bluuebunny/crossref_metadata_2025_split huggingface dataset:
Leaf senescence and decline of end‐of‐season gas exchange in five temperate deciduous tree species grown in elevated CO2concentrations
Authors: McCONNAUGHAY K.D.M. , BASSOW S.L. , BERNTSON G.M. , BAZZAZ F.A. 
Published: April 2006

AbstractWe measured rates of leaf senescence and leaf level gas exchange during autumnal senescence for seedlings of five temperate forest tree species under current and elevated atmospheric CO2concentrations and low‐ and high‐nutrient regimes. Relative indices of whole canopy carbon gain, water loss and water use efficiency through the senescent period were calculated based on a simple integrative model combining gas exchange per unit leaf area and standing canopy area per unit time. Seedlings grown under elevated [CO2] generally had smaller canopies than their current [CO2]‐grown counterparts throughout most of the senescent period. This was a result of smaller pre‐senescent canopies or accelerated rates of leaf drop. Leaf‐level photosynthetic rates were higher under elevated [CO2] for grey birch canopies and for low‐nutrient red maple and high‐nutrient ash canopies, but declined rapidly to values below those of their current [CO2] counterparts by midway through the senescent period. CO2enrichment reduced photosynthetic rates for the remaining species throughout some or all of the senescent period. As a result of smaller canopy sizes and reduced photosynthetic rates, elevated [CO2]‐grown seedlings had lower indices of whole canopy end‐of‐season carbon gain with few exceptions. Leaf level transpiration rates were highly variable during autumnal senescence and neither [CO2] nor nutrient regime had consistent effects on water loss per unit leaf area or integrated whole canopy water loss throughout the senescent period. Indices of whole canopy, end‐of‐season estimates of water use efficiency, however, were consistently lower under CO2enrichment, with few exceptions. These results suggest that whole canopy end‐of‐season gas exchange may be altered significantly in an elevated [CO2] world, resulting in reduced carbon gain and water use efficiency for many temperate forest tree seedlings. Seedling growth and survivorship, and ultimately temperate forest regeneration, could be reduced in CO2‐enriched forests of the future.
Responses of a C3 and a C4 perennial grass to elevated CO2 and temperature under different water regimes
Authors: HUNT H. W. , ELLIOTT E. T. , DETLING J. K. , MORGAN J. A. , CHEN D.‐X. 
Published: April 2006

AbstractAn experiment was carried out to determine the effects of elevated CO2, elevated temperatures, and altered water regimes in native shortgrass steppe. Intact soil cores dominated by Bouteloua gracilis, a C4 perennial grass, or Pascopyrum smithii, a C3 perennial grass, were placed in growth chambers with 350 or 700 μL L−1 atmospheric CO2, and under either normal or elevated temperatures. The normal regime mimicked field patterns of diurnal and seasonal temperatures, and the high‐temperature regime was 4 °C warmer. Water was supplied at three different levels in a seasonal pattern similar to that observed in the field.Total biomass after two growing seasons was 19% greater under elevated CO2, with no significant difference between the C3 and C4 grass. The effect of elevated CO2 on biomass was greatest at the intermediate water level. The positive effect of elevated CO2 on shoot biomass was greater at normal temperatures in B. gracilis, and greater at elevated temperatures in P. smithii. Neither root‐to‐shoot ratio nor production of seed heads was affected by elevated CO2.Plant tissue N and soil inorganic N concentrations were lower under elevated Co2, but no more so in the C3 than the C4 plant. Elevated CO2 appeared to increase plant N limitation, but there was no strong evidence for an increase in N limitation or a decrease in the size of the CO2 effect from the first to the second growing season. Autumn samples of large roots plus crowns, the perennial organs, had 11% greater total N under elevated CO2, in spite of greater N limitation.
Seasonal response of photosynthesis to elevated CO2in loblolly pine (Pinus taedaL.) over two growing seasons
Authors: LEWIS JAMES D. , TISSUE DAVID T. , STRAIN BOYD R. 
Published: April 2006

