Methodological tests of the use of trace elements as tracers to assess root activity

peer-reviewedN.J.H. was funded by the Irish Research Council, co-funded by Marie Curie Actions under FP7. The field experiments A, B and G were supported by the European Community's Seventh Framework Programme (FP7/2007-2013) under the grant agreements FP7-266018 (AnimalChange) and FP7- 244983 (MultiSward). Experiment F was supported by the German Science Foundation (FOR 456).Background and aims There is increasing interest in how resource utilisation in grassland ecosystems is affected by changes in plant diversity and abiotic conditions. Research to date has mainly focussed on aboveground responses and there is limited insight into belowground processes. The aim of this study was to test a number of assumptions for the valid use of the trace elements caesium, lithium, rubidium and strontium as tracers to assess the root activity of several grassland species. Methods We carried out a series of experiments addressing the reliability of soil labelling, injection density, incubation time, application rate and the comparability of different tracers in a multiple tracer method. Results The results indicate that it is possible to achieve a reliable labelling of soil depths. Tracer injection density affected the variability but not the mean level of plant tracer concentrations. Tracer application rates should be based on pilot studies, because of site- and species-specific responses. The trace elements did not meet prerequisites to be used in a multiple tracer method. Conclusions The use of trace elements as tracers is potentially a very useful tool to give insight into plant root activity at different soil depths. This work highlights some of the main benefits and pitfalls of the method and provides specific recommendations to assist the design of tracer experiments and interpretation of the results.N.J.H. was funded by the Irish Research Council, co-funded by Marie Curie Actions under FP7. The field experiments A, B and G were supported by the European Community's Seventh Framework Programme (FP7/2007-2013) under the grant agreements FP7-266018 (AnimalChange) and FP7- 244983 (MultiSward). Experiment F was supported by the German Science Foundation (FOR 456).European Unio

Vitality of bog pine and colonising Norway spruce along environmental gradients within a bog

Bog pine is an endangered species in Europe as drainage of bogs permits colonisation by Norway spruce, resulting in severe bog pine habitat loss in marginal bog forests, and a habitat shift towards the bog centre where growing conditions are extreme. Thus, we investigated the physiological causes that limit bog pine regeneration at the bog margins and growth in the centre. We measured needle nitrogen concentration, chlorophyll content, photosynthetic capacity and the morphological traits of bog pine and spruce along transects from the centre to the margin of a bog in the Black Forest, Germany. Needle nitrogen and chlorophyll contents in the bog pine increased from the centre to the margin. However, photosynthesis was independent of chlorophyll content indicating that other factors, such as light rather than nutrients, may limit regeneration of bog pine. Vitality of bog pine was highest at the edge of the bog centre. This zone appears to be a compromise between nutrient limitation and shallow water levels on the one hand, and light limitation caused by spruce on the other. Therefore, in order to conserve bog pine, it is necessary to maintain wet and open bog forests that cannot be colonised by spruce

Tree species diversity and forest productivity -

Scientists and policy makers have looked at Mediterranean forest biodiversity mainly from a conservation point of view. But biodiversity is increasingly considered an important aspect of ecosystem functioning. In this presentation, we review more specifically diversity-productivity relationships in forests. But it's not an easy task, because the problem is that forest condition and growth are determined by many interacting environmental and management factors. In this context, developing an international network of such experiments, including Mediterranean sites, would be very useful

Relation entre diversité des espèces d'arbres et productivité des forêts -

Les scientifiques et les décideurs se sont penchés sur la biodiversité des forêts méditerranéennes essentiellement d'un point de vue de la conservation. Mais la biodiversité est de plus en plus considérée comme un facteur important du fonctionnement même des écosystèmes. Cet article examine plus particulièrement la relation diversité-productivité en forêt. Mais la tâche n'est pas facile car l'état de la forêt et sa croissance sont déterminés par de nombreux facteurs interdépendants, environnementaux et de gestion. Dans ce cadre, un dispositif expérimental très spécifique serait utile via le développement d'un réseau international d'expériences et, tout particulièrement, sur certains sites méditerranéens

Species richness influences the spatial distribution of trees in European forests

