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  • SpringerLink  (19)
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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: Oecologia, 2016, Vol.182(2), pp.319-333
    Description: Forest diversity-productivity relationships have been intensively investigated in recent decades. However, few studies have considered the interplay between species and structural diversity in driving productivity. We analyzed these factors using data from 52 permanent plots in southwestern Germany with more than 53,000 repeated tree measurements. We used basal area increment as a proxy for productivity and hypothesized that: (1) structural diversity would increase tree and stand productivity, (2) diversity-productivity relationships would be weaker for species diversity than for structural diversity, and (3) species diversity would also indirectly impact stand productivity via changes in size structure. We measured diversity using distance-independent indices. We fitted separate linear mixed-effects models for fir, spruce and beech at the tree level, whereas at the stand level we pooled all available data. We tested our third hypothesis using structural equation modeling. Structural and species diversity acted as direct and independent drivers of stand productivity, with structural diversity being a slightly better predictor. Structural diversity, but not species diversity, had a significant, albeit asymmetric, effect on tree productivity. The functioning of structurally diverse, mixed forests is influenced by both structural and species diversity. These sources of trait diversity contribute to increased vertical stratification and crown plasticity, which in turn diminish competitive interferences and lead to more densely packed canopies per unit area. Our research highlights the positive effects of species diversity and structural diversity on forest productivity and ecosystem dynamics.
    Keywords: Basal area increment ; Complementarity ; Ecosystem functioning ; Biodiversity ; Species diversity
    ISSN: 0029-8549
    E-ISSN: 1432-1939
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  • 3
    Language: English
    In: Oecologia, 2012, Vol.169(4), pp.1105-1115
    Description: The phenomenon of overyielding in species-diverse plant communities is mainly attributed to complementary resource use. Vertical niche differentiation belowground might be one potential mechanism for such complementarity. However, most studies that have analysed the diversity/productivity relationship and belowground niche differentiation have done so for fully occupied sites, not very young tree communities that are in the process of occupying belowground space. Here we used a 5–6 year old forest diversity experiment to analyse how fine-root (〈2 mm) production in ingrowth cores (0–30 cm) was influenced by tree species identity, as well as the species diversity and richness of tree neighbourhoods. Fine-root production during the first growing season after the installation of ingrowth cores increased slightly with tree species diversity, and four-species combinations produced on average 94.8% more fine-root biomass than monocultures. During the second growing season, fine-root mortality increased with tree species diversity, indicating an increased fine-root turnover in species-rich communities. The initial overyielding was attributable to the response to mixing by the dominant species, Pseudotsuga menziesii and Picea abies , which produced more fine roots in mixtures than could be expected from monocultures. In species-rich neighbourhoods, P. abies allocated more fine roots to the upper soil layer (0–15 cm), whereas P. menziesii produced more fine roots in the deeper layer (15–30 cm) than in species-poor neighbourhoods. Our results indicate that, although there may be no lasting overyielding in the fine-root production of species-diverse tree communities, increasing species diversity can lead to substantial changes in the production, vertical distribution, and turnover of fine roots of individual species.
    Keywords: Species diversity ; Species richness ; Fine roots ; Overyielding ; Vertical niche differentiation ; BIOTREE
    ISSN: 0029-8549
    E-ISSN: 1432-1939
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  • 4
    Language: English
    In: Biodiversity and Conservation, 2014, Vol.23(14), pp.3519-3542
    Description: A major goal of the Convention on Biological Diversity (CBD) is to improve the protection of biodiversity. One approach to meet this goal is the implementation of strictly protected forest reserves (SPFRs). Many countries have adopted this approach and set target values for SPFRs, for example Germany aims to set aside 5 % of the forest area by 2020 (BMU, Strategie zur Biologischen Vielfalt, 2007). The contribution of SPFRs to biodiversity conservation cannot be assessed without considering the quality or conservation value of these areas. One challenge lies in the selection of specific criteria to evaluate this contribution of existing SPFRs. For Central Europe we reviewed these specific evaluation criteria and their ecological theory and evidence underpinning their relevance for an assessment as well as the interrelations between criteria. In addition, we present a framework for the integration of these criteria into an evaluation process. To identify criteria typically used or recommended for the evaluation of SPFRs, we analyzed the international conventions and reviewed the scientific literature on biodiversity conservation, specifically on area selection, status assessment and gap analysis. Since nearly all criteria were interrelated and operate at different scales, we developed a coherent evaluation framework to integrate them. Within this framework the criteria cover the fundamental aspects: space (completeness and connectivity), time (habitat continuity and persistence), and function (naturalness, rarity/threat and representativeness). This approach, once it is complemented by indicators, may be used to evaluate the extent to which individual SPFRs as well as a system of SPFRs contribute to the protection of natural forest biodiversity at a national level. It may be particularly relevant for Central European countries with a similar ecological, historical and political context.
