1,721,032 research outputs found
Does root competition asymmetry increase with water availability?
No full textBackground: Below-ground competition as a major structuring force in plant communities can be either symmetric or asymmetric with important consequences for the coexistence of plants. It is a matter of controversy whether asymmetry in competition increases with resource availability or not. Aims: This study tested the hypotheses that root competition between mature Fagus sylvatica and Quercus petraea trees is asymmetric and that asymmetry is more pronounced in non-water-limited environments. Methods: Initially equal-sized tree fine roots were grown for 365-390 days in root growth chambers in situ and exposed to competition by either a conspecific or an allospecific root. Relative root growth rate was used to determine asymmetry in root competition. Different soil moisture regimes were considered by conducting a throughfall reduction experiment and by including data from earlier experiments with contrasting moisture regimes. Results: The competitive interaction between Fagus and Quercus fine roots is asymmetric; root morphology appears to depend on the presence of a competitor; and asymmetry in root competition increases with increasing soil moisture availability. Conclusions: Below-ground competition in temperate broad-leaved mixed forests can be as asymmetric as competition for light, with asymmetry decreasing with increasing water shortage
Root and branch hydraulic functioning and trait coordination across organs in drought-deciduous and evergreen tree species of a subtropical highland forest
No full text<p xmlns:mml="http://www.w3.org/1998/Math/MathML">Vessel traits are key in understanding trees’ hydraulic efficiency, and related characteristics like growth performance and drought tolerance. While most plant hydraulic studies have focused on aboveground organs, our understanding of root hydraulic functioning and trait coordination across organs remains limited. Furthermore, studies from seasonally dry (sub-)tropical ecosystems and mountain forests are virtually lacking and uncertainties remain regarding potentially different hydraulic strategies of plants differing in leaf habit. Here, we compared wood anatomical traits and specific hydraulic conductivities between coarse roots and small branches of five drought-deciduous and eight evergreen angiosperm tree species in a seasonally dry subtropical Afromontane forest in Ethiopia. We hypothesized that largest vessels and highest hydraulic conductivities are found in roots, with greater vessel tapering between roots and equally-sized branches in evergreen angiosperms due to their drought-tolerating strategy. We further hypothesized that the hydraulic efficiencies of root and branches cannot be predicted from wood density, but that wood densities across organs are generally related. Root-to-branch ratios of conduit diameters varied between 0.8 and 2.8, indicating considerable differences in tapering from coarse roots to small branches. While deciduous trees showed larger branch xylem vessels compared to evergreen angiosperms, root-to-branch ratios were highly variable within both leaf habit types, and evergreen species did not show a more pronounced degree of tapering. Empirically determined hydraulic conductivity and corresponding root-to-branch ratios were similar between both leaf habit types. Wood density of angiosperm roots was negatively related to hydraulic efficiency and vessel dimensions; weaker relationships were found in branches. Wood density of small branches was neither related to stem nor coarse root wood densities. We conclude that in seasonally dry subtropical forests, similar-sized coarse roots hold larger xylem vessels than small branches, but the degree of tapering from roots to branches is highly variable. Our results indicate that leaf habit does not necessarily influence the relationship between coarse root and branch hydraulic traits. However, larger conduits in branches and a low carbon investment in less dense wood may be a prerequisite for high growth rates of drought-deciduous trees during their shortened growing season. The correlation of stem and root wood densities with root hydraulic traits but not branch wood points toward large trade-offs in branch xylem towards mechanical properties.</p>
Belowground competition in a broad-leaved temperate mixed forest: pattern analysis and experiments in a four-species stand
No full textWe investigated fine root biomass and distribution patterns in a species-rich temperate Carpinus-Quercus-Fagus-Tilia forest and searched for experimental evidence of symmetry or asymmetry in belowground competition. We conducted extensive root coring and applied the recently introduced in situ-root growth chamber technique for quantifying fine root growth under experimentally altered intra- and interspecific root neighbourhoods in the intact stand. In 75% of all soil cores, fine roots of more than two tree species were present indicating a broad overlap of the root systems of neighbouring trees. Quercus trees had more than ten times less fine root biomass in relation to aboveground biomass or productivity (stem growth) and a much higher leaf area index/root area index ratio than Carpinus, Fagus and Tilia trees. The root growth chamber experiments indicated a high belowground competitive ability of Fagus in interspecific interactions, but a low one of Quercus. We conclude that (1) interspecific root competition is ubiquitous in this mixed stand, (2) root competition between trees can be clearly asymmetric, and (3) tree species may be ranked according to their belowground competitive ability. Fagus was found to be the most successful species in belowground competition which matches with its superiority in aboveground competition in this forest community
Plant roots and spectroscopic methods–analysing species, biomass and vitality
No full textIn order to understand plant functioning, plant community composition and terrestrial biogeochemistry it is decisive to study standing root biomass, (fine) root dynamics and interactions below ground. While most plant taxa can be identified by visual criteria above ground, roots show less distinctive features. Furthermore, root systems of neighbouring plants are rarely spatially segregated; thus, most soil horizons and samples hold roots of more than one species necessitating root sorting according to taxa.In the last decades, various approaches, ranging from anatomical and morphological analyses to differences in chemical composition and DNA sequencing were applied to discern species’ identity and biomass below ground. Among those methods, a variety of spectroscopic methods was used to detect differences in the chemical composition of roots. In this review, spectroscopic methods used to study root systems of herbaceous and woody species in excised samples or in situ will be discussed. In detail, techniques will be reviewed according to their usability to discern root taxa, to determine root vitality, and to quantify root biomass non-destructively or in soil cores holding mixtures of plant roots. In addition, spectroscopic methods which may be able to play an increasing role in future studies on root biomass and related traits are highlighted
