918 research outputs found
Fragments of the Wisdom of Solomon (10:8b–d and 10:15b–17d) from Khirbet Mird (P.Leuven PAM 21 = Rahlfs 888)
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Increased leaf area expansion of hybrid poplar in elevated CO2. From controlled environments to open-top chambers and to FACE
No full textWe examined the response of hybrid poplar to elevated CO2 in contrasting growth environments: controlled environment chamber (CE), open-top chamber (OTC) and poplar free air CO2 enrichment (POPFACE) in order to compare short versus long-term effects and to determine whether generalisations in response are possible for this fast growing tree. Leaf growth, which for poplar is an important determinant of stemwood productivity was followed in all environments, as were the determinants of leaf growth—cell expansion and cell production. Elevated CO2 (550–700 ?mol mol?1, depending on environment) resulted in an increase in final leaf size for Populus trichocarpa×Populus deltoides (Populus×interamericana) and P. deltoides×Populus nigra (Populus×euramericana), irrespective of whether plants were exposed during a short-term CE glasshouse study (90 days), a long-term OTC experiment (3 years) or during the first year of a POPFACE experiment. An exception was observed in the closed canopy POPFACE experiment, where final leaf size remained unaltered by CO2. Increased leaf extension rate was observed in elevated CO2 in all experiments, at some point during leaf development, as determined by leaf length. Again the exception were the POPFACE experiment, where effects were not statistically significant. Leaf production and specific leaf area (SLA) were increased and decreased, respectively, on five out of six occasions, although both were only statistically significant on two occasions and interestingly for SLA never in the FACE experiment. Although both cell expansion and cell production were sensitive to CO2 concentration, effects appeared highly dependent on growth environment and genotype. However, increased leaf cell expansion in elevated CO2 was often associated with changes in the biophysical properties of the cell wall, usually increased cell wall plasticity. This research has shown that enhanced leaf area development was a consistent response to elevated CO2 but that the magnitude of this response is likely to decline, in long-term exposure to elevated CO2. Effects on SLA and leaf production suggest that CE and OTC experiments may not always provide good predictors of the ‘qualitative’ effects of elevated CO2 in long-term ecosystem experiments
Photosynthetic acclimation to elevated CO2 in poplar grown in glasshouse cabinets or in open top chambers depends on duration of exposure
No full textThe effects of elevated CO2 were studied on the photosynthetic gas exchange behaviour and leaf physiology of two contrasting poplar (Populus) hybrids grown and treated in open top chambers (OTCs in Antwerp, Belgium) and in closed glasshouse cabinets (GHCs in Sussex, UK). The CO2 concentrations used in the OTCs were ambient and ambient +350 µmol mol–1 while in the GHCs they were c. 360 µmol mol–1 versus 719 µmol mol–1. Measurements of photosynthetic gas exchange were made for euramerican and interamerican poplar hybrids in combination with measurements of dark respiration rate and Rubisco activity. Significant differences in the leaf anatomy and structure (leaf mass per area and chlorophyll content) were observed between the leaves grown in the OTCs and those grown in the GHCs. Elevated CO2 stimulated net photosynthesis in the poplar hybrids after 1 month in the GHCs and after 4 months in the OTCs, and there was no evidence of downward acclimation (or down-regulation) of photosynthesis when the plants in the two treatments were measured in their growth CO2 concentration. There was also no evidence of down-regulation of Rubisco activity and there were even examples of increases in Rubisco activity. Rubisco exerted a strong control over the light-saturated rate of photosynthesis, which was demonstrated by the close agreement between observed net photosynthetic rates and those that were predicted from Rubisco activities and Michaelis-Menten kinetics. After 17 months in elevated CO2 in the OTCs there was a significant loss of Rubisco activity for one of the hybrid clones, i.e. Beaupré, but not for clone Robusta. The effect of the CO2 measurement concentration (i.e. the short-term treatment effect) on net photosynthesis was always larger than the effect of the growth concentration in both the OTCs or GHCs (i.e. the longterm growth CO2 effect), with one exception. For the interamerican hybrid Beaupré dark respiration rates in the OTCs were not significantly affected by the elevated CO2 concentrations. The results suggest that for rapidly growing tree species, such as poplars, there is little evidence for downward acclimation of photosynthesis when plants are exposed to elevated CO2 for up to 4 months; longer term exposure reveals loss of Rubisco activity
Sustainability reporting in public sector organisations: Exploring the relation between the reporting process and organisational change management for sustainability