    Keywords: Forest biodiversity conservation ; Natural forest development ; Protected areas ; Forest conservation ; Evaluation framework ; CBD
    ISSN: 0960-3115
    E-ISSN: 1572-9710
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  • 5
    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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  • 6
    Language: English
    In: Annals of Forest Science, 2013, Vol.70(2), pp.195-207
    Description: CONTEXT : Since storm damage has a large impact on forest management in Central Europe, we investigated the main storm risk factors for two important conifer species, Douglas-fir (Pseudotsuga menziesii [Mirbel] Franco) and Norway spruce (Picea abies [L.] Karst.). AIMS : We compared general storm damage levels of Douglas-fir and Norway spruce, the latter being known to have high storm risk among European tree species. METHODS : Generalized linear mixed models and boosted regression trees were applied to recorded storm damage of individual trees from long-term experimental plots in southwest Germany. This included two major winter storm events in 1990 and 1999. Over 40 candidate predictors were tested for their explanatory power for storm damage and summarized into predictor categories for further interpretation. RESULTS : The two most important categories associated with storm damage were timber removals and topographic or site information, explaining between 18 and 54 % of storm damage risk, respectively. Remarkably, general damage levels were not different between Douglas-fir and Norway spruce. CONCLUSION : Under current forest management approaches, Douglas-fir may be considered a species with high storm risk in Central Europe, comparable to that of Norway spruce. ; p. 195-207.
    Keywords: Storm damage ; Risk ; Windthrow ; Douglas-fir ; Norway spruce ; Southwest Germany ; Empirical modeling
    ISSN: 1286-4560
    E-ISSN: 1297-966X
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  • 7
    Language: English
    In: Ecosystems, 2012, Vol.15(7), pp.1158-1172
    Description: In spite of the extensive area of bogs in the southern cone of South America, there have been very few studies on structure and dynamics of conifer bog forests in this region. Previously, it has been assumed that in the absence of intensive disturbance, the dominant conifer Pilgerodendron uviferum (D. Don) Florin would be replaced through other angiosperm species. Here we hypothesized (a) that this conifer can persist without intensive disturbances and develop into old-growth forests with continuing regeneration and (b) that high-severity disturbances through fire threaten its local persistence. To test this hypotheses, we analyzed diameter and age structure, foliar and soil nutrient levels and the light environment of old-growth and fire-disturbed P. uviferum stands on Chiloé Island (43ºS) in North Patagonia. Longevity (〉880 years), extremely slow growth (〈1 mm diameter per year) and tolerance to shade and stress are the main mechanisms of P. uviferum persistence in nutrient-poor and waterlogged conditions. Hence, old-growth P. uviferum forests are not a transitional phase in forest succession and may be maintained in the landscape for many centuries or millennia. However, in fire-disturbed stands, live trees of the species were rare and regeneration negligible, showing that high-severity fires can eliminate the species from parts of the landscape, where neither propagules nor seed trees survive. This underpins the importance of biological legacies such as seed trees for the recovery of disturbed sites, and points to the need for active restoration approaches to restore fire-degraded P. uviferum forests.
    Keywords: Chiloé Island ; Forest dynamics ; Light availability ; N/P ratio ; Persistence mechanisms ; Sphagnum
    ISSN: 1432-9840
    E-ISSN: 1435-0629
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  • 8
    Language: English
    In: Ecosystems, 2018, Vol.21(6), pp.1215-1229
    Description: Norway spruce is a widely cultivated species in Central Europe; however, it is highly susceptible to droughts, which are predicted to become more frequent in the future. A solution to adapt spruce forests to droughts could be the conversion to mixed-species stands containing species which are less sensitive to drought and do not increase the drought stress in spruce. Here we assessed the drought response of spruce and the presumably more drought-tolerant silver fir and Douglas fir in mixed-conifer stands. We measured tree ring widths of 270 target trees, which grew in mixed and mono-specific neighbourhoods in 18 managed stands in the Black Forest, to quantify the complementarity effects caused by species interactions on growth during the extreme drought event of 2003 and for a number of years with “normal” growth and climatic conditions. Mixed-species neighbourhoods did not significantly affect tree ring growth in normal years. However, during the drought, silver fir benefitted from mixing, while Douglas fir was more drought-stressed in the mixture. The drought response of spruce was dependent on the density and species composition of the neighbourhood, showing both positive and negative mixing effects. Mixed stands containing these tree species could improve adaptation to drought because the risks of extreme events are spread across species, and the performance of individual species is improved. Our knowledge about specific species interactions needs to be improved to manage tree mixtures more effectively with regard to the participating species and stand density.
