Screening risk areas for sediment and phosphorus losses to improve placement of mitigation measures

Identification of vulnerable arable areas to phosphorus (P) losses is needed to effectively implement mitigation measures. Indicators for source (soil test P, STP), potential mobilization by erosion (soil dispersion), and transport (unit-stream power length-slope, LS) risks were used to screen the vulnerability to suspended solids (SS) and P losses in two contrasting catchments regarding topography, soil textural distribution, and STP. Soils in the first catchment ranged from loamy sand to clay loam, while clay soils were dominant in the second catchment. Long-term SS and total P losses were higher in the second catchment in spite of significantly lower topsoil STP. A higher proportion of areas in the second catchment were identified with higher risk due to the significantly higher risk of overland flow generation (LS) and a significantly higher mobilization risk in the soil dispersion laboratory tests. A simple screening method was presented to improve the placement of mitigation measures.     

Avoiding the pitfalls of adaptive management implementation in Swedish silviculture

There is a growing demand for alternatives to Sweden’s current dominant silvicultural system, driven by a desire to raise biomass production, meet environmental goals and mitigate climate change. However, moving towards diversified forest management that deviates from well established silvicultural practices carries many uncertainties and risks. Adaptive management is often suggested as an effective means of managing in the context of such complexities. Yet there has been scepticism over its appropriateness in cases characterised by large spatial extents, extended temporal scales and complex land ownership—characteristics typical of Swedish forestry. Drawing on published research, including a new paradigm for adaptive management, we indicate how common pitfalls can be avoided during implementation. We indicate the investment, infrastructure, and considerations necessary to benefit from adaptive management. In doing so, we show how this approach could offer a pragmatic operational model for managing the uncertainties, risks and obstacles associated with new silvicultural systems and the challenges facing Swedish forestry.     

The Economics of Conjunctive Groundwater Management with Stochastic Surface Supplies

Groundwater management with stochastic surface flows and artificial recharge is considered. Theoretical analysis characterizes the decision rules and establishes conditions for convergence of socially optimal and common property withdrawals and pumping lifts to limiting probability distributions. An empirical application to Kern County, California finds that optimal withdrawals are generally increasing in hydraulic head and decreasing in surface flows; however, nonmonotone behavior is observed in some instances. Artificial recharge is not observed in the limiting distribution due to an interaction of several factors. Optimal management implies relatively small gains over unregulated groundwater use when preferences are risk neutral.     

Behavioural and metabolic adaptations of marine isopods to the rafting life style

Rafting on floating objects is a common dispersal mechanism for many marine invertebrates. In order to identify adaptations to the rafting life style, we compared behavioural and metabolic characteristics of two isopods, the obligate rafter Idotea metallica and the facultative rafter Idotea baltica. In laboratory experiments, I. metallica showed low locomotive activity and a tight association to the substratum. Idotea baltica, in contrast, was more active with more frequent excursions in the surrounding water column. Oxygen consumption rates were similar in both species. Idotea metallica fed on zooplankton making this species widely independent of autochthonous food resources of the raft. Feeding rates and digestive enzyme activities were low in I. metallica. Reduced egestion rates may indicate slow gut passage and, thus, efficient resorption of nutrients. Efficient food utilization and the ability to accumulate high amounts of storage products, i.e. lipids, indicate a possible adaptation of I. metallica to low food availability or starvation. The feeding behaviour of I. baltica, in contrast, was more herbivorous and appeared wasteful and inefficient. Low lipid contents in I. baltica also indicate poor storage reserves. Thus, I. baltica requires a permanent access to food.     

Male bird song attracts females — a field experiment

Summary The initial stage of pair formation of the pied and the collared flycatcher (Ficedula hypoleuca and F. albicollis) was simulated in a field experiment. Male dummies positioned near nest boxes and singing by means of tape-recorded song from loudspeakers offered prospecting females a nest box combined with an automatic trap. An unequivocal demonstration of female arrival at the male's territory was obtained by the trapping of the female. Control nest-box traps were provided with silent dummies. Factors other than male song causing female attraction were controlled by a daily switch of the position of singing and silent dummies. Nine out of ten females were caught in nest-box traps with singing dummies (one-tailed binomial test, P=0.011). The result supports the hypothesis that male song functions in mate attraction. This hypothesis has never previously been tested in field experiments although circumstantial evidence for it has been available.     

Exhaustible Resource Allocation in an Overlapping Generations Economy

This paper analyzes competitive allocations of an exhaustible resource in an overlapping generations economy. Conditions are given for the existence of equilibrium extraction rules such that both extraction and investment in future stocks are increasing and continuous in the current stock. The paper then considers the time paths of equilibrium allocations and shows that there are economies where equilibrium resource extractions and prices exhibit nonclassical behavior. This is illustrated through a finite horizon example in which extractions increase and prices decrease over the entire time horizon and an infinite horizon example where there are persistent cycles in extractions and prices and multiple equilibria. The paper concludes by examining welfare issues.     

