Leaf litter traits drive community structure and functioning in a natural aquatic microcosm

Abstract

Leaf litter fuels secondary production in many aquatic ecosystems. Although the identity and species richness of leaf litter have been shown to influence ecosystem functioning and food‐web composition, it has been challenging to relate such patterns to mechanisms based on litter traits. Here, we investigate how six different leaf litter species, and their mixture, affect litter decomposition, as well as the colonisation and survival of associated aquatic invertebrates in natural microecosystems (tank bromeliads). We then ask whether these effects of litter composition are explained by chemical and structural traits of the litter. Litter composition affected decomposition rates, assembly of aquatic macroinvertebrates in bromeliads and survival of some detritivores (e.g. Chironomidae). In general, most of this effect of litter composition was due to differences between litter species, not between single‐species and six‐species mixtures, and could be explained in terms of two dominant axes in litter traits. Decomposition was fastest in litters with high specific leaf area (SLA), N:P ratios and N and P contents, and slowest in litters with high lignin content and C:N ratios. Chironomid survival was also greatest on high N, N:P and SLA litters. Our results highlight the importance of considering leaf litter traits on the structure and functioning of freshwater ecosystems in future studies. More broadly, these results add to a growing consensus that functional traits of resource species, rather than the number of resource species, are essential to predicting resource–consumer interactions in food webs.

Warming and leaf litter functional diversity, not litter quality, drive decomposition in a freshwater ecosystem

“…Although such findings have emerged from studies in streams, they are not limited to these ecosystems. Previous studies using tank bromeliads reported similar patterns in litter decomposition 41,48,60 . Indeed, in our study we did not detect differences in decomposition between the two mesh sizes after 80 days, which reinforces the role of microorganisms as the main decomposers in tank bromeliads.…”

“…They suggest that these organisms may be resistant or resilient to changes in temperature as they live in small water bodies and are frequently exposed to temperature variation, being adapted to these environment 4 . However, we cannot rule out the possibility that our coarse-mesh bags may have prevented access to litter for some invertebrate detritivores and thus decreased their effect on overall decomposition, despite previous studies in tank bromeliads also did not find effects of invertebrate detritivores on decomposition 41,48,59 . On the other hand, recent studies have shown that although microorganisms may be the major decomposers of organic matter in bromeliads, macroinvertebrates may have an important role in the interactions with microorganisms 41 .…”

“…Phytotelm bromeliads can house a wide diversity of arthropod fauna, mainly insects in their larval stages, including predators (Tabanidae, Tanypodinae, Zygoptera, Dytiscidae, Corethrellidae), detritivores (Trichoptera, Limoniidae, Scirtidae, Syrphidae, Psychodidae, Chironomidae) and filter feeders (Culicidae). In addition, a diverse terrestrial fauna inhabits the non-submerged parts of bromeliad leaves, including spiders, mites, harvestmen and collembolas 47,48 .…”

Reviewing the role of plant litter inputs to forested wetland ecosystems: leafing through the literature

“…b, Migliorini et al. ). Although taking a trait‐based approach to understanding the effects of litter in lentic systems remains in its infancy, it promises a pathway toward generalizing the role of litter quality and ultimately providing a tangible link between concepts of subsidy quantity and quality.…”

Changes in rainfall level and litter stoichiometry affect aquatic community and ecosystem processes in bromeliad phytotelmata

“…Previous studies have reported declines in species abundances with increasing litter C:N ratios (Richardson, Richardson, Scatena, & Mcdowell, 2000). Also, changes in the litter N:P ratios can influence the survivorship (Migliorini, Srivastava, & Romero, 2018) and performance of aquatic insects living in tank bromeliads (González, Romero, & Srivastava, 2014). Tank bromeliads have been successfully used as natural microcosms to investigate the isolated impacts of environmental changes, such as rainfall regimes, warming and productivity, on community structure and ecosystem functioning (Amundrud & Srivastava, 2016;Antiqueira, Petchey, & Romero, 2018;Bernabé et al, 2018;Dézerald, Céréghino, Corbara, Dejean, & Leroy, 2015;Pires et al, 2016).…”