No full textSustainability Reporting has become a key element in different organisations. Although there have been a number of academic publications discussing the adoption of sustainability reports in the public sector, their numbers have been quite low when compared to those focussing on corporate reports. Additionally, there has been little research on the link between sustainability reporting in Public Sector Organisations (PSOs) and Organisational Change Management for Sustainability (OCMS). This paper focuses on the contribution of sustainability reporting to OCMS. A survey was sent to all PSOs that have published at least one sustainability report based on the GRI guidelines. The study provides a critical analysis of the relation between sustainability reporting and OCMS in PSOs, including the drivers for reporting, the impacts on organisation change management, and the role of stakeholders in the process. Despite still lagging in sustainability reporting journey, PSOs are starting to use sustainability reporting as a communication tool, and this could drive organisational changes for sustainability
Petiole length and biomass investment in support modify light-interception efficiency in dense poplar plantations
No full textLeaf architecture, stand leaf area index and canopy light interception were studied in 13 poplar clones growing in a second rotation of a coppice plantation, to determine the role of leaf architectural attributes on canopy light-harvesting efficiency and to assess biomass investment in leaf support tissue. Stand leaf area index (L) varied from 2.89 to 6.99, but L was only weakly associated with canopy transmittance (TC). The weak relationship between TC and L was a result of a higher degree of foliage aggregation at larger values of L, leading to lower light-interception efficiency in stands with greater total leaf area. We observed a strong increase in leaf aggregation and a decrease in light-harvesting efficiency with decreasing mean leaf petiole length (PL) but not with leaf size, possibly because, in cordate or deltoid poplar leaves, most of the leaf area is located close to the petiole attachment to the lamina. Although PL was the key leaf characteristic of light-harvesting efficiency, clones with longer petioles had larger biomass investments in petioles, and there was a negative relationship between PL and L, demonstrating that enhanced light harvesting may lead to an overall decline in photosynthesizing leaf surface. Upper-canopy leaves were generally larger and had greater dry mass (MA) and nitrogen per unit area (NA) than lower-canopy leaves. Canopy plasticity in MA and NA was higher in clones with higher foliar biomass investment in midrib, and lower in clones with relatively longer petioles. These relationships suggest that there is a trade-off between photosynthetic plasticity and biomass investment in support, and also that high light-harvesting efficiency may be associated with lower photosynthetic plasticity. Our results demonstrate important clonal differences in leaf aggregation that are linked to leaf structure and biomass allocation patterns within the leaf
PowerLAPIM: An application to conduct power analysis for linear and quadratic longitudinal actor-partner interdependence models in intensive longitudinal dyadic designs
No full textsponsorship: The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The research presented in this article was supported by research grants from the Fund for Scientific Research-Flanders (FWO; Project No. G0C9821N) and from the Research Council of KU Leuven (C14/19/054; iBOF/21/090) awarded to E. Ceulemans. (Fund for Scientific Research-Flanders (FWO)|G0C9821N, Research Council of KU Leuven|C14/19/054, Research Council of KU Leuven|iBOF/21/090)status: Publishe
Carbon budget of Pinus sylvestris saplings after four years of exposure to elevated atmospheric carbon dioxide concentration
No full textTo study the responses of Scots pine (Pinus sylvestris L.), a commercially important tree species in Europe, to future increases in atmospheric CO2 concentration [CO2]), we Grew saplings for 4 years in the ground in open-top chambers in ambient or ambient + 400 [mumol mol(-1) CO2, without supplemental addition of nutrients and water. Carbon (C) budgets were developed for trees in both CO2 treatments based on productivity and biomass data obtained from destructive harvests at the end of the third and fourth years of treatment, and simulations of annual gross photosynthesis (P-tot) and maintenance respiration by the model MAESTRA.
Simulated P-tot was enhanced by elevated [CO2], despite significant down-regulation of photosynthetic capacity. The subsequent increase in C uptake was allocated primarily to tissues with limited longevity (needles and fine roots), which explains why the measured annual increment in woody biomass did not differ between CO, treatments. Thus, our results suggest that accelerated stem growth only occurs in the first 2 years in the presence of elevated [CO2] and that forest rotations will not be shortened significantly in response to increasing [CO2].
In elevated [CO2], a higher proportion of available C was allocated below ground, resulting in altered biomass distribution patterns. In trees of equal size, measured ratios of fine root/ needle biomass and belowground/aboveground biomass were almost twice as large in the elevated [CO2] treatment. Although there are uncertainties in scaling from saplings to mature canopies, the data indicate that, in nutrient-limited Scots pine forests, elevated [CO2] is unlikely to accelerate tree Growth significantly, but is likely to increase C inputs to soil
Elevated CO2 concentration, fertilization and their interaction: growth simulation in a short-rotation poplar coppice (EUROFACE)
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