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Berlin Brandenburg

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  • 1
    In: Tree Physiology, 2014, Vol. 34(2), pp.184-193
    Description: Northern red oak ( Quercus rubra L.), a moderately shade-tolerant tree species, is failing to regenerate throughout its native North American range, while successful recruitment in Central Europe has been observed since its introduction. To examine whether comparative photosynthetic performance could explain the regeneration success of this non-native species in Central Europe, we compared the physiological and morphological seedling traits of red oak with three co-occurring tree species under three canopy types in southwestern Germany. Native species included a moderately shade-tolerant native oak ( Quercus robur L.) and two shade-tolerant species ( Acer pseudoplatanus L. and Carpinus betulus L.). The photosynthetic traits of non-native red oak seedlings were similar to those reported for this species in the native range, where shade-tolerant competitors readily outperform red oak under low light conditions. However, compared with native shade-tolerant species in Europe, red oak seedlings photosynthesized efficiently, especially under closed canopies and in small canopy gaps, exhibiting high photosynthetic capacity, low leaf dark respiration and leaf-level light compensation points that were similar to the more shade-tolerant species. The superior net carbon gain of red oak seedlings at low and moderate light levels was likely facilitated by high leaf areas and reflected by seedling dry masses that were greater than the observed native European species. A competitive advantage for red oak was not evident because relative height growth was inferior to seedlings of co-occurring species. In North America, the inability of seedlings to compete with shade-tolerant tree species in deeply shaded understories is central to the problem of poor oak recruitment. Our study suggests that the ability of non-native red oak to perform equally well to native shade-tolerant species under a variety of light conditions could contribute to the consistent success of red oak regeneration in Europe.
    Keywords: European Forests ; Introduced Species ; Invasive Species ; Morphological Plant Traits ; Physiological Plant Traits ; Regeneration Dynamics ; Seedling Growth ; Shade Tolerance
    ISSN: 0829-318X
    E-ISSN: 1758-4469
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  • 2
    In: Tree Physiology, 2012, Vol. 32(10), pp.1199-1213
    Description: Radial stem growth and the isotopic composition of growth rings are commonly used to quantify the effects of droughts on trees. However, often these parameters are quantified only at one stem height, e.g., 1.3 m, and it is not known how representative this is for the whole stem. This study investigated radial growth at four stem heights (1.3, 5.5, 9.8 and 14 m) of 21, and wood Δ 13 C and δ 18 O at two heights (1.3 and 14 m) of 10 (co-)dominant Norway spruce trees from heavily (HT) and moderately thinned (MT) stands to assess whether different thinning intensities influenced the drought response of stems at different tree heights. Annual basal area increments (BAIs) and stable isotopes in earlywood and latewood were compared between thinning treatments and among the different stem heights. For BAIs, linear correlations with climate were analysed as well. The response of radial growth and isotopic composition to drought was similar at different stem heights in HT trees, but varied with height in MT trees, which were also more sensitive to climatic variations. Recovery of radial growth after drought was more rapid in trees from HT compared with MT stands, except for the topmost height. Basal area increments at breast height (1.3 m) provided good estimates of the volume growth response to drought for the whole stem, but not for its recovery. The faster recovery of radial growth at 1.3 m height of HT compared with MT trees after the 2003 drought was not accompanied by differences in recovery of isotopic composition. However, this is likely to be related to differences between treatments in remobilization of stored C and in tree structure (leaf area, root systems).
    Keywords: Carbon/Oxygen Isotopes ; Drought ; 〈Kwd〉〈Italic〉Picea Abies〈/Italic〉〈/Kwd〉 ; Stem Analysis ; Thinning
    ISSN: 0829-318X
    E-ISSN: 1758-4469
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  • 3
    In: Tree Physiology, 2010, Vol. 30(9), pp.1192-1208
    Description: Productivity of tree plantations is a function of the supply, capture and efficiency of use of resources, as outlined in the Production Ecology Equation. Species interactions in mixed-species stands can influence each of these variables. The importance of resource-use efficiency in determining forest productivity has been clearly demonstrated in monocultures; however, substantial knowledge gaps remain for mixtures. This review examines how the physiology and morphology of a given species can vary depending on whether it grows in a mixture or monoculture. We outline how physiological and morphological shifts within species, resulting from interactions in mixtures, may influence the three variables of the Production Ecology Equation, with an emphasis on nutrient resources [nitrogen (N) and phosphorus (P)]. These include (i) resource availability, including soil nutrient mineralization, N 2 fixation and litter decomposition; (ii) proportion of resources captured, resulting from shifts in spatial, temporal and chemical patterns of root dynamics; (iii) resource-use efficiency. We found that more than 50% of mixed-species studies report a shift to greater above-ground nutrient content of species grown in mixtures compared to monocultures, indicating an increase in the proportion of resources captured from a site. Secondly, a meta-analysis showed that foliar N concentrations significantly increased for a given species in a mixture containing N 2 -fixing species, compared to a monoculture, suggesting higher rates of photosynthesis and greater resource-use efficiency. Significant shifts in N- and P-use efficiencies of a given species, when grown in a mixture compared to a monoculture, occurred in over 65% of studies where resource-use efficiency could be calculated. Such shifts can result from changes in canopy photosynthetic capacities, changes in carbon allocation or changes to foliar nutrient residence times of species in a mixture. We recommend that future research focus on individual species' changes, particularly with respect to resource-use efficiency (including nutrients, water and light), when trees are grown in mixtures compared to monocultures. A better understanding of processes responsible for changes to tree productivity in mixed-species tree plantations can improve species, and within-species, selection so that the long-term outcome of mixtures is more predictable.
