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1.
Adrian OrihuelaTorres Juan Manuel PrezGarcía Jos Antonio SnchezZapata Francisco Botella Esther SebastinGonzlez 《Ecology and evolution》2022,12(8)
Invasive Alien Species (IAS) alter ecosystems, disrupting ecological processes and driving the loss of ecosystem services. The common carp Cyprinus carpio is a hazardous and widespread IAS, becoming the most abundant species in many aquatic ecosystems. This species transforms ecosystems by accumulating biomass to the detriment of other species, thus altering food webs. However, some terrestrial species, such as vertebrate scavengers, may benefit from dead carps, by incorporating part of the carp biomass into the terrestrial environment. This study describes the terrestrial vertebrate scavenger assemblage that benefits from carp carcasses in a Mediterranean wetland. We also evaluate the seasonal differences in the scavenger assemblage composition and carrion consumption patterns. Eighty carp carcasses (20 per season) were placed in El Hondo Natural Park, a seminatural mesohaline wetland in south‐eastern Spain, and we monitored their consumption using camera traps. We recorded 14 scavenger species (10 birds and four mammals) consuming carp carcasses, including globally threatened species. Vertebrates consumed 73% of the carrion biomass and appeared consuming at 82% of the carcasses. Of these carcasses consumed, 75% were completely consumed and the mean consumption time of carcasses completely consumed by vertebrates was 44.4 h (SD = 42.1 h). We recorded differences in species richness, abundance, and assemblage composition among seasons, but we did not find seasonal differences in consumption patterns throughout the year. Our study recorded a rich and efficient terrestrial vertebrate scavenger assemblage benefitting from carp carcasses. We detected a seasonal replacement on the scavenger species, but a maintenance of the ecological function of carrion removal, as the most efficient carrion consumers were present throughout the year. The results highlight the importance of vertebrate scavengers in wetlands, removing possible infectious focus, and moving nutrients between aquatic and terrestrial environments. 相似文献
2.
- The societal value, ecological importance and thermal sensitivity of stream‐dwelling salmonids have prompted interest in adaptive management strategies to limit the effects of climate change on their habitats. Additionally, in northern temperate regions, the management and restoration of riparian broadleaf forest is advocated increasingly to dampen variations in stream water temperature and discharge, but might have collateral effects on salmonids by changing allochthonous subsidies.
- Here, in a cross‐sectional analysis of 18 temperate headwaters with different riparian and catchment land use, we use classical fisheries data alongside stable isotope ratios in salmonids and their macroinvertebrate prey to examine whether increasing catchment cover of broadleaf trees could (i) increase the density, biomass and size of salmonids, (ii) increase brown trout (Salmo trutta) dietary reliance on production of terrestrial origin and (iii) mediate allochthonous energy flux between aquatic macroinvertebrates and brown trout.
- Contrary to expectation, catchment broadleaf cover had no systematic effect on salmonid density or individual size, although salmonid biomass was lowest in streams draining non‐native conifers. Moreover, there was no major effect of land use on the dependence of S. trutta on terrestrial production: averaged across all sites, trout used more production from in‐stream (62 ± 3%: mean ± 1 SE) than terrestrial (38 ± 3%) sources. Dependence on terrestrial production varied more substantially among individual streams than with riparian land use, mirroring site‐specific patterns observed in macroinvertebrates.
- Although increased broadleaf cover could benefit salmonids by offsetting the impacts of warming related to climate change, these results imply that broadleaf restoration along temperate, upland headwaters is neutral with respect to salmonid biomass, density and terrestrial subsidies. In contrast, the use of non‐native conifers for stream shading could have negative effects on salmonid production. Knowledge of the ecological implications of climate change adaptation remains rudimentary, and we advocate further evaluations like ours not only for fresh waters, but for ecosystems more generally.
3.
- Biodiversity is globally threatened by the replacement of native species by invasive species and ensuing changes in ecosystem functioning. Although trophic linkages between aquatic and terrestrial ecosystems have received attention, effects of aquatic invasive species on the flow of resource subsidies have been considered only recently.
- We examined how the effects of one of the most invasive macroinvertebrate species in European waterways, the amphipod Dikerogammarus villosus, extend from streams to the terrestrial food web. We quantified aquatic emergence and the contribution of aquatic resources to the diets of two riparian spider taxa in relation to the density of D. villosus.
