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  • 1
    Language: English
    In: PLoS ONE, 01 January 2015, Vol.10(8), p.e0136579
    Description: The present study with young poplar trees aimed at characterizing the effect of O2 shortage in the soil on net uptake of NO3- and NH4+ and the spatial distribution of the N taken up. Moreover, we assessed biomass increment as well as N status of the trees affected by O2 deficiency. For this purpose, an experiment was conducted in which hydroponically grown young poplar trees were exposed to hypoxic and normoxic (control) conditions for 14 days. 15N-labelled NO3- and NH4+ were used to elucidate N uptake and distribution of currently absorbed N and N allocation rates in the plants. Whereas shoot biomass was not affected by soil O2 deficiency, it significantly reduced root biomass and, consequently, the root-to-shoot ratio. Uptake of NO3- but not of NH4+ by the roots of the trees was severely impaired by hypoxia. As a consequence of reduced N uptake, the N content of all poplar tissues was significantly diminished. Under normoxic control conditions, the spatial distribution of currently absorbed N and N allocation rates differed depending on the N source. Whereas NO3- derived N was mainly transported to the younger parts of the shoot, particularly to the developing and young mature leaves, N derived from NH4+ was preferentially allocated to older parts of the shoot, mainly to wood and bark. Soil O2 deficiency enhanced this differential allocation pattern. From these results we assume that NO3- was assimilated in developing tissues and preferentially used to maintain growth and ensure plant survival under hypoxia, whereas NH4+ based N was used for biosynthesis of storage proteins in bark and wood of the trees. Still, further studies are needed to understand the mechanistic basis as well as the eco-physiological advantages of such differential allocation patterns.
    Keywords: Sciences (General)
    E-ISSN: 1932-6203
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  • 2
    In: PLoS ONE, 2015, Vol.10(5)
    Description: Climate change poses direct or indirect influences on physiological mechanisms in plants. In particular, long living plants like trees have to cope with the predicted climate changes (i.e. drought and air warming) during their life span. The present study aimed to quantify the consequences of simulated climate change for foliar N metabolites over a drought-rewetting-drought course. Saplings of three Central European oak species (i.e. Quercus robur , Q . petraea , Q . pubescens ) were tested on two different soil types (i.e. acidic and calcareous). Consecutive drought periods increased foliar amino acid-N and soluble protein-N concentrations at the expense of structural N in all three oak species. In addition, transient effects on foliar metabolite dynamics were observed over the drought-rewetting-drought course. The lowest levels of foliar soluble protein-N, amino acid-N and potassium cation with a minor response to drought and air warming were found in the oak species originating from the driest/warmest habitat ( Q . pubescens ) compared to Q . robur and Q . petraea . Higher foliar osmolyte-N and potassium under drought and air warming were observed in all oak species when grown on calcareous versus acidic soil. These results indicate that species-specific differences in physiological mechanisms to compensate drought and elevated temperature are modified by soil acidity.
    Keywords: Research Article
    E-ISSN: 1932-6203
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  • 3
    Language: English
    In: Forest Ecology and Management, 2011, Vol.262(2), pp.105-114
    Description: ► Competition for N between young and adult beech is reduced by seasonal timing. ► Beech seedlings favour N uptake in spring, adult beech trees in autumn. ► Removal of vegetation components does not play a role in this competition. ► Competition between plants and soil microorganisms is, therefore, not avoided. Plant growth, reproduction, and biomass allocation may be affected differently by nitrogen availability depending on tree size and age. In this context, competition for limited N may be avoided by different strategies of N acquisition between different vegetation components (i.e., seedlings, mature trees, other woody and herbaceous understorey). This study investigated in a field experiment whether the competition for N between different vegetation components in beech forests was prevented via seasonal timing of N uptake and affected by microbial N use. For this purpose, a removal approach was used to study the seasonal effects on N uptake and N metabolites in adult beech trees and beech natural regeneration, as well as soil microbial processes of inorganic N production and utilisation. We found that the competition for N between beech natural regeneration and mature beech trees was reduced by seasonal avoidance strategies (“good parenting”) of N uptake regardless of the N sources used. In spring, organic and inorganic N uptake capacity was significantly higher in beech seedlings compared to adult beech trees, whereas in autumn mature beech trees showed the highest N uptake rates. Removal of vegetation components did not result in changes in soil microbial N processes in the course of the growing season. Thus, N resources released by the removal of vegetation components were marginal. This consistency in soil microbial N processes indicates that competition between plants and soil microorganisms for N was not avoided by timing of acquisition during the vegetation period, but existed during the entire growing season. In conclusion, N nutrition in the studied forest ecosystem seems to be optimally attuned to European beech.
