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Laurel J. Haavik Kevin J. Dodds Jeremy D. Allison 《Agricultural and Forest Entomology》2016,18(4):357-366
- Natural controls may not be effective in limiting non‐native species that invade a new environment. Alternatively, factors present in the new environment can prevent an invader from becoming a serious pest.
- We investigated whether existing natural enemies or the availability of susceptible and suitable host plants limited an established, non‐native species Sirex noctilio F. (Siricidae: Hymenoptera).
- Using several pine forests throughout Ontario, we examined the relationships between parasitism and S. noctilio activity, as well as S. noctilio activity and the availability of susceptible and suitable pine. We also evaluated parasitism at two points in time (5–7 years apart).
- We found correlative evidence indicating that the availability of suitable hosts limited the S. noctilio population in Ontario. Sirex noctilio killed more pine when more pine was available, especially suppressed (highly suitable) pine.
- More co‐dominant (healthy) pines were attacked but not killed by S. noctilio at sites with more S. noctilio activity, indicating that higher densities of S. noctilio were needed to overwhelm healthy pines.
- The role of parasitoids was less clear. Parasitism did not vary consistently with the amount of S. noctilio activity at sites. The two groups of parasitoids, Rhyssa and Ibalia, likely responded differently to presence of S. noctilio.
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1. Stressful abiotic conditions and mycorrhizal fungi have both been shown to influence plant quality significantly, yet the interactive effects of these factors on relationships among plants, herbivores, and natural enemies remain unclear. 2. In this study, the results of a factorial field experiment are reported in which the effects of plant stress and mycorrhizae on density and parasitism of three herbivores of Baccharis halimifolia L. were examined. 3. Plant stress was increased by adding salt to the soil, and association with mycorrhizal fungi was increased by inoculating plant roots. 4. Inoculation with mycorrhizal fungi resulted in increased density of all three herbivore species, but the effects of mycorrhizae on parasitism varied by species and with soil salinity levels. For the gall maker Neolasioptera lathami Gagne, mycorrhizae decreased parasitism regardless of soil salinity levels. For the leaf miners Amauromyza maculosa Malloch and Liriomyza trifolii Burgess, mycorrhizae effectively negated the decrease in parasitism resulting from increased salinity. 5. The results of this study show that the effects of mycorrhizae on parasitism may be context dependent, and can be positive or negative depending upon species and environmental conditions. 相似文献
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Climate fluctuations and human exploitation are causing global changes in nutrient enrichment of terrestrial and aquatic ecosystems and declining abundances of apex predators. The resulting trophic cascades have had profound effects on food webs, leading to significant economic and societal consequences. However, the strength of cascades–that is the extent to which a disturbance is diminished as it propagates through a food web–varies widely between ecosystems, and there is no formal theory as to why this should be so. Some food chain models reproduce cascade effects seen in nature, but to what extent is this dependent on their formulation? We show that inclusion of processes represented mathematically as density‐dependent regulation of either consumer uptake or mortality rates is necessary for the generation of realistic ‘top‐down’ cascades in simple food chain models. Realistically modelled ‘bottom‐up’ cascades, caused by changing nutrient input, are also dependent on the inclusion of density dependence, but especially on mortality regulation as a caricature of, e.g. disease and parasite dynamics or intraguild predation. We show that our conclusions, based on simple food chains, transfer to a more complex marine food web model in which cascades are induced by varying river nutrient inputs or fish harvesting rates. 相似文献
