Tree-based intercropping systems increase growth and nutrient status of hybrid poplar: A case study from two Northeastern American experiments

Tree-based intercropping is considered to be a potentially useful land use system for mitigating negative environmental impacts from intensive agriculture such as nutrient leaching and greenhouse gas emissions. Rapid early growth of trees is critical for rapidly accruing environmental benefits provided by the trees. We tested the hypothesis that intercropping increases the growth and nutrient status of young hybrid poplars (Populus spp.), compared to a harrowing alley treatment (i.e., no intercrop), in two experimental sites (St-Rémi and St-Édouard) in southern Québec, Canada. Three hybrid poplar clones (TD3230, Populus trichocarpa × deltoides; DN3308, P. deltoides × nigra; and NM3729, P. nigra × maximowiczii) were planted at St-Rémi. Clones DN3333 and DN3570 were planted at St-Édouard. At St-Rémi, intercropping comprised a 4-year succession of three crops of soybean (Glycine max (L.) Merr.) and barley (Hordeum vulgare L.). At St-Édouard, intercropping comprised a 3-year succession of buckwheat (Fagopyrum esculentum Moench), winter rye (Secale cereale L.), and winter wheat (Triticum aestivum L.). At St-Rémi, four years after treatment began, leafless aboveground biomass of hybrid poplars in the intercropping treatment was 37% higher compared to that in the harrowing treatment. At St-Édouard, after the third growing season, leafless aboveground biomass of hybrid poplars in the intercropping treatment was significantly higher by 40%. Vector analysis of foliar nutrient concentrations and comparison with critical concentration values showed that N (both sites) and K (St-Édouard) were the most limiting nutrients. Hybrid poplar clones responded similarly to treatments, with no consistent differences in tree growth observed between clones. We conclude that tree-based intercropping systems may offer an effective means of improving the early growth of hybrid poplars planted to provide both environmental services and high-value timber.     

Behavioural reactivation and subjective assessment of the state of vigilance--application to simulated car driving.

The frequency of some behaviour (such as self-centred gestures) increases during a task that leads to the occurrence of low-vigilance episodes. These gestures can be useful in stimulating oneself. A study carried out in 20 adults has enabled us to state that motor activity (recorded with an actimeter) increases with the duration of a monotonous driving task and sleep deprivation. The analysis of the scores recorded using the Karolinska Sleepiness Scale has shown that drivers can assess the deterioration of their state of vigilance according to the actual sleep preceding the driving test. Finally, the joint analysis of the subjective and objective data revealed a co-variation of these two types of indices. We discuss the stimulatory function of the motor activity in a task leading to the occurrence of low-vigilance episodes by investigating, among other things, the use, conscious or not, of this type of activity.     

Cadmium and zinc bioaccumulation and metallothionein response in two freshwater bivalves (Corbicula fluminea and Dreissena polymorpha) transplanted along a polymetallic gradient

This study was designed to compare the metallothionein (MT) response capacity of two freshwater bivalves, Corbicula fluminea and Dreissena polymorpha, along an environmental gradient of polymetallic pollution. The bivalves were transplanted into 4 stations in southwestern France, with a cadmium and zinc pollution gradient. MT and metal concentrations were measured in the soft bodies of the clams and mussels over 2.5 months. In the zebra mussels, variations in MT concentrations were strictly correlated to progressive Cd and Zn bioaccumulation. In contrast, the faster response in the clams appeared positively correlated to Cd accumulation only, with the activation of efficient detoxification mechanisms which limited Cd bioaccumulation and reduced Zn concentrations over time. Nevertheless, despite stronger metal accumulation factors in D. polymorpha, C. fluminea revealed higher sensitivity of MT response along the pollution gradient.     

EPR monitoring of the bioavailability of an organic xenobiotic (4-hydroxy-TEMPO) in model clay suspensions and pastes

Electron paramagnetic resonance spectroscopy is used to monitor the bioavailability of a nitroxide spin probe, 4-hydroxy-Tempo or Tempol, in Ca-hectorite suspensions and pastes, to bacteria capable of degrading this probe co-metabolically. In nutrient solutions with an initial probe concentration of 1.2 mM and in the absence of hectorite, bacteria are able to denature Tempol and eliminate its paramagnetic signal within 48 h. In the presence of hectorite and after flocculation, the effect of bacteria is significantly delayed, but almost complete denaturation still occurs, after roughly 120 h. When hectorite is added but the bacterial/clay suspension is not centrifuged, Tempol denaturation levels off after about 24 h and reaches a plateau with approximately 45% of Tempol remaining. This plateau does not constitute evidence of limited bioavailability, as is widely assumed, since subsequent addition of nutrients causes the denaturation reaction to proceed to a second plateau, with merely 10% of Tempol remaining.     

