Bestimmung von leicht freisetzbarem Cyanid in Böden und Wässern mit der Mikrodestillation

Easy-liberatable cyanide has to be analysed if soils and waters are contaminated by cyanide. The aim of this study was to determine easy-liberatable cyanide in these environmental samples using a micro-distillation apparatus by means of a modified digestion vessel. Pure aqueous solutions of different cyanide species, five contaminated and uncontaminated soil samples and two water samples were analysed by micro-distillation according to the German standards. Recovery was determined by analysis of spiked samples. When using the modified digestion vessels, the pH of 4 which is demanded by the standard method can be adjusted. The recovery of potassium cyanide and weakly-complexed zinc-cyanide ranged from 93–101% for standards, and from 87–98% for spiked samples. In contrast, the recovery of strong iron-cyanide complexes was below 4% both for pure solutions and spiked samples. The precision of the method expressed as a relative standard deviation was 25% in cases of very low easy-liberatable cyanide contents (< 1 mg CN kg^?1) and below 12% in case of high easy-liberatable cyanide contents (> 1 mg CN kg^?1) for contaminated soils. The determination of easily-liberatable cyanide in soils and waters using micro-distillation combined with the modified digestion sample is an alternative to other distillation methods.     

Reasonable creatures: rights and rationalities in valuing the countryside

Debate on the economic valuation of the countryside is typically polarized between absolutist critics who would deny it any valid role and equally fervid proponents who see its techniques as the only way of integrating the environment into policy making. Such debate is structured by conflicting notions of rights, responsibilities and values, rather than by consideration of the role of technique in practical policy‐making. This paper attempts to take the debate forward and begins by examining the ways in which rights, responsibilities and values have been historically created. The techniques of economic valuation rest on particular conceptions of these, making them irreducibly political, and at the same time their results are often used to justify political decisions. Yet the proper role of technique ought to be to explore options. Provided that the sort of clarification that economic valuation offers is understood, it may, along with other types of technique, be used to open up the decision making process.     

Comparison of a matrix solid phase dispersion and a classical extraction method for the determination of chlorinated pesticides in fish muscle

A new multiresidue extraction technique was used to determine incurred chlorinated hydrocarbon pesticide residues in various fish species sampled at 2 locations along the Tensas River in Louisiana. Residue levels of total DDT (combined DDT, DDE, and DDD levels) in fish muscle fillets from paired samples ranged from 0.2 to 3.9 ppm on a wet weight basis. These findings were compared to those of another laboratory that used a different protocol to isolate the residues from the fish muscle fillets. This latter protocol typifies the more complicated, time-consuming protocols used by governmental agencies for screening purposes. Results demonstrated that the new extraction technique reduced analysis time, solvent waste, and cost per sample without affecting the quality of residue detection and measurement.     

Sustainable Use of the Tropical Rain Forest: Evidence from the Avifauna in a Shifting-Cultivation Habitat Mosaic in the Colombian Amazon

We carried out a one-year study of the avifauna along a regeneration gradient created by indigenous shifting cultivation in the Colombian Amazon rain forest. Regenerating one-hectare crop fields, from 1 to 17 years after abandonment, and undisturbed understory sites were compared in a sample effort of 4323 net hours. We made 878 captures of 103 species belonging to 11 trophic groups. Differences in species richness and number of individuals captured between regenerating areas and primary forest were low. A comparison of similarity indices among the sites for each habitat type showed no consistent differences, suggesting similar levels of local heterogeneity. Similarity indices calculated between sites of different-aged habitats, however, showed that young secondary growth at less than 10 years of abandonment was least similar to other sites, whereas old secondary growth between 13 to 17 years of abandonment, and forest understories, had the most similar avifauna. Two trophic groups were absent from the samples of the forest interior, and the abundance of the other nine varied among sites of regeneration. We conclude that slash and burn agriculture represents a high-intensity, small-magnitude disturbance to the forest avifauna. Large changes occur when the crop field is established and last until about 10 years after abandonment. Our data suggest that abandoned crop fields older than this age mimic the natural patch dynamics of the forest, making this type of agriculture an example of a potentially sustainable use of tropical forests, at least from the standpoint of its impact on bird communities.     

Mitigation of the heat island effect in urban New Jersey

Implementation of urban heat island (UHI) mitigation strategies such as increased vegetative cover and higher-albedo surface materials can reduce the impacts of biophysical hazards in cities, including heat stress related to elevated temperatures, air pollution and associated public health effects. Such strategies also can lower the demand for air-conditioning-related energy production. Since local impacts of global climate change may be intensified in areas with UHIs, mitigation strategies could play an increasingly important role as individuals and communities adapt to climate change. We use CITYgreen, a GIS-based modeling application, to estimate the potential benefits of urban vegetation and reflective roofs as UHI mitigation strategies for case study sites in and around Newark and Camden, New Jersey.

