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  • 1
    Electronic Resource
    Electronic Resource
    Photosynthesis, light and nitrogen relationships in a young deciduous forest canopy under open-air CO2 enrichment (2001)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 24 (2001), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Leaf photosynthesis (Ps), nitrogen (N) and light environment were measured on Populus tremuloides trees in a developing canopy under free-air CO2 enrichment in Wisconsin, USA. After 2 years of growth, the trees averaged 1·5 and 1·6 m tall under ambient and elevated CO2, respectively, at the beginning of the study period in 1999. They grew to 2·6 and 2·9 m, respectively, by the end of the 1999 growing season. Daily integrated photon flux from cloud-free days (PPFDday,sat) around the lowermost branches was 16·8 ± 0·8 and 8·7 ± 0·2% of values at the top for the ambient and elevated CO2 canopies, respectively. Elevated CO2 significantly decreased leaf N on a mass, but not on an area, basis. N per unit leaf area was related linearly to PPFDday,sat throughout the canopies, and elevated CO2 did not affect that relationship. Leaf Ps light-response curves responded differently to elevated CO2, depending upon canopy position. Elevated CO2 increased Pssat only in the upper (unshaded) canopy, whereas characteristics that would favour photosynthesis in shade were unaffected by elevated CO2. Consequently, estimated daily integrated Ps on cloud-free days (Psday,sat) was stimulated by elevated CO2 only in the upper canopy. Psday,sat of the lowermost branches was actually lower with elevated CO2 because of the darker light environment. The lack of CO2 stimulation at the mid- and lower canopy was probably related to significant down-regulation of photosynthetic capacity; there was no down-regulation of Ps in the upper canopy. The relationship between Psday,sat and leaf N indicated that N was not optimally allocated within the canopy in a manner that would maximize whole-canopy Ps or photosynthetic N use efficiency. Elevated CO2 had no effect on the optimization of canopy N allocation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.0016-8025.2001.00787.x
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  • 2
    Electronic Resource
    Electronic Resource
    Free Air Temperature Increase (FATI): a new tool to study global warming effects on plants in the field (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 19 (1996), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A new technique, called Free Air Temperature Increase (FATI), was developed to artificially induce increased canopy temperature in field conditions without the use of enclosures. This acronym was chosen in analogy with FACE (Free Air CO2 Enrichment), a technique which produces elevated CO2 concentrations [CO2] in open field conditions. The FATI system simulates global warming in small ecosystems of limited height, using infrared heaters from which all radiation below 800 nm is removed by selective cut-off filters to avoid undesirable photomorpho-genetic effects. An electronic control circuit tracks the ambient canopy temperature in an unheated reference plot with thermocouples, and modulates the radiant energy from the lamps to produce a 2.5°C increment in the canopy temperature of an associated heated plot (continuously day and night). This pre-set target differential is relatively-constant over time due to the fast response of the lamps and the use of a proportional action controller (the standard deviation of this increment was 〈1°C in a 3 week field study with 1007 measurements). Furthermore, the increase in leaf temperature does not depend on the vertical position within the canopy or on the height of the stand. Possible applications and alternative designs are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1996.tb00343.x
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  • 3
    Electronic Resource
    Electronic Resource
    Scaling ozone responses of forest trees to the ecosystem level in a changing climate (2005)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 28 (2005), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Many uncertainties remain regarding how climate change will alter the structure and function of forest ecosystems. At the Aspen FACE experiment in northern Wisconsin, we are attempting to understand how an aspen/birch/maple forest ecosystem responds to long-term exposure to elevated carbon dioxide (CO2) and ozone (O3), alone and in combination, from establishment onward. We examine how O3 affects the flow of carbon through the ecosystem from the leaf level through to the roots and into the soil micro-organisms in present and future atmospheric CO2 conditions. We provide evidence of adverse effects of O3, with or without co-occurring elevated CO2, that cascade through the entire ecosystem impacting complex trophic interactions and food webs on all three species in the study: trembling aspen (Populus tremuloides Michx.), paper birch (Betula papyrifera Marsh), and sugar maple (Acer saccharum Marsh). Interestingly, the negative effect of O3 on the growth of sugar maple did not become evident until 3 years into the study. The negative effect of O3 effect was most noticeable on paper birch trees growing under elevated CO2. Our results demonstrate the importance of long-term studies to detect subtle effects of atmospheric change and of the need for studies of interacting stresses whose responses could not be predicted by studies of single factors. In biologically complex forest ecosystems, effects at one scale can be very different from those at another scale. For scaling purposes, then, linking process with canopy level models is essential if O3 impacts are to be accurately predicted. Finally, we describe how outputs from our long-term multispecies Aspen FACE experiment are being used to develop simple, coupled models to estimate productivity gain/loss from changing O3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.2005.01362.x