    Keywords: Fagus Sylvatica ; N Uptake ; N Metabolites ; Soil Microorganisms ; Soil N Processes ; Removal Approach ; Forestry ; Biology
    ISSN: 0378-1127
    E-ISSN: 1872-7042
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  • 4
    Language: English
    In: Plant and Soil, 2013, Vol.364(1), pp.287-301
    Description: Background and aims: Nitrous oxide (N sub(2)O) and methane (CH sub(4)) can be emitted from surfaces of riparian plants. Data on the emission of these greenhouse gases by upland trees are scarce. We quantified CH sub(4) and N sub(2)O emissions from stems of Fagus sylvatica, an upland tree, and Alnus glutinosa, a riparian tree. Methods: The gas fluxes were investigated in mesocosms under non-flooded control conditions and during a flooding period using static chamber systems and gas chromatographic analyses. Results: Despite differences in the presence of an aerenchyma system, both tree species emitted N sub(2)O and CH sub(4) from the stems. Flooding caused a dramatic transient increase of N sub(2)O stem emissions by factors of 740 (A. glutinosa) and even 14,230 (F. sylvatica). Stem emissions of CH sub(4) were low and even deposition was determined (F. sylvatica controls). The results suggest that CH sub(4) was transported mainly through the aerenchyma, whereas N sub(2)O transport occurred in the xylem sap. Conclusions: For the first time it has been demonstrated that upland trees such as F. sylvatica clearly significantly emit N sub(2)O from their stems despite lacking an aerenchyma. If this result is confirmed in adult trees, upland forests may constitute a new and significant source of atmospheric N sub(2)O.
    Keywords: Methane ; Nitrous oxide ; Soil and stem emission ; Alnus glutinosa ; Fagus sylvatica ; Flooding
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 5
    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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  • 6
    Language: English
    In: Forest Ecology and Management, 01 December 2012, Vol.285, pp.227-238
    Description: ► δ C- and δ O- signatures of tree-rings were used to assess forest management. ► One site showed pronounced differences in δ C between early- and latewood. ► Here, greater productivity was related to greater flexibility in water use efficiency. ► δ O-signatures acted as a proxy record of Vapor Pressure Deficit (VPD). ► The slope of the correlation between δ O and WUE indicated stomatal sensitivity to VPD. Foresters frequently lack sufficient information about site quality to optimize plantation management and logwood production to local conditions. In the present study we explored the potential of δ C- and δ O-signatures of tree-rings to provide such information. We studied stem disks collected from two plantations in south-eastern Australia that had been thinned or treated with fertilizer. Estimated from tree-ring δ C, the sites differed markedly in intrinsic water use efficiency of photosynthesis (WUE = / ). Stem disks from one site (Lyons) showed pronounced differences in δ C between early- and latewood, depending on stand density. Fertilizer application subsequent to thinning transiently increased foliage-N concentrations, without additional effects on and δ C. Thinning (and fertilization) at the other site (Daylesford) had little effect on δ C-variation between early- and late wood. Greater productivity at Lyons is seemingly related to greater flexibility in WUE such that fluctuating water supply was more efficiently exploited. Current theory suggests δ O-signatures in wood at this site acted as a proxy record of Vapor Pressure Deficit (VPD), and the slope of the correlation between δ O and WUE (as an indicator of stomatal sensitivity to VPD) helped identify growth limiting resources and conditions. In general, δ O and WUE were positively correlated and WUE seemed mainly under stomatal control. Employing a General Linear Model, we identified additional influences on WUE . The slope, and closeness of fit of the correlation between δ O and WUE depended on stand density, wood type (early- or late wood), and individual trees. These traits were not correlated in early wood immediately after planting, suggesting WUE was driven by biochemical demand for CO in photosynthesis. Conversely, enhanced competition for soil water after canopy closure resulted in positive correlations between δ O and WUE , indicating enhanced importance of stomatal resistance to CO -diffusion. We discuss the limitations to the use of δ C- and δ O analysis of bulk wood for determining the balance between demand- and supply-driven control of WUE .
    Keywords: Pinus Radiata ; Plantation Management ; Thinning ; Fertilization ; Stable Isotopes ; Δ13c and Δ18o ; Forestry ; Biology
    ISSN: 0378-1127
    E-ISSN: 1872-7042
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  • 7
    Language: English
    In: Plant physiology, November 2012, Vol.160(3), pp.1515-29
    Description: Understanding seasonality and longevity is a major challenge in tree biology. In woody species, growth phases and dormancy follow one another consecutively. In the oldest living individuals, the annual cycle may run for more than 1,000 years. So far, however, not much is known about the processes triggering reactivation from dormancy. In this study, we focused on wood rays, which are known to play an important role in tree development. The transition phase from dormancy to flowering in early spring was compared with the phase of active growth in summer. Rays from wood samples of poplar (Populus × canescens) were enriched by laser microdissection, and transcripts were monitored by poplar whole-genome microarrays. The resulting seasonally varying complex expression and metabolite patterns were subjected to pathway analyses. In February, the metabolic pathways related to flower induction were high, indicating that reactivation from dormancy was already taking place at this time of the year. In July, the pathways related to active growth, like lignin biosynthesis, nitrogen assimilation, and defense, were enriched. Based on "marker" genes identified in our pathway analyses, we were able to validate periodical changes in wood samples by quantitative polymerase chain reaction. These studies, and the resulting ray database, provide new insights into the steps underlying the seasonality of poplar trees.