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1. Algal growth in lotic systems is controlled either from the bottom‐up (e.g. nutrients and light, which determine growth rates) or from the top‐down (e.g. grazing pressure, which reduces accumulated biomass). Nutrient‐enriched streams that support large and diverse grazing macroinvertebrate populations and those with shaded riparian corridors rarely suffer from excessive algal growth. 2. In this study, the density of benthic algivorous macroinvertebrates was experimentally manipulated in shaded and open nutrient‐enriched stream habitats of the Owennagearagh River, south‐west Ireland. The ability of macroinvertebrate grazers and riparian shade to control benthic algal growth [particularly the nuisance alga, Cladophora glomerata (L. Kütz)] was investigated. Three sites with markedly different concentrations of plant nutrients (one site upstream and two sites downstream of the sewage outfall) were selected. The density of grazing invertebrates colonising ceramic tiles was reduced using high‐voltage localised electric pulses. Replicates of treatment (grazer‐excluded) and control (grazed) tiles were deployed in open and shaded (<25 and >80% canopy cover, respectively) patches of stream bed, in each site. 3. After 2‐week Cladophora cover, periphytic chlorophyll a and biofilm ash‐free dry mass (AFDM) were quantified for all experimental tiles. Values for all three parameters were highest on grazer‐excluded tiles from open patches. Grazed tiles from open patches accrued little Cladophora and had significantly lower levels of chlorophyll a and AFDM. Nutrient inputs were found to have an impact on the density of grazing invertebrates, with higher densities of Baetis nymphs at the most nutrient‐enriched site. 4. Our results demonstrate that in eutrophic, high‐light streams, filamentous algae can quickly accumulate to nuisance levels in the absence of invertebrate grazers. In future, greater attention should be paid to the role of grazing invertebrates in controlling nuisance algae in streams, in addition to algal–nutrient relationships. 相似文献
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Many human influences on the world's ecosystems have their largest direct impacts at either the top or the bottom of the food web. To predict their ecosystem-wide consequences we must understand how these impacts propagate. A long-standing, but so far elusive, problem in this endeavour is how to reduce food web complexity to a mathematically tractable, but empirically relevant system. Simplification to main energy channels linking primary producers to top consumers has been recently advocated. Following this approach, we propose a general framework for the analysis of bottom-up and top-down forcing of ecosystems by reducing food webs to two energy pathways originating from a limiting resource shared by competing guilds of primary producers (e.g. edible vs. defended plants). Exploring dynamical models of such webs we find that their equilibrium responses to nutrient enrichment and top consumer harvesting are determined by only two easily measurable topological properties: the lengths of the component food chains (odd-odd, odd-even, or even-even) and presence vs. absence of a generalist top consumer reconnecting the two pathways (yielding looped vs. branched webs). Many results generalise to other looped or branched web structures and the model can be easily adapted to include a detrital pathway. 相似文献
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Vitor D. Tarli Pedro A. C. L. Pequeno Elizabeth Franklin José W. de Morais Jorge L. P. Souza Adriano H. C. Oliveira Diego R. Guilherme 《Biotropica》2014,46(5):598-607
Arthropod abundance and diversity are remarkable in tropical forests, but are also spatially patchy. This has been attributed either to resources, predators, abiotic conditions or disturbances, but whether such factors may simultaneously shape arthropod assemblage structure is little known. We used cockroaches to test for multiple environmental controls on assemblage structure in 25 km2 of Amazonian forest. We performed nocturnal, direct searches for cockroaches in 30 plots (250 m × 2 m) during two seasons, and gathered data on biotic and abiotic factors from previous studies. Cockroach abundance increased with dry litter mass, a measure of resource amount, while species richness increased with litter phosphorus content, a measure of resource availability. Cockroach abundance and species richness decreased with ant relative abundance. Cockroach species composition changed along the gradient of: (1) soil clay content, which correlates with a broad differentiation between flood‐prone and non‐flooded forest; (2) soil relative moisture, consistent with known interspecific variation in desiccation tolerance; and (3) according to the abundance of ants, a potential predator. Turnover in species composition was correlated with abiotic conditions—sorting species according to physiological requirements and to disturbance‐related life history traits—and to ants' selective pressure. Cockroach abundance, diversity, and composition seem to be controlled by distinct sets of environmental factors, but predators which were represented by ants, emerged as a common factor underlying cockroach distribution. Such patterns of community structure may have been previously overlooked by undue focus on single or a few factors, and may be common to tropical forest arthropods. 相似文献
