Open top chamber

Two field experiments were conducted to examine the impact nf a foliar stress (ozone, O.,), alone or in combination with u resource stress, on cavbon giiin of aspen {Populin^ Iremuioidus MicVis.), The tirst experiment involved nitrogen deficiency, and the second, drought stress. The patterns of change in icaf area, photosynthetic rate and carbon gain with leaf position from root to apex were altered by O^ alone. Net photosynthesis and car boxy iation capaeity of older leaves decreased, and of younger leaves increased, in response to O^, Thus younger leaves partially compensated for the decreased photosynthetic capacity nf older leaves. Physiological maturity and senescence were accelerated by O.,. Whole plant carbon gain declined with O3 due-to reductions in both leaf urea and photosynthetk rate. Nitrogen deficiencv-alone decreased carbon gain via reductions in both leaf area and photosyntheric rate across leaf position. The effects of O., and nitrogen deficiencv together on hoth leaf area and phntosyntht'tic rate were additive. Aspen seedlings compensated to O,, stress regardkss of nitrogen level. Plant responses to both of these stresses may have been mediated by ribulose bisphosphate carboxylase/oxygenase iRubisco) content or activity, and thus indirectly by nitrogen content. ln the second expenment, seedlings were subjected to drought during the first six weeks of exposure to O.,, and were measured several weeks after termination cf the drought treatment. Drought caused aspen seedlings to produce fewer and smaller leaves. After termination of drought, they produced larger new leav'es, and net photosynthesis af most leaves was greater than in continuously well-watered plants. In plants not exposed to O^, enhanced photosynthetic rate partially compensated for the smaller leaf area. ()., generallv decreased leaf area and photosynthesis, and hence carhon gain. The effects of prior exposure to drought and O., together were additive for whnle-plant photosynthetic rate, but less than additive for whole-plant kaf area.

In Shenandoah National Park, O 3 monitoring data were characterized and attempts were made to relate O 3 concentration levels to visible foliar injury observed for five plant species surveyed. Foliar injury for three species increased with elevation. The 24-h monthly mean O 3 concentrations tended to increase with elevation; however, the number of elevated hourly occurrences did not. Although the frequency of high hourly O 3 concentrations did not consistently increase with elevation, O 3 exposures in the park may have been high enough to provoke an effect that may have been enhanced by vegetation sensitivities that differed as a function of altitude.

Leaf chemistry alterations due to increasing atmospheric CO2 will reflect plant physiological changes and impact ecosystem function. Longleaf pine was grown for 20 months at two levels of atmospheric CO2 (720 and 365 µmol mol -1 ), two levels of soil N (4 g m -2 year -1 and 40 g m -2 year -1 ), and two soil moisture levels (-0.5 and -1.5 MPa) in open top chambers. After 20 months of exposure, needles were collected and ergastic substances including starch grains and polyphenols were assessed using light microscopy, and calcium oxalate crystals were assessed using light microscopy, scanning electron micros copy, and transmission electron microscopy. Polyphenol content was also determined using the Folin-Denis assay and condensed tannins were estimated by precipitation with protein. Evaluation of phenolic content histochemically was compared to results obtained using the Folin-Denis assay. Total leaf polyphenol and condensed tannin content were increased by main effects of elevated CO2, low soil N and well-watered conditions. Elevated CO2 and low soil N decreased crystal deposition within needle phloem. Ele vated CO2 had no effect on the percentage of cells within the mesophyll, endodermis, or transfusion tissue which contained visible starch inclusions. With respect to starch accumulation in response to N stress, mesophyll > en dodermis > transfusion tissue. The opposite was true in the case of starch accumulation in response to main effects of water stress: mesophyll < endodermis < transfusion tissue. These results indicate that N and water conditions significantly affect deposition of leaf ergastic substances in

Increased atmospheric CO 2 and consequent increases in temperature are two prominent features of climate change, a major challenge to crops. Here, our objectives were to determine: (1) the responses of sugarcane during the first 90 days of elevated CO 2 (ECO 2) and elevated temperature (ETem), both individually and together, and (2) the genotypic variation of these responses. Eight varieties were grown both in open-top chambers in a factorial combination of ambient/ECO 2 concentrations (344-351/777-779 ppm) and ambient/ETem (34.9-35.6/36.6-38.4 C) and in open fields. Significant

Understanding the differential responses of C3 and C4 plants to elevated atmospheric CO₂ and varying light intensities is critical for predicting future plant productivity and ecosystem dynamics under changing climate conditions. This study investigates the photosynthetic performance and carbon assimilation efficiency of C3 and C4 plants grown under controlled environmental conditions with elevated CO₂ concentrations and varying light intensities. Controlled growth chamber experiments were conducted to measure photosynthetic rate, stomatal conductance, water use efficiency (WUE), and biomass accumulation in representative C3 and C4 species. Results indicate that elevated CO₂ enhances photosynthetic performance and carbon assimilation efficiency in C3 plants more significantly than in C4 plants, consistent with the distinct photosynthetic pathways of each group. However, increased light intensity improved performance in C4 plants to a greater extent. These findings suggest that future increases in atmospheric CO₂ may disproportionately benefit C3 plants, whereas C4 plants may rely more on high light availability for optimal productivity. This study highlights the complex interaction between photosynthetic pathways, CO₂ levels, and light intensity, providing insights for agricultural and ecological management under future climate scenarios

The Prairie Heating and CO 2 Enrichment (PHACE) experiment has been initiated at a site in southern Wyoming (USA) to simulate the impact of warming and elevated atmospheric CO 2 on ecosystem dynamics for semiarid grassland ecosystems. • The DAYCENT ecosystem model was parametrized to simulate the impact of elevated CO 2 at the open-top chamber (OTC) experiment in north-eastern Colorado (1996Colorado ( -2001)), and was also used to simulate the projected ecosystem impact of the PHACE experiments during the next 10 yr. • Model results suggest that soil water content, plant production, soil respiration, and nutrient mineralization will increase for the high-CO 2 treatment. Soil water content will decrease for all years, while nitrogen mineralization, soil respiration, and plant production will both decrease and increase under warming depending on yearly differences in water stress. Net primary production (NPP) will be greatest under combined warming and elevated CO 2 during wet years. • Model results are consistent with empirical field data suggesting that water and nitrogen will be critical drivers of the semiarid grassland response to global change.

