Recent changes in forest productivity: An analysis of national forest inventory data for common beech (Fagus sylvatica L.) in north-eastern France

Changes in forest growth have been found in European forests and worldwide. However most observations have been derived from samples of restricted size, whose representativeness at a regional forest scale is questionable. National forest inventories provide an interesting perspective for both regional scale assessment of these trends and the investigation of their variations over environmental gradients, but have been little used.     

Dominant radial and height growth reveal comparable historical variations for common beech in north-eastern France

While forest productivity is usually inferred from height growth indices, retrospective analyses of tree rings have been intensively used to assess long-term trends in forest productivity. However, radial growth is sensitive to the degree of competition between trees and influenced by management practices or local disturbances. Whether radial growth is accurate for diagnosing and quantifying productivity changes remains a debated question.     

Potential of retrofitted urban green infrastructure to reduce runoff - A model implementation with site-specific constraints at neighborhood scale

The urbanization has resulted in significant changes in the water balance. Urban Green Infrastructures (UGI) have become a promising method for reducing reoccurring floods whilst providing additional social and ecological benefits. However, there are several challenges to successfully implementing UGI in already developed areas, such as accounting for retrofitting UGI scenarios and pre-existing use of spaces. Accurate estimations of the potential of UGI in reducing flood-causing at the watershed scale are therefore important. This study investigates the influence of site-specific constraints on the effectiveness of UGI in reducing flood-causing runoff at the watershed scale. In particular, this study takes urban fabric characteristics in the development of UGI implementation strategies for different types of residential and industrial neighborhoods into account. Furthermore, it applies a hydrological simulation-based approach to estimate the runoff reduction potential of these strategies for a case study in the Metropolitan Area of San José, Costa Rica. The results indicate that UGI implementation potential depends on urban fabric characteristics and modelling different UGI implementation scenarios shows differing hydrological performance. In residential areas, either permeable pavement or infiltration trenches and street planters lead to the highest runoff reduction. In industrial areas, only permeable pavements lead to the highest runoff reduction. Overall, industrial areas enable more potential for UGI and reduce runoff generation. The findings of this study can guide the development of retrofitting UGI scenarios and upscaling strategies under heterogeneous settlement characteristics.     

Wind‐induced variability in coastal larval retention areas: a case study on Western Baltic spring‐spawning herring

The investigation of larval dispersal and retention, their variability and dependence on wind conditions, has become a major topic in fisheries research owing to potential effects on stock recruitment and stock structuring. The present study quantifies the wind‐induced variability of larval retention of herring in a highly productive coastal lagoon of the Western Baltic Sea. This lagoon, the Greifswalder Bodden, represents the main spawning area of Western Baltic Spring‐Spawning Herring, a stock that has recently undergone a continuous decline in recruitment. The study tests whether this decline was related to changes in larval retention, more precisely to changes in wind conditions, the main forcing of the lagoon's circulation. To answer this, a model approach was applied. Larvae were tracked as Lagrangian drifters under constant and variable wind conditions, examining the main drift patterns and reconstructing the incidents during the period of recruitment decline. For the latter, weekly cohorts of virtual larvae were released in the lagoon over the entire spawning period (April–June; >16 weeks). The fraction of retained larvae per cohort was related to observed larval abundances. On this basis, a new retention index was defined to evaluate the annual larval retention. The results presented cannot explain the observed recruitment decline but characterize the lagoon as an important larval retention area by virtue of unsteady wind conditions that prevent a steady outflow of larvae.     

Modelling the effects of herbicide dose and weed density on rice‐weed competition

The effects of herbicide dose on rice‐weed competition were investigated to develop a combined model, which can be utilised to estimate an optimum herbicide dose for a given weed density in paddy rice cultivation. Field studies were conducted in Suwon for rice‐Echinochloa crus‐galli competition and Iksan for rice‐Eleocharis kuroguwai during 2007. The competitive effect of the weeds E. crus‐galli and E. kuroguwai decreased with increasing doses of flucetosulfuron and azimsulfuron, respectively, in the same manner as the standard dose–response curve. The combination of the rectangular hyperbolic model and the standard dose–response curve adequately described the complex effects of herbicide dose and weed competition on rice yield. Parameter estimates were used with the model to predict rice yield and estimate the doses of flucetosulfuron and azimsulfuron required to restrict rice yield loss caused by E. crus‐galli and E. kuroguwai, respectively, to an acceptable level. For a rice yield of 5.0 t ha^?1, the model recommended flucetosulfuron doses of 8.7, 13.4 and 20.1 g a.i. ha^?1 when infested with E. crus‐galli at 12, 24 and 48 plants m^?2 respectively. For a rice yield of 5.2 t ha^?1, the model recommended azimsulfuron doses of 3.9, 7.5 and 12.6 g a.i. ha^?1 when infested with E. kuroguwai at 24, 48 and 96 plants m^?2 respectively. The theoretical outputs of the combined model appear robust and indicate there are opportunities for reduced herbicide use in the field. These now require evaluation under field conditions.     

