Leaf decomposition and invertebrate colonization responses to manipulated litter quantity in streams (original) (raw)
Related papers
Leaf-Litter Mixtures Affect Breakdown and Macroinvertebrate Colonization Rates in a Stream Ecosystem
International Review of Hydrobiology, 2009
Previous work in terrestrial and aquatic ecosystems has suggested that the relationship between breakdown rates of leaf litter and plant species richness may change unpredictability due to nonadditive effects mediated by the presence of key-species. By using single-and mixed-species leaf bags (7 possible combinations of three litter species differing in toughness; common alder [Alnus glutinosa], sweet chestnut [Castanea sativa], and Spanish oak [Quercus ilex ilex]), I tested whether leaf species diversity, measured as richness and composition, affects breakdown dynamics and macroinvertebrate colonization (abundance, richness and composition) during 90 days incubation in a stream. Decomposition rates were additive, i.e., observed decomposition rates were not different from expected ones. However, decomposition rates of individual leaf species were affected by the mixture, i.e., there were species-specific responses to mixing litter. The invertebrate communities colonizing the mixtures were not richer and more diverse in mixtures than in single-species leaf bags. On the opposite, mixing leaf species had a negative, non-additive effect on rates of shredder and taxa colonization and on macroinvertebrate diversity.
Freshwater Biology, 2006
1. We examined the relative importance of litter quality and stream characteristics in determining decomposition rate and the macroinvertebrate assemblage living on autumnshed leaves. 2. We compared the decomposition rates of five native riparian tree species (Populus fremontii, Alnus oblongifolia, Platanus wrightii, Fraxinus velutina and Quercus gambelii) across three south-western streams in the Verde River catchment (Arizona, U.S.A.). We also compared the decomposition of three-and five-species mixtures to that of single species to test whether plant species diversity affects rate. 3. Decomposition rate was affected by both litter quality and stream. However, litter quality accounted for most of the variation in decomposition rates. The relative importance of litter quality decreased through time, explaining 97% of the variation in the first week but only 45% by week 8. We also found that leaf mixtures decomposed more quickly than expected, when all the species included were highly labile or when the stream environment led to relatively fast decomposition. 4. In contrast to decomposition rate, differences in the invertebrate assemblage were more pronounced across streams than across leaf litter species within a stream. We also found significant differences between the invertebrate assemblage colonising leaf mixtures compared with that colonising pure species litter, indicating non-additive properties of litter diversity on stream invertebrates. 5. This study shows that leaf litter diversity has the capacity to affect in-stream decomposition rates and stream invertebrates, but that these effects depend on both litter quality and stream characteristics.
Ecosystems, 2019
Plant litter decomposition is an essential ecosystem function in temperate streams. Both riparian vegetation and decomposer communities are major determinants of the decomposition efficiency and the interactions occurring within litter mixtures. However, the extent to which such litter mixture interactions are affected by combined shifts in litter traits and decomposer community is not well understood. We used leaf litter from 10 European tree species in order to study litter decomposition and litter mixture effects occurring in two-species litter mixtures in a temperate forested stream of northwestern France. The study distinguished between (i) decomposition involving microorganisms alone or together with invertebrates, and (ii) decomposition involving litter mixtures of similar or dissimilar nutrient content. Increasing mean litter nutrient concentration favored both microbial activity and litter decomposition rate. Surprisingly, the highest litter mixture effects occurred in mixtures containing two nutrient-rich litters and occurred mainly in macroinvertebrate presence. Both the "mass-ratio hypothesis", expressed as the community weighted mean traits (TraitCWM), and the "niche complementarity hypothesis", expressed as the functional dissimilarity of litter traits (TraitFD), contributed to explain litter mixture effects. However, TraitCWM was found to be a better predictor than TraitFD. Finally, when evaluating the individual contributions of litter nutrients, calcium and magnesium appeared as important drivers of litter mixture effects. Our findings suggest that the mass-ratio hypothesis overrules the niche complementarity hypothesis as a driver of litter diversity effects. Our study highlights the key importance of macroinvertebrates and of leaf nutrients, such as Ca and Mg, which are often neglected in decomposition studies in streams.
