Growth responses of gypsy moth larvae to elevated CO2: the influence of methods of insect rearing

Abstract The effects of elevated CO₂ on foliar chemistry of two tree species (Populus pseudo‐simonii Kitag. and Betula platyphylla) and on growth of gypsy moth (Lymantria dispar L.) larvae were examined. Furthermore, we focused on the comparison of results on the growth responses of larvae obtained from two methods of insect rearing, the no‐choice feeding trial performed in the laboratory or in situ in open‐top chambers. On the whole, both primary and secondary metabolites in the leaves of the two tree species were significantly affected by main effects of time (sampling date), CO₂ and species. Elevated CO₂ significantly increased the C : N ratio and concentrations of the soluble sugar, starch, total nonstructural carbohydrates, total phenolics and condensed tannins, but significantly decreased the concentration of nitrogen. Higher contents of total phenolics and condensed tannins were detected in the frass of larvae reared in elevated CO₂ treatments. Overall, the growth of gypsy moth larvae were significantly inhibited by elevated CO₂ and CO₂‐induced changes in leaf quality. Our study did not indicate the two methods of insect rearing could influence the direction of effects of elevated CO₂ on the growth of individual insects; however, the magnitude of negative effects of elevated CO₂ on larval growth did differ between the two insect rearing methods, and it seems that the response magnitude was also mediated by larval age and host plant species.     

The effects of ozone on growth and stomatal response in the F<Subscript>2</Subscript> generation of hybrid poplar (<Emphasis Type="Italic">Populus trichocarpa × Populus deltoides</Emphasis>)

Thirty-six F₂ hybrid poplar (Populus trichocarpa × P. deltoides) clones were fumigated with ozone to record its effects on growth, correlate them with stomatal response and screen for ozone sensitivity. Fumigation was applied for 6 to 9 h each day for approximately 3 months at ozone concentrations of 85 to 128 μg g⁻¹ using open-top chambers. Height, diameter, number of leaves, stomatal conductance, transpiration rate, total biomass, biomass components and root/shoot ratios were reduced by ozone stress. Percent of leaf fall in ozone-treated plants was nearly three times higher than in control plants exposed to charcoal-filtered air. Leaf senescence, because of ozone exposure, did not appear to be associated with reduced biomass production. Some clones had a high percentage of leaf-fall with ozone exposure, but were able to maintain total biomass production near that of the control. Their response may be an example of an ability to adjust or compensate for ozone damage. There was no significant or consistent relationship between stomatal conductance and total biomass or the change in stomatal conductance as a result of ozone exposure and the change in total biomass. Taken together, these results suggest that effects of ozone on poplar growth cannot be solely correlated to changes in stomatal conductance, more physiological and biochemical parameters should be examined.     

模拟大气中CO＿2浓度对大豆影响的试验

本文利用ＯＴＣ－１型开顶式气室对大豆进行了长时期不同ＣＯ２浓度处理的接触试验,结果表明;不同ＣＯ２浓度处理对大豆生长发育、生物产量、籽粒产量及叶片光合作用率等影响显著,且均为正效应。     

Changes in high arctic tundra plant reproduction in response to long‐term experimental warming

We provide new information on changes in tundra plant sexual reproduction in response to long‐term (12 years) experimental warming in the High Arctic. Open‐top chambers (OTCs) were used to increase growing season temperatures by 1–2 °C across a range of vascular plant communities. The warming enhanced reproductive effort and success in most species; shrubs and graminoids appeared to be more responsive than forbs. We found that the measured effects of warming on sexual reproduction were more consistently positive and to a greater degree in polar oasis compared with polar semidesert vascular plant communities. Our findings support predictions that long‐term warming in the High Arctic will likely enhance sexual reproduction in tundra plants, which could lead to an increase in plant cover. Greater abundance of vegetation has implications for primary consumers – via increased forage availability, and the global carbon budget – as a function of changes in permafrost and vegetation acting as a carbon sink. Enhanced sexual reproduction in Arctic vascular plants may lead to increased genetic variability of offspring, and consequently improved chances of survival in a changing environment. Our findings also indicate that with future warming, polar oases may play an important role as a seed source to the surrounding polar desert landscape.     

