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  • 1
    Language: English
    In: New Phytologist, Sept, 2010, Vol.187, p.885(4)
    Description: To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1469-8137.2010.03332.x Byline: Zachary Kayler (1), Arthur Gessler (1,2), Nina Buchmann (3) Keywords: canopy; coupling; phloem; respiration; soil; stable isotopes Author Affiliation: (1)Institute for Landscape Biogeochemistry, Leibniz-Centre for Agricultural Landscape Research (ZALF), Eberswalderstr. 84, 15374 Muncheberg, Germany (2)Professorship for Landscape Biogeochemistry, Humboldt-University at Berlin, Lentze-Allee 75, 14195 Berlin, Germany (3)Institute of Plant, Animal and Agroecosystem Sciences, LFW C56, ETH Zurich, Universitaetsstrasse 2, 8092 Zurich, Switzerland ((*)Author for correspondence: tel +41 44 632 39 59; emailnina.buchmann@ipw.agrl.ethz.ch)
    Keywords: Agroecosystems ; Biogeochemistry
    ISSN: 0028-646X
    Source: Cengage Learning, Inc.
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  • 2
    Language: English
    In: New Phytologist, Sept, 2010, Vol.187, p.885(4)
    Description: To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1469-8137.2010.03332.x Byline: Zachary Kayler (1), Arthur Gessler (1,2), Nina Buchmann (3) Keywords: canopy; coupling; phloem; respiration; soil; stable isotopes Author Affiliation: (1)Institute for Landscape Biogeochemistry, Leibniz-Centre for Agricultural Landscape Research (ZALF), Eberswalderstr. 84, 15374 Muncheberg, Germany (2)Professorship for Landscape Biogeochemistry, Humboldt-University at Berlin, Lentze-Allee 75, 14195 Berlin, Germany (3)Institute of Plant, Animal and Agroecosystem Sciences, LFW C56, ETH Zurich, Universitaetsstrasse 2, 8092 Zurich, Switzerland ((*)Author for correspondence: tel +41 44 632 39 59; emailnina.buchmann@ipw.agrl.ethz.ch)
    Keywords: Agroecosystems ; Biogeochemistry
    ISSN: 0028-646X
    Source: Cengage Learning, Inc.
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  • 3
    In: New Phytologist, September 2010, Vol.187(4), pp.885-888
    Description: Includes references ; p. 885-888.
    Keywords: Canopy ; Coupling ; Phloem ; Respiration ; Soil ; Stable Isotopes
    ISSN: 0028-646X
    E-ISSN: 1469-8137
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  • 4
    In: PLoS ONE, 2014, Vol.9(12)
    Description: In the future, periods of strongly increased temperature in concert with drought (heat waves) will have potentially detrimental effects on trees and forests in Central Europe. Norway spruce might be at risk in the future climate of Central Europe. However, Douglas-fir is often discussed as an alternative for the drought and heat sensitive Norway spruce, because some provenances are considered to be well adapted to drier and warmer conditions. In this study, we identified the physiological and growth responses of seedlings from two different Douglas-fir provenances to increased temperature and atmospheric drought during a period of 92 days. We analysed (i) plant biomass, (ii) carbon stable isotope composition as an indicator for time integrated intrinsic water use efficiency, (iii) apparent respiratory carbon isotope fractionation as well as (iv) the profile of polar low molecular metabolites. Plant biomass was only slightly affected by increased temperatures and atmospheric drought but the more negative apparent respiratory fractionation indicated a temperature-dependent decrease in the commitment of substrate to the tricarboxylic acid cycle. The metabolite profile revealed that the simulated heat wave induced a switch in stress protecting compounds from proline to polyols. We conclude that metabolic acclimation successfully contributes to maintain functioning and physiological activity in seedlings of both Douglas-fir provenances under conditions that are expected during heat waves (i.e. elevated temperatures and atmospheric drought). Douglas-fir might be a potentially important tree species for forestry in Central Europe under changing climatic conditions.
    Keywords: Research Article ; Biology And Life Sciences ; Ecology And Environmental Sciences
    E-ISSN: 1932-6203
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  • 5
    In: New Phytologist, October 2013, Vol.200(1), pp.144-157
    Description: The oxygen stable isotope composition of plant organic matter (OM) (particularly of wood and cellulose in the tree ring archive) is valuable in studies of plant–climate interaction, but there is a lack of information on the transfer of the isotope signal from the leaf to heterotrophic tissues. We studied the oxygen isotopic composition and its enrichment above source water of leaf water over diel courses in five tree species covering a broad range of life forms. We tracked the transfer of the isotopic signal to leaf water‐soluble OM and further to phloem‐transported OM. Observed leaf water evaporative enrichment was consistent with values predicted from mechanistic models taking into account nonsteady‐state conditions. While leaf water‐soluble OM showed the expected 18O enrichment in all species, phloem sugars were less enriched than expected from leaf water enrichment in Scots pine (Pinus sylvestris), European larch (Larix decidua) and Alpine ash (Eucalyptus delegatensis). Oxygen atom exchange with nonenriched water during phloem loading and transport, as well as a significant contribution of assimilates from bark photosynthesis, can explain these phloem 18O enrichment patterns. Our results indicate species‐specific uncoupling between the leaf water and the OM oxygen isotope signal, which is important for the interpretation of tree ring data.