The effect of elevated carbon dioxide concentration on the changes in the biomass, photosynthesis and nutrient composition was investigated in two leafy vegetables. Spinach (Spinacia oleracea L.) and fenugreek (Trigonella foenum-graecum L.) plants were grown in open top chambers under either ambient (ACO 2 , 350 ± 50 µmol mol -1 ) or elevated (ECO 2 , 600 ± 50 µmol mol -1 ) CO 2 concentration and analyzed 40, 60 and 80 days after exposure. The plants grown in ECO 2 had higher net photosynthetic rate and lower stomatal conductance when compared with the plants grown in ACO 2 . ECO 2 also changed the nutrient composition: a lower N, Mg and Fe contents and higher C and Ca contents were observed in the leaves of plants exposed to ECO 2 than in those grown at ACO 2 .

Texas cotton production is facing challenges from increased temperatures and extended droughts. We sought to determine whether applying a multi-species grass mulch on the surface of cotton fields in a semiarid region would mitigate some of the negative effects of climate change. We used open-top chambers (OTCs) to mimic climate warming and compared whether the effects of residue addition were similar between dryland and irrigated cotton fields located in the High Plains region of Texas during the summer of 2021. The OTCs raised the average air temperature by 2 • C. Under experimental warming, residue addition increased moisture content in non-irrigated (i.e., dryland) soils (+9.2%) and reduced the daily temperature range (by-1.4 • C) relative to uncovered soils. Furthermore, when pooled across irrigation and warming treatments, the addition of residue increased microbial biomass, soil respiration (+78.2%), and cotton yield (+15.2%) relative to uncovered soils. OTCs further enhanced the residue effects on microbial biomass by 34.9%. We also observed higher soil organic matter, microbial biomass, cotton biomass, and yield in irrigated fields compared to dryland, irrespective of residue addition. Our findings suggest that residue addition in dryland agriculture can mitigate the adverse effects of warming by stabilizing soil microclimates and promoting microbial growth and biomass by providing a more labile source of carbon, which, in turn, could boost the yield of cotton plants.

An open-top chamber fumigation system was built in a young Scots pine stand to study the effects of realistic elevated ozone (O3) and carbon dioxide (CO2) concentrations and their combination on trees in natural conditions. Doubled CO2 concentration compared to present ambient concentration, and O3 concentration between 40 ppb and 70 ppb in the first study year (1994) and doubled O3 concentration in years 1995 and 1996 were the target concentrations in the chambers. The O3 concentration in the chambers was successfully maintained close to the target concentration and differences between chambers were small. The mean CO2 concentration in the CO2 treatment was ca. 100 ppm below the target, but was maintained at this level throughout the growing season. Two degrees higher mean air temperature and slightly lower light intensity compared to open air were measured in the chambers. The operation of the fumigation system was satisfactory during the three study years and repeatability of the...

Concentration of CO 2 in the atmosphere is likely to increase up to 550 µmol mol -1 by the middle of 21 st century. Such an increase in the atmospheric CO 2 would affect plant growth, and as well the productivity of crop plants. A field experiment was conducted with two potato cultivars namely Kufri Surya and Kufri Chipsona-3 grown inside Open Top Chambers (OTCs) at ambient (385±30 µmol mol -1 ) vs. elevated CO 2 (570±50 µmol mol -1 ) levels during rabi (winter) season of the year 2009-2010. The photosynthetic rate significantly increased in both cultivars when under high CO 2 concentration, with the enhancement being more in Kufri Chipsona-3 than in Kufri Surya. There were significantly increased accumulations of reducing, non-reducing and total sugars observed in the leaves of both cultivars as due to CO 2 enrichment. Crop Growth Rate (CGR) and Tuber Growth Rate (TGR), in both cultivars, were recorded higher in plants grown under elevated CO 2 as compared with the ambient CO 2 con...

This work investigates the possibility of implementing a nature-based solution (NBS) based on the photosynthetic process of Laurus nobilis L. (common laurel), for reducing peak CO2 concentrations in an airtight museum environment, namely the Refectory of the Santa Maria delle Grazie Church (Milan, Italy), home of Leonardo da Vinci's painting "Last Supper". The phytoremediation potential of laurel plants was evaluated at CO2 ≅ 1000 ppm under controlled environmental conditions. Furthermore, light-saturated net assimilation (Pnmax) was measured at two CO2 concentrations (380 and 1000 ppm) during the growing season. Steady-state gas exchanges were not affected by elevated CO2 in the short-term, while Pnmax was significantly increased, also showing higher values in spring and autumn, and a reduction during summer. Our estimated CO2 removal rates indicate that, in order to control visitors' respiratory CO2 emissions in view of an increase in visitor numbers in the Refectory, a possible NBS in the form of an external greenhouse, connected to the HVAC system of the museum, should allocate from 58 to 112 young laurel plants, depending on their seasonal phytoremediation capacity. These results, although preliminary, allow to hypothesize the possibility of controlling CO2 indoors through a combination of traditional aircleaning systems and a properly designed NBS, thus increasing the sustainability of airtight museum environments.

The impacts of simulated climate change (warming and fertilization treatments) on diazotroph community structure and activity were investigated at Alexandra Fiord, Ellesmere Island, Canada. Open Top Chambers, which increased growing season temperatures by 1-3 °C, were randomly placed in a dwarf-shrub and cushion-plant dominated mesic tundra site in 1995. In 2000 and 2001 20N:20P 2 O 5 :20K 2 O fertilizer was applied at a rate of 5 g m À2 year À1 . Estimates of nitrogen fixation rates were made in the field by acetylene reduction assays (ARA). Higher rates of N fixation were observed 19-35 days post-fertilization but were otherwise unaffected by treatments. However, moss cover was significantly positively associated with ARA rate. NifH gene variants were amplified from bulk soil DNA and analyzed by terminal restriction fragment length polymorphism analysis. Non-metric multidimensional scaling was used to ordinate treatment plots in nifH genotype space. NifH gene communities were more strongly structured by the warming treatment late in the growing season, suggesting that an annual succession in diazotroph community composition occurs.