Effect of Elevated CO2 and Moisture Stress on the Carbon and Nitrogen Contents in Brassica Juncea

The responses of Brassica juncea cv. Pusa Bold to elevated CO₂ was studied under water stress. Carbon accumulation in leaves, stem and roots was significantly higher at elevated CO₂ concentration. The water stress decreased the carbon content in these plant parts and this adverse effect was reduced by CO₂ enrichment. On the contrary nitrogen content of leaves, stem and roots was significantly reduced at elevated CO₂. Water stress caused reduction in nitrogen content in these plant parts, similar at ambient as well as elevated CO₂ concentration. This revised version was published online in July 2006 with corrections to the Cover Date.     

模拟增温对川西亚高山两类针叶林土壤酶活性的影响

采用开顶式生长室(open top chamber,OTC)模拟增温,同步监测了亚高山人工针叶林和天然针叶林表层土壤温、湿度的变化,以及模拟增温初期土壤转化酶、脲酶、过氧化氢酶和多酚氧化酶活性的变化.结果表明：在整个生长季节中,OTC使人工林和天然林5 cm土壤日平均温度分别增加0.61 ℃和0.56 ℃,10 cm体积含水量分别下降4.10%和2.55%;模拟增温增加了土壤转化酶、脲酶、过氧化氢酶和多酚氧化酶活性.增温与林型的交互作用对土壤脲酶和过氧化氢酶活性有显著影响,而对转化酶和多酚氧化酶影响不显著.增温对过氧化氢酶活性的影响与季节变化相关.在各处理下,天然林土壤酶活性显著高于人工林.土壤酶活性季节动态与土壤温度有着较大相关性,而与土壤水分季节变化关系不明显.模拟增温易于增加土壤酶活性,但增温效应和林型、酶种类和季节变化有一定关系;亚高山针叶林土壤酶活性主要受控于土壤温度,而与土壤水分关系不大.     

Responses of fungal root colonization,plant cover and leaf nutrients to long‐term exposure to elevated atmospheric CO2 and warming in a subarctic birch forest understory

Responses of the mycorrhizal fungal community in terrestrial ecosystems to global change factors are not well understood. However, virtually all land plants form symbiotic associations with mycorrhizal fungi, with approximately 20% of the plants' net primary production transported down to the fungal symbionts. In this study, we investigated how ericoid mycorrhiza (ErM), fine endophytes (FE) and dark septate endophytes (DSE) in roots responded to elevated atmospheric CO₂ concentrations and warming in the dwarf shrub understory of a birch forest in the subarctic region of northern Sweden. To place the belowground results into an ecosystem context we also investigated how plant cover and nutrient concentrations in leaves responded to elevated atmospheric CO₂ concentrations and warming. The ErM colonization in ericaceous dwarf shrubs increased under elevated atmospheric CO₂ concentrations, but did not respond to warming following 6 years of treatment. This suggests that the higher ErM colonization under elevated CO₂ might be due to increased transport of carbon belowground to acquire limiting resources such as N, which was diluted in leaves of ericaceous plants under enhanced CO₂. The elevated CO₂ did not affect total plant cover but the plant cover was increased under warming, which might be due to increased N availability in soil. FE colonization in grass roots decreased under enhanced CO₂ and under warming, which might be due to increased root growth, to which the FE fungi could not keep up, resulting in proportionally lower colonization. However, no responses in aboveground cover of Deschampsia flexuosa were seen. DSE hyphal colonization in grass roots significantly increased under warmer conditions, but did not respond to elevated CO₂. This complex set of responses by mycorrhizal and other root‐associated fungi to global change factors of all the fungal types studied could have broad implications for plant community structure and biogeochemistry of subarctic ecosystems.     

How does a wetland plant respond to increasing temperature along a latitudinal gradient?

