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1.
Human-induced increases in atmospheric CO2 concentration have the potential to alter the chemical composition of plant tissue, and thereby affect the amount of tissue consumed by herbivorous arthropods. At the Duke Forest free-air concentration enrichment (FACE) facility in North Carolina (FACTS–1 research facility), we measured the amount of leaf tissue damaged by insects and other herbivorous arthropods during two growing seasons in a deciduous forest understory continuously exposed to ambient (360 l l–1) and elevated (~560 µl l–1) CO2 conditions. In 1999, there was a significant interaction between CO2 and species such that winged elm (Ulmus alata) showed lower herbivory in elevated CO2 plots, whereas red maple (Acer rubra) and sweetgum (Liquidambar styraciflua) did not. In 2000, our results did not achieve statistical significance but the magnitude of the result was consistent with the 1999 results. In 1999 and 2000, we found a decline (10–46%) in community-level herbivory in elevated CO2 plots driven primarily by reductions in herbivory on elm. The major contribution to total leaf damage was from missing tissue (66% of the damaged tissue), with galls, skeletonized, and discolored tissue making smaller contributions. It is unclear whether the decline in leaf damage is a result of altered insect populations, altered feeding, or a combination. We were not able to quantify insect populations, and our measurements did not resolve an effect of elevated CO2 on leaf chemical composition (total nitrogen, carbon, C/N, sugars, phenolics, starch). Despite predictions from a large number of single-species studies that herbivory may increase under elevated CO2, we have found a decrease in herbivory in a naturally established forest understory exposed to a full suite of insect herbivores and their predators. 相似文献
2.
PETER STILING DANIEL MOON† ANTHONY ROSSI† BRUCE A. HUNGATE‡ BERT DRAKE§ 《Global Change Biology》2009,15(8):1895-1902
The effects of elevated CO2 on plant growth and insect herbivory have been frequently investigated over the past 20 years. Most studies have shown an increase in plant growth, a decrease in plant nitrogen concentration, an increase in plant secondary metabolites and a decrease in herbivory. However, such studies have generally overlooked the fact that increases in plant production could cause increases of herbivores per unit area of habitat. Our study investigated leaf production, herbivory levels and herbivore abundance per unit area of leaf litter in a scrub‐oak system at Kennedy Space Center, Florida, under conditions of ambient and elevated CO2, over an 11‐year period, from 1996 to 2007. In every year, herbivory, that is leafminer and leaftier abundance per 200 leaves, was lower under elevated CO2 than ambient CO2 for each of three species of oaks, Quercus myrtifolia, Quercus chapmanii and Quercus geminata. However, leaf litter production per 0.1143 m2 was greater under elevated CO2 than ambient CO2 for Q. myrtifolia and Q. chapmanii, and this difference increased over the 11 years of the study. Leaf production of Q. geminata under elevated CO2 did not increase. Leafminer densities per 0.1143 m2 of litterfall for Q. myrtifolia and Q. chapmanii were initially lower under elevated CO2. However, shortly after canopy closure in 2001, leafminer densities per 0.1143 m2 of litter fall became higher under elevated CO2 and remained higher for the remainder of the experiment. Leaftier densities per 0.1143 m2 were also higher under elevated CO2 for Q. myrtifolia and Q. chapmanii over the last 6 years of the experiment. There were no differences in leafminer or leaftier densities per 0.1143 m2 of litter for Q. geminata. These results show three phenomena. First, they show that elevated CO2 decreases herbivory on all oak species in the Florida scrub‐oak system. Second, despite lower numbers of herbivores per 200 leaves in elevated CO2, increased leaf production resulted in higher herbivore densities per unit area of leaf litter for two oak species. Third, they corroborate other studies which suggest that the effects of elevated CO2 on herbivores are species specific, meaning they depend on the particular plant species involved. Two oak species showed increases in leaf production and herbivore densities per 0.1143 m2 in elevated CO2 over time while another oak species did not. Our results point to a future world of elevated CO2 where, despite lower plant herbivory, some insect herbivores may become more common. 相似文献
3.