AbstractTrees growing in natural systems undergo seasonal changes in environmental factors that generate seasonal differences in net photosynthetic rates. To examine how seasonal changes in the environment affect the response of net photosynthetic rates to elevated CO2, we grewPinus taedaL. seedlings for three growing seasons in open‐top chambers continuously maintained at either ambient or ambient + 30 Pa CO2. Seedlings were grown in the ground, under natural conditions of light, temperature nd nutrient and water availability. Photosynthetic capacity was measured bimonthly using net photosynthetic rate vs. intercellular CO2partial pressure (A‐Ci) curves. Maximum Rubisco activity (Vcmax) and ribulose 1,5‐bisphosphate regeneration capacity mediated by electron transport (Jmax) and phosphate regeneration (PiRC) were calculated fromA‐Cicurves using a biochemically based model. Rubisco activity, activation state and content, and leaf carbohydrate, chlorophyll and nitrogen concentrations were measured concurrently with photosynthesis measurements. This paper presents results from the second and third years of treatment.Mean leaf nitrogen concentrations ranged from 13.7 to 23.8 mg g−1, indicating that seedlings were not nitrogen deficient. Relative to ambient CO2seedlings, elevated CO2increased light‐saturated net photosynthetic rates 60–110% during the summer, but < 30% during the winter. A relatively strong correlation between leaf temperature and the relative response of net photosynthetic rates to elevated CO2suggests a strong effect of leaf temperature. During the third growing season, elevated CO2reduced Rubisco activity 30% relative to ambient CO2seedlings, nearly completely balancing Rubisco and RuBP‐regeneration regulation of photosynthesis. However, reductions in Rubisco activity did not eliminate the seasonal pattern in the relative response of net photosynthetic rates to elevated CO2. These results indicate that seasonal differences in the relative response of net photosynthetic rates to elevated CO2are likely to occur in natural systems.
Effects of elevated atmospheric CO2 on fine root length and distribution in an oak‐palmetto scrub ecosystem in central Florida
Authors: DAY FRANK P. , WEBER EVERETT P. , HINKLE C. ROSS , DRAKE BERT G. 
Published: April 2006

AbstractAtmospheric CO2 concentration is rising and it has been suggested that a portion of the additional carbon is being sequestered in terrestrial vegetation and much of that in below‐ground structures. The objective of the present study was to quantify the effects of elevated atmospheric CO2 on fine root length and distribution with depth with minirhizotrons in an open‐top chamber experiment in an oak‐palmetto scrub ecosystem at Kennedy Space Centre, Florida, USA. Observations were made five times over a period of one and a half years in three ambient chambers (350 p.p.m. CO2), three CO2 enriched chambers (700 p.p.m. CO2), and three unchambered plots. Greater root length densities were produced in the elevated CO2 chambers (14.2 mm cm−2) compared to the ambient chambers (8.7 mm cm−2). More roots may presumably lead to more efficient acquisition of resources. Fine root abundance varied significantly with soil depth, and there appeared to be enhanced proliferation of fine roots near the surface (0–12 cm) and at greater depth (49–61 cm) in the elevated CO2 chambers. The vertical root distribution pattern may be a response to availability of nutrients and water. More studies are needed to determine if increased root length under CO2 enriched conditions actually results in greater sequestering of carbon below ground.
Reefs happen
Authors: KINZIE ROBERT A. , BUDDEMEIER ROBERT W. 
Published: April 2006

AbstractCorals and coral reefs confront us with a variety of paradoxes in terms of their responses to global change. The species appear evolutionarily long‐lived and stable, and combinations of organisms recur and persist at levels ranging from endosymbiosis to palaeocommunity structure. The fact that these organisms and communities occupy a seemingly precarious environment near the common interface of land, sea, and air suggests that they possess powerful adaptive and acclimative mechanisms, and the special characteristics associated with their range of reproductive options, their modular (colonial) form, and their symbiotic associations provide multiple pathways for adaptation. At the same time, they are widely considered to be vulnerable to anthropogenic stresses, and to show signs of deterioration on a global scale.Interest in corals is further enhanced by their unique position with regard to the carbon cycle, with inorganic and organic carbon metabolisms that are of comparable magnitudes. The durable limestone structures they create modify the shallow‐water environment, and their mineral skeletons preserve in their isotopic, chemical, and structural characteristics records of past environmental conditions. Whether as survivors, recorders, or victims, their relationship to global change is fascinating and instructive. This paper provides a general background and context for the specific papers that make up this topical issue of Global Change Biology.
Boundary layer budgets for regional estimates of scalar fluxes
Authors: DENMEAD O.T. , RAUPACH M.R. , DUNIN F.X. , CLEUGH H.A. , LEUNING R. 
Published: April 2006