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Selina Våge Gunnar Bratbak Jorun Egge Mikal Heldal Aud Larsen Svein Norland Maria Lund Paulsen Bernadette Pree Ruth‐Anne Sandaa Evy Foss Skjoldal Tatiana M. Tsagaraki Lise Øvreås T. Frede Thingstad 《Ecology letters》2018,21(9):1440-1452
In food webs, interactions between competition and defence control the partitioning of limiting resources. As a result, simple models of these interactions contain links between biogeochemistry, diversity, food web structure and ecosystem function. Working at hierarchical levels, these mechanisms also produce self‐similarity and therefore suggest how complexity can be generated from repeated application of simple underlying principles. Reviewing theoretical and experimental literature relevant to the marine photic zone, we argue that there is a wide spectrum of phenomena, including single cell activity of prokaryotes, microbial biodiversity at different levels of resolution, ecosystem functioning, regional biogeochemical features and evolution at different timescales; that all can be understood as variations over a common principle, summarised in what has been termed the ‘Killing‐the‐Winner’ (KtW) motif. Considering food webs as assemblages of such motifs may thus allow for a more integrated approach to aquatic microbial ecology. 相似文献
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Katarzyna Izydorczyk Aleksandra Skowron Adrianna Wojtal Tomasz Jurczak 《International Review of Hydrobiology》2008,93(3):257-268
Stream inlets into shallow bays of reservoirs and lakes may be ‘hot‐spots’ for toxic cyanobacterial bloom initiation. These ‘hot‐spots’ may be connected with the permanent inflow of high nutrient concentrations from the catchment, optimal physical conditions (wind protected areas) that occur in shallow areas and/or ineffective top‐down control. Four sampling sites along a transect from stream to reservoir in a shallow bay of Sulejow Reservoir (Poland) were studied to test the above hypothesis, comprising a transition zone between lotic and pelagic habitats. Investigations showed that stream inlet into shallow bay acted as incubator for Microcystis blooms. The nutrient level, especially phosphorus, was identified as the major cause of cyanobacterial bloom growth. The increase of Microcystis biomass strongly correlated with increasing microcystin concentrations, however, a relationship with microcystin content was not observed. Toxicity of bloom demonstrated seasonal variability, reaching its maximum at the initial phase of bloom. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Christine Lourenço‐Amorim Vinicius Neres‐Lima Timothy Peter Moulton Cristiano Yuji Sasada‐Sato Priscila Oliveira‐Cunha Eugenia Zandonà 《Freshwater Biology》2014,59(11):2365-2373
- Periphytic algae are an important source of energy fuelling stream food webs. Periphytic algal biomass can be controlled by bottom‐up and top‐down forces, but there are few studies that have investigated these effects simultaneously, especially in tropical streams, where periphyton can be a very important carbon source. Here, we investigated the bottom‐up effects of nutrients and the top‐down effects of grazers and predators in a coastal tropical stream in Brazil.
- We employed nutrient‐diffusing substrata to test for nutrient limitation, placed inside electric exclosures of different intensities, which prevented consumers from entering the electrified area. We used four types of substrata: one enriched with nitrogen alone (N), one with phosphorus alone (P), one with nitrogen + phosphorus (NP) and one control with no nutrients added (C). The electric exclosure had three treatments: high electricity that excluded both predators (Macrobrachium olfersi shrimps) and grazers (Baetidae mayflies), low electricity that excluded only shrimps, and a control treatment with no electricity where both shrimps and mayflies were allowed to enter.
- The limiting nutrient in the stream was nitrogen. Our results showed a greater magnitude of bottom‐up effects, with periphytic algae responding more strongly to nutrient addition than to grazers or predators. Top‐down control was not as strong, but periphytic algae responded negatively to grazers, especially in the absence of predators. This suggests that shrimps, either directly or indirectly, inhibit mayfly grazing activity. The response of periphytic algae to nutrients was stronger in the absence of grazers. Thus, top‐down effects, both directly and indirectly through a trophic cascade, can dampen the response to nitrogen addition, diminishing the degree of resource limitation.