Global warming affects plant fitness through changes in functional traits and thereby ecosystem function. Wetlands are declining worldwide, and hence, ecosystem functions linked to wetlands are threatened. We use Caltha palustris “a common wetland plant” to study whether warming affects growth and reproduction differently depending on origin of source population, potentially affecting phenotypic response to local climate. We conducted a 2‐year in situ temperature manipulation experiment using clone pairs of C. palustris in four regions, along a 1300‐km latitudinal gradient of Sweden. Open‐top chambers were used to passively increase temperature, paired with controls. Growth and reproductive traits were measured from 320 plants (four regions × five sites × two treatments × eight plants) over two consecutive seasons to assess the effect of warming over time. We found that warming increased plant height, leaf area, number of leaves, and roots. High‐latitude populations responded more strongly to warming than low‐latitude populations, especially by increasing leaf area. Warming increased number of flowers in general, but only in the second year, while number of fruits increased in low‐latitude populations the first year. Prolonged warming leads to an increase in both number of leaves and flowers over time. While reproduction shows varying and regional responses to warming, impacts on plant growth, especially in high‐latitude populations, have more profound effects. Such effects could lead to changes in plant community composition with increased abundance of fast‐growing plants with larger leaves and more clones, affecting plant competition and ecological functions such as decomposition and nutrient retention. Effects of warming were highly context dependent; thus, we encourage further use of warming experiments to predict changes in growth, reproduction, and community composition across wetland types and climate gradients targeting different plant forms.     

Effect of Elevated CO2 Concentration on Leaf Structure of Brassica Juncea under Water Stress

Study on the effect of elevated CO₂ concentration on leaf structure of Brassica juncea L. cv. Bio-141 (95) under moisture stress revealed, that CO₂ elevated to 600 mol mol^–1 increased the length of epidermal cel and length of palisade parenchyma cells, and induced larger chloroplasts and more oval shaped starch granules in comparison with plants grown at ambient CO₂ concentration. This increase in structural sink size helped in check feedback inhibition by excessive photoassimilate which was subsequently used to compensate the adverse moisture stress effect in B. juncea leaves.     

增温对川西北亚高山高寒草甸植物群落碳、氮含量的影响

采用开顶式生长室（OTC）模拟增温实验,研究了川西北亚高山草甸植物群落碳、氮含量对温度升高的响应。由于OTC的增温作用,在整个生长季内,地温（15 cm）、地表温度和气温(30 cm)的平均值在OTC内比对照样地分别高0.28、0.46和1.4℃,OTC内土壤相对含水量也明显减少,低于对照样地5.49%。受增温及土壤含水量减少的影响,一年后,植物群落的生物量积累和碳、氮含量发生了明显的改变。除10月份OTC内地上鲜体生物量略高于对照样地外,OTC内地上鲜体生物量和根系生物量与对照样地相比,都出现了不同程度的减少;OTC内植物群落地上活体的碳浓度在整个生长季高于对照样地,而氮浓度低于对照样地;OTC内植物群落地下活根的碳浓度在整个生长季高于对照样地,并且在8月份统计检验显著,而氮浓度却低于对照样地;OTC内植物碳库在整个生长季较对照样地有不同程度的增加,增幅范围为0.90%～5.65%,而OTC内植物氮库较对照样地有不同程度的减少,减幅范围0.40%～1.28%。     

O3浓度升高对小麦根际土壤酶活性和有机酸含量的影响

近地层臭氧(O₃)浓度升高作为全球气候变化的重要因素之一,对土壤生态环境和农作物生长发育造成了很大影响.本研究采用开顶式气室(OTCs)法,探究臭氧浓度升高对小麦不同生育期(分蘖期、拔节期、孕穗期和成熟期)根际土壤酶活性(过氧化氢酶、多酚氧化酶、脱氢酶和转化酶)和有机酸含量(草酸、柠檬酸和苹果酸)的影响规律,并结合根际土壤理化性质、植株根系生长状况等分析其产生影响的原因.结果表明: O₃浓度升高不同程度地提高了小麦成熟期土壤过氧化氢酶、多酚氧化酶、脱氢酶和转化酶活性,其中过氧化氢酶和多酚氧化酶活性提高达显著水平;在抽穗期,脱氢酶和转化酶活性因臭氧浓度升高而显著提高,增幅最高可达76.7%.在成熟期,O₃浓度升高显著提高了根际土壤中柠檬酸和苹果酸含量;显著降低了根际土壤pH、电导率、总碳和总氮含量,增加了土壤氧化还原电位(Eh);显著降低了小麦根系生物量、总根长和根总表面积,而增加了根平均直径.