A recent study by Loehman and Wilkinson (11) predicted that significant losses are occurring in Indiana due to 3 stress. Ozone, produced during the daylight hours, is generated when sunlight reacts with NO x and hydrocarbons released into the atmosphere as by-products of the combustion of fossil fuels (13). A photolytic reaction reduces N0 2 , producing an oxygen atom which spontaneously reacts with molecular oxygen, forming 3. Sulfur dioxide is released directly into the atmosphere as a byproduct from the combustion of fossil fuel containing sulfur. Indiana is one of the leading states in S02 emissions, releasing > 500,000 tons of S0 2 annually into the atmosphere. Some of Indiana's largest industrial sources of S0 2 are located in SW Indiana, with several in the vicinity of the major melon growing areas in Knox, Sullivan, and Gibson counties (Table 1). The same stationary sources that burn coal, oil, natural gas or other fuels releasing S0 2 , can also contribute to the formation of NO x , the precursor to 3. Regional climatological conditions result in prevailing winds from the west, southwest, south and southeast during the summer Table 1. The Major Sources of Sulfur Dioxide Emissions in Indiana.

In Tunisia, olive trees cover over 33% of the agricultural area [1]. Their cultivation is of great socioeconomic importance, is spread from the North to the South in varying bioclimatic conditions. Olive trees are well adapted to abiotic stress. The severity of climate causes biochemical and nutritional changes in olive trees, such as secondary metabolites and minerals. The olive trees exchanges with the external environment, besides the energy and the water, the volatile organic compounds [2] and the nutritive elements necessary for its process. The requirements

This study is carried in the Laboratory of Aerospace Methods, Faculty of Geography MSU, within the PPS Arctic project, which aims to investigate dynamics of the northern forest boundary in connection with climate change. Images from Landsat satellites available over the last three decades, but their resolution 30 m is not sufficient for clear representation of sparse northern forests. Therefore it is necessary to know what do we have in situ inside the 30x30 m pixel area? We answer this by analysing a very high resolution QuickBird image.

Rising atmospheric [CO 2 ] has the potential to alter soil carbon (C) cycling by increasing the content of recalcitrant constituents in plant litter, thereby decreasing rates of decomposition. Because fine root turnover constitutes a large fraction of annual NPP, changes in fine root decomposition are especially important. These responses will likely be affected by soil resource availability and the life history characteristics of the dominant tree species. We evaluated the effects of elevated atmospheric [CO 2 ] and soil resource availability on the production and chemistry, mycorrhizal colonization, and decomposition of fine roots in an early-and latesuccessional tree species that are economically and ecologically important in north temperate forests. Open-top chambers were used to expose young trembling aspen (Populus tremuloides) and sugar maple (Acer saccharum) trees to ambient (36 Pa) and elevated (56 Pa) atmospheric CO 2. Soil resource availability was composed of two treatments that bracketed the range found in the Upper Lake States, USA. After 2.5 years of growth, sugar maple had greater fine root standing crop due to relatively greater allocation to fine roots (30% of total root biomass) relative to aspen (7% total root biomass). Relative to the low soil resources treatment, aspen fine root biomass increased 76% with increased soil resource availability, but only under elevated [CO 2 ]. Sugar maple fine root biomass increased 26% with increased soil resource availability (relative to the low soil resources treatment), and showed little response to elevated [CO 2 ]. Concentrations of N and soluble phenolics, and C/N ratio in roots were similar for the two species, but aspen had slightly higher lignin and lower condensed tannins contents compared to sugar maple. As predicted by source-sink models of carbon allocation, pooled constituents (C/N ratio, soluble phenolics) increased in response to increased relative carbon availability (elevated [CO 2 ]/low soil resource availability), however, biosynthetically distinct compounds (lignin, starch, condensed tannins) did not always respond as predicted. We found that mycorrhizal colonization of fine roots was not strongly affected by atmospheric [CO 2 ] or soil resource availability, as indicated by root ergosterol contents. Overall, absolute changes in root chemical composition in response to increases in C and soil resource availability were small and had no effect on soil fungal biomass or specific rates of fine root decomposition. We conclude that root contributions to soil carbon cycling will mainly be influenced by fine root production and turnover responses to rising atmospheric [CO 2 ], rather than changes in substrate chemistry.

The effect of elevated carbon dioxide (600±50 cm 3 m-3 ; C 600) on growth performance, biomass production, and photosynthesis of Cenchrus ciliaris L. cv. 3108 was studied. This crop responded significantly by plant height, leaf length and width, and biomass production under C 600. Leaf area index increased triple fold in the crops grown in the open top chamber with C 600. The biomass production in term of fresh and dry biomass accumulation increased by 134.35 (fresh) and 193.34 (dry) % over the control (C 360) condition where the crops were grown for 120 d. The rate of photosynthesis and stomatal conductance increased by 24.51 and 46.33 %, respectively, in C 600 over C 360 plants. In comparison with C 360 , the rate of transpiration decreased by 6.8 % under C 600. Long-term exposure (120 d) to C 600 enhanced photosynthetic water use efficiency by 34 %. Also the contents of chlorophylls a and b significantly increased in C 600. Thus C. ciliaris grown in C 600 throughout the crop season may produce more fodder in terms of green biomass.

Plots of a tallgrassprairieecosystemwere exposed to ambientand twice-ambientCO2 concentrationsin open-topchambersand comparedto unchamberedambientCO2plots duringthe entire growingseasonfrom 1989 through1992. Dominantspecieswere Ar,.:lropogon gerardii,A. scoparius,and Sorghastrumnutans(C4)and Poa pratensis(C3). Aboveground biomassand leaf area were estimatedby periodicsamplingthroughoutthe growing season in 1989 and 1990. In 1991 and 1992, peak biomassand leaf area were estimated by an early Augustharvest. Relativerootproductionamongtreatmentswas estimated using root ingrowthbags whichremainedin placethroughout the growingseason.

ABSTRACTA tallgrass prairie ecosystem was exposed to ambient and twice‐ambient CO2 concentrations in open‐top chambers and compared to unchambered ambient CO2 during the entire growing season from 1989 through 1991. Dominant species were Andropogon gerardii (C4), A. scoparius (C4), Sorghastrum nutans (C4) and Poa pratensis (C3). Nitrogen and phosphorus concentrations in A. gerardii, P. pratensis and dicotyledonous herbs above ground biomass were estimated by periodic sampling throughout the growing season in 1989 and 1990. In 1991, N and P concentrations in peak biomass were estimated by an early August harvest. N and P concentrations in root production as a function of treatment were estimated using root ingrowth bags that remained in place throughout the growing season. Total N and P in above‐ and belowground biomass were calculated as products of concentration and peak biomass by species groups. N concentration in A. gerardii and dicotyledonous herb aboveground biomass was lower ...