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Among both ecologists and the wider community there is a tacit assumption that predators regulate populations of their prey. But there is evidence from a wide taxonomic and geographic range of studies that predators that are adapted to co-evolved prey generally do not regulate their prey. This is because predators either cannot reproduce as fast as their prey and/or are inefficient hunters unable to catch enough prey to sustain maximum reproduction. The greater capacity of herbivores to breed successfully is, however, normally restricted by a lack of enough food of sufficient quality to support reproduction. But whenever this shortage is alleviated by a large pulse of food, herbivores increase their numbers to outbreak levels. Their predators are unable to contain this increase, but their numbers, too, surge in response to this increase in food. Eventually both their populations will crash once the food supply runs out, first for the herbivores and then for the predators. Then an “over-run” of predators will further depress the already declining prey population, appearing to be controlling its abundance. This latter phenomenon has led many ecologists to conclude that predators are regulating the numbers of their prey. However, it is the same process that is revealed during outbreaks that limits populations of both predator and prey in “normal” times, although this is usually not readily apparent. Nevertheless, as all the diverse cases discussed here attest, the abundance of predators and their co-evolved prey are both limited by their food: the predators are passengers, not drivers. 相似文献
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Primary consumers are under strong selection from resource (‘bottom‐up’) and consumer (‘top‐down’) controls, but the relative importance of these selective forces is unknown. We performed a meta‐analysis to compare the strength of top‐down and bottom‐up forces on consumer fitness, considering multiple predictors that can modulate these effects: diet breadth, feeding guild, habitat/environment, type of bottom‐up effects, type of top‐down effects and how consumer fitness effects are measured. We focused our analyses on the most diverse group of primary consumers, herbivorous insects, and found that in general top‐down forces were stronger than bottom‐up forces. Notably, chewing, sucking and gall‐making herbivores were more affected by top‐down than bottom‐up forces, top‐down forces were stronger than bottom‐up in both natural and controlled (cultivated) environments, and parasitoids and predators had equally strong top‐down effects on insect herbivores. Future studies should broaden the scope of focal consumers, particularly in understudied terrestrial systems, guilds, taxonomic groups and top‐down controls (e.g. pathogens), and test for more complex indirect community interactions. Our results demonstrate the surprising strength of forces exerted by natural enemies on herbivorous insects, and thus the necessity of using a tri‐trophic approach when studying insect‐plant interactions. 相似文献
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Carola Winkelmann Jana Schneider Daniela Mewes Susanne I. Schmidt Susanne Worischka Claudia Hellmann Jürgen Benndorf 《Freshwater Biology》2014,59(4):803-818
- We conducted a paired large‐scale predation experiment over 32 months in two streams being seasonally shaded by deciduous riparian trees, using the benthivorous fish species gudgeon (Gobio gobio) and stone loach (Barbatula barbatula) as top predators. The biomass of benthic grazers and periphyton in the presence/absence of fish was measured and the periphyton production was compared with the consumption rates using a model‐based approach.
- A three‐level trophic cascade from benthivorous fish via benthic grazers to periphyton was evident from the field experiment. Integrated over the whole study period, fish reduced the biomass of benthic grazers and indirectly increased the periphyton biomass.
- Scenario analyses, using a simple dynamic model, indicated top‐down control of periphyton to be strongest during autumn, when periphyton growth was light‐limited, and weaker in the spring, when periphyton growth was not light‐limited. The seasonal light supply variation was caused by shading due to deciduous riparian trees during the vegetation period.
- This asymmetry in temporal processes weakened the top‐down control in a natural benthic community. Even though grazer biomass is naturally reduced in summer, due to the emergence of the most abundant species (mayflies), a grazer biomasses high enough to reduce the spring periphyton peak could not be sustained by the low summer periphyton growth.
- We suppose that the temporal decoupling of grazer biomass from periphyton biomass might be caused by the very short generation time of the primary producers (days) compared with the long generation time of the primary consumers (mostly 1 year).