Effects of elevated CO2 on five plant-aphid interactions 总被引:3,自引:0,他引:3
We investigated interactions between five species of phloem-feeding aphids (Homoptera: Aphididae) and their host plants at elevated CO2; Acyrthosiphon pisum (Harris) on Vicia faba L., Aphis nerii Boyer de Fonscolombe on Asclepias syriaca L., Aphis oenotherae Oestlund on Oenothera biennis L., Aulacorthum solani (Kaltenbach) on Nicotiana sylvestris Speg. & Comes and Myzus persicae (Sulzer) on Solanum dulcamara L. Host plants grown at elevated CO2 generally had greater biomass, leaf area and C:N ratios than those grown at ambient CO2, while plants with aphids had lower biomass and leaf area than those without aphids.The responses of aphid populations to elevated CO2 were species-specific with one species increasing (M. persicae), one decreasing (A. pisum), and the other three being unaffected. CO2 treatment did not affect the proportion of alate individuals produced. In general, aphid abundance was not significantly related to foliar nitrogen concentration.We performed separate analyses to test whether either aphid presence or aphid abundance modified the response of host plants to elevated CO2. In terms of aphid presence, only three of the potential 15 interactions (five aphid species x three plant traits) were significant; A. solani slightly modified the response of the plant biomass to elevated CO2 and M. persicae affected the response of leaf area and allocation. In terms of aphid abundance, only two of the potential 15 interactions were significant with A. nerii modifying the plant response to CO2 in terms of total leaf area and allocation.We conclude that, in contrast to other insect groups such as leaf chewers, populations of most phloem-feeders may not be negatively affected by increased CO2 concentrations in the future. The reasons for this difference include the possibility that aphids may be able to compensate for changes in host plant quality by altering feeding behaviour or by synthesizing amino acids. In addition, there is little evidence that aphid herbivory, even at high levels, will substantially modify the response of plants to elevated CO2. 相似文献
4.
The direct and indirect effects of increasing levels of atmospheric carbon dioxide (CO2) on plant nitrogen (N) content were studied in a shortgrass steppe ecosystem in northeastern Colorado, USA. Beginning in 1997 nine experimental plots were established: three open-top chambers with ambient CO2 levels (approximately 365 mol mol–1), three open-top chambers with twice-ambient CO2 levels (approximately 720 mol mol–1), and three unchambered control plots. After 3 years of growing-season CO2 treatment, the aboveground N concentration of plants grown under elevated atmospheric CO2 decreased, and the carbon–nitrogen (C:N) ratio increased. At the same time, increased aboveground biomass production under elevated atmospheric CO2 conditions increased the net transfer of N out of the soil of elevated-CO2 plots. Aboveground biomass production after simulated herbivory was also greater under elevated CO2 compared to ambient CO2. Surprisingly, no significant changes in belowground plant tissue N content were detected in response to elevated CO2. Measurements of individual species at peak standing phytomass showed significant effects of CO2 treatment on aboveground plant tissue N concentration and significant differences between species in N concentration, suggesting that changes in species composition under elevated CO2 will contribute to overall changes in nutrient cycling. Changes in plant N content, driven by changes in aboveground plant N concentration, could have important consequences for biogeochemical cycling rates and the long-term productivity of the shortgrass steppe as atmospheric CO2 concentrations increase. 相似文献
5.
Development of gypsy moth larvae feeding on red maple saplings at elevated CO<Subscript>2</Subscript> and temperature 总被引:3,自引:0,他引:3
Predicted increases in atmospheric CO2 and global mean temperature may alter important plant-insect associations due to the direct effects of temperature on insect development and the indirect effects of elevated temperature and CO2 enrichment on phytochemicals important for insect success. We investigated the effects of CO2 and temperature on the interaction between gypsy moth (Lymantria dispar L.) larvae and red maple (Acer rubrum L.) saplings by bagging first instar larvae within open-top chambers at four CO2/temperature treatments: (1) ambient temperature, ambient CO2, (2) ambient temperature, elevated CO2
(+300 l l-1
CO2), (3) elevated temperature (+3.5°C), ambient CO2, and (4) elevated temperature, elevated CO2. Larvae were reared to pupation and leaf samples taken biweekly to determine levels of total N, water, non-structural carbohydrates, and an estimate of defensive phenolic compounds in three age classes of foliage: (1) immature, (2) mid-mature and (3) mature. Elevated growth temperature marginally reduced (P <0.1) leaf N and significantly reduced (P <0.05) leaf water across CO2 treatments in mature leaves, whereas leaves grown at elevated CO2 concentration had a significant decrease in leaf N and a significant increase in the ratio of starch:N and total non-structural carbohydrates:N. Leaf N and water decreased and starch:N and total non-structural carbohydrates:N ratios increased as leaves aged. Phenolics were unaffected by CO2 or temperature treatment. There were no interactive effects of CO2 and temperature on any phytochemical measure. Gypsy moth larvae reached pupation earlier at the elevated temperature (female =8 days,
P <0.07; male =7.5 days,
P <0.03), whereas mortality and pupal fresh weight of insects were unrelated to either CO2, temperature or their interaction. Our data show that CO2 or temperature-induced alterations in leaf constituents had no effect on insect performance; instead, the long-term exposure to a 3.5°C increase in temperature shortened insect development but had no effect on pupal weight. It appears that in some tree-herbivorous insect systems the direct effects of an increased global mean temperature may have greater consequences for altering plant-insect interactions than the indirect effects of an increased temperature or CO2 concentration on leaf constituents. 相似文献
6.
