Dipartimento di Scienze dell'Ambiente e del Territorio, Università degli Studi di Milano Bicocca, Piazza della Scienza 1, 20126 Milano, Italy.
Ecol Appl. 2011 Jun;21(4):1272-82. doi: 10.1890/10-0431.1.
Semiaquatic organisms depend on the features of both water bodies and landscapes; the interplay between terrestrial and aquatic systems might influence the semiaquatic communities, determining the scale at which management would be more effective. However, the consequences of such interplay are not frequently quantified, particularly at the community level. We analyzed the distribution of amphibians to evaluate whether the influence of landscape features on freshwater ecosystems can have indirect consequences at both the species and community level. We surveyed 74 streams in northern Italy to obtain data on breeding amphibians, water, and microhabitat features; we also measured features of surrounding landscapes. We used an information-theoretic approach and structural equation models to compare hypotheses on causal relationships between species distribution and variables measured at multiple levels. We also used a constrained redundancy analyses to evaluate causal relationships between multivariate descriptors of habitat features and community composition. Distribution of Salamandra salamandra was related to landscape, hydrological, and water characteristics: salamanders were more frequent in permanent streams with low phosphate concentration within natural landscapes. Water characteristics were dependent on landscape: streams in natural landscapes had less phosphates. Landscape influenced the salamander both directly and indirectly through its influence on phosphates. Community structure was determined by both landscape and water characteristics. Several species were associated with natural landscapes, and with particular water characteristics. Landscape explained a significant proportion of variability of water characteristics; therefore it probably had indirect effects on community. Upland environments play key roles for amphibians, for example, as the habitat of adults, but upland environments also have indirect effects on the aquatic life stages, mediated through their influence on water characteristics. Synergistic effects can magnify the negative consequences of landscape alteration on amphibians; landscape management can be particularly effective, as it can also improve wetland features.
半水生生物依赖于水体和景观的特征；陆地和水生系统之间的相互作用可能会影响半水生生物群落，决定管理更有效的规模。然而，这种相互作用的后果并不经常被量化，特别是在群落水平上。我们分析了两栖动物的分布，以评估景观特征对淡水生态系统的影响是否会在物种和群落水平上产生间接后果。我们调查了意大利北部的 74 条溪流，以获取关于繁殖两栖动物、水和微生境特征的数据；我们还测量了周围景观的特征。我们使用信息理论方法和结构方程模型来比较物种分布与在多个水平上测量的变量之间因果关系的假设。我们还使用约束冗余分析来评估生境特征和群落组成的多元描述符之间的因果关系。 Salamandra salamandra 的分布与景观、水文学和水特征有关：在自然景观中，磷酸盐浓度低的永久性溪流中， Salamandra salamandra 更为常见。水特征依赖于景观：自然景观中的溪流磷酸盐含量较低。景观通过其对磷酸盐的影响直接和间接影响 Salamandra salamandra。群落结构由景观和水特征决定。一些物种与自然景观和特定的水特征有关。景观解释了水特征可变性的很大一部分；因此，它可能对群落有间接影响。高地环境对两栖动物起着关键作用，例如，作为成体的栖息地，但高地环境也通过其对水特征的影响对水生生命阶段产生间接影响。协同作用可以放大景观改变对两栖动物的负面影响；景观管理可以特别有效，因为它还可以改善湿地特征。