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1. There is an ongoing debate about the relative importance of top‐down and bottom‐up regulation of herbivore dynamics in the wild. Secondary metabolites, produced by plants, have negative effects on survival and growth of some herbivore species, causing bottom‐up regulation of population dynamics. Herbivore natural enemies may use plant secondary metabolites as cues to find their prey, but their survival and reproduction can also be influenced by the upward cascade of secondary metabolites through the food web. Thus plant chemistry might also affect herbivore populations by mediating top‐down regulation. 2. We investigated the influence of heritable variation in aliphatic glucosinolates, a class of secondary metabolites produced by Brassica plants, on the relative importance of top‐down and bottom‐up regulation of Brevicoryne brassicae (mealy cabbage aphid) colonies in natural Brassica oleracea (wild cabbage) populations. We manipulated natural enemy pressure on plants differing in their glucosinolate profiles, and monitored aphid colony growth and disperser production. 3. Aphid colony sizes were significantly smaller on plants producing sinigrin, compared with plants producing alternative aliphatic glucosinolates. Aphid natural enemy numbers correlated with aphid colony size, but there was no additional effect of the plants' chemical phenotype on natural enemy abundance. Furthermore, experimental reduction of natural enemy pressure had no effect on aphid colony size or production of winged dispersers. 4. Our results provide evidence for glucosinolate‐mediated, bottom‐up regulation of mealy cabbage aphid colonies in natural populations, but we found no indication of top‐down regulation. We emphasise that more studies of these processes should focus on tritrophic interactions in the wild. 相似文献
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NELSON VALDIVIA JARROD D. STEHBENS BJÖRN HERMELINK SEAN D. CONNELL MARKUS MOLIS MARTIN WAHL 《Austral ecology》2008,33(8):951-962
Local dynamics such as resource enhancement (e.g. nutrient supply) and stochastic events of destruction (disturbances that provide new space) are hypothesized to counteractively affect species diversity and composition. We tested the independent and interactive effects of nutrients and disturbance on the development of assemblages of epibiota attached to vertical surfaces in an oligotrophic system. Nutrient concentrations were manipulated at three levels (ambient, medium and high) while disturbance was manipulated by removing biomass at seven frequencies (0×, 2×, 3×, 4×, 5×, 7×, 12×). Nutrient and disturbance regimes had opposing effects on diversity such that species richness increased with resource enhancement (nutrients) and declined with disturbance. These results support the model that increased heterogeneity of distribution of limiting resources allows the coexistence of species with low and high resource requirements. 相似文献
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Cédric L. Meunier Michael J. Gundale Irene S. Sánchez Antonia Liess 《Global Change Biology》2016,22(1):164-179
Increased reactive nitrogen (Nr) deposition has raised the amount of N available to organisms and has greatly altered the transfer of energy through food webs, with major consequences for trophic dynamics. The aim of this review was to: (i) clarify the direct and indirect effects of Nr deposition on forest and lake food webs in N‐limited biomes, (ii) compare and contrast how aquatic and terrestrial systems respond to increased Nr deposition, and (iii) identify how the nutrient pathways within and between ecosystems change in response to Nr deposition. We present that Nr deposition releases primary producers from N limitation in both forest and lake ecosystems and raises plants' N content which in turn benefits herbivores with high N requirements. Such trophic effects are coupled with a general decrease in biodiversity caused by different N‐use efficiencies; slow‐growing species with low rates of N turnover are replaced by fast‐growing species with high rates of N turnover. In contrast, Nr deposition diminishes below‐ground production in forests, due to a range of mechanisms that reduce microbial biomass, and decreases lake benthic productivity by switching herbivore growth from N to phosphorus (P) limitation, and by intensifying P limitation of benthic fish. The flow of nutrients between ecosystems is expected to change with increasing Nr deposition. Due to higher litter production and more intense precipitation, more terrestrial matter will enter lakes. This will benefit bacteria and will in turn boost the microbial food web. Additionally, Nr deposition promotes emergent insects, which subsidize the terrestrial food web as prey for insectivores or by dying and decomposing on land. So far, most studies have examined Nr‐deposition effects on the food web base, whereas our review highlights that changes at the base of food webs substantially impact higher trophic levels and therefore food web structure and functioning. 相似文献
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TUBA BUCAK ECE SARAOĞLU ETİ E. LEVİ Ü. NİHAN TAVŞANOĞLU A. İdİl ÇAKİROĞLU ERIK JEPPESEN MERYEM BEKLİOĞLU 《Freshwater Biology》2012,57(8):1631-1642
1. Water‐level fluctuations are typical of lakes located in the semi‐arid Mediterranean region, which is characterised by warm rainy winters and hot dry summers. Ongoing climate change may exacerbate fluctuations and lead to more severe episodes of drought, so information on the effects of water level on the functioning of lake ecosystems in such regions is crucial. 2. In eutrophic Lake Eymir, Turkey, we conducted a 4‐month (summer) field experiment using cylindrical 0.8‐m‐ (low‐water‐level) and 1.6‐m‐deep (high‐water‐level) mesocosms (kept open to the sediment and atmosphere). Fish (tench, Tinca tinca, and bleak, Alburnus escherichii) were added to half of the mesocosms, while the rest were kept fishless. Ten shoots of Potamogeton pectinatus were transplanted to each mesocosm. 3. Sampling for physicochemical variables, chlorophyll a (chl‐a), zooplankton and per cent plant volume inhabited (PVI%) by macrophytes was conducted weekly during the first 5 weeks, and subsequently biweekly. Macrophytes were harvested on the last sampling date. During the course of the experiment, the water level decreased by 0.41 ± 0.06 m. 4. Throughout the experiment, fish affected zooplankton abundance (?), nutrient concentrations (+), chl‐a (+) and water clarity (?) most strongly in the low‐water‐level mesocosms and the zooplankton community shifted towards dominance of small‐sized forms. The fishless mesocosms had a higher zooplankton/phytoplankton ratio, suggesting higher grazing. 