的食物来源和微生物分解者的底物，其价值在不同的落叶类型中差异很大。我们测量了分解率和大型无脊椎动物的定殖叶凋落物从一系列的本地和外来植物的不同资源质量和适口性的消费者[如碳：氮：磷（C：N：P）的比例，木质素和纤维素含量]，在现场实验。我们还测量了C：N：P比率的主要叶粉碎无脊椎动物，这表明强烈的化学计量不平衡的营养水平：C：N和C：P比率通常不同的消费者和资源之间的至少一个数量级，而N：P不平衡不太明显。应用阈值元素比方法，结合动物生物能量学和身体元素组成来研究消费者和资源之间的营养缺乏，比基于上述简单算术差异的方法显示出更小的C：P不平衡。凋落物分解率下降的营养失衡扩大和资源质量下降，但他们是独立的资源是外来的还是本地的。总的，微生物和无脊椎动物介导的分解率的主要驱动因素是木质素：N，木质素：P和真菌生物量，分别。然而，使用正交预测的多元回归产生了更有效的模型凋落物分解，消费者对资源质量的一个以上的方面。例如，真菌生物量和凋落物C：N均影响无脊椎动物介导的分解.大化学计量的不平衡和资源质量的变化很可能对河流生态系统功能产生严重后果，特别是当河岸带被外来植物物种入侵时，其化学成分与本地植物群明显不同。因此，分解率变化的幅度和方向以及资源消耗将在很大程度上由常驻和入侵植物群的生物化学特性（而不是分类学特性本身）驱动。
1. Resource quality and stoichiometric imbalances in carbon : nutrient ratios between consumers and resources can influence key ecosystem processes. In many streams, this has important implications for food webs that are based largely upon the utilization of terrestrial leaf-litter, which varies widely among litter types in its value as a food source for detritivores and as a substrate for microbial decomposers.2. We measured breakdown rates and macroinvertebrate colonization of leaf-litter from a range of native and exotic plants of differing resource quality and palatability to consumers [e.g. carbon : nitrogen : phosphorus (C : N : P) ratios, lignin and cellulose content], in a field experiment. We also measured C : N : P ratios of the principal leaf-shredding invertebrates, which revealed strong stoichiometric imbalances across trophic levels: C : N and C : P ratios typically differed by at least one order of magnitude between consumers and resources, whereas N : P imbalances were less marked. Application of the threshold elemental ratio approach, which integrates animal bioenergetics and body elemental composition in examining nutrient deficiency between consumers and resources, revealed less marked C : P imbalances than those based on the simpler arithmetic differences described above.3. Litter breakdown rates declined as nutrient imbalances widened and resource quality fell, but they were independent of whether resources were exotic or native. The principal drivers of total, microbial and invertebrate-mediated breakdown rates were lignin : N, lignin : P and fungal biomass, respectively. However, multiple regression using orthogonal predictors yielded even more efficient models of litter breakdown, as consumers responded to more than one aspect of resource quality. For example, fungal biomass and litter C : N both influenced invertebrate-mediated breakdown.4. Large stoichiometric imbalances and changes in resource quality are likely to have serious consequences for stream ecosystem functioning, especially when riparian zones have been invaded by exotic plant species whose chemical composition differs markedly from that of the native flora. Consequently, the magnitude and direction of change in breakdown rates and, thus, resource depletion, will be driven to a large extent by the biochemical traits (rather than taxonomic identity per se) of the resident and invading flora.