- Our results indicated that the effects of this invasive species carry over to the terrestrial system via cross‐ecosystem flow of resource subsidy. The contribution of aquatic resources to the diet of the terrestrial web‐building spider Tetragnatha decreased from 60% at low densities of D. villosus to 10% at a D. villosus density >5000 individuals m?2. This correlates with a decreasing emergence rate of merolimnic midges (species with an aquatic larval phase) from 12 to <3 mg dry biomass m?2 day?1 at the respective densities of D. villosus.
- The magnitude of biomass flow from the aquatic to the terrestrial ecosystem is most likely decreased by D. villosus, and this decrease extends to the diet of riparian web‐building spiders. Effects of this aquatic invader may also extend to a decoupling of the terrestrial ecosystem from the aquatic ecosystem in terms of subsidy flux.
4.
Birds experience a sequence of critical events during their life cycle, and past events can subsequently determine future performance via carry‐over effects. Events during the non‐breeding season may influence breeding season phenology or productivity. Less is understood about how events during the breeding season affect individuals subsequently in their life cycle. Using stable carbon isotopes, we examined carry‐over effects throughout the annual cycle of prairie warblers (Setophaga discolor), a declining Nearctic–Neotropical migratory passerine bird. In drier winters, juvenile males that hatched earlier at our study site in Massachusetts, USA, occupied wetter, better‐quality winter habitat in the Caribbean, as indicated by depleted carbon isotope signatures. For juveniles that were sampled again as adults, repeatability in isotope signatures indicated similar winter habitat occupancy across years. Thus, hatching date of juvenile males appears to influence lifetime winter habitat occupancy. For adult males, reproductive success did not carry over to influence winter habitat occupancy. We did not find temporally consecutive “domino” effects across the annual cycle (breeding to wintering to breeding) or interseasonal, intergenerational effects. Our finding that a male''s hatching date can have a lasting effect on winter habitat occupancy represents an important contribution to our understanding of seasonal interactions in migratory birds. 相似文献
5.
- Rivers and their adjacent riparian zones are intimately linked by fluxes of water, air masses, nutrients and organisms. Intermittent rivers constitute ideal systems to examine these linkages because they are characterised by alternating wet and dry phases, and hence, natural and contrasting variations occur in aquatic resources and environmental conditions.
- We addressed the effects of river drying on riparian communities by collecting ground‐dwelling arthropods at three perennial sites and at four intermittent sites during a wet and a dry phase in the Albarine River (France). We first predicted that during dry phases, declines in aquatic resources and loss of water would create harsh environmental conditions and alter community structure and composition, due to decreases in predators and hygrophilous taxa. Second, we predicted that alternating wet and dry phases would enhance cumulative taxonomic richness over time owing to an increase in species turnover.
- We found similar decreasing temporal patterns in taxonomic richness and abundance at intermittent and perennial sites, indicating that river drying had no effect on the structure of riparian arthropod communities. Community composition at intermittent and perennial sites differed only during the dry phase, indicating that intermittent and perennial sites gained and lost different sets of taxa as the river dried. Nevertheless, species turnover did not differ between sites, while taxonomic richness was always higher at intermittent sites.
- Although some taxa were sensitive to river drying, the Albarine River supports rich and abundant riparian arthropod communities. While several studies have reported a strong dependence of riparian populations on aquatic resources, our results indicate that the effects of river drying on riparian arthropods at the community level are weak and discrete in time in the Albarine River.
6.
JEFF S. WESNER 《Freshwater Biology》2012,57(12):2465-2474
1. Empirical and theoretical research over the past decade has demonstrated the widespread importance of aquatic subsidies to terrestrial food webs. In particular, adult aquatic insects that emerge from streams and lakes are prey for terrestrial predators. While variation in the magnitude of this subsidy is clearly important, the potential top‐down effects of the predatory adults of some aquatic insects in terrestrial food webs are largely unknown. 2. I used published data on benthic insect density (as a proxy for emergence) in North and South America to explore how the proportion of benthic insects that are predatory as adults varies across a gradient of mean annual stream temperature. 3. The proportion of benthic insects that are predatory as adults varied widely across sites (0–12% by abundance; 0–86% by biomass). There was a positive relationship between mean annual stream temperature and the proportion of predatory adults across all sites, driven largely by the greater abundance/biomass of predatory taxa (e.g. odonates), relative to non‐predators (e.g. midges, mayflies, caddisflies), in tropical than in temperate streams. 4. The ‘trophic structure’ (i.e. the proportion of predators) of emerging adult aquatic insects is an understudied source of variation in aquatic–terrestrial interactions. Incorporation of trophic structure in future studies is needed to understand how future modification of fresh waters may affect adjacent terrestrial food webs through both bottom‐up and top‐down effects. 相似文献
7.
