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Little is known regarding consequences of climate change on riparian plant functional types (PFTs) related to leaf traits, with putative domino effects on stream food webs, plausible even if the tipping point of stream-desiccation is not reached. We hypothesized that, as stream food-webs are highly dependent on riparian subsidies, climate change might alter PFTs to the point of weakening terrestrial-aquatic linkages. We conducted a gradient analysis to assess the relative effects of climate, soil and riparian physical characteristics on PFTs. If PFTs differ significantly in leaf traits and climate had major influences on them, we could assume space-for-time interchangeability forward in time to predict leaf traits changes, and consequences for stream food webs under future climate change scenarios. Results indicated a clear distinction in leaf traits among PFTs: woody deciduous plants showed leaf traits associated to high decomposability and nutritional value for invertebrate shredders compared to evergreen woody and giant graminoid groups. We found a prime role of climate predicting changes in abundance and diversity of PFTs: 1) a warming and precipitation-decline scenario, coupled with soil characteristics related to aridification, would have detrimental effects on deciduous plants, while fostering giant graminoids; 2) in a scenario of no precipitation-reduction in wetter areas, warming might promote the expansion of evergreen to the detriment of deciduous plants. In both scenarios the net outcome implies increasing recalcitrance of leaf litter inputs, potentially weakening terrestrial-aquatic linkages in headwater streams.

Plant litter decomposition is a key ecosystem process that can be altered by global changes such as biodiversity loss. These effects can be particularly important in detritus-based ecosystems, such as headwater streams, which are mainly fuelled by allochthonous plant litter inputs. However, experiments examining effects of plant diversity on litter decomposition in streams have not reached consensus about which measures of biodiversity are more relevant. We explored the influence of two of these measures, plant species richness (SR; monocultures vs. 3-species mixtures) and phylogenetic distance (PD; species belonging to the same family vs. different families), on leaf litter decomposition and associated processes and variables (nutrient dynamics, fungal biomass and detritivore growth), in a stream microcosm experiment using litter from 9 tree species belonging to 3 families. We found a negative effect of SR on decomposition (which contradicted the results of previous experiments) but a positive effect on fungal biomass. While PD did not affect decomposition, both SR and PD altered nutrient dynamics: there was greater litter and detritivore N loss in low-PD mixtures, and greater litter P loss and detritivore P gain in monocultures. This suggested that the number of species in mixtures and the similarity of their traits both modulated nutrient availability and utilization by detritivores. Moreover, the greater fungal biomass with higher SR could imply positive effects on detritivores in the longer term. Our results provide new insights of the functional repercussions of biodiversity loss by going beyond the often-explored relationship between SR and decomposition, and reveal an influence of plant species phylogenetic relatedness on nutrient cycling that merits further investigation.

Aim Leaf litter inputs from riparian vegetation and its decomposition play a key role in energy and nutrient transfer in many stream ecosystems. Instream leaf litter decomposition is driven by both leaf traits and environmental conditions. Therefore, understanding and predicting leaf trait variation under current environmental changes and their putative interactive effects on stream food webs is a critical challenge. Most studies have focussed on the assumed higher interspecific leaf trait variability, with little research addressing an intraspecific perspective. Location Andalusia, Spain. Methods We assessed the relative effects of climate and soil conditions on the plasticity of leaf traits of four common woody riparian species in permanent low‐order Mediterranean streams across a wide aridity gradient. We used a space‐for‐time substitution approach to predict leaf trait changes and consequences for stream food webs in a future climate change scenario. Results Overall, we found that aridity had a major influence on leaf trait plasticity but with opposite patterns depending on plant functional type, although soil was the strongest predictor in some cases. Results indicated that leaf quality—linked to palatability and decomposability—of Alnus glutinosa, Salix atrocinerea and Rubus ulmifolius (deciduous/semi‐deciduous) will decrease with forecasted aridification, whereas the palatability of the evergreen Nerium oleander will increase. We observed higher trait plasticity than interspecific variation for leaf P, Ca and Mg concentrations and C:P ratio. Main conclusions Our findings suggest a decrease of intraspecific leaf quality in riparian deciduous species with global warming in a relatively short term. In a longer term, this may merge with the forecasted dieback of deciduous species in riparian corridors of temperate climate zones. These changes have the potential to significantly impair ecosystem functioning of Mediterranean mountain streams currently under deciduous gallery forests.