Effects of elevated CO2 and O3 on leaf damage and insect abundance in a soybean agroecosystem 总被引:1,自引:0,他引:1
Orla Dermody Bridget F. O’Neill Arthur R. Zangerl May R. Berenbaum Evan H. DeLucia 《Arthropod-Plant Interactions》2008,2(3):125-135
By altering myriad aspects of leaf chemistry, increasing concentrations of CO2 and O3 in the atmosphere derived from human activities may fundamentally alter the relationships between insect herbivores and plants.
Because exposure to elevated CO2 can alter the nutritional value of leaves, some herbivores may increase consumption rates to compensate. The effects of O3 on leaf nutritional quality are less clear; however, increased senescence may also reduce leaf quality for insect herbivores.
Additionally, changes in secondary chemistry and the microclimate of leaves may render plants more susceptible to herbivory
in elevated CO2 and O3. Damage to soybean (Glycine max L.) leaves and the size and composition of the insect community in the plant canopy were examined in large intact plots exposed
to elevated CO2 (~550 μmol mol−1) and elevated O3 (1.2*ambient) in a fully factorial design with a Soybean Free Air Concentration Enrichment system (SoyFACE). Leaf area removed
by folivorous insects was estimated by digital photography and insect surveys were conducted during two consecutive growing
seasons, 2003 and 2004. Elevated CO2 alone and in combination with O3 increased the number of insects and the amount of leaf area removed by insect herbivores across feeding guilds. Exposure
to elevated CO2 significantly increased the number of western corn rootworm (Diabrotica virgifera) adults (foliage chewer) and soybean aphids (Aphis glycines; phloem feeder). No consistent effect of elevated O3 on herbivory or insect population size was detected. Increased loss of leaf area to herbivores was associated with increased
carbon-to-nitrogen ratio and leaf surface temperature. Soybean aphids are invasive pests in North America and new to this
ecosystem. Higher concentrations of CO2 in the atmosphere may increase herbivory in the soybean agroecosystem, particularly by recently introduced insect herbivores.
Handling editor: Gary Felton. 相似文献
7.
Ellen D. Currano Rachel Laker Andrew G. Flynn Kari K. Fogt Hillary Stradtman Scott L. Wing 《Ecology and evolution》2016,6(13):4318-4331
Paleoecological studies document the net effects of atmospheric and climate change in a natural laboratory over timescales not accessible to laboratory or ecological studies. Insect feeding damage is visible on well‐preserved fossil leaves, and changes in leaf damage through time can be compared to environmental changes. We measured percent leaf area damaged on four fossil leaf assemblages from the Bighorn Basin, Wyoming, that range in age from 56.1 to 52.65 million years (Ma). We also include similar published data from three US sites 49.4 to ~45 Ma in our analyses. Regional climate was subtropical or warmer throughout this period, and the second oldest assemblage (56 Ma) was deposited during the Paleocene–Eocene Thermal Maximum (PETM), a geologically abrupt global warming event caused by massive release of carbon into the atmosphere. Total and leaf‐chewing damage are highest during the PETM, whether considering percent area damaged on the bulk flora, the average of individual host plants, or a single plant host that occurs at multiple sites. Another fossil assemblage in our study, the 52.65 Ma Fifteenmile Creek paleoflora, also lived during a period of globally high temperature and pCO2, but does not have elevated herbivory. Comparison of these two sites, as well as regression analyses conducted on the entire dataset, demonstrates that, over long timescales, temperature and pCO2 are uncorrelated with total insect consumption at the ecosystem level. Rather, the most important factor affecting herbivory is the relative abundance of plants with nitrogen‐fixing symbionts. Legumes dominate the PETM site; their prevalence would have decreased nitrogen limitation across the ecosystem, buffering generalist herbivore populations against decreased leaf nutritional quality that commonly occurs at high pCO2. We hypothesize that nitrogen concentration regulates the opposing effects of elevated temperature and CO2 on insect abundance and thereby total insect consumption, which has important implications for agricultural practices in today's world of steadily increasing pCO2. 相似文献
8.