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  • 4
    Electronic Resource
    Electronic Resource
    Stomatal regulation in a changing climate: a field study using Free Air Temperature Increase (FATI) and Free Air CO2 Enrichment (FACE) (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 20 (1997), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: This study investigates effects of climate warming (+ 2.5°C ubove ambient) and elevated CO2 concentration (600 μmol mol−1) on the stomatal functioning and the water relations of Lolium perenne, using Free Air Temperature Increase (FATI) and Free Air CO2 Enrichment (FACE). Compared to growth at ambient temperature, whole-season temperature increase reduced leaf stomatal conductance, but only at the top of the canopy (-14.6 and -8.8% at ambient and elevated CO2, respectively). However, because higher canopy temperature raised the leaf-to-air vapour pressure difference, leaf transpiration rate increased (+28% at ambient and +48% at elevated CO2) and instantaneous leaf water use efficiency, derived from short-term measurements of assimilation and transpiration rate, declined (-11% at ambient and -13% at elevated CO2). Nevertheless, at the stand level, growth at + 2.5°C reduced transpiration due to fewer tillers per plant and a smaller leaf area per tiller. This sparser vegetation was also more closely coupled to the atmosphere and maintained a drier internal microclimate. To assess whether the stomatal behaviour observed in this experiment could be explained by prevailing concepts of stomatal functioning, three models were applied (Cowan 1977; Ball, Woodrow & Berry 1987; Leuning 1995). The latter model accounted for the highest proportion of variability in the data (58%) and was insensitive to CO2 and temperature regime, which suggests that the principles of stomatal regulation are not affected by changes in CO2 or climate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1997.tb00680.x
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  • 5
    Electronic Resource
    Electronic Resource
    Source-sink relations in Lolium perenne L. as reflected by carbohydrate concentrations in leaves and pseudo-stems during regrowth in a free air carbon dioxide enrichment (FACE) experiment (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 20 (1997), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effect of an elevated partial pressure of CO2 (pCO2) on carbohydrate concentrations in source leaves and pseudo-stems (stubble) of Lolium perenne L. (perennial ryegrass) during regrowth was studied in a regularly defoliated grass sward in the field. The free air carbon dioxide enrichment (FACE) technology enabled natural environmental conditions to be provided. Two levels of nitrogen (N) supply were used to modulate potential plant growth. Carbohydrate concentrations in source leaves were increased at elevated pCO2, particularly at low N supply. Elevated leaf carbohydrate concentrations were related to an increased structural carbon (C) to N ratio and thus reflected an increased C availability together with a N-dependent sink limitation. Immediately after defoliation, apparent assimilate export rates (differences in the carbohydrate concentrations of young source leaves measured in the evening and on the following morning) showed a greater increase at elevated pCO2 than at ambient pCO2; however, replenishment of carbohydrate reserves was not accelerated. Distinct, treatment-dependent carbohydrate concentrations in pseudo-stems suggested an increasing degree of C-sink limitation from the treatment at ambient pCO2 with high N supply to that at elevated pCO2 with low N supply. During two growing seasons, no evidence of a substantial change in the response of the carbohydrate source in L. perenne to elevated pCO2 was found. Our results support the view that the response of L. perenne to elevated pCO2 is restricted by a C-sink limitation, which is particularly severe at low N supply.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1997.d01-131.x
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  • 6
    Electronic Resource
    Electronic Resource
    Long-term responsiveness to free air CO2 enrichment of functional types, species and genotypes of plants from fertile permanent grassland (1997)
    Springer
    Oecologia 113 (1997), S. 37-45 
    Details
    ISSN: 1432-1939