The linkage between leaf-litter and macroinvertebrate shredders is pivotal for stream food webs. Global change is predicted to decrease the nutritional quality of litter inputs to streams. However, little is known about shredder’s ability to develop local interpopulation adaptations to face nutrient-depleted leaf-litter. We hypothesized that this adaptation could be present in populations receiving low-quality leaf-litter. We performed feeding tests on three abundant shredders species from lowland (a snail) and mountain (two insects) streams. Two populations of each species were derived from two subregions contrasting in average quality of litter inputs. Individuals were fed on four diets of contrasting quality: two leaf-litter species with two qualities each, and their feeding rates, survivorship, growth, and energetic storage were evaluated. Results suggest that local population adaptation to low-quality litters is not common, being essentially a fixed species trait that varies across species, in particular among snails and insects. The ability of the snail to cope with low-quality litters suggests that ecosystem processes in lowland streams may resist reductions in litter quality. Conversely, potential alterations of riparian vegetation linked to global changes might disrupt mountain stream ecosystem functioning.

The relationship between detritivore diversity and decomposition can provide information on how biogeochemical cycles are affected by ongoing rates of extinction, but such evidence has come mostly from local studies and microcosm experiments. We conducted a globally distributed experiment (38 streams across 23 countries in 6 continents) using standardised methods to test the hypothesis that detritivore diversity enhances litter decomposition in streams, to establish the role of other characteristics of detritivore assemblages (abundance, biomass and body size), and to determine how patterns vary across realms, biomes and climates. We observed a positive relationship between diversity and decomposition, stron- gest in tropical areas, and a key role of abundance and biomass at higher latitudes. Our results suggest that litter decomposition might be altered by detritivore extinctions, parti- cularly in tropical areas, where detritivore diversity is already relatively low and some environmental stressors particularly prevalent.

The relationship between detritivore diversity and decomposition can provide information on how biogeochemical cycles are affected by ongoing rates of extinction, but such evidence has come mostly from local studies and microcosm experiments. We conducted a globally distributed experiment (38 streams across 23 countries in 6 continents) using standardised methods to test the hypothesis that detritivore diversity enhances litter decomposition in streams, to establish the role of other characteristics of detritivore assemblages (abundance, biomass and body size), and to determine how patterns vary across realms, biomes and climates. We observed a positive relationship between diversity and decomposition, strongest in tropical areas, and a key role of abundance and biomass at higher latitudes. Our results suggest that litter decomposition might be altered by detritivore extinctions, particularly in tropical areas, where detritivore diversity is already relatively low and some environmental stressors particularly prevalent. It is unclear whether stream detritivore diversity enhances decomposition across climates. Here the authors manipulate litter diversity and examine detritivore assemblages in a globally distributed stream litterbag experiment, finding a positive diversity-decomposition relationship stronger in tropical streams, where detritivore diversity is lower.

Currently, microwaves, ultrasound, and ultrasound‐microwaves are technologies with several applications, one of which is their use as a method of pasteurization. So far, these techniques have not been used for the pasteurization of a functional aguamiel beverage. This beverage was pasteurized and enriched with probiotic LAB to generate an antihypertensive effect. The physicochemical characteristics (pH, total soluble solids, and color) of the aguamiel beverage were evaluated. Microbiological analysis of the product was also carried out. The probiotic LAB were added to the beverage with the selected pasteurization technique. The growth of LAB in the aguamiel beverage and the prebiotic effects that this product as well as the antihypertensive activity of the beverage were evaluated. It was shown that there is no significant effect of the techniques used on the physicochemical characteristics of the product. However, the storage time may be affected. Compared to traditional pasteurization, microwave, ultrasound, and ultrasound‐microwave techniques were found to reduce the concentration of some pathogenic microorganisms. The microwave technique was selected as the most effective for pasteurization. The probiotic LAB were able to grow in the pasteurized aguamiel beverage and produce an antihypertensive effect. In summary, a functional microwavable pasteurized aguamiel beverage with antihypertensive activity was produced. Aguamiel was pasteurized and enriched with probiotic LAB to generate a functional beverage with antihypertensive effect. The physicochemical characteristics (pH, total soluble solids, and color) of this beverage were evaluated. Microbiological analysis of the product was also carried out. The growth of LAB in the aguamiel beverage and the prebiotic effects as well as the antihypertensive activity of this beverage were evaluated. Compared to traditional pasteurization, microwave, ultrasound, and ultrasound‐microwave techniques were found to reduce the concentration of some pathogenic microorganisms. The microwave technique was selected as the most effective for pasteurization. The probiotic LAB were able to grow in the pasteurized aguamiel beverage and produce an antihypertensive effect. In summary, a functional microwavable pasteurized aguamiel beverage with antihypertensive activity was produced.