Though field data for naturally senesced leaf litter are rare, it is commonly assumed that rising atmospheric CO2 concentrations will reduce leaf litter quality and decomposition rates in terrestrial ecosystems and that this will lead
to decreased rates of nutrient cycling and increased carbon sequestration in native ecosystems. We generally found that the
quality of␣naturally senesced leaf litter (i.e. concentrations of C, N and lignin; C:N, lignin:N) of a variety of native plant
species produced in alpine, temperate and tropical communities maintained at elevated CO2 (600–680 μl l−1) was not significantly different from that produced in similar communities maintained at current ambient CO2 concentrations (340–355 μl l−1). When this litter was allowed to decompose in situ in a humid tropical forest in Panama (Cecropia peltata, Elettaria cardamomum, and Ficus benjamina, 130 days exposure) and in a lowland temperate calcareous grassland in Switzerland (Carex flacca and a graminoid species mixture; 261 days exposure), decomposition rates of litter produced under ambient and elevated CO2 did not differ significantly. The one exception to this pattern occurred in the high alpine sedge, Carex curvula, growing in the Swiss Alps. Decomposition of litter produced in situ under elevated CO2 was significantly slower than that of litter produced under ambient CO2 (14% vs. 21% of the initial litter mass had decomposed over a 61-day exposure period, respectively). Overall, our results
indicate that relatively little or no change in leaf litter quality can be expected in plant communities growing under soil
fertilities common in many native ecosystems as atmospheric CO2 concentrations continue to rise. Even in situations where small reductions in litter quality do occur, these may not necessarily
lead to significantly slower rates of decomposition. Hence in many native species in situ litter decomposition rates, and the time course of decomposition, may remain relatively unaffected by rising CO2.
Received: 12 September 1996 / Accepted: 30 November 1996 相似文献
9.
MARTIN SCHÄDLER MAREIKE ROEDER† ROLAND BRANDL DIETHART MATTHIES† 《Global Change Biology》2007,13(5):1005-1015
By affecting plant growth and phytochemistry elevated CO2 may have indirect effects on the performance of herbivores. These effects show considerable variability across studies and may depend on nutrient availability, the carbon/nutrient‐balance in plant tissues and the secondary metabolism of plants. We studied the responses to elevated CO2 and different nutrient availability of 12 herbaceous plant species differing in their investment into secondary compounds. Caterpillars of the generalist herbivore Spodoptera littoralis were reared on the leaves produced and their consumption and growth rates analysed. Elevated CO2 resulted in a similar increase of biomass in all plant species, whereas the positive effect of fertilization varied among plant species. Specific leaf weight was influenced by elevated CO2, but the effect depended on nutrient level and identity of plant species. Elevated CO2 increased the C/N ratio of the leaves of most species. Caterpillars consumed more leaf material when plants were grown under elevated CO2 and low nutrients. This indicates compensatory feeding due to lower tissue quality. However, the effects of elevated CO2, nutrient availability and plant species identity on leaf consumption interacted. Both the effects of CO2 and nutrient availability on the relative growth rate of the herbivore depended on the plant species. The feeding rate of S. littoralis on plant species that do not produce nitrogen‐containing secondary compounds (NCSC) was higher under low nutrient availability. In contrast, in plants producing NCSC nutrient availability had no effect on the feeding rate. This suggests that compensatory feeding in response to low nutrient contents may not be possible if plants produce NCSC. We conclude that elevated CO2 causes species‐specific changes in the quality of plant tissues and consequently in changes in the preferences of herbivores for plant species. This could result in changes in plant community composition. 相似文献
10.
Increase of fast nutrient cycling in grassland microcosms through insect herbivory depends on plant functional composition and species diversity
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Norma Nitschke Kerstin Wiesner Ines Hilke Nico Eisenhauer Yvonne Oelmann Wolfgang W. Weisser 《Oikos》2015,124(2):161-173
Nutrient cycling in terrestrial ecosystems is affected by various factors such as plant diversity and insect herbivory. While several studies suggest insect herbivory to depend on plant diversity, their interacting effect on nutrient cycling is unclear. In a greenhouse experiment with grassland microcosms of one to six plant species of two functional groups (grasses and legumes), we tested the influence of plant species richness (diversity) and functional composition on plant community biomass production, insect foliar herbivory, soil microbial biomass, and nutrient concentrations in throughfall. To manipulate herbivory, zero, three or six generalist grasshoppers (Chorthippus parallelus) were added to the plant communities. Increasing plant species richness increased shoot biomass and grasshopper performance, without significantly affecting root biomass or insect herbivory. Plant functional composition affected all of these parameters, e.g. legume communities showed the highest shoot biomass, the lowest grasshopper performance and suffered the least herbivory. Nutrient concentrations (dissolved mineral N, PO4‐P, SO4‐S) and pH in throughfall increased with herbivory. PO4‐P and pH increases were positively affected by plant diversity, especially under high herbivore pressure. Plant functional composition affected several throughfall variables, sometimes fully explaining diversity effects. Increasing plant diversity tended to increase soil microbial biomass, but only under high herbivore pressure. Faeces quantities strongly correlated with changes in pH and PO4‐P; frass may therefore be an important driver of throughfall pH and a main source of PO4‐P released from living plants. Our results indicate that insect herbivory may significantly influence fast nutrient cycling processes in natural communities, particularly so in managed grasslands. 相似文献
11.