Predicting the effects of whale population recovery on Northeast Pacific food webs and fisheries: an ecosystem modelling approach

The recovery of whale populations from historical depletion may have the potential to noticeably affect Northeast Pacific ecosystems and fisheries. Surplus production models based on whaling catch records were used to reconstruct the historical abundances of five large whale species in the waters surrounding Haida Gwaii, British Columbia. The results suggest that the local abundances of all five species were vastly higher before the onset of modern whaling. A comparison of ecosystem models representing the states of the local marine food web before and after full whale recovery indicates that abundant whales could consume large proportions of the annual production of their principal prey, ranging up to 87% for Pacific herring (Clupea pallasii) and 72% for piscivorous rockfish (Sebastes spp.). Dynamic modelling of the food web effects of whale recovery, including simulations of simultaneous top‐down and bottom‐up forcing and a Monte Carlo sensitivity analysis, revealed noticeable (～6–12%) top‐down effects on Pacific herring biomass owing to increased predation by humpback and fin whales. However, these effects cannot explain the magnitude of recent declines in local herring biomass. The dynamic modelling results also suggest that top‐down effects of whale recovery could result in reduced biomasses of large rockfish as a result of predation by sperm whales, as well as potential cascading effects on many demersal fish groups. These findings have numerous practical implications for ecosystem‐based fisheries management and whale conservation strategies in Northeast Pacific waters.     

Generating information for aquaculture development: The art and science of economic policy modelling

Abstract

The rapid growth of aquaculture and concerns about economic and ecological ‘sustainability’ have focused attention on industry externalities. Developing institutions which ‘sustain’ aquaculture will require skills in the ‘art and science’ of public policy modelling. Analysis of existing approaches demonstrates that no single modelling paradigm is ‘best’ for all aquaculture policy situations. Modelling approaches other than cost‐benefit including multiobjective analysis may be more appropriate if the objective of the modeller is to improve the effectiveness of the policy process itself. A review of the relatively small but growing literature on aquaculture policy models reveals a wide range of issues and approaches. In general, economic models have focused on the single objective of maximizing efficiency; in contrast, models used in actual aquacultural policy and planning focus on controlling environmental pollution. The findings suggest that economic models have not yet played a significant role in aquacultural policy development. This raises concerns that myopic views of ‘sustainability’ will result in institutions which do not promote socially efficient aquacultural industry growth.     

A conceptual framework for guiding the participatory development of agricultural decision support systems

Scientists develop decision support systems (DSSs) to make agricultural science more accessible for farmers and extension officers. Despite the growing use of participatory approaches in agricultural DSS development, reflection on this endeavour has largely focused on the ‘doing’ of participation or the ‘problem of implementation’ when DSSs have not been adopted by stakeholders. There has been little reference to relevant theoretical approaches to the social processes involved in ‘participation’ or ‘implementation’. However, if DSS use is to reach its full potential, a more conceptually informed understanding of how stakeholders collaborate in the participatory development of DSSs is required. To contribute to this conceptualisation, we developed a framework based on three concepts drawn from the field of science and technology studies: technological frames, interpretative flexibility and boundary objects. The framework highlights the importance and value of social learning for participatory DSS development, which relies upon exploring the participating parties’ different perspectives on the agricultural system represented in the DSS. Our framework provides a broad definition of success for participatory DSS development, placing greater weight on learning during the participatory process compared with subsequent use of the DSS by farmers and/or advisors. Two case studies of stakeholder collaboration to develop an irrigation scheduling DSS for sugarcane production were used to explore the relevance of the framework. The concepts in the framework were clearly displayed during the case studies. At the conclusion of the studies there were contrasting outcomes for the DSS. One group of farmers was keen to apply it in their ongoing irrigation management, while another saw little relative advantage in use of the DSS. In both instances co-learning occurred amongst case study participants, so the participatory process was clearly a success.     

Development of a fish-based index for the assessment of river health in Europe: the European Fish Index

Abstract  A fish-based index applicable at the pan-European scale should encompass the relative importance of regional and local factors influencing the distribution of riverine fish. An effective way of using information available from fish assemblages to establish such a multimetric index is through the use of the reference condition approach that involves testing a fish assemblage exposed to a potential stressor against a reference condition. In this study, a variety of metrics based on count and abundance data and reflecting different aspects of the fish assemblage structure and function were selected from the literature for their potential to indicate degradation. Logistic and multiple linear regression procedures were applied, using an initial data set of 1000 reference sites fairly evenly distributed across European rivers (11 countries) and defined by some easily measured regional and local characteristics, to elaborate the simplest possible response model that adequately explains the observed patterns of each metric for a given site. A final list of 10 metrics was retained and the European Fish Index was tested using new independent datasets. The advantage of the resulting index to serve as a practical technical reference for cost-effective biological assessments of lotic systems in Europe is related to its ability to encompass basins and river size, and its sensitivity to physical and chemical alteration of the river ecosystem.