Using a stand-level model to predict light absorption in stands with vertically and horizontally heterogeneous canopies

Background： Forest ecosystem functioning is strongly influenced by the absorption of photosynthetically active radiation （APAR）, and therefore, accurate predictions of APAR are critical for many process-based forest growth models. The Lambert-Beer law can be applied to estimate APAR for simple homogeneous canopies composed of one layer, one species, and no canopy gaps. However, the vertical and horizontal structure of forest canopies is rarely homogeneous. Detailed tree-level models can account for this heterogeneity but these often have high input and computational demands and work on finer temporal and spatial resolutions than required by stand-level growth models. The aim of this study was to test a stand-level light absorption model that can estimate APAR by individual species in mixed-species and multi-layered stands with any degree of canopy openness including open-grown trees to closed canopies. Methods： The stand-level model was compared with a detailed tree-level model that has already been tested in mixed-species stands using empirical data. Both models were parameterised for five different forests, including a wide range of species compositions, species proportions, stand densities, crown architectures and canopy structures. Results： The stand-level model performed well in all stands except in the stand where extinction coefficients were unusually variable and it appears unlikely that APAR could be predicted in such stands using （tree- or stand-level） models that do not allow individuals of a given species to have different extinction coefficients, leaf-area density or analogous parameters. Conclusion： This model is parameterised with species-specific information about extinction coefficients and mean crown length, diameter, height and leaf area. It could be used to examine light dynamics in complex canopies and in stand-level growth models.     

Vespa velutina: a new invasive predator of honeybees in Europe

The yellow-legged hornet (Vespa velutina) is the first invasive Vespidae predator of honeybees to be accidentally introduced into Europe from Asia. In the current pollinator decline, V. velutina is an additional stressor for honeybees and other pollinators. Although V. velutina contributes to the loss of honeybee colonies, little is known about its biology and behaviour both in the native and in the invaded area. Here, we review the current knowledge of this species and describe its life cycle and life history traits (reproduction, overwintering, foraging and dispersal) in the light of the biology of other Vespidae. We also review the impact of this species on ecosystems, on the economics of beekeeping, and on human health (this species being potentially deadly for allergic people). Based on this information and on previous worldwide experiences with Vespidae invasions, we propose key research topics for the development of effective management plans. We identify methods to limit the impact and proliferation of V. velutina in Europe that are based on nest destruction, trapping, population genetics, and biological control. In our opinion, research effort on the means to detect and destroy V. velutina nests at an early stage is required in order to short-circuit the colony cycle and thus limit both its impact on honeybees and its expansion through Europe. Finally, we discuss the impact of this biological invasion on the development of methods that should be used to manage alien species in the future.     

Development of nursery culture techniques for the mud crab Scylla paramamosain (Estampador)

Cannibalism is one of the main causes of mortality in the culture of the mud crab Scylla paramamosain, particularly in the early post‐larval and juvenile stages when the densities of hatchery‐reared crabs may be very high before stocking into ponds or release into the wild for stock enhancement. In a series of experiments investigating cannibalism mitigation, the influence of stocking density, the effectiveness of sand substrate, brick and shell shelters and feed type were compared in culture of crabs from instar 1 for short nursery periods of 15–30 days. Inclusion of brick and shell shelters significantly increased survival over sand substrate alone. However, inclusion of shelters did not affect growth rates. In scaled‐up nursery production in lined‐ponds, with shelters, live Artemia biomass and fresh chopped shrimp or tilapia were found to be equally effective feeds for juvenile crabs stocked at a density of 70 m⁻² from instar 1 and grown for 30 days [52–66% survival, 21.6–24.6 mm carapace width (CW)]. In an extended nursery period for a further 30 days, crabs of 22 mm CW, stocked at 30 m⁻² in the same ponds, attained a final size of 34.5–36.2 mm CW with a survival of 64.3–67.0% using the same feeds.     

Using ecological trajectories to track long-term taxonomic and functional changes in benthic shallow soft-bottom communities (Bay of Saint-Brieuc,English Channel)

1. Taxonomic and functional trajectories of benthic assemblages were studied in shallow soft-bottom sediments in the bay of Saint-Brieuc (Western English Channel). Changes were assessed at different spatial and temporal scales using a macrobenthic dataset based on 38 stations sampled in 1987 and 2019, coupled with data from one station sampled annually between 2005 and 2019 as part of the European Water Framework Directive monitoring programme.
2. Taxonomic trajectories indicated 1) changes in the structure and distribution of benthic assemblages, 2) an homogenization of the assemblages, and 3) significant functional shifts.
3. Fishing activities and nutrient enrichment are probably strong drivers of the observed changes, as suggested by the higher mortality rate of fragile, flexible, tubiculous and burrowing species, and the increase in the abundance of opportunistic species in the assemblages. Certain populations of macroinvertebrates seem jointly controlled by climate change and by the aforementioned local factors of disturbance.
4. The Community Trajectory Analysis framework appears as a new and interesting method to track ecological changes in marine ecosystems by measuring change with respect to a baseline state, to help define ecological recovery (station returning to the initial ecological state) and departure (station presenting increased changes over time), and to analyse trajectory similarity.
5. According to the degradation of habitat over time, we identify the need for the implementation of knowledge-based conservation strategies, especially within Natura 2000 sites.