In central U.S. grasslands, plant and ecosystem responses to elevated CO 2 are most pronounced when water availability is limited. In a northeast Kansas grassland, responses to elevated CO 2 in leaf area, number, development, and longevity were quantified for the tallgrass prairie dominant, Andropogon gerardii. Plants were grown in open-top chambers (OTCs) modified to limit water availability and to maximize responses to elevated CO 2. In OTCs with elevated (#2 ambient) levels of CO 2 , aboveground biomass production and leaf water potentials were increased significantly compared with those of plants in OTCs with ambient CO 2. There were no differences in leaf area or leaf number per tiller in A. gerardii in elevated compared with ambient OTCs. However, leaf area in adjacent unchambered plots with greater water availability was significantly higher than in the OTCs. The time required for developing leaves to achieve maximum leaf area was reduced by 29%, and the period of time until leaves senesced was increased by 20% for plants exposed to elevated compared with ambient CO 2. Thus, leaves of this C 4 grass species expanded more rapidly (6 d) and remained green longer (9 d) when exposed to elevated CO 2. Such CO 2-mediated increases in leaf longevity in the dominant species may allow this grassland to respond more opportunistically to temporally variable rainfall patterns in high-CO 2 environments. These responses should be included in leaf-based simulation models that attempt to mechanistically link physiological alterations to predicted canopy responses to increased CO 2 .

Increasing concentrations of atmospheric CO, may alter the carbon and water relations of prairie ecosystems. A Cd-dominated tallgrass prairie near Manhattan, KS, was exposed to 2 X ambient CO, concentrations using 4.5 m-diameter open-top chambers. Whole-chamber net CO, exchange (NCE) and evapotranspiration (ET) were continuously monitored in CO,-enriched and ambient (no enrichment) plots over a 34-d period encompassing the time of peak biomass in July and August, 1993. Soil-surface CO, fluxes were measured with a portable surface chamber, and sap flow (water transport in xylem) in individual grass culms was monitored with heat balance techniques. Environmental measurements were used to determine the effect of CO, on the surface energy balance and canopy resistances to vapor flux. In 1993, frequent rainfall kept soil water near field capacity and minimized plant water stress. Over the 34-d measurement period, average daily NCE (canopy photosynthesis-soil and canopy respiration) was 9.3 g CO, m-* in the ambient treatment and 11.4 g CO, m-* under COz enrichment. However, differences in NCE were caused mainly by delayed senescence in the CO,-enriched plots at the end of the growing season. At earlier stages of growth, elevated CO, had no effect on NCE. Soil-surface CO, fluxes typically ranged from 0.4 to 0.66 mg CO, m-' s-', but were slightly greater in the CO,-enriched chambers. CO, enrichment reduced daily ET by 22%. reduced sap flow by 18%, and increased canopy resistance to vapor flux by 24 s m-'. Greater NCE and lower ET resulted in higher daytime water use efficiency (WUE) under CO, enrichment vs. ambient (9.84 vs. 7.26 g CO, kg-' H,O). However, record high precipitation during the 1993 season moderated the effect of ' Contribution No.

Carbon emissions related to human activities have been significantly contributing to the elevation of atmospheric [CO 2 ] and temperature. More recently, carbon emissions have greatly accelerated, thus much stronger effects on crops are expected. Here, we revise literature data concerning the physiological effects of CO 2 enrichment and temperature rise on crop species. We discuss the main advantages and limitations of the most used CO 2-enrichment technologies, the Open-Top Chambers (OTCs) and the Free-Air Carbon Enrichment (FACE). Within the conditions expected for the next few years, the physiological responses of crops suggest that they will grow faster, with slight changes in development, such as flowering and fruiting, depending on the species. There is growing evidence suggesting that C 3 crops are likely to produce more harvestable products and that both C 3 and C 4 crops are likely to use less water with rising atmospheric [CO 2 ] in the absence of stressful conditions. However, the beneficial direct impact of elevated [CO 2 ] on crop yield can be offset by other effects of climate change, such as elevated temperatures and altered patterns of precipitation. Changes in food quality in a warmer, high-CO 2 world are to be expected, e.g., decreased protein and mineral nutrient concentrations, as well as altered lipid composition. We point out that studies related to changes in crop yield and food quality as a consequence of global climatic changes should be priority areas for further studies, particularly because they will be increasingly associated with food security.

Carbon emissions related to human activities have been significantly contributing to the elevation of atmospheric [CO 2 ] and temperature. More recently, carbon emissions have greatly accelerated, thus much stronger effects on crops are expected. Here, we revise literature data concerning the physiological effects of CO 2 enrichment and temperature rise on crop species. We discuss the main advantages and limitations of the most used CO 2 -enrichment technologies, the Open-Top Chambers (OTCs) and the Free-Air Carbon Enrichment (FACE). Within the conditions expected for the next few years, the physiological responses of crops suggest that they will grow faster, with slight changes in development, such as flowering and fruiting, depending on the species. There is growing evidence suggesting that C 3 crops are likely to produce more harvestable products and that both C 3 and C 4 crops are likely to use less water with rising atmospheric [CO 2 ] in the absence of stressful conditions. However, the beneficial direct impact of elevated [CO 2 ] on crop yield can be offset by other effects of climate change, such as elevated temperatures and altered patterns of precipitation. Changes in food quality in a warmer, high-CO 2 world are to be expected, e.g., decreased protein and mineral nutrient concentrations, as well as altered lipid composition. We point out that studies related to changes in crop yield and food quality as a consequence of global climatic changes should be priority areas for further studies, particularly because they will be increasingly associated with food security.

