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  • 1
    Electronic Resource
    Electronic Resource
    Heat tolerance of two Cladonia species and Campylopus praemorsus in a hot steam vent area of Hawaii (1980)
    Springer
    Oecologia 47 (1980), S. 184-189 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Temperatures were measured in soil, Cladonia skottsbergii, Cl. oceanica, and Campylopus praemorsus growing in the almost barren geothermal area at Puhimau, Hawaii. The measurements were made in the early morning in winter when insolation and air temperatures were minimal and the geothermal effects were predominant. Measurements were made on healthy, dew moistened plants. Close to steam vents Campylopus praemorsus forms thick cushions on hot soil and temperatures up to 29.8°C are recorded in the active parts of the moss. Cladonia oceanica grows exclusively on moss in this area, but not as close to steam vents as the moss itself. Maximum temperatures were 27.2°C in stunted and 23°C in ramified growth forms. In this area Cl. skottsbergii normally colonizes tree stumps of Metrosideros only where the steam is already cool. Maximum temperatures were 23°C in normal thalli, through higher temperatures were measured in partly damaged or killed thalli overhanging the stump where they are immersed in hot steam. With respect to heat tolerance only Campylopus can be considered as adapted to the hot environment. Therefore it is able to colonize the hot dry soil while deriving its moisture from adjacent steam vents. The lichens, particularly Cl. skottsbergii, are not adapted and are as sensitive to heat as most other lichens. Therefore they can only survive where there is at most a small geothermal impact yet they are obviously dependent on moisture from the steam vents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00346818
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  • 2
    Electronic Resource
    Electronic Resource
    Leaf water relations of black alder [Alnus glutinosa (L.) Gaertn.] growing at neighbouring sites with different water regimes (1999)
    Springer
    Trees 14 (1999), S. 28-38 
    Details
    ISSN: 0931-1890
    Keywords: Key words Alnus glutinosa ; Black alder ; Conductance ; Transpiration ; Water potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The tree species black alder [Alnus glutinosa (L.) Gaertn.] typically inhabits wet sites in central Europe but is also successful on well drained soils. To test the physiological adjustment of the species in situ, conductances, transpiration rates and water potentials (Scholander pressure chamber) of black alder leaves were investigated at two neighbouring sites with different water regimes: alder trees at an occasionally water logged alder forest and alder shrubs in a nearby, much drier hedgerow. Additional experiments with alder cuttings in nutrient culture showed that leaf conductances and gas exchange were both strongly influenced by the substrate water potential. In situ however, there was little spatial variability within the different parts of a crown and we found that physiological regulation at leaf level was hardly influenced by different site water regimes or different tree sizes. Diurnal courses of leaf water relations as well as their regulation at the leaf level (e.g. the hyperbolic relationship between conductances and ΔW) were strikingly similar at both sites. Leaf water potential in black alder was shown to be a consequence of immediate transpiration rates, which were high in comparison to other tree species (up to 4 mmol H2O m–2 s–1), rather than the water potentials being a factor that influenced conductance and, therefore, transpiration. The always high leaf conductances and consequent high transpiration rates are interpreted as a strategy to maximise productivity through low stomatal limitation at sites where water supply is usually not limited. However, at the same time this behaviour restricts black alder to sites where at least the deep-going roots can exploit water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004680050004
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  • 3
    Electronic Resource
    Electronic Resource
    Bedeutung einiger nichtflüchtiger carbonsäuren für die frostresistenz des halophyten Halimione portulacoides unter dem einfluß verschieden hoher kochsalzbelastung (1973)
    Springer
    Oecologia 12 (1973), S. 241-250 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Plants of Halimione portulacoides (L.) Aellen were grown in natural temperature and light conditions but with different concentrations of NaCl in the nutrient solution. From August 1971 to April 1972 freezing tolerance, water content, succulence, accumulation of different sugars, citrate, malate, and chloride were simultaneously determined. If no NaCl was supplied the chloride content of the leaves decreased continuously within the period of investigation. During repeated and increasing addition of NaCl the chloride content of the leaves generally increased. However, there was a reversible decrease during the frost period, although no new leaves were formed and loss through leaves and dilution of the nutrient medium by precipitation was prevented (Fig. 1). In spite of being in minimum the chloride content was relatively high in winter. No regulation of the concentration