    Keywords: Abies alba ; biodiversity ; climate change ; dendroecology ; drought stress ; Europe ; forest management ; mixed forest ; Picea abies ; Pseudotsuga menziesii
    ISSN: 1432-9840
    E-ISSN: 1435-0629
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  • 9
    Language: English
    In: European Journal of Forest Research, 2012, Vol.131(1), pp.229-247
    Description: Storms represent the most important disturbance factor in forests of Central Europe. Using data from long-term growth and yield experiments in Baden-Wuerttemberg (south-western Germany), which permit separation of storm damage from other causes of mortality for individual trees, we investigated the influence of soil, site, forest stand, and tree parameters on storm damage, especially focusing on the influence of silvicultural interventions. For this purpose, a four-step modeling approach was applied in order to extract the main risk factors for (1) the general stand-level occurrence of storm damage, (2) the occurrence of total stand damage, and (3) partial storm damage within stands. The estimated stand-level probability of storm damage obtained in step 3 was then offset in order to describe the damage potential for the individual trees within each partially damaged stand (4). Generalized linear mixed models were applied. Our results indicate that tree species and stand height are the most important storm risk factors, also for characterizing the long-term storm risk. Additionally, data on past timber removals and selective thinnings appear more important for explaining storm damage predisposition than for example stand density, soil and site conditions or topographic variables. When quantified with a weighting method (summarizing the relative weight of single predictors or groups of predictors), removals could explain up to 20% of storm risk. The stepwise modeling approach proved an important methodological feature of the analysis, since it enabled consideration of the large number of observations without damage (“zero inflation”) in a statistically correct way. These results form a reliable basis for quantifying forest management’s direct impact on the risk of storm damage.
    Keywords: Long-term storm damage ; Windthrow ; Generalized linear mixed models ; Empirical modeling ; Silviculture ; Thinning
    ISSN: 1612-4669
    E-ISSN: 1612-4677
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  • 10
    Language: English
    In: Annals of Forest Science, 2014, Vol.71(3), pp.381-393
    Description: CONTEXT : Cluster planting has become a conventional establishment method for oaks in Central Europe, where the spacing of seedlings within clusters varies between ‘nests’ (0.2 × 0.2� m) and ‘groups’ (1 × 1� m). Although the space between clusters is expected to fill with voluntary regeneration, its competitive effect on oak growth and quality had not been studied yet. AIMS : The aim of the study was to analyse the effects of inter- and intraspecific interactions on growth and quality of oaks grown in cluster plantings by quantifying the influence of neighbouring trees. In addition, we analysed whether the spatial position of oaks within groups (inner section or periphery) influenced their quality development. METHODS : Using Hegyi’s competition index, the influence of competition from intra- and interspecific trees from early, mid- and late-successional species, on diameter, height, slenderness and quality (length of branch-free bole) of 10- to 26-year-old oaks grown in cluster planting stands was quantified at seven sites in Baden-Württemberg and Hessen, Germany. RESULTS : In general, mid- and late-successional trees exerted a stronger competitive influence on growth of target oaks in clusters than the conspecific oaks and pioneer tree species. Oak quality development benefited from intraspecific competition, but self-pruning was not further promoted through additional interspecific competition. Within groups, inner oaks had a higher probability of developing into potential future crop trees than outer oaks. CONCLUSION : Our study showed that intra- and interspecific competition had different effects on target oak trees and that these effect differed between nest and group plantings. The development of naturally regenerated and planted trainer trees in group plantings should be monitored carefully and if necessary be controlled through thinning or pollarding. ; p. 381-393.
    Keywords: Intraspecific competition ; Interspecific competition ; Facilitation ; Stem quality ; Cluster planting ; Generalized linear models
    ISSN: 1286-4560
    E-ISSN: 1297-966X
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