The response of crop growth and yield to CO 2 and ozone is known to depend on climatic conditions and is difficult to quantify due to the complexity of the processes involved. Two modified mechanistic crop simulation models (AFRCWHEAT2-O3 and LINTULCC), which differ in the levels of mechanistic detail, were used to simulate the effects of CO 2 (ambient, ambient ×2) and ozone (ambient, ambient ×1.5) on growth and developmental processes of spring wheat in response to climatic conditions. Simulations were analysed using data from the ESPACE-wheat project in which spring wheat cv. Minaret was grown in open-top chambers at nine sites throughout Europe and for up to 3 years at each site. Both models closely predicted phenological development and the average measured biomass at maturity. However, intermediate growth variables such as biomass and leaf area index (LAI) at anthesis, seasonal accumulated photosynthetically active radiation intercepted by the crop (SIPAR), the average seasonal light use efficiency (LUE) and the light saturated rate of flag leaf photosynthesis (A sat) were predicted differently and less accurately by the two models. The effect of CO 2 on the final biomass was underestimated by AFRCWHEAT2-O3 due to its poor simulation of the effect of CO 2 on tillering, and LAI.LINTULCC overestimated the response of biomass production to changes in CO 2 level due to an overprediction of the effect of CO 2 on LUE. The measured effect of ozone exposure on final biomass was predicted closely by the two models. The models also simulated the observed interactive effect of CO 2 and ozone on biomass production. However, the effects of ozone on LAI, SIPAR and A sat were simulated differently by the models and less accurately with LINTULCC for the ozone effects on LAI and SIPAR. Predictions of the variation between sites and years of growth and development parameters and of their responses to CO 2 and ozone were poor for both AFRCWHEAT2-O3 and LINTULCC. It was concluded that other factors than those considered in the models such as chamber design and soil properties may have affected the growth and development of cv. Minaret. An analysis of the relationships between growth parameters calculated from the simulations supported this conclusion. In order to apply models for global change impact assessment studies, the difficulties in simulating biomass production in response to CO 2 need to be considered. We suggest that the simulation of leaf area dynamics deserves particular attention in this regard.

In this study, we used the modelling package Expert-N to investigate the ability of four generic-mechanistic crop models, which were originally developed under fi eld conditions, to simulate plant growth of spring wheat grown in open-top chambers (OTC) under different environmental conditions. Thereby we focus on the impacts of drought stress and elevated atmospheric CO2concentration on biomass production. Expert-N facilitates the comparison of the components of agroecosystem models, as it allows exchanging single modules while leaving the rest of the model unchanged. Here the crop growth part of the models SPASS, CERES-Wheat, SUCROS and GECROS were combined with the Penmen-Monteith equation for potential evapotranspiration, the HYDRUS-1D model for water transport and the LEACH-N model for nitrogen transport and turnover simulation. The models were applied to a data set provided by OTC experiments with spring wheat (Triticum aestivum L. cv. 'Minaret') which was grown under two atmospheric CO2-concentration levels (ambient/elevated), two irrigation schemes (unlimited water supply/water limitation) and two soil types (Cambisol/Chernosem) in two subsequent vegetation periods (1998/1999). We show that the crop models are able to simulate CO2 effects on spring wheat growth on organ level under the conditions of the OTC experiments. Based on model calibration using experimental and literature data, the best simulation results describing the impact of the considered environmental conditions were obtained using the model SPASS followed by the models SUCROS, GECROS and CERES. A more sensitive response of atmospheric CO2-concentrations on crop growth was simulated using GECROS and SPASS.

Elevated global temperatures are expected to alter vegetation dynamics by interacting with physiological processes, biotic relationships and disturbance regimes. However, few studies have explicitly modeled the effects of these interactions on rates of vegetation change, despite such information being critical to forecasting temporal patterns in vegetation dynamics. In this study, we build and parameterize rate-change models for three dominant alpine life forms using data from a 7-year warming experiment. These models allowed us to examine how the interactions between experimental warming, the abundance of bare ground (a measure of past disturbance) and neighboring life forms (a measure of life form interaction) affect rates of cover change in alpine shrubs, graminoids and forbs. We show that experimental warming altered rates of life form cover change by reducing the negative effects of neighboring life forms and positive effects of bare ground. Furthermore, we show that our models...

Although certain factors controlling plant emission rates of volatile organic compounds (VOCs) are reasonably well understood, the influence of elevated ozone concentrations as abiotic stress is mostly unknown. Therefore, we studied the effects of ozone concentrations on seasonal biogenic volatile organic compound (BVOC) emissions by different Mediterranean plant species in open top chambers (OTC). Three ozone treatments were established: filtered air (F), non-filtered air (NF), and fumigated air (NF+) adding 40 nl l À1 of ozone over NF. We studied the response of VOC emission in saplings of four Mediterranean woody plant species and subspecies: Ceratonia siliqua L., Olea europaea L., Quercus ilex spp. ilex L., and Quercus ilex spp. rotundifolia L. as representative of natural Mediterranean vegetation. No visible symptoms were detected on the leaves. No significant effect was found on net photosynthetic rates or stomatal conductance except for an increase in net photosynthetic rates in Quercus ilex ilex in spring and summer and an overall slight increase in Quercus ilex rotundifolia. Emissions of the total VOCs from Ceratonia siliqua in summer, and from Olea europaea and Quercus ilex rotundifolia in spring increased in ozone fumigated OTC in comparison with F or NF OTC. Decreased emissions were found in Quercus ilex rotundifolia in summer. There were no significant differences between ozone fumigation treatments for the other plant species and seasons. When considering particular VOCs, the results were also variable among species and time of the year. While a-pinene emissions decreased with ozone fumigation in Olea europaea, a-pinene and limonene emissions increased in Quercus ilex ilex. The responses of these particular VOCs did not always match the responses of total VOCs. In spite of this strong variability, when considering overall annual data for all species and seasons, there were increased net photosynthetic rates (37%) and limonene (95%) and total VOC (45%) emission rates in ozone-fumigated plants, whereas stomatal conductance did not change. Since VOCs are precursors of ozone, the increase in BVOC emission as a consequence of elevated tropospheric ozone concentrations may lead to positive feedback mechanisms in ozone formation.

The effects of nitrogen [75 and 150 kg (N) ha-1 ] and elevated CO 2 on growth, photosynthetic rate, contents of soluble leaf proteins and activities of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and nitrate reductase (NR) were studied on wheat (Triticum aestivum L. cv. HD-2285) grown in open top chambers under either ambient (AC) or elevated (EC) CO 2 concentration (350 ± 50, 600 ± 50 µmol mol-1) and analyzed at 40, 60 and 90 d after sowing. Plants grown under EC showed greater photosynthetic rate and were taller and attained greater leaf area along with higher total plant dry mass at all growth stages than those grown under AC. Total soluble and Rubisco protein contents decreased under EC but the activation of Rubisco was higher at EC with higher N supply. Nitrogen increased the NR activity whereas EC reduced it. Thus, EC causes increased growth and P N ability per unit uptake of N in wheat plants, even if N is limiting.