Influence of salinity on root hydraulic properties of three olive varieties
No full textThree varieties of olive, Barnea, Arbequina and Proline, varying in salt tolerance, were examined to check the sensitivity of their root system hydraulic properties to salinity. Up to three levels of saline water (EC=1.2, 4.2 and 7.5 dS m-1) were used for long-term irrigation of mature trees. Specific conductivities and embolism rates of roots and branches were estimated by low-pressure conductivity measurement; variability and plasticity of root and branch axial conductivities were calculated. Cross-sections of roots were analysed with respect to xylem anatomy. Barnea, and to a minor degree Arbequina, were found to be more salt-resistant than Proline. Axial root hydraulics under salt stress reacted in a more plastic fashion than branch conductivities. Increased specific conductivities of roots, different plasticities of root hydraulics and modifications in mean conduit diameters can be dismissed as foremost reasons of the observed differences in salt resistance. Instead, a high within-population variability in root conductivity, as found in the salt-tolerant Barnea and Arbequina varieties, coming to full effect in high conductivity roots of Barnea trees, and an increased bimodal distribution of conduit sizes may represent favourable traits to enhance water uptake in soils with heterogeneous salinity.European Unio
Influence of saline drip-irrigation on fine root and sap-flow densities of two mature olive varieties
No full textSalt stress is known to influence water use and carbon allocation in trees; however, information about the effects of salt exposure on water uptake and below-ground carbon investment is scant, especially for adult trees. Consequently, this study examined these variables in two mature olive varieties (Olea europaea L) that differ in their NaCl tolerance: Barnea (tolerant) and Proline (sensitive). Trees were irrigated using water with electrical conductivities of 1.2, 4.2 (both varieties) and 7.5 dS m(-1) (Barnea only) for 11 years. At each treatment level, we measured soil properties, root morphology, root biomass:necromass ratio, root xylem sap osmolality, and root sap-flow as well as leaf conductance and morphology. Both varieties exhibited reduced fine root biomass under salinity which was only partially compensated for by higher specific root areas under moderate salinity. Proline variety exhibited a smaller fine root system under moderate salinity than Barnea trees, likely causing the lower sap-flow density in coarse roots of Proline compared to Barnea. The higher biomass:necromass ratio of the Barnea root system under moderate salinity is indicative of lower root turnover rates and thus a more efficient carbon use than in Proline trees. Besides differences in ion exclusion capacities, the ability of the fine root system to resist the deleterious effects of salinity seems to affect the salt resistance of mature olive varieties by influencing water uptake and carbon allocation. (C) 2011 Elsevier B.V. All rights reserved.European Union; Jacob Blaustein Centre for Scientific Cooperation (BCSC
Beyond meteorological data: Modelling tree growth with ERA5-Land
Full text linkForests are increasingly impacted by climate change, affecting tree growth and carbon sequestration. Tree-ring width, closely related to tree growth, is a key climate proxy, yet models describing ring width or growth often lack comprehensive environmental data. This study assesses ERA5-Land data for tree-ring width prediction compared to automatic weather station observations, emphasizing the value of extended and global climate data. We analyzed 723 site-averaged and detrended tree-ring chronologies from two broadleaved and two gymnosperm species across Europe, integrating them with ERA5-Land climate data, CO2 concentration, and a drought index (SPEI12). A subset was compared with weather station data. For modelling interannual variations of tree-ring width we used linear models to assess parameter importance. ERA5-Land and weather-station-based models performed similarly, maintaining stable correlations and consistent errors. Models based on meteorological data from weather stations highlighted SPEI12, sunshine duration, and temperature extremes, while ERA5-Land models emphasized SPEI12, dew-point temperature (humidity), and total precipitation. CO2 positively influenced the growth of gymnosperm species. ERA5-Land facilitated broader spatial analysis and incorporated additional factors like evaporation, snow cover, and soil moisture. Monthly assessments revealed the importance of parameters for each species. Our findings confirm that ERA5-Land is a reliable alternative for modeling tree growth, offering new insights into climate-vegetation interactions. The ready availability of underutilized parameters, such as air humidity, soil moisture and temperature, and runoff, enables their inclusion in future growth models. Using ERA5-Land can therefore deepen our understanding of forest responses to diverse environmental drivers on a global scale.OA-hybri
Root taxa identification in plant mixtures – current techniques and future challenges
No full textStudying root biomass, root system distribution and belowground interactions is essential for understanding the composition of plant communities, the impact of global change, and terrestrial biogeochemistry. Most soil samples and minirhizotron pictures hold roots of more than one species or plant individual. The identification of taxa by their roots would allow species-specific questions to be posed; information about root affiliation to plant individuals could be used to determine intra-specific competition. Researchers need to be able to discern plant taxa by roots as well as to quantify abundances in mixed root samples. However, roots show less distinctive features that permit identification than aboveground organs. This review discusses the primary use of available methods, outlining applications, shortcomings and future developments. Methods are either non-destructive, e.g. visual examination of root morphological criteria in situ, or require excavated and excised root samples. Among the destructive methods are anatomical keys, chemotaxonomic approaches and molecular markers. While some methods allow for discerning the root systems of individual plants, others can distinguish roots on the functional group or plant taxa level; methods such as IR spectroscopy and qPCR allow for quantifying the root biomass proportion of species without manual sorting.Jacob Blaustein Center for Scientific Cooperation (BCSC), Israe
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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