    Keywords: Broadleaf ; Conifer ; Diel Course ; Oxygen Atom Exchange ; Phloem Transport
    ISSN: 0028-646X
    E-ISSN: 1469-8137
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  • 6
    Language: English
    In: Science of the Total Environment, 01 January 2017, Vol.574, pp.46-56
    Description: Kettle holes are glaciofluvially created depressional wetlands that collect organic matter (OM) and nutrients from their surrounding catchment. Kettle holes mostly undergo pronounced wet-dry cycles. Fluctuations in water table, land-use, and management can affect sediment biogeochemical transformations and perhaps threaten the carbon stocks of these unique ecosystems. We investigated sediment and water of 51 kettle holes in NE Germany that differ in hydroperiod (i.e. the duration of the wet period of a kettle hole) and land-use. Our objectives were 1) to test if hydroperiod and land management were imprinted on the isotopic values (δ C, δ N) and C:N ratios of the sediment OM, and 2) to characterize water loss dynamics and kettle hole-groundwater connectivity by measuring the stable δ O and δD isotope values of kettle hole water over several years. We found the uppermost sediment layer reflected recent OM inputs and short-term processes in the catchment, including land-use and management effects. Deeper sediments recorded the degree to which OM is processed within the kettle hole related to the hydroperiod. We see clear indications for the effects of wet-dry cycles for all kettle holes, which can lead to the encroachment of terrestrial plants. We found that the magnitude of evaporation depended on the year, season, and land-use type, that kettle holes are temporarily coupled to shallow ground water, and, as such, kettle holes are described best as partially-closed to open systems.
    Keywords: Depressional Wetlands ; Wet-Dry Cycles ; Biogeochemical Transformations ; Stable Isotopes ; Evaporation ; Landscape Functioning ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 7
    In: Global Change Biology, August 2016, Vol.22(8), pp.2861-2874
    Description: Drought duration and intensity are expected to increase with global climate change. How changes in water availability and temperature affect the combined plant–soil–microorganism response remains uncertain. We excavated soil monoliths from a beech ( L.) forest, thus keeping the understory plant–microbe communities intact, imposed an extreme climate event, consisting of drought and/or a single heat‐pulse event, and followed microbial community dynamics over a time period of 28 days. During the treatment, we labeled the canopy with with the goal of (i) determining the strength of plant–microbe carbon linkages under control, drought, heat and heat–drought treatments and (ii) characterizing microbial groups that are tightly linked to the plant–soil carbon continuum based on C‐labeled s. Additionally, we used 16S sequencing of bacteria from the Ah horizon to determine the short‐term changes in the active microbial community. The treatments did not sever within‐plant transport over the experiment, and carbon sinks belowground were still active. Based on the relative distribution of labeled carbon to roots and microbial s, we determined that soil microbes appear to have a stronger carbon sink strength during environmental stress. High‐throughput sequencing of the 16S revealed multiple trajectories in microbial community shifts within the different treatments. Heat in combination with drought had a clear negative effect on microbial diversity and resulted in a distinct shift in the microbial community structure that also corresponded to the lowest level of label found in the s. Hence, the strongest changes in microbial abundances occurred in the heat–drought treatment where plants were most severely affected. Our study suggests that many of the shifts in the microbial communities that we might expect from extreme environmental stress will result from the plant–soil–microbial dynamics rather than from direct effects of drought and heat on soil microbes alone.