    Keywords: Seasons ; Populus -- Cytology ; Trees -- Physiology ; Wood -- Cytology
    ISSN: 00320889
    E-ISSN: 1532-2548
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  • 8
    Language: English
    In: Forest Ecology and Management, 2010, Vol.259(6), pp.1190-1199
    Description: We examined water use by maturing , growing with or without an mid-storey stratum of spp. ( or . ), for 〉180 consecutive days. Study sites were located in the Upper Yarra catchment area in south-eastern Australia. Depending on their contribution to stand basal area, mid-storey spp. increased total stand water use by up to 30%. Monthly water use in such stands reached more than 640,000 L ha (compared to 545,000 L ha in stands where acacias were absent) in early spring. Water use was curvilinearly related to sapwood area of spp. and logistically related to sapwood area of . . Water use of all three species showed a strong relation to daily maximum air temperatures. Distinct and simple relationships provide clear guides to the likely impacts of climate change and forest management on water yield. We compared a traditional up-scaling approach, from individual tree water use to stand water use, to a new approach that incorporates variation in temperature. Development of this approach can lead to greater precision of stand water use estimates – and in turn catchment water yield – under current climate change scenarios, which predict a rise in air temperatures of 0.6–2.5 °C by 2050 for the study area. Our temperature-dependent approach suggests that under conditions of non-limiting water availability, stand water use will rise by 2% for every 0.25 °C increase in maximum air temperatures during winter, and possibly more than that during summer.
    Keywords: Eucalyptus Regnans ; Acacia Dealbata ; Acacia Melanoxylon ; Tree Water Use ; Stand Structure ; Water Management ; Climate Change ; Forestry ; Biology
    ISSN: 0378-1127
    E-ISSN: 1872-7042
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  • 9
    Language: English
    In: Forest Ecology and Management, 01 July 2012, Vol.275, pp.60-67
    Description: ► We study two adult populations under different microclimatic conditions. ► We compare genetic diversity of the adult populations and their natural regeneration. ► Case study based on isozymes and microsatellite markers. ► We identified two “outlier microsatellite loci”, exhibiting directional selection. ► Natural selection account for different genetic structures of the adult populations. Due to its drought sensitivity, the performance and competitiveness of beech as a favoured species of forest management in Central Europe is likely to be negatively affected by the prognosticated climate change, leading to major impacts on the vulnerability of managed forest ecosystems. We studied the genetic differentiation between two populations from a relatively cold and wet northeast (representing the current climate of the majority of beech forests in Central Europe) and a relatively warm and dry southwest facing slope (representing the future climate of an increasing area covered by beech forests in Central Europe) at the same forest site to investigate the adaptation processes in these two populations under different microclimatic conditions. For this purpose, two different techniques, , nuclear microsatellites (neutral) and isozyme markers (adaptive), were applied to adult trees and natural regeneration at both slopes. Although microsatellites are considered to be neutral markers, they have been shown in several studies to give signals of selectively-driven changes. In our study, two of the five microsatellites behaved as “outlier loci”, exhibiting directional selection. Our results show independent of the technique applied that natural regeneration of the southwest slope and the natural regeneration and adult trees of the northeast slope were genetically closer than the adult trees from the southwest slope. Thus, we conclude that natural selection and potential adaptation account for genetic changes and different genetic structures among the two adult populations in this case study.
    Keywords: Fagus Sylvatica ; Climate Change ; Isozymes ; Nuclear Microsatellites ; Beech ; Adaptation ; Forestry ; Biology
    ISSN: 0378-1127
    E-ISSN: 1872-7042
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  • 10
    Language: English
    In: Forests, 01 August 2015, Vol.6(8), pp.2820-2835
    Description: Nitrogen (N) is an essential nutrient that is highly abundant as N2 in the atmosphere and also as various mineral and organic forms in soils. However, soil N bioavailability often limits the net primary productivity of unperturbed temperate forests with low atmospheric N input. This is because most soil N is part of polymeric organic matter, which requires microbial depolymerization and mineralization to render bioavailable N forms such as monomeric organic or mineral N. Despite this N limitation, many unfertilized forest ecosystems on marginal soil show relatively high productivity and N uptake comparable to agricultural systems. The present review article addresses the question of how this high N demand is met in temperate forest ecosystems. For this purpose, current knowledge on the distribution and fluxes of N in marginal forest soil and the regulation of N acquisition and distribution in trees are summarized. The related processes and fluxes under N limitation are compared with those of forests exposed to high N loads, where chronic atmospheric N deposition has relieved N limitation and caused N saturation. We conclude that soil microbial biomass is of decisive importance for nutrient retention and provision to trees both in high and low N ecosystems.
    Keywords: Tree Nitrogen Uptake ; Soil Microbial Nitrogen Turnover ; N Limitation ; N Saturation ; Atmospheric Nitrogen Deposition ; Höglwald Spruce Forest ; Tuttlingen Beech Forest ; Forestry
    E-ISSN: 1999-4907
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