AbstractThe paper considers the theory and application of budget techniques for regional scalar flux estimation using the daytime convective boundary layer (CBL) and the nocturnal boundary layer (NBL). CBL techniques treat the well mixed layer of air between heights of, say, 100 m and 1000 m as an integrator of surface fluxes along the path of a column of air moving over the landscape. They calculate the average surface flux from the scalar concentration in and above the mixed layer, and the CBL height. The flux estimates are averaged over regions of 10–104 km2 extending 10 to 100 km upwind.An integral form of the CBL budget is used to estimate daily regional rates of CO2 uptake and evaporation from three data sets. There was plausible agreement between the estimates and locally measured fluxes. CBL budgets have great potential for estimating regional scalar fluxes, but there is an urgent need for validation through direct measurements of fluxes and budget parameters.NBL budgets are useful when low‐level, radiative inversions inhibit vertical mixing. Surface scalar fluxes can then be estimated from the rate of concentration change below the inversion. An example application for estimating the nocturnal CO2 flux is given. While simple in concept, NBL budgets are more difficult to apply in practice because of the unpredictability of the depth of the layer and sometimes, its absence altogether. On the other hand, the depth of the atmospheric mixing chamber is better defined, few assumptions are required and the concentration changes usually will be larger and hence more easily detectable than in CBL budgetting.
Eddy‐correlation system for long‐term monitoring of fluxes of heat, water vapour and CO2
Authors: GRELLE ACHIM , LINDROTH ANDERS 
Published: April 2006

AbstractAn eddy‐correlation system is presented that was designed with special focus on long‐term measurements of turbulent fluxes in the atmospheric boundary layer. It consists of a SOLENT sonic anemometer, a fast temperature sensor, and a LI‐COR LI 6262 closed‐path infrared gas analyser. The use of a fast temperature sensor turned out to be necessary because of errors in the sound virtual temperature measured by the sonic anemometer at high wind speeds. The components are combined with special attention paid to protection against lightning and other environmental stresses. The data acquisition program SOLCOM runs on standalone systems or in a network environment and performs ‘quasi on‐line’ data processing, on‐line graphical display of single data and fluxes, and on‐line correction of the raw data. Raw data can be stored continuously on DAT tapes. All data handling can be done by remote access, thus only a minimum amount of m situ maintenance is required. Power spectra of vertical and longitudinal wind speed, air temperature, air humidity and carbon dioxide concentration showed to follow the ‐2/3 law quite well. There was some noise in the high frequency range of the carbon dioxide spectrum. However, the corresponding cross spectra with the vertical wind component showed less deviation from a straight line in the high frequency range. The sum of convective heat fluxes and soil heat flux showed good agreement with the measured net radiation for several months and it was concluded that the system described here constitute a good platform for long‐term flux measurements over forest.
Early needle senescence and thinning of the crown structure of Picea abies as induced by chronic SO2 pollution. II. Field data basis, model results and tolerance limits
Authors: SLOVIK STEFAN 
Published: April 2006