Litter breakdown and invertebrate detritivores in a resource-depleted Appalachian stream
Archiv fur Hydrobiologie, 2003
Litter breakdown and invertebrate detritivores in a resource-depleted Appalachian stream S. L. ~ggertl* and J. B. ~a l l a c e~v~ With 6 figures and 4 tables Abstract: We measured breakdown rates of leaves and small wood for the first three years in a stream in which detrital inputs were excluded for 7 years and in a reference stream located in the Appalachian Mountains of North Carolina, USA. Leaf and wood inputs were excluded using a gill-net canopy constructed over a 170-m section of stream. We hypothesized that red maple (Acer rubrum) and rhododendron (Rhododendron m i m a) leaf breakdown rates would decline in the litter exclusion stream as shredder production decreased with each year of litter exclusion. In contrast, we expected faster wood breakdown rates in the litter exclusion stream as microbes and invertebrates shifted from leaves to wood as their primary organic matter resource. Consistent with our predictions, wood breakdown rates were significantly faster in the litter exclusion stream. We also found sigdicantly slower processing rates of maple leaves in the litter exclusion stream compared to the reference stream during years 2 and 3. Slower breakdown rates for red maple leaves in the litter exclusion stream were associated with lower shredder production and estimated consumption rates in years 2 and 3. Shredder production and consumption rate estimates were also lower in the exclusion stream for rhododendron leaves, but leaf breakdown rates were not affected. We also found that shredder production in litterbags was 3-4 x greater than in benthic substrates in the litter exclusion stream. In contrast, shredder production in litterbags was similar to that in benthic substrates in the reference stream. These differences were probably due to the relatively low availability of organic matter in benthic substrates in the litter exclusion stream. Our data show shredders track high quality organic matter resources (leaves) and contribute to their loss rate, illustrating the interdependence of stream organisms and terrestrial organic matter input.
Leaf-litter quality effects on stream ecosystem functioning: a comparison among five species
Fundamental and Applied Limnology / Archiv für Hydrobiologie, 2013
The replacement of native vegetation by exotic species has the potential to impact detritus based stream ecosystems. To test the possible consequences of vegetation alteration on stream ecosystem functioning we compared the processing rate and invertebrate colonisation of leaves from fi ve different tree species, two natives (Alnus glutinosa and Quercus pyrenaica) and three exotics (Populus × canadensis, Platanus hispanica and Pinus radiata) in three unaltered forested streams in the Atlantic region of northern Spain. Breakdown rates, nitrogen concentration and C:N ratio of incubated leaves, and invertebrate communities in the benthos and bags were analysed. Breakdown rates differed among leaf species and were positively related to initial nitrogen concentration and negatively to the C:N ratio. After the incubation period (6 -7 weeks), the differences in nutritional quality among leaf species and the relationship between breakdown rates and litter quality persisted. The density and biomass of macroinvertebrates and shredders associated with litter bags correlated with leaf-nitrogen concentration and explained the differences in breakdown rates. The results indicate that the replacement of native deciduous forest by plant commercial species with leaf-litter of low quality such as plane and pine can affect in-stream organic matter processing and the subsequent transference of energy throughout the food web.
International Review of Hydrobiology, 2008
This study evaluated if there are differences in leaf breakdown and invertebrate colonization among tree species differing in quality (toughness), and which factors could influence these differences. Common alder leaves decomposed significantly faster then either sweet chestnut or Spanish oak (k values of -0.0332, -0.0108, and -0.0112, respectively) during the first 2 months. Shredder abundance was highest when leaf mass remaining was 50%, and the samples clustered in mixed groups of sampling dates and leaf species, suggesting that stage of decomposition was an important factor influencing shredder colonization. During the first two months of decomposition, the physicochemical characteristics of leaf litter and the interaction between leaf toughness and the occurrence of frequent spates seemed to be the main factors affecting leaf breakdown rates in the stream.
