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  • Species Diversity
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  • 1
    In: Journal of Ecology, May 2017, Vol.105(3), pp.761-774
    Description: Promoting mixed‐species forests is an important strategy for adaptation and risk reduction in the face of global change. Concurrently, a main challenge in ecology is to quantify the effects of species diversity on ecosystem functioning. In forests, the effects of individual tree species on ecosystem functions depend largely on their dimensions, which are commonly predicted using allometric equations. However, little is known about how diversity influences allometry or how to incorporate this effect into allometric equations. Ignoring the effects of interspecific interactions on allometric relationships may result in severely biased predictions. This study examined the effects of tree‐species diversity, competition and tree social status on crown‐projection area (cpa), height (h) and live‐crown length (lcl) of trees using a European‐wide data set containing 17 target species and 12 939 trees. The cpa, h and lcl were predicted as functions of stem diameter at 1·3 m, tree‐species diversity, tree height relative to the stand mean height (rh) and a competition index (CI) that accounted for stand density and interspecific differences in competitive ability based on species‐specific wood density or shade tolerance. Averaged across species, diameter had the greatest effect on cpa and lcl, followed by the competition index, while rh had the greatest effect on lcl. Tree‐species diversity had the smallest effect on cpa, h and lcl. Interspecific variability in cpa, h or lcl responses to diversity, CI, or rh was sometimes related to wood density or shade tolerance. Synthesis. This study shows the strong influence of stand structure and species composition on allometric relationships. These influences can be quantified using measures of competition, tree‐species diversity and relative tree height so that general equations can be developed for a given species to be applied to a wide range of species compositions and stand structures. This new approach will greatly improve predictions of biomass and carbon stocks in structurally and compositionally diverse forests. Tree allometry is influenced by, and influences, many forest functions. However, little is known about how allometry of a given species varies with forest structure and tree‐species composition, or whether any interspecific differences in allometric responses relate to species traits. Using a European wide data set, this study shows how stand structural characteristics and tree‐species diversity can influence tree allometry.
    Keywords: Biodiversity ; Biomass Partitioning ; Complementarity ; Plant Allometry ; Plant–Plant Interactions ; Stand Structure ; Tree Height
    ISSN: 0022-0477
    E-ISSN: 1365-2745
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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
    In: PLoS ONE, 2016, Vol.11(12)
    Description: Tree diversity in forests is an important driver of ecological processes including herbivory. Empirical evidence suggests both negative and positive effects of tree diversity on herbivory, which can be, respectively, attributed to associational resistance or associational susceptibility. Tree diversity experiments allow testing for associational effects, but evidence regarding which pattern predominates is mixed. Furthermore, it is unknown if herbivory on tree species of native vs. exotic origin is influenced by changing tree diversity in a similar way, or if exotic tree species escape natural enemies, resulting in lower damage that is unrelated to tree diversity. To address these questions, we established a young tree diversity experiment in temperate southwestern Germany that uses high planting density (49 trees per plot; plot size 13 m 2 ). The species pool consists of six congeneric species pairs of European and North American origin (12 species in total) planted in monocultures and mixtures (1, 2, 4, 6 species). We assessed leaf damage by leaf-chewing insects on more than 5,000 saplings of six broadleaved tree species. Plot-level tree species richness increased leaf damage, which more than doubled from monocultures to six-species mixtures, strongly supporting associational susceptibility. However, leaf damage among congeneric native and exotic species pairs was similar. There were marked differences in patterns of leaf damage across tree genera, and only the genera likely having a predominately generalist herbivore community showed associational susceptibility, irrespective of the geographical origin of a tree species. In conclusion, an increase in tree species richness in young temperate forests may result in associational susceptibility to feeding by generalist herbivores.