Assessment of ecotoxicological risks related to depositing dredged materials from canals in northern France on soil

The implementation of an ecological risk assessment framework is presented for dredged material deposits on soil close to a canal and groundwater, and tested with sediment samples from canals in northern France. This framework includes two steps: a simplified risk assessment based on contaminant concentrations and a detailed risk assessment based on toxicity bioassays and column leaching tests. The tested framework includes three related assumptions: (a) effects on plants (Lolium perenne L.), (b) effects on aquatic organisms (Escherichia coli, Pseudokirchneriella subcapitata, Ceriodaphnia dubia, and Xenopus laevis) and (c) effects on groundwater contamination. Several exposure conditions were tested using standardised bioassays. According to the specific dredged material tested, the three assumptions were more or less discriminatory, soil and groundwater pollution being the most sensitive. Several aspects of the assessment procedure must now be improved, in particular assessment endpoint design for risks to ecosystems (e.g., integration of pollutant bioaccumulation), bioassay protocols and column leaching test design.     

Radiological Dispersion Devices: are we prepared?

Already before the events of September 11th 2001 concern was raised about the spread of orphan sources and their potential use in Radiological Dispersion Devices by terrorist groups. Although most of the simulated scenarios foresee a rather limited direct health impact on the population, the affected region would suffer from the indirect consequences such as social disruption, cleanup requirements and economic costs. The nature of such a radiological attack would anyway be different compared to conventional radiological accidents, basically because it can happen anywhere at any time. Part of the response resides in a general preparedness scheme incorporating attacks with Radiological Dispersion Devices. Training of different potential intervention teams is essential. The response would consist of a prioritised list of actions adapted to the circumstances. As the psychosocial dimension of the crisis could be worse than the purely radiological one, an adapted communication strategy with the public aspect would be a key issue.     

Neocembrene A, a major component of the trail-following pheromone in the genus Prorhinotermes (Insecta, Isoptera, Rhinotermitidae)

Summary. The diterpene neocembrene A or (1E,5E,9E,12R)-1,5,9-trimethyl-12-(1-methylethenyl)-1,5,9-cyclotetradecatriene, known as the trail-following pheromone of the advanced Termitidae Nasutitermitinae Nasutitermes exitiosus and Trinervitermes bettonianus, has been identified after SPME-GC/MS as the major component of the trail-following pheromone of the Rhinotermitidae Prorhinotermitinae, Prorhinotermes canalifrons and P. simplex. In all the other Rhinotermitidae studied until now, the major component of their trail pheromones is dodecatrienol ((3Z,6Z,8E)-dodeca-3,6,8-trien-1-ol). This biochemical data further add to the anatomical and molecular characteristics that give a special status to the taxon Prorhinotermes among Rhinotermitidae. In Prorhinotermes canalifrons and P. simplex, neocembrene A was the only secretory compound specific to the sternal gland surface that could be detected after SPME. It elicited orientation as well as recruitment behavioral effects. However, the comparison of the respective biological activities triggered by neocembrene A and by sternal gland secretion suggests that minor components of the latter are acting in synergy with neocembrene A.     

加拿大北方森林过去、当前和未来的火灾频率:对于森林可持续经营的意义

在过去的几十年里,对基于对历史上自然干预动力的理解的森林经营方法的开发兴趣日益增加.这一方法的理由是,有利于景观组成和林分结构及自然生态系统的经营活动也应当保持生物多样性和基本的生态功能.在火灾居支配地位的景观,用森林经营替代火灾这一方法只在当前火频率和未来火频率比工业化以前的火频率低得多的情况下才有可能.通过将当前火频率、未来火频率与在加拿大北方森林中再现的森林火灾历史的比较,我们讨论了这一问题.对于多块研究地而言,当前火频率和2倍CO.及3倍CO2情形下模拟的未来火频率都低于过去火频率,这暗示着森林经营可以被用于重建受控于火灾的、工业化以前景观的林木年龄结构.但对目前的同龄林经营来说,还有一些重要的限制因子.