by increase of succulence was observed. The concentration did, however, increase due to a diminished water uptake in the coldest period. Sugars, which are regarded as protective agents against the influence of freezing and salts, accumulated only slightly in the frost period. Predominantly sucrose, raffinose and stachyose were remarkable. Their concentration was not sufficient to compensate the salt burden and thus could not increase the freezing tolerance. The sugar content was even lowered when the salt content was higher. In contrast, citrate and to a lesser extent malate were intensively increased in the cold season (Fig. 3). Thus organic acid to chloride ratios of between 1:2 and 1:6 were established for Halimione, which expresses the effective protection of the membrane systems against freezing injury (Fig. 4), as has been shown in vitro for e.g. spinach chloroplasts by Santarius (1971). Accumulation of these acids was even enhanced by an increasing salt burden. Consequently accumulation of organic acids or their salts such as citrate and probably malate indicates an adaptation of halophytes, which enables them to survive freezing under salt stress on the sea shore and in cold desert regions during the winter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00347565
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  • 4
    Electronic Resource
    Electronic Resource
    Cellular compartmentalization of salt ions and protective agents with respect to freezing tolerance of leaves (1979)
    Springer
    Oecologia 38 (1979), S. 303-316 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Evidence was given that the freezing tolerance of Halimione portulacoides, a wintergreen halophyte, can be explained by protection of sensitive cellular membranes in vivo. Experiments were done with cloned cuttings of a plant from the German North Sea coast. One series received no NaCl (O-plants) the other 3% NaCl (NaCl-plants) in the nutrient solution. During the annual course Na+ and Cl- of the O-plant leaves remained on a nearly constant low level. In the leaves of the NaCl-plants Na+ and Cl- concentrations changed strongly during year and reached a maximum in winter. Potassium was always on a low level. The freezing tolerance curves showed a minimum in summer and a maximum in winter. The small difference between the freezing tolerance peaks of the NaCl- and O-plants indicated that the increased salt stress did not affect freezing tolerance very much. Freezing stress in cellular membranes, like thylacoids, acts in the same way as increasing salt concentration; consequently both together must amplify the stress. For the analysis of their ion contents chloroplasts of H. portulacoides were non-aqueously isolated from leaves with different freezing tolerance during the year. In midwinter, when freezing tolerance was highest, the chloroplasts of the NaCl-plants contained about 250 mM chloride (O-plants c. 150 mM), while the non-plastidic fraction of the cell contained about 1 M (O-plants c. 400 mM) chloride. On the other hand citrate reached high concentrations in the chloroplasts in winter. Non-volatile organic acids like citrate are known to compensate colligatively the injurious action of the inorganic salt ions on thylacoids in vitro (Heber and Santarius, 1976). The molar proportion between chloride and citrate in H. portulacoides chloroplasts decreased with increasing freezing tolerance and reached values which were protective on chloroplast membranes in vitro. This relationship in vivo with H. portulacoides provides evidence supplying the concept of colligative protection of cellular membranes. Besides citrate also malate may act as a colligatively protecting agent against the amplified salt stress by freezing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00345190
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  • 5
    Electronic Resource
    Electronic Resource
    Aspects of carbon and nitrogen cycling in soils of the Bornhöved Lake district. I. Microbial characteristics and emissions of carbon dioxide and nitrous oxide of arable and grassland soils (1997)
    Springer
    Biogeochemistry 39 (1997), S. 189-205 
    Details
    ISSN: 1573-515X
    Keywords: agricultural soils ; arginine ammonification ; basal respiration ; CO2 emission ; microbial biomass content ; N2O emission
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Soil microbial biomass content, organic carbonmineralization as well as arginine ammonificationrates were estimated in samples from arable andgrassland soils and carbon dioxide and nitrous oxideemission rates were measured in situ at four sitesalong a catena. Soil microbial biomass contentincreased in the order, maize monoculture 〈 croprotation 〈 dry grassland 〈 wet grassland. The twoarable soils had similar rates of carbonmineralization in the laboratory at 22 °C (basalrespiration) as well as in situ (carbon dioxideemission) at field temperature. Under crop rotation,maize monoculture and dry grassland, the arginineammonification rate significantly correlated to themicrobial biomass content. In contrast, thebiomass-specific ammonification rate was low in wetgrassland soil, as were in situ N2O emission rates.Data from all sites together revealed no generalrelationship between microbial biomass content and Cand N mineralization rates. In