    Keywords: 13 Co 2 Pulse Labeling ; 16s Rrna Next‐Generation Sequencing ; Climate Extremes ; Drought ; Forest Understory ; Heat‐Pulse ; Microbial Community Structure ; Plant–Soil–Microbe Carbon Continuum ; Plfa S
    ISSN: 1354-1013
    E-ISSN: 1365-2486
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  • 8
    Language: English
    In: Soil Biology and Biochemistry, 2010, Vol.42(3), pp.435-444
    Description: By measuring the isotopic signature of soil respiration, we seek to learn the isotopic composition of the carbon respired in the soil ( C ) so that we may draw inferences about ecosystem processes. Requisite to this goal is the need to understand how C is affected by both contributions of multiple carbon sources to respiration and fractionation due to soil gas transport. In this study, we measured potential isotopic sources to determine their contributions to C and we performed a series of experiments to investigate the impact of soil gas transport on C estimates. The objectives of these experiments were to: i) compare estimates of C derived from aboveground and belowground techniques, ii) evaluate the roles of diffusion and advection in a forest soil on the estimates of C , and iii) determine the contribution of new and old carbon sources to C for a Douglas-fir stand in the Pacific Northwest during our measurement period. We found a maximum difference of −2.36‰ between estimates of C based on aboveground vs. belowground measurements; the aboveground estimate was enriched relative to the belowground estimate. Soil gas transport during the experiment was primarily by diffusion and the average belowground estimate of C was enriched by 3.8–4.0‰ with respect to the source estimates from steady-state transport models. The affect of natural fluctuations in advective soil gas transport was little to non-existent; however, an advection–diffusion model was more accurate than a model based solely on diffusion in predicting the isotopic samples near the soil surface. Thus, estimates made from belowground gas samples will improve with an increase in samples near the soil surface. We measured a −1‰ difference in C as a result of an experiment where advection was induced, a value which may represent an upper limit in fractionation due to advective gas transport in forest ecosystems. We found that aboveground measurements of C may be particularly susceptible to atmospheric incursion, which may produce estimates that are enriched in C. The partitioning results attributed 69–98% of soil respiration to a source with a highly depleted isotopic signature similar to that of water-soluble carbon from foliage measured at our site.
    Keywords: Soil Respiration ; Carbon Isotope ; Advection ; Diffusion ; Steady-State ; Partitioning ; Douglas-Fir Forest ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 9
    Language: English
    In: Oecologia, 2010, Vol.163(1), pp.227-234
    Description: Patterns in the isotopic signal (stable C isotope composition; δ 13 C) of respiration (δ 13 C R ) have led to important gains in understanding the C metabolism of many systems. Contained within δ 13 C R is a record of the C source mineralized, the metabolic pathway of C and the environmental conditions during which respiration occurred. Because gas samples used for analysis of δ 13 C R contain a mixture of CO 2 from respiration and from the atmosphere, two-component mixing models are used to identify δ 13 C R . Measurement of ecosystem δ 13 C R , using canopy airspace gas samples, was one of the first applications of mixing models in ecosystem ecology, and thus recommendations and guidelines are based primarily on findings from these studies. However, as mixing models are applied to other experimental conditions these approaches may not be appropriate. For example, the range in [CO 2 ] obtained in gas samples from canopy air is generally less than 100 μmol mol −1 , whereas in studies of respiration from soil, foliage or tree stems, the range can span as much as 10,000 μmol mol −1 and greater. Does this larger range in [CO 2 ] influence the precision and accuracy of δ 13 C R estimates derived from mixing models? Does the outcome from using different regression approaches and mixing models vary depending on the range of [CO 2 ]? Our research addressed these questions using a simulation approach. We found that it is important to distinguish between large (〉1,000 μmol mol −1 ) and small (〈100 μmol mol −1 ) ranges of CO 2 when applying a mixing model (Keeling plot or Miller–Tans) and regression approach (ordinary least squares or geometric mean regression) combination to isotopic data. The combination of geometric mean regression and the Miller–Tans mixing model provided the most accurate and precise estimate of δ 13 C R when the range of CO 2 is ≥1,000 μmol mol −1 .
    Keywords: Carbon ; Respiration ; Soil ; Regression ; Isotope
    ISSN: 0029-8549
    E-ISSN: 1432-1939
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  • 10
    Language: English
    In: Environmental and Experimental Botany, March 2017, Vol.135, pp.21-26
    Description: The time span needed for carbon fixed by plants to induce belowground responses of root and rhizosphere microbial metabolic processing is of high importance for quantifying the coupling between plant canopy physiology and soil biogeochemistry, but recent observations of a rapid link cannot be explained by new assimilate transport by phloem mass flow alone. We performed CO labeling experiments designed to test if belowground respiration response to photosynthesis is faster than the arrival of new assimilates and to shed light on potential mechanisms. We provide experimental evidence that at least two mechanisms are employed by plants to couple rhizosphere respiration to canopy assimilation. We observed a fast increase of belowground respiration with the onset of photosynthesis, which we assume is induced by pressure concentration waves travelling through the phloem. A second, much later occurring, peak in respiration is fueled by new assimilates labeled with C. Plants and the rhizosphere are thus more tightly coupled than previously thought. Ultimately, the addition of a faster assimilate delivery mechanism to our conceptual framework of ecosystem dynamics will lead to a better understanding of belowground carbon and nutrient cycling and subsequent ecosystem response to disturbance and environmental stress.
    Keywords: Speed of Link ; Phloem Transport ; Soil Respiration ; Pressure Concentration Wave ; Carbon Isotope ; Rhizosphere ; Environmental Sciences ; Botany
    ISSN: 0098-8472
    E-ISSN: 1873-7307
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