    Keywords: Key words Interspecific variability ; Intraspecific variability ; Perennial species ; Elevated CO2 ; Fertile permanent grassland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To test inter- and intraspecific variability in the responsiveness to elevated CO2, 9–14 different genotypes of each of 12 perennial species from fertile permanent grassland were grown in Lolium perenne swards under ambient (35 Pa) and elevated (60 Pa) atmospheric partial pressure of CO2 (pCO2) for 3 years in a free air carbon dioxide enrichment (FACE) experiment. The plant species were grouped according to their functional types: grasses (L. perenne, L. multiflorum, Arrhenatherum elatius, Dactylis glomerata, Festuca pratensis, Holcus lanatus, Trisetum flavescens), non-legume dicots (Rumex obtusifolius, R. acetosa, Ranunculus friesianus), and legumes (Trifolium repens, T. pratense). Yield (above a cutting height of 4.5 cm) was measured three times per year. The results were as follow. (1) There were highly significant differences in the responsiveness to elevated pCO2 between the three functional types; legumes showed the strongest and grasses the weakest yield increase at elevated pCO2. (2) There were differences in the temporal development of responsiveness to elevated pCO2 among the functional types. The responsiveness of the legumes declined from the first to the second year, while the responsiveness of the non-legume dicots increased over the 3 years. During the growing season, the grasses and the non-legume dicots showed the strongest response to elevated pCO2 during reproductive growth in the spring. (3) There were no significant genotypic differences in responsiveness to elevated pCO2. Our results suggest that, due to interspecific differences in the responsiveness to elevated pCO2, the species proportion within fertile temperate grassland may change if the increase in pCO2 continues. Due to the temporal differences in the responsiveness to elevated pCO2 among species, complex effects of elevated pCO2 on competitive interactions in mixed swards must be expected. The existence of genotypic variability in the responsiveness to elevated pCO2, on which selection could act, was not found under our experimental conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050351
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  • 7
    Electronic Resource
    Electronic Resource
    Does nitrogen nutrition restrict the CO2 response of fertile grassland lacking legumes? (1997)
    Springer
    Oecologia 112 (1997), S. 17-25 
    Details
    ISSN: 1432-1939
    Keywords: Key words Nitrogen nutrition ; Elevated partial pressure of carbon dioxide ; Lolium perenne ; Trifolium repens ; Transfer of symbiotically fixed nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The extent of the response of plant growth to atmospheric CO2 enrichment depends on the availability of resources other than CO2. An important growth-limiting resource under field conditions is nitrogen (N). N may, therefore, influence the CO2 response of plants. The effect of elevated CO2 (60 Pa) partial pressure (pCO2) on the N nutrition of field-grown Lolium perenne swards, cultivated alone or in association with Trifolium repens, was investigated using free air carbon dioxide enrichment (FACE) technology over 3 years. The established grassland ecosystems were treated with two N fertilization levels and were defoliated at two frequencies. Under elevated pCO2, the above-ground plant material of the L. perenne monoculture showed a consistent and significant decline in N concentration which, in general, led to a lower total annual N yield. Despite the decline in the critical N concentration (minimum N concentration required for non-N-limited biomass production) under elevated pCO2, the index of N nutrition (ratio of actual N concentration and critical N concentration) was lower under elevated pCO2 than under ambient pCO2 in frequently defoliated L. perenne monocultures. Thus, we suggest that reduced N yield under elevated pCO2 was evoked indirectly by a reduction of plant-available N. For L. perenne grown in association with T. repens and exposed to elevated pCO2, there was an increase in the contribution of symbiotically fixed N to the total N yield of the grass. This can be explained by an increased apparent transfer of N from the associated N2-fixing legume species to the non-fixing grass. The total annual N yield of the mixed grass/legume swards increased under elevated pCO2. All the additional N yielded was due to symbiotically fixed N. Through the presence of an N2-fixing plant species more symbiotically fixed N was introduced into the system and consequently helped to overcome N limitation under elevated pCO2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050278
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  • 8
    Electronic Resource
    Electronic Resource
    Can photosynthesis respond to short-term fluctuations in atmospheric carbon dioxide? (1997)
    Springer
    Photosynthesis research 51 (1997), S. 179-184 
    Details
    ISSN: 1573-5079