Seedlings of loblolly pine Pinus taeda (L.), were grown in open-topped field chambers under three CO2 regimes: ambient, 150 l l–1 CO2 above ambient, and 300 l l–1 CO2 above ambient. A fourth, non-chambered ambient treatment was included to assess chamber effects. Needles were used in 96 h feeding trials to determine the performance of young, second instar larvae of loblolly pine's principal leaf herbivore, red-headed pine sawfly, Neodiprion lecontei (Fitch). The relative consumption rate of larvae significantly increased on plants grown under elevated CO2, and needles grown in the highest CO2 regime were consumed 21% more rapidly than needles grown in ambient CO2. Both the significant decline in leaf nitrogen content and the substantial increase in leaf starch content contributed to a significant increase in the starch:nitrogen ratio in plants grown in elevated CO2. Insect consumption rate was negatively related to leaf nitrogen content and positively related to the starch:nitrogen ratio. Of the four volatile leaf monoterpenes measured, only -pinene exhibited a significant CO2 effect and declined in plants grown in elevated CO2. Although consumption changed, the relative growth rates of larvae were not different among CO2 treatments. Despite lower nitrogen consumption rates by larvae feeding on the plants grown in elevated CO2, nitrogen accumulation rates were the same for all treatments due to a significant increase in nitrogen utilization efficiency. The ability of this insect to respond at an early, potentially susceptible larval stage to poorer food quality and declining levels of a leaf monoterpene suggest that changes in needle quality within pines in future elevated-CO2 atmospheres may not especially affect young insects and that tree-feeding sawflies may respond in a manner similar to herb-feeding lepidopterans. 相似文献
12.
Jep Agrell Brian Kopper† Evan P. McDonald‡ Richard L. Lindroth§ 《Global Change Biology》2005,11(4):588-599
Elevated levels of CO2 and O3 affect plant growth and phytochemistry, which in turn can alter physiological performance of associated herbivores. Little is known, however, about how generalist insect herbivores respond behaviorally to CO2‐ and O3‐mediated changes in their host plants. This research examined the effects of elevated CO2 and O3 levels on host plant preferences and consumption of forest tent caterpillar (FTC, Malacosoma disstria Hbn.) larvae. Dual choice feeding assays were performed with foliage from birch (Betula papyrifera Marsh.) and aspen (Populus tremuloides Michx., genotypes 216 and 259). Trees were grown at the Aspen Free Air CO2 Enrichment (FACE) facility near Rhinelander, WI, USA, and had been exposed to ambient or elevated concentrations of CO2 and/or O3. Levels of nutritional and secondary compounds were quantified through phytochemical analyses. The results showed that elevated O3 levels increased FTC larval preferences for birch compared with aspen, whereas elevated CO2 levels had the opposite effect. In assays with the two aspen genotypes, addition of both CO2 and O3 caused a shift in feeding preferences from genotype 259 to genotype 216. Consumption was unaffected by experimental treatments in assays comparing aspen and birch, but were increased for larvae given high O3 foliage in the aspen genotype assays. Elevated levels of CO2 and O3 altered tree phytochemistry, but did not explain shifts in feeding preferences. The results demonstrate that increased levels of CO2 and O3 can alter insect host plant preferences both between and within tree species. Also, consequences of altered host quality (e.g., compensatory consumption) may be buffered by partial host shifts in situations when alternative plant species are available. Environmentally induced changes in host plant preferences may have the potential to alter the distribution of herbivory across plant genotypes and species, as well as competitive interactions among them. 相似文献
13.