Efficient and sustainable management of complex forest ecosystems

A large range of models has been developed for the analysis of optimal forest management strategies, with the well-known Faustmann models dating back to the mid-19th century. To date, however, there has been relatively little attention for the implications of complex ecosystem dynamics for optimal forest management. This paper examines the implications of irreversible ecosystem responses for efficient and sustainable forest management. The paper is built around two forest models that comprise two ecosystem components, forest cover and topsoil, the interactions between these components, and the supply of the ecosystem services ‘wood’ and ‘erosion control’. The first model represents a forest that responds in a reversible way to overharvesting. In the second model, an additional ecological process has been included and the ecosystem irreversibly collapses below certain thresholds in forest cover and topsoil depth. The paper presents a general model, and demonstrates the implications of pursuing efficient as well as sustainable forest management for the two forest ecosystems. Both fixed and variable harvesting cycles are examined. Efficient and sustainable harvesting cycles are compared, and it is shown that irreversible ecosystem behaviour reduces the possibilities to reconcile efficient and sustainable forest management through a variable harvesting cycle.     

No cultural transmission of species recognition between parents and offspring in free-living great tits and blue tits

Imprinting plays a key role in the development of species recognition, with young imprinting upon the morphological characters of their parents. However, the potential role that cultural transmission might play in species recognition remains largely uninvestigated. Great tits (Parus major) and blue tits (Cyanistes caeruleus) do not normally perceive each other as sexual competitors or potential partners. However, after reciprocal interspecific cross-fostering, both species may perceive individuals of the foster species as potential rivals or mates. Although the experience of being raised by heterospecifics clearly has affected the species recognition of cross-fostered birds, some of them breed naturally with conspecifics. The offspring of such cross-fostered birds (OCF) are hence raised by parents that look like ordinary conspecifics but display deviant species recognition as compared to controls in terms of aggressive response towards rivals. Comparing the aggressive behavior of OCF, cross-fostered birds and controls towards territorial intruders may thus help tease apart the influence of morphological vs behavioral cues of parents in the development of offspring species recognition. To this end, we compared birds from all three treatments with respect to their aggressive response to territorial intruders of both species during the breeding season. OCF and controls did not differ in their pattern of response towards heterospecific and conspecific stimuli. Compared to cross-fostered birds, OCF and controls showed less aggression towards heterospecific intruders, while the response towards conspecific intruders did not differ between treatments. These results demonstrate that both tit species imprint on the morphological characters of their parents, but that parental behavior is not important for the development of species recognition in terms of aggressive response towards territorial intruders.     

Chlorinated guaiacols and catechols bioaccumulation potential in bleaks (Alburnus alburnus, Pisces) and reproductive and toxic effects on the har-pacticoid Nitocra spinipes (Crustacea)

The bioaccumulation potential in bleaks (Alburnus alburnus, Pisces) and acute toxic and reproductive effects on Nitocra spinipes (Crustacea), of 4,5,6-trichloroguaiacol (I), tetrachloroguaiacol (II) and tetrachlorocatechol (III) was investigated. Continuous flow tests with I and II (10 μg/l) gave a rapid bi-phasic uptake in the fish with I and II reaching a level of 4 μg/g fresh weight after 14 d. An equally rapid excretion was determined with the detection limit of I and II being reached after 10 days in pure water. The 96-h LC50 values for I, II and III to N. spinipes was determined to 5.2, 3.9 and 3.3 mg/l, respectively, in static tests. The fecundity of N. spinipes was reduced to 50 % of the control values at 37±6 and 54±4 μg/l (II) per liter in static and continuous flow tests, respectively.     

Effective field sampling for predicting the spatial distribution of reindeer (Rangifer tarandus) with help of the Gibbs sampler

We describe an approach to estimation of the spatial distribution of reindeer (Rangifer tarandus). Spatial autocorrelation, inherent to the data describing the distribution of wildlife species, contains information that can be utilized to improve the effciency of field inventories. Our data included reindeer fecal pellet counts, satellite imagery and a digital terrain model. We applied ordinary logistic regression, autologistic regression, and the Gibbs sampler to predict spatial distribution of reindeer based on the combined data. A training set was used to compare the outcome for different field sampling designs for each method. Results suggested the possibility to reduce the number of plots by up to 75% with a 15% reduction in prediction accuracy (quality). We also showed that the Gibbs sampler outperformed, in terms of accuracy, the logistic regression. The outcome, however, was dependent on the spectral homogeneity of the area and on the relative position of the sampling design to the elevation curves. Our results justify the incorporation of spatial information when modeling the distribution of reindeer at finer scales (< 1 km).