AbstractField data on the sulphur and cation budget of growing Norway spruce canopies (Picea abies [L.] Karst.) are summarized. They are used to test a spruce decline model capable of quantifying effects of chronic SO2 pollution on spruce forests. At ambient SO2 concentrations, acute SO2 damage is rare, but exposure to polluted air produces reversible thinning of the canopy structure with a half‐time of a few years. Canopy thinning in the spruce decline model is highest (i) at elevated SO2 pollution, (ii) in the mountains, (iii) at unfertilized sites with poor K+, Mg2+ or Zn2+ supply, (iv) at low spruce litter decomposition rates, and (v) acidic, shallow soils at high annual precipitation rates in the field and vice versa. Model application using field data from Würzburg (moderate SO2 pollution, alkaline soils, no spruce decline) and from the Erzgebirge (extreme SO2 pollution, acidic soils in the mountains, massive spruce decline) predicts canopy thinning by 2–11% in Würzburg and by 45–70% in the Erzgebirge. The model also predicts different SO2‐tolerance limits for Norway spruce depending on the site elevation and on the nutritional status of the needles. If needle loss of more than 25% (damage class 2) is taken to indicate ‘real damage’ exceeding natural variances, then for optimum soil conditions SO2 tolerance limits range from (27.3 ± 7.4) μg m−3 to (62.6 ± 16.5) μg m−3. For shallow and acidic soils, SO2 tolerance limits range from (22.0 ± 5.5) μg m−3 to (37.4 ± 7.5) μ m−3. These tolerance limits, which are calculated on an ecophysiological data basis for Norway spruce are close to epidemiological SO2‐toIerance limits as recommended by the IUFRO, UN‐ECE and WHO. The observed statistical regression slope of the plot (damaged spruce trees vs. SO2‐pollution) in west Germany is confirmed by modelling (6% error). Model application to other forest trees allows deduction of the observed sequence of SO2‐sensitivity: Abies > Picea > Pinus > Fagus > Quercus. Thus, acute phytotoxicity of SO2 seems not to be involved in ‘forest decline’. Chronic SO2‐pollution induces massive canopy thinning of Abies alba and Picea abies only at unfavourable sites, where natural stress factors and secondary effects of SO2pollution act together to produce tree decline.
THE USE OF SODIUM METABISULPHITE IN SILAGE MAKING
Authors: Murdoch J. C. , Holdsworth Muriel C. 
Published: April 2006

Three trials in which metabisulphite was used as a silage additive are described and the results discussed.The data from two small‐scale trials suggests that metabisulphite and molasses each have a similar effect on the quality of the silage produced, and that wilting appeared to be more effective than either of these two additives.A comparison of silages in two large‐scale trials indicates the necessity for uniform distribution of the metabisulphite.
THE USE OF EPIDERMAL CHARACTERISTICS FOR THE IDENTIFICATION OF GRASSES IN THE LEAFY STAGE
Authors: Davies Ieuan 
Published: April 2006

The possibility of using microscopic characteristics of the leaf epidermis as aids to the identification of some British agricultural grasses in the vegetative condition has been investigated.The occurrence of the following types of differentiated cells on the leaf‐sheath was markedly affected by the stage of growth of the tiller: silica cells, silico‐suberose couples, cork cells, asperities and incipient asperities. These cells were frequently absent or confined to the base of the sheath in vegetative tillers, but they occurred over most of the sheath in culm leaves. Silica cells tended to preponderate in young tillers and silico‐suberose couples and cork cells in the reproductive stage. The inter‐nerve epidermis of the leaf‐blade was generally the least affected by growth stage; although less differentiated than the sheath, it was found to be the most useful location for identification purposes. Species separable on the basis of the above‐mentioned characters of the leaf‐blade were:—

Tall fescue (Festuca arundinacea) from meadow fescue (F. pratensis)
Heath‐grass (Sieglingia decumbens) from smooth‐stalked meadow grass (Poa pratensis)
Sheep's fescue (F. ovina), from mat‐grass (Nardus stricta) wavy hair‐grass (Deschampsia flexuosa) and bristle‐leaved bent (Agrostis setacea).

Timothy (Phleum pratense), meadow foxtail (Ahpecurus pratensis) and bent (Agrostis spp.) were separable on the following characteristics, which were not affected by growth stage: the occurrence of crystal clusters precipitated by hot water in timothy and occasionally in meadow foxtail, but not in Agrostis species, the peculiar shape of undifferentiated cells of the nerve epidermis in Agrostis species, and the dense cover of asperities on the ligules of Agrostis spp. and Ahpecurus pratensis.
PARTIAL WILTING OF GRASS CROPS FOR SILAGE
Authors: Nash M. J. 
Published: April 2006