    Keywords: Research Article ; Biology And Life Sciences ; Biology And Life Sciences ; Ecology And Environmental Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Ecology And Environmental Sciences ; Biology And Life Sciences ; Biology And Life Sciences ; Ecology And Environmental Sciences ; Biology And Life Sciences ; Research And Analysis Methods ; Biology And Life Sciences ; Ecology And Environmental Sciences ; Biology And Life Sciences ; Ecology And Environmental Sciences ; Biology And Life Sciences ; Biology And Life Sciences
    E-ISSN: 1932-6203
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  • 5
    In: Journal of Animal Ecology, January 2016, Vol.85(1), pp.213-226
    Description: Arthropod communities in water‐filled tree holes may be sensitive to impacts of forest management, for example via changes in environmental conditions such as resource input. We hypothesized that increasing forest management intensity (ForMI) negatively affects arthropod abundance and richness and shifts community composition and trophic structure of tree hole communities. We predicted that this shift is caused by reduced habitat and resource availability at the forest stand scale as well as reduced tree hole size, detritus amount and changed water chemistry at the tree holes scale. We mapped 910 water‐filled tree holes in two regions in Germany and studied 199 tree hole inhabiting arthropod communities. We found that increasing ForMI indeed significantly reduced arthropod abundance and richness in water‐filled tree holes. The most important indirect effects of management intensity on tree hole community structure were the reduced amounts of detritus for the tree hole inhabiting organisms and changed water chemistry at the tree hole scale, both of which seem to act as a habitat filter. Although habitat availability at the forest stand scale decreased with increasing management intensity, this unexpectedly increased local arthropod abundance in individual tree holes. However, regional species richness in tree holes significantly decreased with increasing management intensity, most likely due to decreased habitat diversity. We did not find that the management‐driven increase in plant diversity at the forest stand scale affected communities of individual tree holes, for example via resource availability for adults. Our results suggest that management of temperate forests has to target a number of factors at different scales to conserve diverse arthropod communities in water‐filled tree holes. This paper focuses on the mechanisms underlying the negative effects of forest management intensity on diversity and functional composition of arthropods. This not only improves our understanding of community assembly, but also helps to improve conservation strategies aiming at reducing ongoing species loss.
    Keywords: Aquatic Larvae ; Biodiversity Exploratories ; Community Composition ; Dispersal ; Diversity ; Habitat Filter ; Land‐Use Intensity ; Metacommunity ; Phytotelmata ; Species Sorting
    ISSN: 0021-8790
    E-ISSN: 1365-2656
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  • 6
    Language: English
    In: Biological Conservation, November 2015, Vol.191, pp.577-586
    Description: Managed forests are important landscape components in tropical regions and may contribute to biodiversity conservation. Yet, managing tropical forests sustainably requires an understanding of ecosystem responses to silvicultural interventions. We investigated how silvicultural intervention intensity affects tree species composition and diversity over 30 years in the Brazilian Amazon by comparing them to pre-logging conditions and to an unlogged control. The interventions comprised logging in 1982 and thinning in 1993–1994 and ranged in intensity from 19 to 53% reduction in the original basal area (BA). Trees with a diameter at breast height (DBH) ≥ 5 cm were measured on eight occasions in 41 permanent sample plots of 0.25 ha each. Silvicultural intervention intensity influenced both tree species composition and its trajectory within 30 years. In contrast, tree species diversity was not impaired. High intervention intensities (with BA reduction 〉 6.6 m ha ) had a substantial influence on the community of trees (DBH ≥ 10 cm), which did not show signs of return to pre-logging species composition. The reduction of BA through harvesting damage and thinning had a stronger effect on species composition than logging of mature trees itself. Thus, damage should be kept to a minimal level and strong thinning interventions should be avoided. This may enhance ecosystem recovery and maintenance of biodiversity at other trophic levels. Since current permitted harvesting intensities in the Brazilian Amazon are lower than the lowest intensity examined in our study, legal harvesting practices are unlikely to cause substantial, long-term changes in tree species composition.
    Keywords: Brazilian Amazon ; Forest Recovery ; Selective Logging ; Species Diversity ; Stand Thinning ; Time-Constrained Clustering ; Agriculture ; Biology ; Ecology
    ISSN: 0006-3207
    E-ISSN: 18732917
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  • 7
    Language: English
    In: Forests, 01 February 2018, Vol.9(3), p.104
    Description: Tree-related microhabitats are an important determinant of forest biodiversity. Habitat trees, which typically provide many microhabitats such as hollows, crown dead wood, etc., are therefore selected to maintain those structural attributes within managed forests. To what extent the occurrence...