5. Greatest macrophyte growth was observed in the low‐water‐level fishless mesocosms. However, despite high nutrient concentrations and low water clarity, macrophytes were also abundant in the fish mesocosms and particularly increased following a water‐level decrease from midsummer onwards. Macrophyte growth was poor in the high‐water‐level mesocosms, even in the fishless ones with high water clarity. This was ascribed to extensive periphyton development reducing light availability for the macrophytes. 6. Our results indicate that a reduction in water level during summer may help maintain the growth of macrophytes in Mediterranean eutrophic shallow lakes, despite a strong negative effect of fish predation on water clarity. It is therefore probable that an expected negative effect of global climate change on water clarity because of eutrophication and enhanced top‐down control of fish may be, at least partly, counteracted by reduced water level, provided that physical disturbance is not severe. 相似文献
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Francisco Rivera Vasconcelos Sebastian Diehl Patricia Rodríguez Per Hedstrm Jan Karlsson Pr Bystrm 《Global Change Biology》2019,25(2):504-521
Productivity and trophic structure of aquatic ecosystems result from a complex interplay of bottom‐up and top‐down forces that operate across benthic and pelagic food web compartments. Projected global changes urge the question how this interplay will be affected by browning (increasing input of terrestrial dissolved organic matter), nutrient enrichment and warming. We explored this with a process‐based model of a shallow lake food web consisting of benthic and pelagic components (abiotic resources, primary producers, grazers, carnivores), and compared model expectations with the results of a browning and warming experiment in nutrient‐poor ponds harboring a boreal lake community. Under low nutrient conditions, the model makes three major predictions. (a) Browning reduces light and increases nutrient supply; this decreases benthic and increases pelagic production, gradually shifting productivity from the benthic to the pelagic habitat. (b) Because of active habitat choice, fish exert top‐down control on grazers and benefit primary producers primarily in the more productive of the two habitats. (c) Warming relaxes top‐down control of grazers by fish and decreases primary producer biomass, but effects of warming are generally small compared to effects of browning and nutrient supply. Experimental results were consistent with most model predictions for browning: light penetration, benthic algal production, and zoobenthos biomass decreased, and pelagic nutrients and pelagic algal production increased with browning. Also consistent with expectations, warming had negative effects on benthic and pelagic algal biomass and weak effects on algal production and zoobenthos and zooplankton biomass. Inconsistent with expectations, browning had no effect on zooplankton and warming effects on fish depended on browning. The model is applicable also to nutrient‐rich systems, and we propose that it is a useful tool for the exploration of the consequences of different climate change scenarios for productivity and food web dynamics in shallow lakes, the worldwide most common lake type. 相似文献
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Herbivorous insect communities are structured by multiple processes operating locally (e.g. bottom–up effects of plants) and regionally (e.g. dispersal limitation). Although the relative strength of these processes has been well documented, how it varies in time is less understood, especially in relation with the temporal dynamics of plant communities. If temporal turnover of local plant species composition is too rapid for insect community assembly to keep up with, bottom–up effects are expected to be weak. Here, in plant and herbivorous insect communities in Japanese grasslands, we studied how the relative importance of local (bottom–up effects of plants, structures of plant communities and top–down effects of predators) and regional (dispersal limitation) processes varies over the growing season. In addition, we tested the hypothesis that larger temporal turnover of plant species composition is related to the weaker bottom–up effects, that is, the lower explanation power of plant communities for insect communities. We found that, throughout the growing season, the insect species composition was mainly explained by local variables (plant species composition, vegetation height and predator abundance), and their explanation power was higher during later phases of the season (late summer). Furthermore, the variation not explained by plant species composition was correlated with the degree of temporal turnover of plants, suggesting that insect communities failed to track the temporal turnover of plant species. These results were pronounced when we focused on leaf sucker insects, whose host plant range is presumably more limited. We conclude that herbivorous insect communities are mainly regulated by local processes, especially bottom–up effects from plants, while stochasticity may have played a role in early phases of the season. Furthermore, we underscore the importance of considering relative time scale of community assembly and environmental shifts, especially in systems characterized by dynamic changes. 相似文献