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Berlin Brandenburg

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  • 1
    Language: English
    In: Trees, 2013, Vol.27(6), pp.1609-1619
    Description: Sorbus torminalis L. (Crantz) is a rare species in Central European forests with very limited quantitative information on its regeneration and growth dynamics. Since coppicing is no longer practiced in the most parts of Central Europe, it is unclear whether S. torminalis , which has usually a shorter end height than companion species, can persist in high forest systems. Here, we quantified species frequency on three 1 ha sample plots of former oak coppice forest. To determine whether S. torminalis regenerated continuously and how it might compete with oaks, the age of 80 trees was determined, and diameter and height growth were reconstructed for the 20 largest trees by stem analysis. To assess its shade tolerance, photosynthesis was measured for leaves located in high and low light conditions. Dendrochronological data demonstrated that, over the last 80 years, continuous recruitment of S. torminalis occurred. Growth patterns and photosynthesis measurements suggest that S. torminalis is a highly shade-tolerant species. We conclude that abandonment of coppicing in these forests does not threaten the status of S. torminalis , which can persist beneath the canopy of oaks.
    Keywords: Coppice ; Age structure ; Growth ; Light ecology ; Sorbus torminalis ; Wild Service Tree
    ISSN: 0931-1890
    E-ISSN: 1432-2285
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  • 2
    Language: English
    In: Trees, 2013, Vol.27(3), pp.555-566
    Description: Tree growth and form are both influenced by crown architecture and how it effects leaf distribution and light interception. This study examined the vertical distribution of foliage in 4-year-old plantation-grown Eucalyptus pilularis Sm. and E. cloeziana F. Muell. trees. Leaf area (LA) distribution was determined at two different sites using allometric approaches to determine LA in crown sections and for whole trees. Leaf area was distributed more towards the upper crowns when canopies had been closed for longer. Leaf area was also skewed more towards the upper crowns for Eucalyptus pilularis than E. cloeziana . These species differences were consistent with differences in vertical light availability gradients as determined by point quantum sensors. Leaf area of individual branches was highly correlated with branch cross-sectional area (CSA) and whole-tree LA was closely related to stem CSA. Branch-level allometric relationships were influenced by site and crown position. However, the general allometric equations between stem size and whole-tree leaf area could be applied across sites. Results from this study suggest that pruning of live branches in these species should follow species-specific guides for the timing and height of pruning to optimise the effects on stem growth and form.
    Keywords: Leaf area index ; Leaf area distribution ; Pruning ; Crown architecture
    ISSN: 0931-1890
    E-ISSN: 1432-2285
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  • 3
    Language: English
    In: Trees, 2014, Vol.28(4), pp.1035-1051
    Description: KEY MESSAGE : The muted wood isotopic signal in slow-growing trees of unthinned stands indicates lower responsiveness to changing environmental conditions compared to fast-growing trees in thinned stands. To examine the physiological processes associated with higher growth rates after thinning, we analyzed the oxygen isotopic values in wood (δ¹⁸Ow) of 12 ponderosa pine (Pinus ponderosa) trees from control, moderately, and heavily thinned stands and compared them with wood-based estimates of carbon isotope discrimination (∆¹³C), basal area increment (BAI), and gas exchange. We found that (heavy) thinning led to shifts and increased inter-annual variability of both stable carbon and oxygen isotope ratios relative to the control throughout the first post-thinning decade. Results of a sensitivity analysis suggested that both an increase in stomatal conductance (g ₛ) and differences in source water among treatments are equally probable causes of the δ¹⁸Ow shift in heavily thinned stands. We modeled inter-annual changes in δ¹⁸Ow of trees from all treatments using environmental and physiological data and found that the significant increase in δ¹⁸Ow inter-annual variance was related to greater δ¹⁸Ow responsiveness to changing environmental conditions for trees in thinned stands when compared to control stands. Based on model results, the more muted climatic response of wood isotopes in slow-growing control trees is likely to be the consequence of reduced carbon sink strength causing a higher degree of mixing of previously stored and fresh assimilates when compared to faster-growing trees in thinned stands. Alternatively, the muted response of δ¹⁸Ow to climatic variation of trees in the control stand may result from little variation in the control stand in physiological processes (photosynthesis, transpiration) that are known to affect δ¹⁸Ow. ; p. 1035-1051.
    Keywords: Oxygen isotopes ; Thinning ; (ponderosa pine) ; Gas exchange ; Sensitivity analysis
    ISSN: 0931-1890
    E-ISSN: 1432-2285
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