    Keywords: Tree Microhabitats ; Structural Diversity ; Mixed Mountain Forest ; Habitat Tree ; Retention Tree ; Forestry
    E-ISSN: 1999-4907
    Source: Directory of Open Access Journals (DOAJ)
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  • 8
    Language: English
    In: Forests, 01 November 2016, Vol.7(11), p.289
    Description: Recent studies have reported superior tree quality and comparable tree growth of oaks planted in group compared with row planting. However, a comparative assessment of the potential future crop trees (PFCTs) between group and row planting is still lacking. Here, we compared the density and...
    Keywords: Oak Regeneration ; Group Planting ; Potential Future Crop Tree ; Tree Quality and Growth ; Forest Restoration ; Low-Density Planting ; Forestry
    E-ISSN: 1999-4907
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  • 9
    In: Canadian Journal of Forest Research, 2016, Vol.47(2), pp.139-148
    Description: Oaks ( Quercus spp.) are becoming increasingly important for future forest management as the climate in central Europe warms. Owing to the high costs of conventional row planting, artificial oak stand establishment in the form of “clusters” became popular in central Europe beginning in the 1970s. In cluster plantings, oaks are planted either in groups of ca. 20–25 at 1 m spacing between trees (i.e., group planting) or in denser groups with 20–30 oaks·m −2 (i.e., nest planting). In both cases, the clusters are spaced apart at a distance that represents the target density of future crop trees. A comprehensive review of the history, growth, tree quality development, and economic aspects of oak cluster plantings suggests that initial growing space was the most important factor influencing development of oaks in clusters. Consequently, survival, growth, quality, and biomass production were comparable in group and row plantings but lower in nest plantings. In addition, group plantings resulted in greater stand-level tree species diversity than nest or row plantings. We conclude that oak group planting is a comparatively inexpensive option for the artificial regeneration of oak-dominated broadleaved forests for a range of situations such as reforestation of disturbed areas or the afforestation of abandoned agricultural land. Future research needs regarding development and tending of forests established by oak group planting are highlighted.
    Description: L’importance des chênes ( Quercus spp.) pour l’aménagement forestier du futur augmente avec le réchauffement du climat de l’Europe centrale. En raison des coûts élevés de la plantation conventionnelle en rangée, l’établissement de chênaies artificielles selon une répartition par grappes est devenu populaire en Europe centrale au cours des années 1970. Dans les plantations en grappes, les chênes sont plantés en groupes d’environ 20 à 25 avec un espacement d’un mètre entre les arbres (c.-à-d. la plantation en groupes) ou en groupes plus denses de 20 à 30 chênes par m 2 (c.-à-d. la plantation en nids). Dans les deux cas, l’espacement entre les grappes est déterminé de façon à obtenir la densité cible des arbres d’avenir. Une analyse complète de l’histoire, de la croissance, du développement de la qualité des arbres et des aspects économiques de la plantation de chênes en grappes indique que l’espacement initial entre les plants est le facteur qui influence le plus le développement des chênes dans les grappes. Ainsi, la survie, la croissance, la qualité et la production de biomasse étaient semblables dans les plantations en groupes et en rangées, mais étaient moindres dans les plantations en nids. De plus, à l’échelle du peuplement, une plus grande diversité en espèces d’arbres a été observée dans les plantations en groupes comparativement aux plantations en nids ou en rangées. Nous concluons que la plantation de chênes en groupes est une option relativement peu coûteuse pour la régénération artificielle des forêts feuillues dominées par les chênes pour une variété de situations incluant le reboisement de zones perturbées ou le boisement de terres agricoles abandonnées. Nous mettons en évidence les besoins de recherche concernant le développement et l’entretien des forêts établies à l’aide de la plantation de chênes en groupes. [Traduit par la Rédaction]
    Keywords: Oak Regeneration ; Tree Quality And Growth ; Species Diversity And Productivity ; Plant Competition ; Forest Restoration ; Régénération Du Chêne ; Croissance Et Qualité Des Arbres ; Diversité Et Productivité Des Espèces ; Compétition Végétale ; Restauration Forestière
    ISSN: 0045-5067
    E-ISSN: 1208-6037
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  • 10
    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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