The study was executed to assess individual and interactive effects of elevated ultraviolet-B (eUV-B) radiation and chromium (Cr) on a medicinal plant Adhatoda vasica Nees. The experiment was conducted under field conditions involving control, Cr, eUV-B, and Cr+eUV-B treatments. The results showed that Cr content was the highest in roots as compared to other parts under Cr+eUV-B. Significant reductions in photosynthetic rate, intercellular CO2 concentration, and stomatal conductance were observed under all treatments with maximum under Cr+eUV-B. Chlorophyll (Chl) fluorescence parameters showed variable responses under Cr and Cr+eUV-B. Chl content showed reductions under all treatments whereas Chl a/b ratio and carotenoids showed increment under eUV-B and reductions under Cr and Cr+eUV-B. The ultrastructure of leaves showed changes in chloroplasts under treatments. Vasicine (medicinally important secondary metabolite) increased under treatments. Our study revealed that A. vasica showed variable responses towards individual and interactive stress of Cr and eUV-B. Highlights • The eUV-B and Cr individually and in combination showed variable responses • Higher reductions in photosynthesis, chlorophylls, and dry mass were observed under Cr+eUV-B • Vasicine (medicinally important compound) increased maximally under Cr+eUV-B

This study was con ducted to de ter mine re cip ro cal ef fects of low to high doses of ni trog e nous fer til izer (N 30 , N 40 , N 50 , N 60 and N 70-30, 40, 50, 60 and 70 kg•ha-1 re spec tively) and CO 2 en riched en vi ron ment on C and N par ti tion ing in soy bean (Glycine max (L.) Merril cv JS-335). Plants were grown from seed ling emer gence to ma tu rity in side open top cham bers under am bi ent, AC (350±50 µmol•mol-1) and el e vated, EC (600±50 µmol•mol-1) CO 2 and an a lyzed at seed ling, veg e tative, flow er ing, pod set ting and ma tu rity stages. Soy bean responded to both CO 2 en rich ment and N sup ply. Leaves, stem and root re serves at dif fer ent growth stages were an a lyzed for to tal C and N con tents. Con sis tent in crease in the C con tents of the leaf, stem and root was ob served un der EC than in AC. N con tents in the dif fer ent plant parts were found to be de creased un der EC-grown plants spe cially at seed ling and veg e ta tive stage de spite pro vid ing N doses to the soil. Sig nif i cant in crease ob served for C to N dry mass ra tio un der EC in the root, stems and leaves at seed ling and veg e ta tive stage was de creased in the mid dle and later growth stages pos si bly due to com bined im pact of N doses to the soil and in creased N 2 fix ing ac tiv i ties due to EC con di tions. Crit i cal anal y sis of our find ings re veals that the com po si tion and par ti tion ing of C and N of soy bean un der vari able rates of N sup ply and CO 2 en rich ment al ter accord ing to need un der al tered met a bolic pro cess. These changes even tu ally may lead to al ter ation in up take of not only N but other es sen tial nu tri ents also un der chang ing at mosphere.

Future climate change will likely represent a major stress to shallow aquatic and coastal marine communities around the world. Most climate change research, particularly in regards to increased pCO 2 and ocean acidification, relies on ex situ mesocosm experimentation, isolating target organisms from their environment. Such mesocosms allow for greater experimental control of some variables, but can often cause unrealistic changes in a variety of environmental factors, leading to "bottle effects." Here we present an in situ technique of altering dissolved pCO 2 within nearshore benthic communities (e.g., macrophytes, algae, and/or corals) using submerged clear, open-top chambers. Our technique utilizes a flow-through design that replicates natural water flow conditions and minimizes caging effects. The clear, open-top design additionally ensures that adequate light reaches the benthic community. Our results show that CO 2 concentrations and pH can be successfully manipulated for long durations within the open-top chambers, continuously replicating forecasts for the year 2100. Enriched chambers displayed an average 0.46 unit reduction in pH as compared with ambient chambers over a 6-month period. Additionally, CO 2 and HCO 3 concentrations were all significantly higher within the enriched chambers. We discuss the advantages and disadvantages of this technique in comparison to other ex situ mesocosm designs used for climate change research.

The present study explores the use of micromorphological leaf epidermal characters of Ficus benjamina (evergreen) and Fraxinus pennsylvanica (deciduous) as indicators of pollution in the Metropolitan Area of Buenos Aires. Mature leaves of both species were sampled along an urbanperiurban gradient, with a rural area as control for epidermal characters. Parameters examined from abaxial and upper epidermis were: (1) length and width of stomata, (2) number of stomata per area unit, (3) length and width of epidermal cells, (4) number of epidermal cells per area unit. Data were analysed with basic statistical and multivariate techniques. Principal Component Analysis (PCA) clearly grouped foliar samples according to three zones: urban, periurban and rural areas with different pollution values. No correlations were observed between epider mal character variations and climate variables, air pollutants or C, N, P and metals concentration in soil. Only one positive correlation (p = 0.006) was ...

Grazing is the predominant land use practice in arid environments; however, there are relatively few studies of grazing effects on ecosystem functioning. We assessed the impact of grazing on soil moisture, evapotranspiration (ET), canopy conductance (Gc), and root water uptake in the Patagonian steppe. Studies were done in 3 sites along a gradient of grazing intensity. High grazing intensity increased the soil water storage by 24% and decreased the amount of water extracted from deep layers compared to the low grazing intensity. Grazing affected ET and its partitioning into transpiration (T) and evaporation. High shrub cover and Gc increased ET and T or ET partitioning in the heavily grazed site. Annual ET increased from 78% to 92% of the annual precipitation from the lowest to the highest grazing intensity, respectively. Total T was 21% higher in the highest intensity site compared to the lowest intensity site. Changes in Gc suggest that grazing modified the canopy architecture, an...