Kehong Wang Xingzhong Yuan Shuaikai Wu Guanxiong Zhang Hong Liu Lilei Zhou Mengjie Zhang 《Ecohydrology》2019,12(3)
River damming is one of the most serious anthropogenic disturbances impacting river ecosystems. Little is known about the consequences of river damming on ground‐dwelling arthropods, although they represent a functionally important component of riverine ecosystems because they provide an essential link between aquatic and terrestrial ecosystems. We investigated the effects of river damming on the composition and structure of arthropod communities in the Baijia Stream located in the centre of the Three Gorges Reservoir. Our results revealed that (a) river damming modified the community composition of riparian arthropods, as 24 taxa disappeared and 11 taxa colonized the new habitat after damming; (b) river damming altered the community structure of arthropods because higher richness and abundance of arthropods were recorded in the regulated section, especially for predators, detritivores, and herbivores; and (c) river damming altered the lateral distribution along riparian–upland gradients and the temporal dynamics of arthropod communities. Interestingly, upland habitats of streams supported more species than the riparian habitat in the regulated section, suggesting that uplands may become an important habitat for riparian species after river damming. Although higher total abundance and richness and higher abundance of some feeding guilds of arthropods were observed in the regulated section, the negative effects of river damming on biodiversity are addressed in this paper. Thus, ground‐dwelling arthropods appear to be sensitive indicators of the ecological effects of river damming. Assessment of the consequences of river damming and dam management plans should consider ground‐dwelling arthropod communities in associated riparian and upland habitats. 相似文献
8.
Rolanda J. Steenweg Glenn T. Crossin Holly L. Hennin H. Grant Gilchrist Oliver P. Love 《Ecology and evolution》2022,12(2)
- The availability and investment of energy among successive life‐history stages is a key feature of carryover effects. In migratory organisms, examining how both winter and spring experiences carryover to affect breeding activity is difficult due to the challenges in tracking individuals through these periods without impacting their behavior, thereby biasing results.
- Using common eiders Somateria mollissima, we examined whether spring conditions at an Arctic breeding colony (East Bay Island, Nunavut, Canada) can buffer the impacts of winter temperatures on body mass and breeding decisions in birds that winter at different locations (Nuuk and Disko Bay, Greenland, and Newfoundland, Canada; assessed by analyzing stable isotopes of 13‐carbon in winter‐grown claw samples). Specifically, we used path analysis to examine how wintering and spring environmental conditions interact to affect breeding propensity (a key reproductive decision influencing lifetime fitness in female eiders) within the contexts of the timing of colony arrival, pre‐breeding body mass (body condition), and a physiological proxy for foraging effort (baseline corticosterone).
- We demonstrate that warmer winter temperatures predicted lower body mass at arrival to the nesting colony, whereas warmer spring temperatures predicted earlier arrival dates and higher arrival body mass. Both higher body mass and earlier arrival dates of eider hens increased the probability that birds would initiate laying (i.e., higher breeding propensity). However, variation in baseline corticosterone was not linked to either winter or spring temperatures, and it had no additional downstream effects on breeding propensity.
- Overall, we demonstrate that favorable pre‐breeding conditions in Arctic‐breeding common eiders can compensate for the impact that unfavorable wintering conditions can have on breeding investment, perhaps due to greater access to foraging areas prior to laying.
9.