    Keywords: chlorophyll fluorescence ; FACE ; global change ; photosynthesis ; Photosystem II ; quantum yield ; quenching analysis ; rising CO2 concentration ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Rapid and irregular variations of atmospheric CO2 concentrations (ca) occur in nature but are often very much more pronounced and frequent when artificially enriching CO2 concentrations in simulating the future atmosphere. Therefore, there is the danger that plant responses at elevated CO2 in fumigation experiments might reflect the increased frequency and amplitude of fluctuation in concentration as well as the increase in average concentration. Tests were conducted to determine whether the photosynthetic process could sense such fluctuations in ca. Instantaneous chlorophyll fluorescence (Ft) was monitored for wheat leaves (Triticum aestivum cv. Hereward) exposed to ca oscillating symmetrically by 225 μmol mol-1 about a ca set point concentration of 575 or 650 μmol mol-1. No Ft response was detected to half-cycle step changes in ca lasting less than two seconds, but at half-cycles of two seconds or longer, the response of Ft was pronounced. In order to determine the in vivo linear electron transport rate (J) the O2 concentration was maintained at 21 mmol mol-1 to eliminate photorespiration. J which is directly proportional to the rate of CO2 uptake under these conditions, was not significantly changed at half-cycles of 30 s or less but was decreased by half-cycles of 60 s or longer. It was inferred that if duration of an oscillation is less than 1 minute and is symmetrical with respect to mean CO2 concentration, then there is no effect on current carbon uptake, but oscillations of 1 minute or more decrease photosynthetic CO2 uptake in wheat.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005804203928
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  • 9
    Electronic Resource
    Electronic Resource
    Free-air CO2 enrichment of cotton: vertical and lateral root distribution patterns (1994)
    Springer
    Plant and soil 165 (1994), S. 33-44 
    Details
    ISSN: 1573-5036
    Keywords: Gossypium hirsutum ; rising CO2 ; root dry weight density ; root length density ; root lineal density
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The objective of this investigation was to determine how free-air carbon dioxide enrichment (FACE) of cotton (Gossypium hirsulam L.) affects root distribution in a natural soil environment. For two years cotton was grown on a Trix clay loam under two atmospheric CO2 concentrations (370 and 550 μmol mol−1) and two water treatments [wet, 100% of evapotranspiration (ET) replaced and dry, 75% (1990) and 67% (1991) of ET replaced] at Maricopa, AZ. At early vegetative and mid-reproductive growth, 90 cm soil cores were taken at 0,0.25, and 0.5 m perpendicular to row center; root variables were ascertained at three 30 cm depth increments. The effect of water stress alone or its interaction with CO2 on measured variables during both samplings were rare and showed no consistent pattern. There was a significant CO2 × position interaction for root length density at the vegetative stage (both years) and reproductive stage (1990 only); the positive effects of extra CO2 were more evident at interrow positions (0.25 and 0.5 m). A CO2 × depth × position interaction at the vegetative phase (1990) indicated that FACE increased root dry weight densities for the top soil depth increment at all positions and at the middle increment at the 0.5 m position. Similar trends were seen at the reproductive sampling for this measure as well as for root length density at both sample dates in 1990. In 1991, a CO2 × depth interaction was noted at both periods; CO2 enhancement of root densities (i.e., both length and dry weight) were observed within the upper and middle depths. Although variable in response, increases for root lineal density under high CO2 were also seen. In general, results also revealed that the ambient CO2 treatment had a higher proportion of its root system growing closer to the row center, both on a root length and dry wight basis. On the other hand, the FACE treatment had proportionately more of its roots allocated away from row center (root length basis only). Results from this field experiment clearly suggest that increased atmospheric CO2 concentration will alter root distribution patterns in cotton.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00009960
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  • 10
    Electronic Resource
    Electronic Resource
    Potential effects of acid precipitation on soil nitrogen and productivity of forest ecosystems (1982)
    Springer
    Water, air & soil pollution 18 (1982), S. 405-412 
    Details
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Numerous field and laboratory studies have shown measureable effects of soil acidification on soil processes and yet there is no indication to date that forest production is being affected even in heavily impacted areas. A discussion of possible reasons for this apparent contradiction is presented along with results of two computer simulations of possible responses to acid rain induced changes in (a) N availability and (b) soil organic matter decomposition rate. The first simulation shows a direct relationship between N availability and forest production. The second indicates the possibility for a more complex response with changes in total soil organic matter more than compensating for changes in decomposition rate and producing an inverse relationship between decomposition rate and N availability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02419427
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