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  • Botany
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  • 1
    Language: English
    In: Plant and Soil, 2010, Vol.333(1), pp.93-103
    Description: Assessment of belowground interactions in mixed forests has been largely constrained by the ability to distinguish fine roots of different species. Here, we explored near infrared reflectance spectroscopy (NIRS) to predict the proportion of woody fine roots in mixed samples and analyzed whether the prediction quality of NIRS models is related to the complexity of the fine-root mixture. For model calibration and validation purposes, 11 series of artificial mixed species samples containing known amounts of fine roots of up to four temperate tree species and non-woody plants were prepared. Three types of models with different calibration/validation approaches were developed and tested against external independent data for additional validation. With these models the proportion of each species in root mixtures was predicted accurately with low standard error of prediction (RMSECV/RMSEP 〈6.5%) and high coefficient of determination (r 2  〉 0.93) for all fine-root mixtures. In addition, NIRS models also provided satisfactory estimates for samples with low (〈15%) or no content of particular components. The predictive power of the NIRS models did not decrease substantially with increasing complexity of the root samples. The approach presented here is a promising alternative to hand sorting of fine roots, which may be influenced substantially by operator variation, and it will facilitate investigating belowground interactions between woody species.
    Keywords: Fine roots ; Belowground diversity ; Near-infrared reflectance spectroscopy (NIRS) ; NIRS model ; Species proportions
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 2
    Language: English
    In: Journal of Ecology, 01/2013, Vol.101(1), pp.220-230
    Description: Partitioning of tree mortality into different modes of death allows the tracing and mechanistic modelling of individual key processes of forest dynamics each varying depending on site, species and individual risk factors. This, in turn, may improve long-term predictions of the development of old-growth forests.Six different individual tree mortality modes (uprooted and snapped (both with or without rot as a predisposing factor), standing dead and crushed by other trees) were analysed, and statistical models were derived for three tree species (European beech Fagus sylvatica, hornbeam Carpinus betulus and common ash Fraxinus excelsior) based on a repeated inventory of more than 13 000 trees in a 28 ha near-natural deciduous forest in Central Germany.The frequently described U-shaped curve of size-dependent mortality was observed in beech and hornbeam (but not ash) and could be explained by the joint operation of processes related to the six distinct mortality modes. The results for beech, the most abundant species, suggest that each mortality mode is prevalent in different life-history stages: small trees died mostly standing or being crushed, medium-sized trees had the highest chance of survival, and very large trees experienced increased rates of mortality, mainly by uprooting or snapping. Reduced growth as a predictor also played a role but only for standing dead, all other mortality modes showed no relationship to tree growth.Synthesis. Tree mortality can be partitioned into distinct processes, and species tend to differ in their susceptibility to one or more of them. This forms a fundamental basis for the understanding of forest dynamics in natural forests, and any mechanistic modelling of mortality in vegetation models could be improved by correctly addressing and formulating the various mortality processes. Modelled annual mortality logits and probabilities over d.b.h. (cm) for beech. Median estimates and 95% credible interval. Tree mortality can be partitioned into different processes related to six distinct mortality modes, jointly explaining the emergent U-shaped curve of size-dependent mortality. This forms a fundamental basis for the understanding of forest dynamics in natural forests and may improve mechanistic modelling thereof.
    Keywords: Mortality ; Mortality ; Carpinus Betulus ; Ash ; 1010 ; Environment ; 04040;
    ISSN: Journal of Ecology
    E-ISSN: 00220477
    E-ISSN: 13652745
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  • 3
    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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  • 4
    Language: English
    In: Dendrochronologia, April 2018, Vol.48, pp.1-9
    Description: Norway spruce is one of the economically most important tree species in Central European forestry. However, its high susceptibility to droughts poses a strong challenge to its cultivation under future conditions with likely more frequent and prolonged droughts and shifts in the seasonal climate. To compensate for expected losses of forest areas suitable for the cultivation of spruce, more drought-tolerant species are required. Silver fir and Douglas fir are two potential candidates, which promise lower drought susceptibility and equal or even higher yield when compared to Norway spruce. Using the Black Forest as a regional case study, we assessed the effects of seasonal climate change, including drought stress, on tree-ring width formation of these three economically relevant conifer species over the last 60 years. In addition, we projected potential species-specific growth changes under different climate change scenarios until 2100. Our results suggest that both silver fir and Douglas fir will possibly experience growth increases in a warmer future climate, as predicted under the 4.5 and 8.5 Representative Concentration Pathway (RCP) climate change scenarios, whereas growth of spruce is expected to decline. Moreover, drought susceptibility in silver fir and Douglas fir is lower than in spruce, as shown for past drought events, and their ability to benefit from milder winters and springs could play a major role in their capacity to compensate for drier summers in the near to mid-term future. This study highlights the need to advance our understanding of the processes that drive drought resistance and resilience in tree species to guide management strategies in the face of climate change.