Rivers can provide important sources of energy for riparian biota. Stable isotope analysis (δ13C, δ15N) together with linear mixing models, were used to quantify the importance of aquatic insects as a food source for a riparian
arthropod assemblage inhabiting the shore of the braided Tagliamento River (NE Italy). Proportional aquatic prey contributions
to riparian arthropod diets differed considerable among taxa. Carabid beetles of the genus Bembidion and Nebria picicornis fed entirely on aquatic insects. Aquatic insects made up 80% of the diet of the dominant staphylinid beetle Paederidus rubrothoracicus. The diets of the dominant lycosid spiders Arctosa cinerea and Pardosa wagleri consisted of 56 and 48% aquatic insects, respectively. In contrast, the ant Manica rubida fed mainly on terrestrial sources. The proportion of aquatic insects in the diet of lycosid spiders changed seasonally, being
related to the seasonal abundance of lycosid spiders along the stream edge. The degree of spatial and seasonal aggregation
of riparian arthropods at the river edge coincided with their proportional use of aquatic subsidies. The results suggest that
predation by riparian arthropods is a quantitatively important process in the transfer of aquatic secondary production to
the riparian food web. 相似文献
10.
Daniel C. Allen;James Larson;Christina A. Murphy;Erica A. Garcia;Kurt E. Anderson;Michelle H. Busch;Alba Argerich;Alice M. Belskis;Kierstyn T. Higgins;Brooke E. Penaluna;Veronica Saenz;Jay Jones;Matt R. Whiles; 《Ecology letters》2024,27(3):e14401
Ecosystems that are coupled by reciprocal flows of energy and nutrient subsidies can be viewed as a single “meta-ecosystem.” Despite these connections, the reciprocal flow of subsidies is greatly asymmetrical and seasonally pulsed. Here, we synthesize existing literature on stream–riparian meta-ecosystems to quantify global patterns of the amount of subsidy consumption by organisms, known as “allochthony.” These resource flows are important since they can comprise a large portion of consumer diets, but can be disrupted by human modification of streams and riparian zones. Despite asymmetrical subsidy flows, we found stream and riparian consumer allochthony to be equivalent. Although both fish and stream invertebrates rely on seasonally pulsed allochthonous resources, we find allochthony varies seasonally only for fish, being nearly three times greater during the summer and fall than during the winter and spring. We also find that consumer allochthony varies with feeding traits for aquatic invertebrates, fish, and terrestrial arthropods, but not for terrestrial vertebrates. Finally, we find that allochthony varies by climate for aquatic invertebrates, being nearly twice as great in arid climates than in tropical climates, but not for fish. These findings are critical to understanding the consequences of global change, as ecosystem connections are being increasingly disrupted. 相似文献
11.
MICHAEL DOERING URS UEHLINGER THEKLA ACKERMANN MICHAEL WOODTLI KLEMENT TOCKNER 《Freshwater Biology》2011,56(7):1297-1311
1. In their natural state, river floodplains are composed of a complex mosaic of contrasting aquatic and terrestrial habitats. These habitats are expected to differ widely in their properties and corresponding ecological processes, although empirical data on their capacity to produce, store and transform organic matter and nutrients are limited. 2. The objectives of this study were (i) to quantify the spatiotemporal variation of respiration, a dominant carbon flux in ecosystems, in a complex river floodplain, (ii) to identify the environmental drivers of respiration within and among floodplain habitat types and (iii) to calculate whole‐floodplain respiration and to put these values into a global ecosystem context. 3. We measured soil and sediment respiration (sum of root and heterotrophic respiration; SR) throughout an annual cycle in two aquatic (pond and channel) and four terrestrial (gravel, large wood, vegetated island and riparian forest) floodplain habitat types in the island‐braided section of the near‐natural Tagliamento River (NE Italy). 4. Floodplain habitat types differed greatly in substratum composition (soil to coarse gravel), organic matter content (0.63 to 4.1% ash‐free dry mass) and temperature (seasonal range per habitat type: 8.6 to 33.1 °C). Average annual SR ranged from 0.54 ± 1.56 (exposed gravel) to 3.94 ± 3.72 μmol CO2 m?2 s?1 (vegetated islands) indicating distinct variation in respiration within and among habitat types. Temperature was the most important predictor of SR. However, the Q10 value ranged from 1.62 (channel habitat) to 4.57 (riparian forest), demonstrating major differences in habitat‐specific temperature sensitivity in SR. 5. Total annual SR in individual floodplain habitats ranged from 160 (ponds) to 1205 g C m?2 (vegetated islands) and spanned almost the entire range of global ecosystem respiration, from deserts to tropical forests. 相似文献
12.
