大气二氧化碳浓度升高对植物-昆虫相互关系的影响

综述了CO2浓度升高对植物与昆虫相互关系影响的研究结果。大量研究表明,高浓度CO2对植物生理生化活动有显著的影响,植物营养物质的变化对植食性昆虫亦产生不同程度的影响,高浓度CO2条件对咀嚼式口器昆虫的取食、生长发育和生殖有不同程度的不良影响,昆虫为了获得足够的氮素营养而增加取食强度和时间,从而更易于受到天敌的攻击,这些昆虫的生长率、繁殖和生存率有下降的趋势;而对刺吸韧皮部汁液的昆虫来说,多引起种群数量增加或无显著影响。并对研究中存在的问题进行了分析,提出了今后研究的方向。     

Influence of plant diversity and elevated atmospheric carbon dioxide levels on belowground bacterial diversity

Background  

Changes in aboveground plant species diversity as well as variations of environmental conditions such as exposure of ecosystems to elevated concentrations of atmospheric carbon dioxide may lead to changes in metabolic activity, composition and diversity of belowground microbial communities, both bacterial and fungal.     

The interactive effects of elevated carbon dioxide and water table draw-down on carbon cycling in a Welsh ombrotrophic bog

The effects of elevated atmospheric CO₂ (eCO₂) and water table draw-down on soil carbon sequestration in an ombrotrophic bog ecosystem were examined. Peat monoliths (11 cm diameter, 25 cm deep) with intact bog vegetation were exposed to ambient or elevated (ambient + 200 mg l^?1) atmospheric CO₂, combined with a natural water table (level with the peat surface) or a water table draw-down (?5 cm). Eight observations per treatment were included in the study, which was conducted over a 12 week period. Concentration of dissolved organic carbon (DOC), phenolic compounds and the fluxes of CO₂ and CH₄ were measured. The eCO₂ treatment caused an increase in the CH₄ and CO₂ fluxes and a small decrease in both the DOC and phenolic concentrations. The water table draw-down invoked decreases in phenolic and DOC concentrations, a decrease in CH₄ flux and a small increase in CO₂ flux. The combined (eCO₂ + water table draw-down) treatment caused a larger than expected CH₄ flux decrease and CO₂ flux increase and an increase in DOC concentration. Our results suggest very different effects on the system dependent on the treatment applied. The draw-down treatment principally increased oxidation of the rhizosphere resulting in increased decomposition and as such a removal of material from the dissolved carbon pool. The data also suggest labile carbon availability may be limiting the rate of decomposition and so slowing inorganic nutrient and carbon pool turn-over. The elevated CO₂ addressed the labile-carbon limitation. Under the environment of the combined treatment, these limitations were effectively removed, culminating in a destabilisation of the carbon-sequestering environment to a weaker sink (or even a source) of atmospheric carbon.     

Effects of elevated carbon dioxide, ozone and water availability on spring wheat growth and yield

Spring wheat (Triticum aestivum L. cv. Dragon) was exposed to elevated carbon dioxide (CO₂), alone (1995) or in combination with two levels of increased ozone (O₃) (1994) or increased irrigation (1996) during three successive growing seasons as part of the EU ESPACE‐wheat programme and conducted in open‐top chambers (OTCs) and ambient air (AA) plots at Östad, 50 km north‐east of Göteborg, Sweden. Doubling the CO₂ concentration had a positive effect on grain yield in all 3 years (+21, +7 and +11%, respectively), although only statistically significant in 1994. That year was characterised by a warm and dry summer in comparison with 1995 and 1996, in which the summers were more humid and typical for south‐west Sweden. In 1994, the CO₂‐induced increase in grain yield was associated with an increase in the duration of the green leaf area, a positive effect on straw yield and on the number of ears per square metre and a negative effect (?13%) on grain protein concentration. Harvest index was unaffected by the elevated CO₂ concentration. The only statistically significant effect of elevated CO₂ in 1995 was a decrease in the grain protein concentration (?11% in both CO₂ concentrations), and in 1996 an increase (+21%) in the straw yield. In 1996 the soil water potential was less negative in elevated CO₂, which is likely to reflect a lower water consumption of these plants. Addition of extra O₃ significantly affected the grain yield (?6 and ?10%, respectively) and the 1 000‐grain weight negatively (?3 and ?6%). Statistically significant interactions between CO₂ and O₃ were obtained for the number of ears per unit area and for the 1 000‐grain weight. The 1 000‐grain weight was negatively affected by O₃ in low CO₂, but remained unaffected in the high CO₂ treatment. There was a significant decrease (?6%) in the grain protein concentration induced by elevated irrigation. The chambers, compared with AA plots, had a positive effect on plant development and on grain yield in all 3 years.     