Bernd Schäppi 《Oecologia》1996,106(1):93-99
Leaf expansion, population dynamics and reproduction under elevated CO2 were studied for two dominant and four subdominant species in a high alpine grassland (2500 above sea level, Swiss Central Alps). Plots of alpine heath were exposed to 335 l l-1 and 680 l l-1 CO2 in open-top chambers over three growing seasons. Treatments also included natural and moderately improved mineral nutrient supply (40 kg N ha-1 year-1 in an NPK fertilizer mix). Seasonal dynamics of leaf expansion, which was studied for the dominant graminoid Carex curvula only, were not affected by elevated CO2 during two warm seasons or during a cool season. Improved nutrient supply increased both the expansion rate and the duration of leaf growth but elevated CO2 did not cause any further stimulation. Plant and tiller density (studied in all species) increased under elevated CO2 in the codominant Leontodon helveticus and the subdominant Trifolium alpinum, remained unchanged in two other minor species Poa alpina and Phyteuma globulariifolium, and decreased in Carex curvula. In Potentilla aurea elevated CO2 compensated for a natural decline in shoot number. By year 3 the number of fertile shoots in Leontodon and individual seed weight in Carex were slightly increased under elevated CO2, indicating CO2 effects on sexual reproduction in these two dominant species. The results suggest that the effects of elevated CO2 on the population dynamics of the species studied were not general, but species-specific and rather moderate effects. However, the reduction of tiller density in Carex curvula, in contrast to the increases observed in Leontodon helveticus and Trifolium alpinum, indicates that elevated CO2 may negatively affect the abundance of the species most characteristic of this alpine plant community. 相似文献
14.
Summary Seeds of Gliricidia sepium (Jacq.) Walp., a tree native to seasonal tropical forests of Central America, were inoculated with N-fixing Rhizobium bacteria and grown in growth chambers for 71 days to investigate interactive effects of atmospheric CO2 and plant N status on early seedling growth, nodulation, and N accretion. Seedlings were grown with CO2 partial pressures of 350 and 650 bar (current ambient and a predicted partial pressure of the mid-21st century) and with plus N or minus N nutrient solutions to control soil N status. Of particular interest was seedling response to CO2 when grown without available soil N, a condition in which seedlings initially experienced severe N deficiency because bacterial N-fixation was the sole source of N. Biomass of leaves, stems, and roots increased significantly with CO2 enrichment (by 32%, 15% and 26%, respectively) provided seedlings were supplied with N fertilizer. Leaf biomass of N-deficient seedlings was increased 50% by CO2 enrichment but there was little indication that photosynthate translocation from leaves to roots or that plant N (fixed by Rhizobium) was altered by elevated CO2. In seedlings supplied with soil N, elevated CO2 increased average nodule weight, total nodule weight per plant, and the amount of leaf nitrogen provided by N-fixation (as indicated by leaf 15N). While CO2 enrichment reduced the N concentration of some plant tissues, whole plant N accretion increased. Results support the contention that increasing atmospheric CO2 partial pressures will enhance productivity and N-fixing activity of N-fixing tree seedlings, but that the magnitude of early seedling response to CO2 will depend greatly on plant and soil nutrient status. 相似文献
15.
Xoaquín Moreira Luis Abdala‐Roberts Jorge C. Berny Mier y Teran Felisa Covelo Raúl de la Mata Marta Francisco Bess Hardwick Ricardo Matheus Pires Tomas Roslin Dmitry S. Schigel Jan P. J. G. ten Hoopen Bart G. H. Timmermans Laura J. A. van Dijk Bastien Castagneyrol Ayco J. M. Tack 《Oikos》2019,128(1):113-123
Systematic comparisons of species interactions in urban versus rural environments can improve our understanding of shifts in ecological processes due to urbanization. However, such studies are relatively uncommon and the mechanisms driving urbanization effects on species interactions (e.g. between plants and insect herbivores) remain elusive. Here we investigated the effects of urbanization on leaf herbivory by insect chewers and miners associated with the English oak Quercus robur by sampling trees in rural and urban areas throughout most of the latitudinal distribution of this species. In performing these comparisons, we also controlled for the size of the urban areas (18 cities) and gathered data on CO2 emissions. In addition, we assessed whether urbanization affected leaf chemical defences (phenolic compounds) and nutritional traits (phosphorus and nitrogen), and whether such changes correlated with herbivory levels. Urbanization significantly reduced leaf chewer damage but did not affect leaf miners. In addition, we found that leaves from urban locations had lower levels of chemical defences (condensed and hydrolysable tannins) and higher levels of nutrients (nitrogen and phosphorus) compared to leaves in rural locations. The magnitude of urbanization effects on herbivory and leaf defences was not contingent upon city size. Importantly, while the effects of urbanization on chemical defences were associated with CO2 emissions, changes in leaf chewer damage were not associated with either leaf traits or CO2 levels. These results suggest that effects of urbanization on herbivory occur through mechanisms other than changes in the plant traits measured here. Overall, our simultaneous assessment of insect herbivory, plant traits and abiotic correlates advances our understanding of the main drivers of urbanization effects on plant–herbivore interactions. 相似文献
16.