Ioanna Salvarina 《Mammal Review》2016,46(2):131-143
- Many bats use aquatic habitats for foraging and for drinking water.
- Interactions between aquatic and terrestrial systems are important for understanding food web dynamics and for conserving species and ecosystems. Therefore, in this review, I examined the data available on bats’ use of aquatic habitats.
- The objectives of the present review were to evaluate the importance of aquatic resources for bats and to identify the effects that eutrophication, water pollution, and other anthropogenic impacts on water bodies have on bats.
- Most studies on bats and aquatic habitats have been conducted in Europe or in North America. They show, directly or indirectly, how bats use aquatic resources.
- Acoustic survey is the most common technique employed to assess habitat use by bats, although some researchers have used radio telemetry or other methods.
- Myotis daubentonii is the most commonly studied species. Within this topic, research does not tend to be focused more on threatened species.
- The effects of water pollution and eutrophication on bats remain unclear: different effects are reported for different species and in different areas.
- More studies are needed from Africa, South America, and Asia, regions for which few data are available, as well as from arid regions where fresh water is a limited resource.
13.
Francis TB Schindler DE Holtgrieve GW Larson ER Scheuerell MD Semmens BX Ward EJ 《Ecology letters》2011,14(4):364-372
While the importance of terrestrial linkages to aquatic ecosystems is well appreciated, the degree of terrestrial support of aquatic consumers remains debated. Estimates of terrestrial contributions to lake zooplankton have omitted a key food source, phytoplankton produced below the mixed layer. We used carbon and nitrogen stable isotope data from 25 Pacific Northwest lakes to assess the relative importance of particulate organic matter (POM) from the mixed layer, below the mixed layer and terrestrial detritus to zooplankton. Zooplankton and deep POM were depleted in 13C relative to mixed layer POM in lakes that can support deep primary production. A Bayesian stable isotope mixing model estimated that terrestrial detritus contributed <5% to zooplankton production, and confirms the role of lake optical and thermal properties; deep POM accounted for up to 80% of zooplankton production in the clearest lakes. These results suggest terrestrial support of lake zooplankton production is trivial. 相似文献
14.
Knowledge of aquatic food resources entering terrestrial systems is important for food web studies and conservation planning. Bats, among other terrestrial consumers, often profit from aquatic insect emergence and their activity might be closely related to such events. However, there is a lack of studies which monitor bat activity simultaneously with aquatic insect emergence, especially from lakes. Thus, our aim was to understand the relationship between insect emergence and bat activity, and investigate whether there is a general spatial or seasonal pattern at lakeshores. We assessed whole‐night bat activity using acoustic monitoring and caught emerging and aerial flying insects at three different lakes through three seasons. We predicted that insect availability and seasonality explain the variation in bat activity, independent of the lake size and characteristics. Spatial (between lakes) differences of bat activity were stronger than temporal (seasonal) differences. Bat activity did not always correlate to insect emergence, probably because other factors, such as habitat characteristics, or bats’ energy requirements, play an important role as well. Aerial flying insects explained bat activity better than the emerged aquatic insects in the lake with lowest insect emergence. Bats were active throughout the night with some activity peaks, and the pattern of their activity also differed among lakes and seasons. Lakes are important habitats for bats, as they support diverse bat communities and activity throughout the night and the year when bats are active. Our study highlights that there are spatial and temporal differences in bat activity and its hourly nocturnal pattern, that should be considered when investigating aquatic–terrestrial interactions or designing conservation and monitoring plans. 相似文献
15.