2016
Riparian areas are fundamental to aquatic ecosystems by regulating temperature and light regimes, and providing allochthonous subsidies critical to the survival of aquatic and terrestrial species. On a global scale, increased rates of anthropogenic disturbance from agricultural activities and urbanization have caused the degradation of aquatic habitats. As a result, billions of dollars have been spent on stream restoration projects to protect aquatic resources; however, fundamental ecosystem processes like litter decomposition are rarely addressed. We conducted a litterbag experiment in a degraded high desert stream proposed for large-scale restoration to test the effects of reach location, canopy cover, and temperature on the rates of leaf litter breakdown attributed to microbial activity and macroinvertebrate shredders. Results from coarse mesh litterbags indicated that total leaf breakdown rates per degree-day were significantly faster in upstream, less degraded reaches, associat...
Pathways, Mechanisms, and Consequences of Nutrient-Stimulated Plant Litter Decomposition in Streams
The Ecology of Plant Litter Decomposition in Stream Ecosystems, 2021
Excess nitrogen (N) and phosphorus (P) inputs to streams occur globally, and affect not only stream autotrophs, but also heterotrophic microbes and detrital carbon processing. Detrital carbon, such as leaf litter, supports stream food webs and their connectivity via downstream detritus fluxes. Nutrient enrichment increases litter decomposition rates across multiple scales and trophic levels by stimulating activity of microbial decomposers and enhancing interactions among microbial decomposers, detritivores, and physical abrasion. Nutrient effects on microbial and detritivore-mediated decomposition are typically greater for recalcitrant vs. labile litter, especially when coupled to low initial nutrient concentrations. Recent studies and syntheses show that (1) dissolved N and P affect litter by stimulating fungal activity and nutrient immobilization, thus, increasing detrital nutrient content, (2) nutrient effects are greatest with N and P together (vs. individually) and when detritivores are present, and (3) ecosystem-level effects of nutrient enrichment can be predicted from small-scale measurements. Despite extensive studies of leaf litter decomposition, its application as a tool to manage nutrient enrichment issues trails comparable tools for autotrophic (i.e., algal) pathways. Thus, better understanding of the consequences of nutrient enrichment on leaf litter and other detrital carbon is important to predict how nutrients will affect stream ecosystem functioning.
Hydrobiologia, 1997
Benthic invertebrates, litter decomposition, and litterbag invertebrates were examined in streams draining pine monoculture and undisturbed hardwood catchments at the Coweeta Hydrologic Laboratory in the southern Appalachian Mountains, USA. Bimonthly benthic samples were collected from a stream draining a pine catchment at Coweeta during 1992, and compared to previously collected (1989)(1990) benthic data from a stream draining an adjacent hardwood catchment. Litter decomposition and litterbag invertebrates were examined by placing litterbags filled with pine or maple litter in streams draining pine catchments and hardwood catchments during 1992-1993 and 1993-1994. Total benthic invertebrate abundance and biomass in the pine stream was ca. 57% and 74% that of the hardwood stream, respectively. Shredder biomass was also lower in the pine stream but, as a result of higher Leuctra spp. abundance, shredder abundance was higher in the pine stream than the hardwood stream. Decomposition rates of both pine and red maple litter were significantly faster in pine streams than adjacent hardwood streams (p<0.05). Total shredder abundance, biomass, and production were similar in maple bags from pine and hardwood streams. However, trichopteran shredder abundance and biomass, and production of some trichopteran taxa such as Lepidostoma spp., were significantly higher in maple litterbags from pine streams than hardwood streams (p<0.05). In contrast, plecopteran shredders (mainly Tallaperla sp.) were more important in maple litterbags from hardwood streams. Shredders were well represented in pine litterbags from pine streams, but low shredder values were obtained from pine litterbags in hardwood streams. Results suggest conversion of hardwood forest to pine monoculture influences taxonomic composition of stream invertebrates and litter decomposition dynamics. Although the impact of this landscape-level disturbance on invertebrate shredder communities appeared somewhat subtle, significant differences in decomposition dynamics indicate vital ecosystem-level processes are altered in streams draining pine catchments.