    Keywords: Abies Alba ; Central Europe ; Climate Change ; Dendroecology ; Forest Management ; Picea Abies ; Pseudotsuga Menziesii ; Meteorology & Climatology ; Botany
    ISSN: 1125-7865
    E-ISSN: 1612-0051
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  • 5
    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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  • 6
    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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  • 7
    Language: English
    In: Mycological Progress, 2014, Vol.13(3), pp.959-964
    Description: Managing forests by selection cutting is a promising silvicultural technique for maintaining forest biodiversity. Despite the importance of fungi in decomposition and nutrient cycling in forest ecosystems, no study to date has investigated the effects of selection cutting on fungal communities, especially using a culture-independent molecular technique to assess more than just the species that are fruiting at the time of sampling. Based on operational taxonomic units (OTUs) found in coarse woody debris, we compared the richness and community composition of wood-inhabiting fungi from selection cutting, age-class, and unmanaged European beech-dominated forests. We found that fungal OTU richness in selection cutting and unmanaged forests was not significantly different ( P  〉 0.05), but it was higher, in both cases, than that in the age-class forest ( P  = 0.0002). Fungal community composition was not significantly different among the three forest types ( P  〉 0.05). Abundances of common, wood-inhabiting fungal OTUs in different forest types were significantly correlated: the highest and lowest correlations were found between unmanaged forests and selection cutting ( ρ  = 0.52, P  〈 0.0001, n  = 94), and between unmanaged and age-class forests ( ρ  = 0.30, P  = 0.0080, n  = 79), respectively.
    Keywords: Fungal diversity ; Silviculture ; Forest management ; F-ARISA ; Culture-independent molecular method
    ISSN: 1617-416X
    E-ISSN: 1861-8952
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  • 8
    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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  • 9
    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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  • 10
    Language: English
    In: Fungal Diversity, 2016, Vol.77(1), pp.367-379
    Description: Fungi play vital roles in the decomposition of deadwood due to their secretion of various enzymes that break down plant cell-wall complexes. The compositions of wood-inhabiting fungal (WIF) communities change over the course of the decomposition process as the remaining mass of wood decreases and both abiotic and biotic conditions of the wood significantly change. It is currently not resolved which substrate-related factors govern these changes in WIF communities and whether such changes influence the deadwood decomposition rate. Here we report a study on fungal richness and community structure in deadwood of Norway spruce and European beech in temperate forest ecosystems using 454 pyrosequencing. Our aims were to disentangle the factors that correspond to WIF community composition and to investigate the links between fungal richness, taxonomically-resolved fungal identity, and microbial-mediated ecosystem functions and processes by analyzing physico-chemical wood properties, lignin-modifying enzyme activities and wood decomposition rates. Unlike fungal richness, we found significant differences in community structure between deadwood of different tree species. The composition of WIF communities was related to the physico-chemical properties of the deadwood substrates. Decomposition rates and the activities of lignin-modifying enzymes were controlled by the succession of the fungal communities and competition scenarios rather than fungal OTU richness. Our results provide further insights into links between fungal community structure and microbial-mediated ecosystem functions and processes.
    Keywords: Ecosystem processes ; Enzyme activity ; Wood decay ; Physico-chemical wood properties ; Ascomycetes ; Basidiomycetes ; Pyrosequencing
    ISSN: 1560-2745
    E-ISSN: 1878-9129
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