It is plausible that the nutritional quality of C3 plants will decline more under elevated atmospheric CO2 than will the nutritional quality of C4 plants, causing herbivorous insects to increase their feeding on C3 plants relative to C4 plants. We tested this hypothesis with a C3 and C4 grass and two caterpillar species with different diet breadths. Lolium multiflorum (C3) and Bouteloua curtipendula (C4) were grown in outdoor open top chambers at ambient (370 ppm) or elevated (740 ppm) CO2. Bioassays compared the performance and digestive efficiencies of Pseudaletia unipuncta (a grass-specialist noctuid) and Spodoptera frugiperda (a generalist noctuid). As expected, the nutritional quality of L. multiflorum changed to a greater extent than did that of B. curtipendula when grown in elevated CO2; levels of protein (considered growth limiting) declined in the C3 grass, while levels of carbohydrates (sugar, starch and fructan) increased. However, neither insect species increased its feeding rate on the C3 grass to compensate for its lower nutritional quality when grown in an elevated CO2 atmosphere. Consumption rates of P. unipuncta and S. frugiperda were higher on the C3 grass than the C4 grass, the opposite of the result expected for a compensatory response to the lower nutritional quality of the C4 grass. Although our results do not support the hypothesis that grass-specialist insects compensate for lower nutritional quality by increasing their consumption rates more than do generalist insects, the performance of the specialist was greater than that of the generalist on each grass species and at both CO2 levels. Mechanisms other than compensatory feeding, such as increased nutrient assimilation efficiency, appear to determine the relative performance of these herbivores. Our results also provide further evidence against the hypothesis that C4 grasses would be avoided by insect herbivores because a large fraction of their nutrients is unavailable to herbivores. Instead, our results are consistent with the hypothesis that C4 grasses are poorer host plants primarily because of their lower nutrient levels, higher fiber levels, and greater toughness. 相似文献
17.
The elevated concentration of atmospheric CO2 may result in a decline of leaf nutritional quality (especially N) and an increase in some kinds of defensive secondary components
(such as phenolics). The changes in the phytochemistry of trees, combined with the effect of elevated CO2
per se, have a potential negative influence on insect herbivores. Here, we review the effect of elevated CO2 on the performance of leaffeeding forest insects at individual-level and community-level. The elevated CO2
per se have little influence on the metabolism of insects. Over half of the tree-insect experimental systems show that the performance
of individual insect become poorer under high-CO2 grown trees; but the others show that the insects have just little or no response to the treatments. The direction and magnitude
of the changes in the performance of insects could be mediated by various factors. The effects of treatment are strongly species-dependent.
The magnitude of changes in the phytochemistry, the sensitivity and adaptive capacity of insects to the poorer leaf quality,
the differences in plant growth conditions and experimental methods, and the mediated effects of other environmental factors
(such as soil nutrient availability, light, temperature, O3) were all closely related to the final performance of insects. However, the larvae’s consumption usually increased under
enriched CO2 treatment, which was widely thought to be a compensatory response to poorer plant quality. The experiments on forest community-level
found identically a reduction in herbivory, which was contrary to the results from small-scale experiments. The changes in
insect population and the actual response of consumption by leaf-feeding forest insects under CO2 enrichment remain unclear, and more field-based experiments need to be conducted.
__________
Translated from Chinese Journal of Applied Ecology, 2006, 17(4): 720–726 [译自: 应用生态学报] 相似文献
18.
The increasing CO2 concentration in Earths atmosphere is expected to cause a greater decline in the nutritional quality of C3 than C4 plants. As a compensatory response, herbivorous insects may increase their feeding disproportionately on C3 plants. These hypotheses were tested by growing the grasses Lolium multiflorum C3) and Bouteloua curtipendula C4) at ambient (370 ppm) and elevated (740 ppm) CO2 levels in open top chambers in the field, and comparing the growth and digestive efficiencies of the generalist grasshopper Melanoplus sanguinipes on each of the four plant × CO2 treatment combinations. As expected, the nutritional quality of the C3 grass declined to a greater extent than did that of the C4 grass at elevated CO2; protein levels declined in the C3 grass, while levels of carbohydrates (sugar, fructan and starch) increased. However, M. sanguinipes did not significantly increase its consumption rate to compensate for the lower nutritional quality of the C3 grass grown under elevated CO2. Instead, these grasshoppers appear to use post-ingestive mechanisms to maintain their growth rates on the C3 grass under elevated CO2. Consumption rates of the C3 and C4 grasses were also similar, demonstrating a lack of compensatory feeding on the C4 grass. We also examined the relative efficiencies of nutrient utilization from a C3 and C4 grass by M. sanguinipes to test the basis for the C4 plant avoidance hypothesis. Contrary to this hypothesis, neither protein nor sugar was digested with a lower efficiency from the C4 grass than from the C3 grass. A novel finding of this study is that fructan, a potentially large carbohydrate source in C3 grasses, is utilized by grasshoppers. Based on the higher nutrient levels in the C3 grass and the better growth performance of M. sanguinipes on this grass at both CO2 levels, we conclude that C3 grasses are likely to remain better host plants than C4 grasses in future CO2 conditions. 相似文献
19.