大气中CO2浓度升高对植物的影响

大气中CO_2浓度升高以及由此所引起的温室效应已成为人们普遍关注的议题。在未来的世界里,CO_2浓度将持续上升。预计到21世纪中叶,CO_2浓度可能达到700ppm。一些试验结果表明;CO_2浓度升高对多数植物的个体生长发育有促进作用,其中包括种子的发芽率提高,幼苗生长加快,叶面积增大,根系数量增多,气孔数量减少,茎干生长轮加宽,开花期提早,种子产量提高等。但是,CO_2浓度升高对植物也有不利影响。在高CO_2浓度环境中,由于过量产生的碳水化合物在叶片中的积累和矿物质的不平衡,许多植物在生长后期生长缓慢或出现负增长;个体生长发育规律的变化将导致一些增长种群逐渐向衰退种群过渡;C_3类杂草的加速生长将引起农业欠收;群落结构与组成的变化将促使一些植物走向绝灭;植物残渣中碳氮比的改变将引起生态系统生产力的下降等。因此,对于今后大气中CO_2浓度升高的影响还要做大量的研究。     

大气二氧化碳浓度升高对植物的影响

现代人类的活动,特别是矿场燃料的大量使用和植被的破坏,导致大气CO2浓度持续上升。该文阐述了CO2浓度升高对植物的形态、生理、产量和品质,种群消长,群落组成,生态系统结构与功能的影响。     

大气CO2浓度升高对花蜜及传粉昆虫的影响

植物依赖昆虫传授花粉,昆虫从植物获得花粉和花蜜作为食物,两者在漫长的进化过程中形成了密切的互惠共生关系.大量研究表明,CO2浓度升高对植物花蜜的产量和组成有显著的影响.CO2浓度增加后,有花植物花蜜的产量和组分在不同物种之间的变化差异很大,即使是种内不同基因型植株的花蜜对CO2浓度增加的反应也有所不同.大部分种类花蜜的...     

Potential effects of elevated carbon dioxide on leaf-feeding forest insects

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 leaf-feeding forest insects at individual-level and commu-nity-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 magni-tude 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 compensa-tory 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 popula-tion 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.     

Potential effects of elevated carbon dioxide on leaf-feeding forest insects

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]     

大气CO2浓度升高对森林食叶昆虫的潜在影响

评述了大气CO₂浓度升高对森林食叶昆虫的影响,昆虫对森林取食为害水平的潜在变化,以及研究中的主要实验方法.大气CO₂浓度升高通过引起叶片化学变化进而影响食叶昆虫个体的取食和生长;但物种对环境变化反应的特异性、植物化学对高浓度CO₂的反应强度、昆虫对植物生理变化的敏感性和适应性、研究周期的长短、其它环境因子的协同效应以及不同实验中植物生长条件和研究方法的差异均将影响昆虫反应的方向和强度;CO₂气体浓度增高本身可能不足以对食叶昆虫个体的新陈代谢构成影响;大气CO₂浓度升高也可能影响森林食叶昆虫种群的大小.     

Response of plant roots to elevated atmospheric carbon dioxide

Plant root response to atmospheric CO₂ enrichment can be great. Results from this controlled environment investigation demonstrate substantial effects on root system architecture, micromorphology and physiology. The most pronounced effects were an increase in root length (110%) and root dry weight (143%). Root diameter, stele diameter, cortex width, root/shoot and root weight ratios all increased; root numbers did not increase. The long-term implications for belowground processes could be enormous.     

Responses of soil biota to elevated atmospheric carbon dioxide

Increasing concentrations of atmospheric CO₂ could have dramatic effects upon terrestrial ecosystems including changes in ecosystem structure, nutrient cycling rates, net primary production, C source-sink relationships and successional patterns. All of these potential changes will be constrained to some degree by below ground processes and mediated by responses of soil biota to indirect effects of CO₂ enrichment. A review of our current state of knowledge regarding responses of soil biota is presented, covering responses of mycorrhizae, N-fixing bacteria and actinomycetes, soil microbiota, plant pathogens, and soil fauna. Emphasis will be placed on consequences to biota of increasing C input through the rhizosphere and resulting feedbacks to above ground systems. Rising CO₂ may also result in altered nutrient concentrations of plant litter, potentially changing decomposition rates through indirect effects upon decomposer communities. Thus, this review will also cover current information on decomposition of litter produced at elevated CO₂. Summary Predictably, the responses of soil biota to CO₂ enrichment and the degree of experimental emphasis on them increase with proximity to, and intimacy with, roots. Symbiotic associations are all stimulated to some degree. Total plant mycorrhization increases with elevated CO₂. VAM fungi increase proportionately with fine root length/mass increase. ECM fungi, however, exhibit greater colonization per unit root length/mass at elevated CO₂ than at current atmospheric levels. Total N-fixation per plant increases in all species examined, although the mechanisms of increase, as well as the eventual benefit to the host relative to N uptake may vary. Microbial responses are unclear. The assumption that changes in root exudation will drive increased mineralization and facilitate nutrient uptake should be examined experimentally, in light of recent models. Microbial results to date suggest that metabolic activity (measured as changes in process rates) is stimulated by root C input, rather than population size (measured by cell or colony counts). Insufficient evidence exists to predict responses of either soil-borne plant pathogens or soil fauna (i.e., food web responses). These are areas requiring attention, the first for its potential to limit ecosystem production through disease and the second because of its importance to nutrient cycling processes. Preliminary data on foliar litter decomposition suggests that neither nutrient ratios nor decomposition rates will be affected by rising CO₂. This is another important area that may be better understood as the number of longer term studies with more realistic CO₂ exposures increase. Evidence continues to mount that C fixation increases with CO₂ enrichment and that the bulk of this C enters the belowground component of ecosystems. The global fate and effects of this additional C may affect all hierarchical levels, from organisms to ecosystems, and will be largely determined by responses of soil biota.     