Previously we found that cloned cottonwood saplings (Populus deltoides) grew twice as large in New York, New York, USA, compared to surrounding rural environments and that soils, temperature, CO 2 , nutrient deposition, and microclimatic variables could not account for the greater urban plant biomass. Correlations between final season biomass and cumulative O 3 exposures, combined with twofold growth reductions in an open-top chamber experiment provided strong evidence that higher cumulative O 3 exposures in rural sites reduced growth in the country. Here, we assess the field gas exchange, growth and development, and allocation responses underlying the observed growth differences and compare them with isolated O 3 responses documented in the open-top chamber experiment. Cottonwoods showed no visible foliar injury, reduced photosynthesis of recently expanded foliage, early leaf senescence, protective reduction in stomatal conductance, or compensatory allocation to shoot relative to root biomass for either the chamber or field experiment. Instead, O 3-impacted chamber plants had significantly higher conductance and reduced photosynthesis of older foliage that led to reduced leaf area production and a twofold biomass reduction in the absence of visible injury. Rural-grown field plants showed the same pattern of significantly higher conductance in the absence of concomitant increases in photosynthesis that was indicative of a loss of stomatal control. Incremental changes in foliar production were also significantly inversely related to fluctuations in ambient O 3 exposures. The similarity in biomass, gas exchange, phenological, and allocation responses between chamber and field experiments indicate that mechanisms accounting for reduced growth at rural sites were consistent with those in the open-top chamber O 3 experiment. This study shows the limitation of visible symptoms as a sole diagnostic factor for documenting detrimental O 3 impacts and points toward a new approach to show O 3 impacts when visible injury is not present. Namely, O 3-impacted vegetation showed an unusual inverse relationship of increased conductance with lower photosynthesis of older foliage that was indicative of a loss of stomatal control. This increased stomatal conductance of O 3-impacted vegetation accentuates pollutant flux into affected foliage and has important implications for system water balance during warm, dry portions of the growing season when O 3 concentrations are highest.

Previously we found that cloned cottonwood saplings (Populus deltoides) grew twice as large in New York, New York, USA, compared to surrounding rural environments and that soils, temperature, CO 2 , nutrient deposition, and microclimatic variables could not account for the greater urban plant biomass. Correlations between final season biomass and cumulative O 3 exposures, combined with twofold growth reductions in an open-top chamber experiment provided strong evidence that higher cumulative O 3 exposures in rural sites reduced growth in the country. Here, we assess the field gas exchange, growth and development, and allocation responses underlying the observed growth differences and compare them with isolated O 3 responses documented in the open-top chamber experiment. Cottonwoods showed no visible foliar injury, reduced photosynthesis of recently expanded foliage, early leaf senescence, protective reduction in stomatal conductance, or compensatory allocation to shoot relative to root biomass for either the chamber or field experiment. Instead, O 3 -impacted chamber plants had significantly higher conductance and reduced photosynthesis of older foliage that led to reduced leaf area production and a twofold biomass reduction in the absence of visible injury. Rural-grown field plants showed the same pattern of significantly higher conductance in the absence of concomitant increases in photosynthesis that was indicative of a loss of stomatal control. Incremental changes in foliar production were also significantly inversely related to fluctuations in ambient O 3 exposures. The similarity in biomass, gas exchange, phenological, and allocation responses between chamber and field experiments indicate that mechanisms accounting for reduced growth at rural sites were consistent with those in the open-top chamber O 3 experiment. This study shows the limitation of visible symptoms as a sole diagnostic factor for documenting detrimental O 3 impacts and points toward a new approach to show O 3 impacts when visible injury is not present. Namely, O 3 -impacted vegetation showed an unusual inverse relationship of increased conductance with lower photosynthesis of older foliage that was indicative of a loss of stomatal control. This increased stomatal conductance of O 3 -impacted vegetation accentuates pollutant flux into affected foliage and has important implications for system water balance during warm, dry portions of the growing season when O 3 concentrations are highest.

The effect of elevated atmospheric CO 2 concentration (C a) on the aboveground biomass of three oak species, Quercus myrtifolia, Q. geminata, and Q. chapmanii, was estimated nondestructively using allometric relationships between stem diameter and aboveground biomass after four years of experimental treatment in a naturally ®re-regenerated scrub-oak ecosystem. After burning a stand of scruboak vegetation, re-growing plants were exposed to either current ambient (379 mL L ±1 CO 2) or elevated (704 mL L ±1 CO 2) C a in 16 open-top chambers over a four-year period, and measurements of stem diameter were carried out annually on all oak shoots within each chamber. Elevated C a signi®cantly increased aboveground biomass, expressed either per unit ground area or per shoot; elevated C a had no effect on shoot density. The relative effect of elevated C a on aboveground biomass increased each year of the study from 44% (May 96±Jan 97), to 55% (Jan 97±Jan 98), 66% (Jan 98±Jan 99), and 75% (Jan 99±Jan 00). The effect of elevated C a was species speci®c: elevated C a signi®cantly increased aboveground biomass of the dominant species, Q. myrtifolia, and tended to increase aboveground biomass of Q. chapmanii, but had no effect on aboveground biomass of the subdominant, Q. geminata. These results show that rising atmospheric CO 2 has the potential to stimulate aboveground biomass production in ecosystems dominated by woody species, and that species-speci®c growth responses could, in the long term, alter the composition of the scrub-oak community.

Simultaneous measurements of net ecosystem CO2 exchange (NEE) were made in a Florida scrub‐oak ecosystem in August 1997 and then every month between April 2000 to July 2001, using open top chambers (NEEO) and eddy covariance (NEEE). This study provided a cross validation of these two different techniques for measuring NEE. Unique characteristics of the comparison were that the measurements were made simultaneously, in the same stand, with large replicated chambers enclosing a representative portion of the ecosystem (75 m2, compared to approximately 1–2 ha measured by the eddy covariance system). The value of the comparison was greatest at night, when the microclimate was minimally affected by the chambers. For six of the 12 measurement periods, night NEEO was not significantly different to night NEEE, and for the other periods the maximum difference was 1.1 µmol m−2s−1, with an average of 0.72 ± 0.09 µmol m−2s−1. The comparison was more difficult during the photoperiod, because of d...