addition, there was nogeneral relationship between the quantity of soilmicrobial biomass and the emission rates of thegreenhouse gases CO2 and N2O. The maize monocultureinduced a soil microbial community that was lessefficient in using organic carbon compounds, as shownby the high metabolic quotient (respiration rate perunit of biomass). However, microbial biomass contentwas proportional to basal respiration rate in soilsunder crop rotation, dry and wet grassland. Arginineammonification rate was related to microbial biomasscontent only in fertilized soils. Applications of highquantities of inorganic nitrogen and farmyard manureapparently increase in situ N2O emission rates,particularly under crop rotation. The microbialbiomass in the unfertilized wet grassland soil seemsto be a sink for nitrogen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005867931015
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  • 6
    Electronic Resource
    Electronic Resource
    The influence of microclimatic conditions on potential photosynthesis ofUsnea sphacelata: A model (1989)
    Springer
    Ecological research 4 (1989), S. 297-307 
    Details
    ISSN: 1440-1703
    Keywords: Antarctica ; Lichen activity ; Microclimate ; Modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract At a boulder on a hill near Casey Station, Wilkes Land, sensors for light, temperature and humidity were installed facing the four cardinal directions. The measurements lasted for about two months of the summer season 1985/86. The data recording was carried out at intervals of 6 minutes for all probes by automatic recording instruments. Data analysis was carried out with special regard to the biological effects of the parameters analyzed. These data of the microclimatic features taken from its original place of growth were used to a regression model of potential photosynthetic activity ofUsnea sphacelata, which is a characteristic species of this area. Although the individual time courses of the above mentioned parameters show long periods of favourable conditions for possible growth and metabolic processes, the combined analysis of these variables considering threshold values for metabolism shortens these time spans drastically. Thus, cross relationships within the physical descriptors and their effects on the actual values of photosynthesis as well as respiration become evident. They are illustrated by the results of models on photosynthesis and respiration ofU. sphacelata regarding the different cardinal directions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02348450
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  • 7
    Electronic Resource
    Electronic Resource
    Aspects of carbon and nitrogen cycling in soils of the Bornhöved Lake district II. Modelling the influence of temperature increase on soil respiration and organic carbon content in arable soils under different managements (1997)
    Springer
    Biogeochemistry 39 (1997), S. 207-224 
    Details
    ISSN: 1573-515X
    Keywords: agricultural soils ; climatic change ; modelling ; Q10-value ; soil organic matter ; soil respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Based on field measurements in two agriculturalecosystems, soil respiration and long-term response ofsoil organic carbon content (SOC) was modelled. Themodel predicts the influence of temperature increaseas well as the effects of land-use over a period ofthirty years in a northern German glacial morainelandscape. One of the fields carried a maizemonoculture treated with cattle slurry in addition tomineral fertilizer (“maize monoculture”), the otherwas managed by crop rotation and recieved organicmanure (“crop rotation”). The soils of both fieldswere classified as cambic Arenosols. The soilrespiration was measured in the fields by means of theopen dynamic inverted-box method and an infrared gasanalyser. The mean annual soil respiration rates were 268 (maizemonoculture) and 287 mg CO2 m-2 h-1(crop rotation). Factors controlling soil respirationwere soil temperature, soil moisture, root respirationand carbon input into the soil. Q10-valuesof soil respiration were generally higher in winterthan in summer. This trend is interpreted as anadaptive response of the soil microbial communities.In the model a novel mathematical approach withvariable Q10-values as a result oftemperature and moisture adjustment is proposed. Withthe calibrated model soil respiration and SOC werecalculated for both fields and simulations over aperiod of thirty years were established. Simulationswere based on (1) local climatic data, 1961 until1990, and (2) a regional climate scenario for northernGermany with an average temperature increase of 2.1 K.Over the thirty years period with present climateconditions, the SOC pool under “crop rotation” wasnearly stable due to the higher carbon inputs, whereasabout 16 t C ha-1 were lost under “maizemonoculture”. Under global warming the mean annualsoil respiration for both fields increased and SOCdecreased by ca. 10 t C ha-1 under “croprotation” and by more than 20 t C ha-1 under“maize monoculture”. It was shown that overestimationof carbon losses in long-term prognoses can be avoidedby including a Q10-adjustment in soilrespiration models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005859629197
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