Soil carbon dioxide partial pressure and dissolved inorganic carbonate chemistry under elevated carbon dioxide and ozone

Global emissions of atmospheric CO₂ and tropospheric O₃ are rising and expected to impact large areas of the Earths forests. While CO₂ stimulates net primary production, O₃ reduces photosynthesis, altering plant C allocation and reducing ecosystem C storage. The effects of multiple air pollutants can alter belowground C allocation, leading to changes in the partial pressure of CO₂ (pCO₂) in the soil , chemistry of dissolved inorganic carbonate (DIC) and the rate of mineral weathering. As this system represents a linkage between the long- and short-term C cycles and sequestration of atmospheric CO₂, changes in atmospheric chemistry that affect net primary production may alter the fate of C in these ecosystems. To date, little is known about the combined effects of elevated CO₂ and O₃ on the inorganic C cycle in forest systems. Free air CO₂ and O₃ enrichment (FACE) technology was used at the Aspen FACE project in Rhinelander, Wisconsin to understand how elevated atmospheric CO₂ and O₃ interact to alter pCO₂ and DIC concentrations in the soil. Ambient and elevated CO₂ levels were 360±16 and 542±81 l l^–1, respectively; ambient and elevated O₃ levels were 33±14 and 49±24 nl l^–1, respectively. Measured concentrations of soil CO₂ and calculated concentrations of DIC increased over the growing season by 14 and 22%, respectively, under elevated atmospheric CO₂ and were unaffected by elevated tropospheric O₃. The increased concentration of DIC altered inorganic carbonate chemistry by increasing system total alkalinity by 210%, likely due to enhanced chemical weathering. The study also demonstrated the close coupling between the seasonal ¹³C of soil pCO₂ and DIC, as a mixing model showed that new atmospheric CO₂ accounted for approximately 90% of the C leaving the system as DIC. This study illustrates the potential of using stable isotopic techniques and FACE technology to examine long- and short-term ecosystem C sequestration.     

Increased mercury in forest soils under elevated carbon dioxide

Fossil fuel combustion is the primary anthropogenic source of both CO₂ and Hg to the atmosphere. On a global scale, most Hg that enters ecosystems is derived from atmospheric Hg that deposits onto the land surface. Increasing concentrations of atmospheric CO₂ may affect Hg deposition to terrestrial systems and storage in soils through CO₂-mediated changes in plant and soil properties. We show, using free-air CO₂ enrichment (FACE) experiments, that soil Hg concentrations are almost 30% greater under elevated atmospheric CO₂ in two temperate forests. There were no direct CO₂ effects, however, on litterfall, throughfall or stemflow Hg inputs. Soil Hg was positively correlated with percent soil organic matter (SOM), suggesting that CO₂-mediated changes in SOM have influenced soil Hg concentrations. Through its impacts on SOM, elevated atmospheric CO₂ may increase the Hg storage capacity of soils and modulate the movement of Hg through the biosphere. Such effects of rising CO₂, ones that transcend the typically studied effects on C and nutrient cycling, are an important next phase for research on global environmental change.     

Decreased hydraulic conductance in plants at elevated carbon dioxide

Previous work indicated that long-term exposure to elevated carbon dioxide levels can reduce hydraulic conductance in some species, but the basis of the response was not determined. In this study, hydraulic conductance was measured at concentrations of both 350 and 700 cm³ m^–3 carbon dioxide for plants grown at both concentrations, to determine the reversibility of the response. In Zea mays and Amaranthus hypochondriacus , exposure to the higher carbon dioxide concentration for several hours reduced whole-plant transpiration rate by 22–40%, without any consistent change in leaf water potential, indicating reversible reductions in hydraulic conductance at elevated carbon dioxide levels. Hydraulic conductance in these species grown at both carbon dioxide concentrations responded similarly to measurement concentration of carbon dioxide, indicating that the response was reversible. In Glycine max , which in earlier work had shown a long-term decrease in hydraulic conductance at elevated carbon dioxide levels, and in Abutilon theophrasti , no short-term changes in hydraulic conductance with measurement concentration of carbon dioxide were found, despite lower transpiration rates at elevated carbon dioxide. In G. max and Medicago sativa , growth at high dew-point temperature reduced transpiration rate and decreased hydraulic conductance. The results indicate that both reversible and irreversible decreases in hydraulic conductance can occur at elevated carbon dioxide concentrations, and that both could be responses to reduced transpiration rate, rather than to carbon dioxide concentration itself.