Randall K. Kolka Christian P. Giardina Jason D. McClure Alex Mayer Martin F. Jurgensen 《Ecohydrology》2010,3(3):315-324
Over the past century, annual snowfall has increased across the ‘snow‐belt’ region of the Upper Peninsula of Michigan, yet total annual precipitation has not changed, with potential impacts on hydrological processes and ecosystem composition. Using an integrated hydrochemical approach, we characterized groundwater discharge and quantified the contribution of snow‐ and rain‐derived waters to groundwater for an old‐growth riparian area within the Huron Mountains in northern Michigan. We then quantified the relative contribution of lateral, hillslope‐derived groundwater and upstream lake water to streamwater, and the extent of hyporheic zone expansion and contraction during one growing season. During a period of above‐average snowfall, yet below average growing season precipitation, ∼80% of the riparian area's groundwater reservoir was derived from snowmelt. The relative contribution of groundwater to streamflow ranged from 70% in June to 100% in August. The remainder was derived from upstream lakes and wetlands, which dropped in elevation and relative contribution from June to August. Finally, the extent of the hyporheic zone was small (<50 cm from streambed surface) and contracted towards the stream during the recession limb of the hydrograph. We conclude that if snowfall continues to rise while total annual precipitation declines, in line with climate change scenarios for the region, then water fluxes from snowmelt will increasingly dominate summer baseflow and could potentially increase spring flooding. However, because of overall declines in precipitation, streamflow patterns will likely change towards lower overall flow following the influence of the snowmelt period. Published in 2010 by John Wiley & Sons, Ltd. 相似文献
16.
1. Recent stable isotope studies have revealed that C4 plants play a minor role in aquatic food webs, despite their often widespread distribution and production. We compared the breakdown of C3 (Eucalyptus) and C4 (Saccharum and Urochloa) plant litter in a small rain forest stream and used laboratory feeding experiments to determine their potential contribution to the aquatic food web. 2. All species of litter broke down at a fast rate in the stream, although Urochloa was significantly faster than Eucalyptus and Saccharum. This was consistent with the observed higher total organic nitrogen of Urochloa compared with the other two species. 3. The breakdown of Urochloa and Saccharum was, however, not associated with shredding invertebrates, which were poorly represented in leaf packs compared with the native Eucalyptus. The composition of the invertebrate fauna in packs of Urochloa quickly diverged from that of the other two species. 4. Feeding experiments using a common shredding aquatic insect Anisocentropus kirramus showed a distinct preference for Eucalyptus over both C4 species. Anisocentropus was observed to ingest C4 plant litter, particularly in the absence of other choices, and faecal material collected was clearly of C4 origin, as determined by stable isotope analysis. However, the stable carbon isotope values of the larvae did not shift away from their C3 signature in any of the feeding trials. 5. These data suggest that shredders avoid the consumption of C4 plants, in favour of native C3 species that appear to be of lower food quality (based on C : N ratios). Lower rates of consumption and lack of assimilation of C4 carbon also suggest that shredders may have a limited ability to process this material, even in the absence of alternative litter sources. Large scale clearing of forest and vegetation for C4 crops such as sugarcane will undoubtedly have important consequences for stream ecosystem function. 相似文献
17.
- We measured bidirectional arthropod fluxes at 12 river reaches distributed across an urban‐rural gradient of riparian land use and land cover in the Scioto River system of Ohio (U.S.A.).
- For the terrestrial‐to‐aquatic arthropod flux (i.e. inputs of terrestrial arthropods to the river from the land), urban development was positively related to density of inputs but negatively related to biomass, partially explained by shifts in community composition and body size. Riparian grassland, typical of rural (i.e. non‐urban) landscapes, was positively associated with both density (range: 2.8–18.9 individuals m?2 day?1) and biomass (range: 7.1–58.7 mg m?2 day?1) of inputs.
- For the aquatic‐to‐terrestrial flux of adult aquatic insects (i.e. emergent aquatic insects exported from the river), riparian grassland cover was positively associated with both density (R2 = 0.61; range: 12.8–116.8 individuals m?2 day?1) and biomass (R2 = 0.65; range: 1.4–27.9 mg m?2 day?1), with relatively larger‐bodied taxa dominating emergence at rural reaches.
- Riparian landscape composition relates to reciprocal fluxes of arthropods (aquatic insects out, terrestrial insects and other arthropods in) in river‐riparian systems as we found human landscape disturbances were associated with changes in the taxonomic composition of both aquatic emergence and terrestrial input, and an overall decrease in the magnitude of emergence and terrestrial input. Furthermore, landscape changes that alter arthropod fluxes may have broader consequences for linked river‐riparian biodiversity and food webs and should be taken into account in conservation, restoration and management of these systems.
18.