The possibilities of the wilting process have been investigated, with the ultimate object of determining its effect on the quality of farm silage. Attention has been confined mainly to mild or partial wilting, rather than severe wilting, since the danger of ensiling excessively dry material, especially when it is not chopped, is well recognised.Preliminary field tests were conducted to determine the rate and extent of the fall in moisture content in long and in bruised herbage, wilted for periods not exceeding 24 hours. Subsequently the wilted silages were made in experimental silos and, finally, in trench silos on a farm scale. This first paper deals with the field trials. Results show that important reductions in moisture content can be obtained in all but very poor weather. In good weather, moisture content may easily fall from the 80% to the 70% level; in poor weather (cool, overcast, with occasional showers) moisture loss still occurs.
THE EFFECT OF PRE‐WILTING HERBAGE ON THE COMPOSITION OF SILAGE AND ITS INTAKE BY COWS
Authors: Murdoch J. C. 
Published: April 2006

Lucerne was ensiled at various dry matter contents, within the range of 19·8% to 39·6%. An increase was found in lactic acid production, with a consequent decrease in volatile acid and volatile base content, up to the level of 33·9% dry matter.The dry matter intake of cows was increased by feeding silage with a high dry matter content.
LEY DETERIORATION AND SOIL INSECTS
Authors: Heath G. W. 
Published: April 2006

Two insecticides were applied to a 5‐year‐old ley and their effects on yield and soil fauna were studied a year later. Aldrin (2 lb. actual toxicant per acre) or dieldrin (1 lb. actual toxicant per acre) was incorporated in a standard dressing of compound fertilizer.One year after treatment the yield of dry matter was significantly higher on dieldrin plots than on plots receiving fertilizer alone. The soil fauna was examined in dieldrin and control plots. The wireworm (Agriotes spp.) populations were 80,000 and 400,000 per acre respectively. The increase in herbage yield was ascribed to the reduction in the number of wireworms. Mite and Collembola populations were very significantly reduced by dieldrin: the effect of this reduction on the breakdown of soil organic matter is discussed. A reduction in numbers of predaceous insects also followed insecticidal treatment, but it is thought that the resurgence rate of these insects would keep pace with that of wireworms.
A REVIEW OF NUTRIENT LOSSES AND EFFICIENCY OF CONSERVING HERBAGE AS SILAGE, BARN‐DRIED HAY AND FIELD‐CURED HAY
Authors: Carter W. R. B. 
Published: April 2006

A review of American literature indicates that barn drying of hay and silage making are both greatly superior to the field curing of hay in preserving nutrients. This is true of total dry matter, crude protein, ether extract and ash; crude‐fibre losses are greater in silage making. Energy losses run parallel with dry matter. Bam drying of hay with heat preserves a rather greater proportion of nutrients than does silage making.Chemical composition and digestibility are mostly a function of stage of maturity of the crop at the time of cutting. Actual carbohydrate (energy) losses are greater than protein losses in all methods. The influence of method of conservation is unimportant if conservation is properly carried out, but considerable deterioration can result from bad application. Field‐cured hay usually suffers most in this respect, due to weather damage.The conservation processes reviewed have no influence per se on feeding value where each is applied under ideal conditions. Differences found in practice are usually linked to the stage of maturity or to weather damage, which explains the usually superior feeding value of silage and barn‐dried hay over field‐cured hay.When the efficiency of each method is compared by determining the quantity of milk produced from equal areas of forage, conserved in the three different ways, barn‐dried hay is somewhat superior to silage, but both are greatly superior to field‐cured hay.
THE DELAYED APPLICATION OF NITROGEN FOR THE ESTABLISHMENT OF SURFACE‐SEEDED SWARDS
Authors: Roberts H. W. 
Published: April 2006

It has been observed that, where surface seeding has been attempted, disappointing results occur on some sites due to delays in sowing the seeds mixture after lime and fertilizer applications have been made.An experiment is described in which the time of application of nitrogen, in relation to the establishment and development of S24 and S23 perennial ryegrass seedlings in pots, was varied. The results of trials on this aspect of surface seeding, under conditions experienced in the north of Scotland, are also given.More efficient utilization of nitrogen was obtained when applications were delayed until the seedlings had developed sufficiently to utilize the applied nitrogen. This delay enhanced the establishment of sown grasses under conditions where natural species, capable of responding to applied nitrogen, were present.Where surface seeding is undertaken, consideration should be given to delaying the application of nitrogen until the sown seeds have brairded.