Drought is a normal, recurrent feature of climate. In order to understand the potential effect of increasing atmospheric CO 2 concentration (C a) on ecosystems, it is essential to determine the combined effects of drought and elevated C a (EC) under field conditions. A severe drought occurred in Central Florida in 1998 when precipitation was 88 % less than the average between 1984 and 2002. We determined daytime net ecosystem CO 2 exchange (NEE) before, during, and after the drought in the Florida scrub-oak ecosystem exposed to doubled C a in open-top chamber since May 1996. We measured diurnal leaf net photosynthetic rate (P N) of Quercus myrtifolia Willd, the dominant species, during and after the drought. Drought caused a midday depression in NEE and P N at ambient CO 2 concentration (AC) and EC. EC mitigated the midday depression in NEE by about 60 % compared to AC and the effect of EC on leaf P N was similar to its effect on NEE. Growth in EC lowered the sensitivity of NEE to air vapor pressure deficit under drought. Thus EC would help the scrub-oak ecosystem to survive the consequences of the effects of rising atmospheric CO 2 on climate change, including increased frequency of drought, while simultaneously sequestering more anthropogenic carbon.

This study has been carried out in the southern Italy, under conditions favourable to ozone pollution, together with soil and atmospheric drought. Soybean was subjected to well-watered and water stress conditions, and three levels of ozone (filtered, low and high) in open top chambers during three growing seasons. Cumulated AOT40 values were zero, 3400 and 9000 ppb.h for filtered (control), low and high ozone concentration treatments, respectively. Under well-watered conditions, the increase of ozone concentration levels leads to a reduction in daily actual evapotranspiration (AET) and yield. On the contrary, under water stress conditions, the increase of ozone concentration levels does not affect both parameters. Compared to the control treatment under well-watered conditions, total AET reduction was 14% and 28% at low and high ozone levels, respectively. In well-watered conditions, at a high level of ozone concentration, there was a 47% reduction in yield. Whereas an increase in ozone had no effect on yield of plants in water-stressed conditions. Cumulated (during the soybean season) data of AET (ΣAET) and grain yield (Y) allow to calculate the water use efficiency (WUE) by the ratio WUE = Y/ΣAET. As a result, during the 3-year study, significant relationships were found between AOT40 and relative (low or high to control ozone treatments) water use efficiency.

Two black cherry families diering in sensitivity to ozone (O 3) were used to test the hypothesis that leaf morphology is related to foliar sensitivity to O 3. Two uninjured sections of leaf tissue were sampled from a single leaf collected from each of 12 open-grown O 3-tolerant and 12 O 3-sensitive seedlings. Standard histological techniques and light microscopy were used to examine 11 morphological characteristics. The O 3-sensitive genotype had signi®cantly greater stomatal density, thinner palisade mesophyll layer and thicker spongy mesophyll layer, lower ratio of palisade to spongy mesophyll, greater leaf weight and leaf area. In addition, total leaf thickness, guard cell length, and speci®c leaf mass were also slightly greater for the O 3-sensitive genotype.

Concentration of CO 2 in the atmosphere is likely to increase up to 550 µmol mol-1 by the middle of 21 st century. Such an increase in the atmospheric CO 2 would affect plant growth, and as well the productivity of crop plants. A field experiment was conducted with two potato cultivars namely Kufri Surya and Kufri Chipsona-3 grown inside Open Top Chambers (OTCs) at ambient (385±30 µmol mol-1) vs. elevated CO 2 (570±50 µmol mol-1) levels during rabi (winter) season of the year 2009-2010. The photosynthetic rate significantly increased in both cultivars when under high CO 2 concentration, with the enhancement being more in Kufri Chipsona-3 than in Kufri Surya. There were significantly increased accumulations of reducing, non-reducing and total sugars observed in the leaves of both cultivars as due to CO 2 enrichment. Crop Growth Rate (CGR) and Tuber Growth Rate (TGR), in both cultivars, were recorded higher in plants grown under elevated CO 2 as compared with the ambient CO 2 content. High CO 2 increased the partitioning of dry matter towards the tubers at all the harvesting stages. Potato plants grown under elevated CO 2 exhibited increased tuber yield due to the enhanced number of tubers per plant. At the final harvest, total tuber fresh weight was by 36% higher, under high CO 2 treatments, as compared with that in the ambient. The response of K. Chipsona-3 was more pronounced, to elevated CO 2 concentration, as compared with K. Surya. It is concluded that rising atmospheric CO 2 in the future climatic change scenario may be beneficial to such tuber crops like potato to enhance growth as well as tuber number and finally yield.

Due to climate change, the attainment of global food security is facing serious challenges in meeting the growing food demand. Abiotic stresses are the foremost limiting factors for agricultural productivity. However, not much information is available on the effect of multiple abiotic stresses on the morphological and biochemical aspects of kale and mustard. Therefore, an experiment was designed to study the effects of UV-B radiation, CO2 concentration, and high temperature on the growth, yield, and biochemistry of two Brassica species, namely B. oleracea L. var. acephala Winterbor F1 (hybrid kale) and B. juncea var. Green wave O.G. (mustard greens), which were grown under optimal nutrients and soil moisture conditions in soil–plant–atmosphere–research (SPAR) units. Two levels of UV-B radiation (0 and 10 kJ m−2 d−1), two concentrations of CO2 (420 and 720 ppm), and two different temperature treatments (25/17 °C and 35/27 °C) were imposed 12 days after sowing (DAS). Several morpholog...

Warming with open top chambers decreased initial decomposition rate but not stabilization during decomposition in tundras. • Soil moisture, temperature and metal concentrations explained differences in the tea bag index between vegetation types. • In dry locations, initial decomposition rate and stabilization were not affected by soil temperature. • In wetter locations, initial decomposition rate decreased and stabilization increased with increasing soil temperature. • Increased soil metal concentrations impeded decomposition, which may affect decomposition irrespective of climate change.

Changes in growing season temperature and duration may have profound effects on the population dynamics of arctic and alpine plant species in snow-bed and fell-field habitats. We examined how a typical herbaceous pioneer species, Ranunculus glacialis, responded to experimental climate change in open-top chambers for three seasons at an alpine site in southern Norway. Warming had no significant effect on any reproductive, growth or phenological variables, except for seed weight, which increased significantly during the first 2 ears. Despite large differences in average date of snowmelt among years, average reproductive output and ramet size differed little among years. Within-year variation in date of snowmelt had no impact on seed number or weight in either control or warmed plots. Leaf width and ramet leaf number decreased significantly with later snowmelt within a year. Experimental warming reduced the negative effect on ramet size of late snowmelt within a year to some extent. In general, R. glacialis reacts contrary to most other arctic/alpine species to experimental warming. Species with such low responsiveness to environmental conditions may be particularly vulnerable to climatic change, especially if their habitat is invaded by other species with higher phenotypic plasticity and a better competitive ability.