    Keywords: Light - Use Efficiency ; Litter Decomposition ; Nitrogen Fixation ; Nitrogen - Use Efficiency ; Phosphorus - Use Efficiency ; Root Stratification ; Water - Use Efficiency.
    ISSN: 0829-318X
    E-ISSN: 1758-4469
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  • 4
    In: Tree Physiology, 2007, Vol. 27(9), pp.1319-1328
    Description: Eucalyptus globulus Acacia mearnsii E. globulus 2 A. mearnsii 2 A. mearnsii 2 15 E. globulus A. mearnsii A. mearnsii A. mearnsii E. globulus 2 2 −1 −1 A. mearnsii A. mearnsii 15 A. mearnsii 2 E. globulus 15 E. globulus A. mearnsii 2 E. globulus Mixtures of Eucalyptus globulus Labill. and Acacia mearnsii de Wildeman are twice as productive as E. globulus monocultures growing on the same site in East Gippsland, Victoria, Australia, possibly because of increased nitrogen (N) availability owing to N 2 fixation by A. mearnsii . To investigate whether N 2 fixation by A. mearnsii could account for the mixed-species growth responses, we assessed N 2 fixation by the accretion method and the 15 N natural abundance method. Nitrogen gained by E. globulus and A. mearnsii mixtures and monocultures was calculated by the accretion method with plant and soil samples collected 10 years after plantation establishment. Nitrogen in biomass and soil confirmed that A. mearnsii influenced N dynamics. Assuming that the differences in soil, forest floor litter and biomass N of plots containing A. mearnsii compared with E. globulus monocultures were due to N 2 fixation, the 10-year annual mean rates of N 2 fixation were 38 and 86 kg ha −1 year −1 in 1:1 mixtures and A. mearnsii monocultures, respectively. Nitrogen fixation by A. mearnsii could not be quantified on the basis of the natural abundance of 15 N because such factors as mycorrhization type and fractionation of N isotopes during N cycling within the plant confounded the effect of the N source on the N isotopic signature of plants. This study shows that A. mearnsii fixed significant quantities of N 2 when mixed with E. globulus . A decline in δ 15 N values of E. globulus and A. mearnsii with time, from 2 to 10 years, is further evidence that N 2 was fixed and cycled through the stands. The increased aboveground biomass production of E. globulus trees in mixtures when compared with monocultures can be attributed to increases in N availability.
    Keywords: Accretion ; Mycorrhizae ; N Natural Abundance
    ISSN: 0829-318X
    E-ISSN: 1758-4469
    Source: Oxford University Press
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  • 5
    Language: English
    In: Tree physiology, September 2007, Vol.27(9), pp.1319-28
    Description: Mixtures of Eucalyptus globulus Labill. and Acacia mearnsii de Wildeman are twice as productive as E. globulus monocultures growing on the same site in East Gippsland, Victoria, Australia, possibly because of increased nitrogen (N) availability owing to N(2) fixation by A. mearnsii. To investigate whether N(2) fixation by A. mearnsii could account for the mixed-species growth responses, we assessed N(2) fixation by the accretion method and the (15)N natural abundance method. Nitrogen gained by E. globulus and A. mearnsii mixtures and monocultures was calculated by the accretion method with plant and soil samples collected 10 years after plantation establishment. Nitrogen in biomass and soil confirmed that A. mearnsii influenced N dynamics. Assuming that the differences in soil, forest floor litter and biomass N of plots containing A. mearnsii compared with E. globulus monocultures were due to N(2) fixation, the 10-year annual mean rates of N(2) fixation were 38 and 86 kg ha(-1) year(-1) in 1:1 mixtures and A. mearnsii monocultures, respectively. Nitrogen fixation by A. mearnsii could not be quantified on the basis of the natural abundance of (15)N because such factors as mycorrhization type and fractionation of N isotopes during N cycling within the plant confounded the effect of the N source on the N isotopic signature of plants. This study shows that A. mearnsii fixed significant quantities of N(2) when mixed with E. globulus. A decline in delta(15)N values of E. globulus and A. mearnsii with time, from 2 to 10 years, is further evidence that N(2) was fixed and cycled through the stands. The increased aboveground biomass production of E. globulus trees in mixtures when compared with monocultures can be attributed to increases in N availability.
    Keywords: Acacia -- Metabolism ; Eucalyptus -- Metabolism ; Nitrogen -- Metabolism ; Nitrogen Fixation -- Physiology ; Soil -- Analysis
    ISSN: 0829-318X
    E-ISSN: 17584469
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