The analysis showed that urban vegetation can reduce health hazards associated with the UHI effect by removing pollutants from the air. Less affluent, inner-city neighborhoods are the ones in which the hazard potential of the UHI effect is shown to be greatest. However, these neighborhoods have less available open space for tree planting and therefore a lower maximum potential benefit. As the climate warms, these neighborhoods may face greater consequences due to interactions between the UHI effect and global climate change. Results also show that urban vegetation is an effective and economically efficient way to reduce energy consumption and costs at the sites.     

Causes and consequences of unequal seedling production in forest trees: a case study in red oaks

Inequality in reproductive success has important implications for ecological and evolutionary dynamics, but lifetime reproductive success is challenging to measure in long-lived species such as forest trees. While seed production is often used as a proxy for overall reproductive success, high mortality of seeds and the potential for trade-offs between seed number and quality draw this assumption into question. Parentage analyses of established seedlings can bring us one step closer to understanding the causes and consequences of variation in reproductive success. In this paper we demonstrate a new method for estimating individual seedling production and average percentage germination, using data from two mixed-species populations of red oaks (Quercus rubra, Q. velutina, Q. falcata, and Q. coccinea). We use these estimates to examine the distribution of female reproductive success and to test the relationship between seedling number and individual seed production, age, and growth rate. We show that both seed and seedling production are highly skewed, roughly conforming to zero-inflated lognormal distributions, rather than to the Poisson or negative-binomial distributions often assumed by population genetics analyses. While the number of established offspring is positively associated with mean annual seed production, a lower proportion of seeds from highly fecund individuals become seedlings. Our red oak populations also show evidence of trade-offs between growth rate and reproductive success. The high degree of inequality in seedling production shown here for red oaks, and by previous studies in other species, suggests that many trees may be more vulnerable to genetic drift than previously thought, if immigration in limited by fragmentation or other environmental changes.     

Experimental manipulation of seed shadows of an Afrotropical tree determines drivers of recruitment

The loss of animals in tropical forests may alter seed dispersal patterns and reduce seedling recruitment of tree species, but direct experimental evidence is scarce. We manipulated dispersal patterns of Manilkara mabokeensis, a monkey-dispersed tree, to assess the extent to which spatial distributions of seeds drive seedling recruitment. Based on the natural seed shadow, we created seed distributions with seeds deposited under the canopy ("no dispersal"), with declining density from the tree ("natural dispersal"), and at uniform densities ("good dispersal"). These distributions mimicked dispersal patterns that could occur with the extirpation of monkeys, low levels of hunting, and high rates of seed dispersal. We monitored seedling emergence and survival for 18 months and recorded the number of leaves and damage to leaves. "Good dispersal" increased seedling survival by 26%, and "no dispersal" decreased survival by 78%, relative to "natural dispersal." Using a mixed-effects survival model, we decoupled the distance and density components of the seed shadow: seedling survival depended on the seed density, but not on the distance from the tree. Although community seedling diversity tended to decrease with longer dispersal distances, we found no conclusive evidence that patterns of seed dispersal influence the diversity of the seedling community. Local seed dispersal does affect seedling recruitment and survival, with better dispersal resulting in higher seedling recruitment; hence the loss of dispersal services that comes with the reduction or extirpation of seed dispersers will decrease regeneration of some tree species.     

Vertebrate herbivory impacts seedling recruitment more than niche partitioning or density-dependent mortality

In tropical forests, resource-based niches and density-dependent mortality are mutually compatible mechanisms that can act simultaneously to limit seedling populations. Differences in the strengths of these mechanisms will determine their roles in maintaining species coexistence. In the first assessment of these mechanisms in a Congo Basin forest, we quantified their relative strengths and tested the extent to which density-dependent mortality is driven by the distance-dependent behavior of seed and seedling predators predicted by the Janzen-Connell hypothesis. We conducted a large-scale seed addition experiment for five randomly selected tropical tree species, caging a subset of seed addition quadrats against vertebrate predators. We then developed models to assess the mechanisms that determine seedling emergence (three months after seed addition) and survival (two years after seed addition). As predicted, both niche differentiation and density-dependent mortality limited seedling recruitment, but predation had the strongest effects on seedling emergence and survival. Seedling species responded differently to naturally occurring environmental variation among sites, including variation in light levels and soil characteristics, supporting predictions of niche-based theories of tropical tree species coexistence. The addition of higher densities of seeds into quadrats initially led to greater seedling emergence, but survival to two years decreased with seed density. Seed and seedling predation reduced recruitment below levels maintained by density-dependent mortality, an indication that predators largely determine the population size of tree seedlings. Seedling recruitment was unrelated to the distance to or density of conspecific adult trees, suggesting that recruitment patterns are generated by generalist vertebrate herbivores rather than the specialized predators predicted by the Janzen-Connell hypothesis. If the role of seed and seedling predation in limiting seedling recruitment is a general phenomenon, then the relative abundances of tree species might largely depend on species-specific adaptations to avoid, survive, and recover from damage induced by vertebrate herbivores. Likewise, population declines of herbivorous vertebrate species (many of which are large and hunted) may trigger shifts in species composition of tropical forests.