     

Ciguatoxin in moray eels raising the risk for seafood safety in Viet Nam

Fisheries Science - Recently, suspected ciguatera fish poisoning (CFP) cases caused by the consumption of moray eels, popular seafood for locals and tourists, have been reported in Viet Nam....     

Preliminary experiences with the treatment of shock in horses with a plasma expander from a starch base

HAES Steril 10% is a colloidal plasma expander rarely used in veterinary medicine. In this study HAES was used in clinical cases for the treatment of shock and in a comparative hypervolemic hemodilution study (HAES versus lactated Ringer's solution) using two experimental horses. Injection of a HAES volume equivalent to 10% of estimated blood volume resulted in a highly significant drop in PCV and in a significant drop in total protein concentration. Half live of HAES was approximately two hours. No incompatibility reactions were observed. In man HAES improves microcirculation. Studies in progress may confirm a similar effect in the equine.     

Conservation costs: Nature‐based tourism as development at Cuc Phuong National Park,Vietnam

Abstract: Local communities are frequently displaced from areas selected for environmental protection. Development of nature‐based tourism, believed to be more environmentally benign than traditional agricultural systems, has been encouraged by governments and national park managers in the hope of providing alternative livelihoods for local people. This paper examines the extent to which indigenous peoples resettled from within one Vietnamese national park have engaged with the nascent tourism industry, thereby providing a perspective on the success of their resettlement, through the eyes of those communities affected. The perspectives of resettled peoples are contrasted with those of villagers who have continued to reside within the national park, using traditional means of survival, along with new initiatives designed to supplement their livelihoods and to reduce their dependence on national park resources for survival. Resettled villagers are unable to survive on agricultural activity alone, tourism has done little to provide an alternate livelihood and the park environment is still threatened by the use of park resources by resettled communities in their struggle to survive.     

Genetic organization of aromatic rice as revealed by RAPD markers: A case study in conserving crop genetic resources on farm

Summary On-farm conservation of landraces is one strategy to maintain the diversity of crop germplasm in local agro-ecosystems. The genetic structures of landraces are a key biological factor in on-farm conservation strategies. To accumulate a genetic understanding that will help establish a methodology for on-farm conservation, the genetic organization of landraces of aromatic rice in Namdinh province, Vietnam was analyzed using RAPD markers. Eighteen RAPD markers detected 38 genotypes among 320 aromatic rice samples growing at 23 sites of farmers' fields and in the experimental field that derived from 13 sites. Geographical variation was observed in the frequency of genotypes, whereas individual landraces could not be distinguished by RAPD markers. Genetic variation within a site was generally smaller than that among sites. The degree of genetic similarity of the plants in a site varied among sites, as did the number of genotypes. Changes in genetic structure over time were investigated using experimental populations each derived from approximately 30 plants from 13 farmers' fields. The differences detected by DNA markers between the genetic structural in the farmers' fields and those in experimental fields suggested that genetic drift is a major cause of these differences. The present study suggests that DNA markers are an essential means to monitor the genetic structures of heterogeneous landraces of rice, and are useful for selecting study sites for the on-farm conservation of genetic diversity as well as for successive monitoring.     

Genetic variability for resistance to sorghum downy mildew (Peronosclerospora sorghi) and Rajasthan downy mildew (P. heteropogoni) in the tropical/sub-tropical Asian maize germplasm

Downy mildews cause considerable damage to maize (Zea mays L.) worldwide, particularly in the tropical Asia. We have evaluated a set of 42 tropical/sub-tropical maize inbred lines developed in different countries in Asia (India, Thailand and Philippines), and Mexico, for analysing the genetic variability for resistance to sorghum downy mildew [Peronosclerospora sorghi; SDM] and Rajasthan downy mildew [P. heteropogoni; RDM]. Experiments were carried out in replicated trials under artificial infection in field conditions against SDM and RDM at Mandya in Karnataka, India, and Udaipur in Rajasthan, India, respectively, during 1999 and 2000. The study resulted in identification of five inbred lines offering consistent and strong resistance to both SDM and RDM, while several inbred lines revealed resistance only to RDM. It was also revealed that the SDM-resistant inbreds are invariably resistant to RDM, while the RDM-resistant inbreds might show differential responses to the SDM. The maize inbred lines identified in this study with broad-spectrum resistance to downy mildews could be potentially useful for basic and applied research work on downy mildews in tropical Asia. This revised version was published online in August 2006 with corrections to the Cover Date.