Effects of elevated CO2 on development and larval food-plant preference in the butterfly Coenonympha pamphilus (Lepidoptera, Satyridae) 总被引:1,自引:0,他引:1
The objective of this study was to determine how increasing atmospheric CO2 change plant tissue quality in four native grassland grass species (Agrostis stolonifera, Anthoxanthum odoratum, Festuca rubra, Poa pratensis) which are all larval food‐plants of Coenonympha pamphilus (Lepidoptera, Satyridae). We assessed the effect of these changes on the performance and larval food‐plant preference of C. pamphilus in a greenhouse experiment. Furthermore, we tested the interactive effects of elevated CO2 and soil nutritional availability in F. rubra and its effect an larval development of C. pamphilus. In general, elevated CO2 decreased leaf water concentration, nitrogen concentration and specific leaf area (SLA), while leaf starch concentration was increased in all grass species. A species‐specific reaction to elevated CO2 was only found for foliar starch concentration. P. pratensis did not increase its starch concentration under elevated CO2 conditions, whereas the other three species did. Fertilisation, investigated only for F. rubra, increased leaf nitrogen concentration and amplified the CO2‐induced decrease in leaf nitrogen. Development time of C. pamphilus was on the average prolonged by two days under elevated CO2 and the prolongation differed from 0.7 to 5.3 days among food‐plant species. Pupal fresh weight differed marginally between CO2 treatments. Fertilisation of the larval food‐plant F. rubra shortened development time by one day and significantly increased pupal and adult fresh weights. C. pamphilus larvae showed a clear food‐plant preference among grass species at the age of 36 h or older. Additionally, a change of food‐plant preference under elevated CO2 was found. Larvae at ambient CO2 preferred Agrostis stolonifera and F. rubra, while under elevated CO2Anthoxanthum odoratum and P. pratensis were preferred. The present study demonstrates that larval development of C. pamphilus is affected by food‐plant species and CO2 induced changes in foliar chemistry. Although we found some species‐specific reactions to elevated CO2 for foliar chemistry, no such CO2 by species interaction was found for insect development. The change in food‐plant preference of larvae under elevated CO2 implies potential changes in selection pressure for grass species and might therefore affect evolutionary processes. 相似文献
20.
Summary The scale insect, Toumeyella sp., feeds exclusively on the subtropical hammock tree lignum vitae (Guaiacum sanctum L.). The combined effects of scale herbivory and shading on leaf gas exchange characteristics and growth of lignum vitae trees were studied using a factorial design. Trees grown in full sun or in 75% shade were manually infested with scale or left noninfested. Beginning 4 weeks after infestation, net CO2 assimilation, stomatal conductance, transpiration, internal partial pressure of CO2, and water-use efficiency were determined on single-leaves at 4-week intervals for trees in each treatment. At the end of the experiment, net CO2 assimilation was determined for whole plants. Total leaf area, leaf, stem, and root dry weights, and leaf chlorophyll and nitrogen concentrations were also determined. Scale infested trees generally had lower net CO2 assimilation, stomatal conductance, and transpiration rates as well as less leaf area, and root, stem, and leaf dry weights than noninfested trees. Twenty four weeks after the shade treatment was imposed, sun-grown trees had approximately twice the leaf area of shade-grown trees. Shade-grown trees compensated for the reduced leaf area by increasing their photosynthetic efficiency. This resulted in no difference in light saturated net CO2 assimilation on a whole plant basis between sun-grown and shade-grown trees. Chlorophyll and nitrogen concentrations per unit leaf area were greater in leaves of shade-grown trees than in leaves of sun-grown trees. Shading and herbivory by Toumeyella sp. each resulted in decreased growth of Guaiacum sanctum. Scale insect herbivory did not result in greater detrimental effects on leaf gas exchange characteristics for shade-grown than for sun-grown trees. Herbivory by Toumeyella resulted in a greater decrease in tree growth for sun-grown than for shade-grown trees. 相似文献