Exotic riparian vegetation lowers fungal diversity but not leaf decomposition in Portuguese streams

Abstract

1. We characterised the fungal communities of eight streams in Portugal, four bordered by native deciduous forest and four bordered by pure stands of Eucalyptus globulus. 2. Aquatic hyphomycete species richness and evenness, but not numbers of water‐borne conidia, of aquatic hyphomycetes were significantly lower in eucalypt bordered streams. 3. Multivariate analyses subdivided the fungal communities into two distinct groups corresponding to riparian vegetation. 4. Despite these differences in the dominant decomposer community, decay rates of eucalypt leaves (accounting for ≥98% of naturally occurring leaves in eucalypt bordered streams, absent in native forest) and chestnut leaves (occurring naturally in native forests) did not differ between the two groups of streams.

The influence of water quality and macroinvertebrate colonization on the breakdown process of native and exotic leaf types in sub-alpine stream

“…Some studies suggested that invasive species can cause alterations at different levels in the structure and functioning of ecosystems (Ehrenfeld 2010). Moreover, the establishment of exotic riparian plants can alter the exchange of organic material between terrestrial and lotic ecosystems, both changing the quantity (Mineau et al 2011(Mineau et al , 2012 or the quality (B€ arlocher & Graça 2002) of terrestrial litter inputs, leading to alterations in the composition (Serra et al 2013) and density (Lester et al 1994) of benthic assemblages. Many studies have shown that, for instance, the introduction and spread of Eucalyptus globulus plantations in Spain had a strong effect on in-stream terrestrial detritus colonization and degradation (Chauvet et al 1997;Pozo et al 1998;Ferreira et al 2006), while other studies have shown weak influence of exotic species on streams (Braatne et al 2007).…”

Comparison of leaf decomposition and macroinvertebrate colonization between exotic and native trees in a freshwater ecosystem

“…Thirdly, the energy of the flowing water also helps to fragment the litter, facilitating macro and micro-organism colonization and speeding up breakdown processes, regardless of the origin (native or exotic) of the litter. The effects of the replacement of native riparianforest species by exotic ones in terrestrial and aquatic ecosystems are context-dependent (Ba¨rlocher and Grac¸a 2002;Harner et al 2009). For example, studies comparing litter decomposition between the exotic Eleagnus angustifolia and the native Populus deltoides, found faster decay in the nitrogen-rich litter of Eleagnus in a lotic aquatic ecosystem, but found the reverse trend in a terrestrial ecosystem (Harner et al 2009).…”

“…Therefore, replacements of native by exotic tree species in riparian ecosystems can affect the quality and quantity of detrital inputs (Reinhart and VandeVoort 2006;Swan et al 2008). Such changes can modify detritus processing through changes in microbial communities or macrodetritivorous colonization (Ba¨rlocher and Grac¸a 2002;Reinhart and VandeVoort 2006). All these changes finally alter nutrient cycling and community structure of the aquatic ecosystems.…”

Influence of invasiveAcer negundoleaf litter on benthic microbial abundance and activity in the littoral zone of a temperate river in Lithuania

“…Several studies have been performed to examine invasive species effects on leaf decomposition rates in aquatic ecosystems by litterbags method, but still have found mixed effects (Swan et al, 2008;Marano et al, 2013;Serra et al, 2013). Variability in leaf litter decomposition rates in aquatic systems may be linked to the direct or indirect effect of leaf litter on the changes of benthic communities composition and activity (Bärlocher and Graça, 2002;Medina-Villar et al, 2015), that highlights the importance of specific studies in order to understand the effects of invasions on ecosystem functioning (Fargen et al, 2015).…”