The functioning of plant communities is strongly influenced by the number of species in the community and their spatial arrangement. This is because plants interact with their nearest neighbors and this interaction is expected to be stronger when the interacting individuals are ecologically similar in terms of resource use. Recent evidence shows that species richness alters the balance of intra- versus interspecific competition, but the effect of species richness, and phylogenetic and functional diversity on the spatial pattern of the plant communities remain less studied. Even far, how forest stand structure derived from past management practices can influence the relationship between species richness and spatial pattern is still unknown. Here, we evaluate the spatial distribution of woody individuals (DBH >7.5 cm) in 209 forest stands (i.e. plots) with an increasing level of species richness (from 1 up to 10 species) in six forest types along a latitudinal gradient in Europe. We used completely mapped plots to investigate the spatial pattern in each forest stand with point pattern techniques. We fitted linear models to analyze the effect of species richness (positively correlated with phylogenetic diversity) and functional diversity on tree spatial arrangements. We also controled this relationship by forest type and stand structure as a proxy of the management legacy. Our results showed a generalized positive effect of species richness and functional diversity on the degree of spatial clustering of trees, and on the spatial independence of tree sizes regardless of the forest type. Moreover, current tree spatial arrangements were still conditioned by its history of management; however its effect was independent of the number of species in the community. Our study showed that species richness and functional diversity are relevant attributes of forests influencing the spatial pattern of plant communities, and consequently forest functioning. © 2019 Nordic Society Oikos. Published by John Wiley & Sons LtdThis research was supported by the FunDivEUROPE project, receiving funding from the European Union Seventh Framework Programme (FP7/2007–2013) under grant agreement no.265171, the Spanish‐funded project REMEDINAL TE‐CM S2018/EMT‐4338 and COMEDIAS FEDER/Ministerio de Ciencia, Innovación y Universidades – Agencia Estatal de Investigación/_Proyecto CGL2017‐83170‐R. RB was funded by a Marie Skłodowska‐Curie Intra‐European fellowship (grant agreement no. 302445)

Biodiversity-stability relationships strengthen over time in a long-term grassland experiment.

Numerous studies have demonstrated that biodiversity drives ecosystem functioning, yet how biodiversity loss alters ecosystems functioning and stability in the long-term lacks experimental evidence. We report temporal effects of species richness on community productivity, stability, species asynchrony, and complementarity, and how the relationships among them change over 17 years in a grassland biodiversity experiment. Productivity declined more rapidly in less diverse communities resulting in temporally strengthening positive effects of richness on productivity, complementarity, and stability. In later years asynchrony played a more important role in increasing community stability as the negative effect of richness on population stability diminished. Only during later years did species complementarity relate to species asynchrony. These results show that species complementarity and asynchrony can take more than a decade to develop strong stabilizing effects on ecosystem functioning in diverse plant communities. Thus, the mechanisms stabilizing ecosystem functioning change with community age

Biodiversity–stability relationships strengthen over time in a long-term grassland experiment

Numerous studies have demonstrated that biodiversity drives ecosystem functioning, yet how biodiversity loss alters ecosystems functioning and stability in the long-term lacks experimental evidence. We report temporal effects of species richness on community productivity, stability, species asynchrony, and complementarity, and how the relationships among them change over 17 years in a grassland biodiversity experiment. Productivity declined more rapidly in less diverse communities resulting in temporally strengthening positive effects of richness on productivity, complementarity, and stability. In later years asynchrony played a more important role in increasing community stability as the negative effect of richness on population stability diminished. Only during later years did species complementarity relate to species asynchrony. These results show that species complementarity and asynchrony can take more than a decade to develop strong stabilizing effects on ecosystem functioning in diverse plant communities. Thus, the mechanisms stabilizing ecosystem functioning change with community age

Designing forest biodiversity experiments : general considerations illustrated by a new large experiment in subtropical China

Funded by German Research Foundation. Grant Number: DFG FOR 891/1 and 2 National Natural Science Foundation of China. Grant Numbers: NSFC 30710103907, 30930005, 31170457 , 31210103910 Swiss National Science Foundation (SNSF) Sino-German Centre for Research Promotion in BeijingPeer reviewedPublisher PD