Effects of Salmon-Borne Nutrients on Riparian Soils and Vegetation in Southwest Alaska 总被引:1,自引:0,他引:1
Spawning Pacific salmon (Oncorhynchus spp.) contribute marine-derived nutrients to riparian ecosystems, potentially affecting characteristics of the associated soils and vegetation. We quantified these effects by comparing soil and vegetative characteristics upstream and downstream of natural migratory barriers on ten spawning streams in southwest Alaska. Mean δ15N values—indicative of salmon-borne nutrients—were significantly higher in the O horizon and surface mineral soils downstream of barriers (near spawning reaches) than in soils upstream of barriers (near non-spawning reaches). However, the mean total N concentration in surface mineral soil was lower downstream than upstream. Mean foliar δ15N values were higher downstream for three plant species (Picea glauca, Salix alaxensis and Arctagrostis latifolia) with contrasting physiognomies. Mean overstory stem density was 100% higher downstream, primarily due to a fivefold difference in the density of large-diameter willows (Salix spp.). Mean understory stem density was 47% lower downstream, also driven by a difference in willow density. Mean ground layer non-vascular and dwarf shrub species covers were 28% and 73% lower downstream, respectively. Of the ten soil and vegetative characteristics that differed upstream to downstream, two (O horizon and Picea glauca δ15N) were correlated with the density of spawning salmon. Collectively, the data suggest that salmon-borne nutrients alter riparian soils and vegetation, while factors unrelated to salmon are responsible for the ultimate expression of many community characteristics. 相似文献
19.
The role of resource subsidies across ecosystem boundaries has emerged as an important concept in contemporary ecology. For lake ecosystems, this has led to interest in quantifying the contribution of terrestrial allochthonous carbon to aquatic secondary production. An inverse relationship between habitat area and the role of allochthonous subsidies has been documented on marine islands and assumed for lakes, yet there have been no tests of this pattern among benthic (lake bottom) consumers. Here, we used carbon stable isotopes to trace terrestrial allochthonous and benthic autochthonous carbon use by the crayfish Pacifastacus leniusculus over a gradient of lake area, productivity and urbanization. Consistent with findings from terrestrial islands, habitat size dictated the importance of allochthonous subsidies, as P. leniusculus transitioned from using predominantly terrestrial carbon in small lakes to an increased reliance on autochthonous production in larger lakes. However, shoreline urbanization interacted with this pattern, particularly for small lakes where greater urbanization resulted in reduced use of allochthonous resources. As such, we provide, to our knowledge, the first confirmation of the predicted relationship between habitat size and importance of allochthonous subsidies to lake benthic consumers, but found that urbanization can interfere with this pattern. 相似文献
20.
William S. Pearman Sarah J. Wells Olin K. Silander Nikki E. Freed James Dale 《Ecology and evolution》2020,10(24):13624
Population genetic structure in the marine environment can be influenced by life‐history traits such as developmental mode (biphasic, with distinct adult and larval morphology, and direct development, in which larvae resemble adults) or habitat specificity, as well as geography and selection. Developmental mode is thought to significantly influence dispersal, with direct developers expected to have much lower dispersal potential. However, this prediction can be complicated by the presence of geophysical barriers to dispersal. In this study, we use a panel of 8,020 SNPs to investigate population structure and biogeography over multiple spatial scales for a direct‐developing species, the New Zealand endemic marine isopod Isocladus armatus. Because our sampling range is intersected by two well‐known biogeographic barriers (the East Cape and the Cook Strait), our study provides an opportunity to understand how such barriers influence dispersal in direct developers. On a small spatial scale (20 km), gene flow between locations is extremely high, suggestive of an island model of migration. However, over larger spatial scales (600 km), populations exhibit a clear pattern of isolation‐by‐distance. Our results indicate that I. armatus exhibits significant migration across the hypothesized barriers and suggest that large‐scale ocean currents associated with these locations do not present a barrier to dispersal. Interestingly, we find evidence of a north‐south population genetic break occurring between Māhia and Wellington. While no known geophysical barrier is apparent in this area, it coincides with the location of a proposed border between bioregions. Analysis of loci under selection revealed that both isolation‐by‐distance and adaption may be contributing to the degree of population structure we have observed here. We conclude that developmental life history largely predicts dispersal in the intertidal isopod I. armatus. However, localized biogeographic processes can disrupt this expectation, and this may explain the potential meta‐population detected in the Auckland region. 相似文献