Seasonal Variation in the Capacity for Plant Trait Measures to Predict Grassland Carbon and Water Fluxes

There is a need for accurate predictions of ecosystem carbon (C) and water fluxes in field conditions. Previous research has shown that ecosystem properties can be predicted from community abundance-weighted means (CWM) of plant functional traits and measures of trait variability within a community (FDvar). The capacity for traits to predict carbon (C) and water fluxes, and the seasonal dependency of these trait-function relationships has not been fully explored. Here we measured daytime C and water fluxes over four seasons in grasslands of a range of successional ages in southern England. In a model selection procedure, we related these fluxes to environmental covariates and plant biomass measures before adding CWM and FDvar plant trait measures that were scaled up from measures of individual plants grown in greenhouse conditions. Models describing fluxes in periods of low biological activity contained few predictors, which were usually abiotic factors. In more biologically active periods, models contained more predictors, including plant trait measures. Field-based plant biomass measures were generally better predictors of fluxes than CWM and FDvar traits. However, when these measures were used in combination traits accounted for additional variation. Where traits were significant predictors their identity often reflected seasonal vegetation dynamics. These results suggest that database derived trait measures can improve the prediction of ecosystem C and water fluxes. Controlled studies and those involving more detailed flux measurements are required to validate and explore these findings, a worthwhile effort given the potential for using simple vegetation measures to help predict landscape-scale fluxes.     

Life cycle assessment capacity roadmap (section 1): decision-making support using LCA

When life cycle assessment (LCA) results do not show a clear and certain environmental preference of one choice over one or several alternatives, current methods are limited in their ability to inform decision-makers. To address this and related cross-cutting issues, a group of LCA practitioners has been working on a roadmap for capacity development in LCA. The roadmap is identifying common needs for development in LCA, which can then be addressed by the broader LCA community. The roadmap document on decision-making support, having undergone a public comment period, outlines the current state as well as needs and milestones to ensure progress continues apace. The roadmap document, available for download, covers five main areas of development: (1) performance measures of confidence, which identify the acceptable uncertainty for study results, while minimizing expenditures; (2) selection of impact categories, an area with multiple existing methods. The roadmap suggests codifying these methods and identifying their suitability to various applications; (3) normalization; while several methods of normalization are in use, the method with the greatest acceptance in the LCA community (i.e., relying on total or per capita regional emissions/extractions) has a number of methodological drawbacks; (4) weighting, which is a form of multi-criteria decision analysis (MCDA). The broader MCDA field can enrich LCA by providing studied methods of assessing trade-offs; and (5) visualization of results. Many other LCA capacity needs would benefit from documentation. These include but are not limited to the following: addressing ill-characterized uncertainty, life cycle inventory data needs, data format needs, and tool capabilities. Other roadmapping groups are forming and are looking for practitioners to support the effort.     

Clamp-loader-helicase interaction in Bacillus. Leucine 381 is critical for pentamerization and helicase binding of the Bacillus tau protein

Recently, we revealed the architecture of the clamp-loader-helicase (tau-DnaB) complex in Bacillus by atomic force microscopy imaging and constructed a structural model, whereby a pentameric clamp-loader interacts with the hexameric helicase. Crucial to this model is the assumption that the clamp-loader forms a pentamer in the absence of other components of the clamp-loader complex such as deltadelta'. Here, we show that the Bacillus subtilis tau protein, even in the absence of deltadelta', interacts as a pentamer with the hexameric DnaB and that the L381 of tau is critical for the integrity of the tau oligomer and interaction with DnaB. The effects of the L381A mutation were confirmed by gel filtration, ultracentrifugation, circular dichroism, cross-linking studies, and genetic replacement of the dnaX gene with a mutant L381A dnaX gene in vivo. The L381A protein is able to support growth in vivo only when expressed in high quantities. Finally, despite the fact that a mutation at P465 has been reported to result in a thermosensitive gene in vivo, a P465L mutant protein interacts with DnaB in vitro suggesting that this defect is not a result of a defective tau-DnaB interaction.     

Assembling a clock for all seasons: are there M and E oscillators in the genes?

The hypothesis is advanced that the circadian pacemaker in the mammalian suprachiasmatic nucleus (SCN) is composed at the molecular level of a nonredundant double complex of circadian genes (per1, cry1, and per2, cry2). Each one of these sets would be sufficient for the maintenance of endogenous rhythmicity and thus constitute an oscillator. Each would have slightly different temporal dynamics and light responses. The per1/cry1 oscillator is accelerated by light and decelerated by darkness and thereby tracks dawn when day length changes. The per2 /cry2 oscillator is decelerated by light and accelerated by darkness and thereby tracks dusk. These M (morning) and E (evening) oscillators would give rise to the SCN's neuronal activity in an M and an E component. Suppression of behavioral activity by SCN activity in nocturnal mammals would give rise to adaptive tuning of the endogenous behavioral program to day length. The proposition-which is a specification of Pittendrigh and Daan's E-M oscillator model-yields specific nonintuitive predictions amenable to experimental testing in animals with mutations of circadian genes.     

Female sex pheromone of Cameraria ohridella Desch. and Dim. (Lepidoptera: Gracillariidae): structure confirmation,synthesis and biological activity of (8E,10Z)-8,10-tetradecadienal and some analogues

Mass spectrometric investigations confirmed the structure of the female produced sex pheromone of the horse-chestnut leafminer Cameraria ohridella Desch. and Dim. to be (8E,IOZ)-8,10-tetradecadienal. Pure samples, prepared in a straightforward synthesis, were highly attractive in field tests and proved to be suitable for monitoring of flight activities and population dynamics. In mixtures with the synthetic pheromone, analogues like 9-tridecynal and 7-dodecynyl formate were shown to reduce trap catches. In electroantennographic experiments, pheromone analogues were less active than the pheromone. 9-Tridecynal was the most EAG active analogue tested, followed by 7-dodecyn-1-yl formate and 7-undecyn-1-yl formate.     

Combining theoretical and experimental approaches to understand the circadian clock

This review is intended as a summary of our work carried out as part of the German Research Association (DFG) Center Program on Circadian Rhythms. Over the last six years, our approach to understanding circadian systems combined theoretical and experimental tools, and Gonyaulax and Neurospora have proven ideal for these efforts. Both of these model organisms demonstrate that even simple circadian systems can have multiple light input pathways and more than one rhythm generator. They have both been used to elaborate basic circadian features in conjunction with formal models. The models introduce the “zeitnehmer,” i.e., a clock-regulated input pathway, to the conceptual framework of circadian systems, and proposes networks of individual feedbacks as the basis for circadian rhythmicity.