Quantifying the effects of trampling and habitat edges on forest understory vegetation – A field experiment

We investigated the effects of human trampling on boreal forest understory vegetation on, and off paths from suburban forest edges towards the interiors and on the likelihood of trampling-aided dispersal into the forests for three years by carrying out a trampling experiment. We showed that the vegetation was highly sensitive to trampling. Even low levels of trampling considerably decreased covers of the most abundant species on the paths. Cover decreased between 10 and 30% on paths which had been trampled 35 times, and at least by 50% on those trampled 70–270 times. On-path vegetation cover decreased similarly at forest edges and in the interiors. However, some open habitat plant species that occurred outside the forest patches and at forest edges dispersed into the forests, possibly through the action of trampling. A higher cover percentage of an open habitat species at the forest edge line increased its probability to disperse into the forest interior. The vegetation community on, next to, and away from lightly trampled paths remained the same throughout the trampling experiment. For heavily trampled paths, the community changed drastically on the paths, but stayed relatively similar next to and away from the paths. As boreal vegetation is highly sensitive to the effects of trampling, overall ease of access throughout the forest floor should be restricted to avoid the excessive creation of spontaneous paths. To minimize the effects of trampling, recreational use could be guided to the maintained path network in heavily used areas.     

Development of SuperSmart Grids for a more efficient utilisation of electricity from renewable sources

If Europe is serious about reaching its target to keep global mean temperature increase below 2 °C, it must strive for a 100% renewable electricity system by 2050. The SuperSmart Grid approach combines what is often perceived as two exclusive alternatives: wide area power generation and decentralised power generation. We argue that by combining these, in fact, complementary measures, it is possible to address the crucial issue of renewable generation—fluctuating supply—in a comprehensive as well as in a technologically and economically viable manner. Thus, the SuperSmart Grid simultaneously can contribute to energy security, climate security, social security, and national security.     

Coexistence between People and Elephants in African Savannas

Abstract: The decline in the range and numbers of elephants as a result of expanding human activity in Africa is recognized as one of the continent's more serious conservation problems. Understanding the relationship between human settlement patterns and elephant abundance is fundamental to predicting the viability of elephant populations. The prevailing model of human-elephant interaction predicts a negative linear relationship between rising human density and declining elephant density at a coarse (national or subcontinental) scale. Using observed elephant densities and human population data, we tested this prediction in a study area of 15,000 km² in northwestern Zimbabwe. The results did not fit a linear model. Elephant and human coexistence occurs at various levels of human density, up to a threshold of human density beyond which elephant populations disappear. This threshold seems to be related to a particular stage in the process of agriculturally transformed land becoming spatially dominant over the natural woodland that constitutes elephant habitat. Within the contexts of conservation and sustainable development in African savannas, investigating spatial relationships between elephant and human abundance should be a priority topic for future research.     

农场协作以提高可持续发展力

本文表明农场主之间的联合经营体(partnership arrangements)可能是保障农场经济生存能力和提高效益的途径之一.本文讨论了三种不同协作类型的经验分析,并强调了与协作经营关联的环境改善.在第一个案例中,对牛奶场和种植农场的协作进行了分析,结果表明多样化的提高和轮作具有实质的潜在效益,当协作包括机械时,其潜在效益更高.第二个例子论及生猪育崽和精饲管理的外部综合条件.协作利润源于生物因子和技术因子两方面,诸如提高生长率和增加猪舍的利用率等.最后,本文对一组种植农场协作进行了评估,认为效益的增加主要得益于机械费用的减少和/或来自其它因素的收益,如轮作和管理、营销策略等的改善.     

Aluminium metabolism in chronic renat failure: Environmental influences and regional differences in Norway

Many aspects of Al metabolism in chronic renal failure are poorly understood. A longitudinal study of serum Al concentrations in predialysis patients and healthy control subjects revealed very high values during the autumn of 1984 and 1985. Renal Al clearance was low during the autumnal spike in serum Al but increased substantially when the serum Al concentration declined. A second study confirmed that by using citric acid as a chelator, the gastrointestinal absorption of Al from Al(OH)₃ may be considerably augmented as reflected by increases in both serum Al concentrations and renal Al clearance. The individual differences in Al absorption in this study were large.The first study suggests the existence of an unidentified environmental factor, possibly water borne, with profound effects on Al absorption and excretion. The citric acid/Al(OH)₃ experiment suggests that the existence of such a factor is likely. The implications of these results are not known.A histomorphometric study of bone biopsies from 138 hemodialysis and 66 predialysis patients without clinical evidence of Al related disease, revealed Al deposits after staining with aurin tricarboxylic acid in 78% of the biopsies from the former and 24% of the latter patients. Serum Al concentrations did not differ between predialysis and hemodialysis patients with Al positive biopsies. Stratification of the hemodialysis patients, who came from all parts of Norway, revealed that patients living in regions with slightly Al contaminated drinking water (Al <30 g/L) had lower serum Al concentrations than patients from regions with highly contaminated water (Al >100 g/L). The prevalence of Al-positive biopsies was the same in both regions. Patients with Al-positive biopsies did not differ in serum Al level from those with Al-negative biopsies within the same region. Predialysis patients with Al-positive biopsies had significantly higher serum Al levels than predialysis patients with Al negative biopsies.Stainable Al deposits are commonly found in the bone of patients with chronic renal failure. Cross-sectionally obtained serum Al concentrations do not reflect the prevalence of stainable bone Al in renal patients but are related to the degree of Al contamination of water of the region.     

Split-second escape decisions in blue tits (Parus caeruleus)

Bird mortality is heavily affected by birds of prey. Under attack, take-off is crucial for survival and even minor mistakes in initial escape response can have devastating consequences. Birds may respond differently depending on the character of the predator's attack and these split-second decisions were studied using a model merlin (Falco columbarius) that attacked feeding blue tits (Parus caeruleus) from two different attack angles in two different speeds. When attacked from a low attack angle they took off more steeply than when attacked from a high angle. This is the first study to show that escape behaviour also depends on predator attack speed. The blue tits responded to a high-speed attack by dodging sideways more often than when attacked at a low speed. Escape speed was not significantly affected by the different treatments. Although they have only a split-second before escaping an attack, blue tits do adjust their escape strategy to the prevailing attack conditions.     

Interdisciplinary knowledge integration through group model building: recognizing dualities and triadizing the conversation

As part of the inquiry into managing an interdisciplinary research process on adaptive water governance, we investigated the process of group model building (GMB) and, more specifically, the role of Unified Modeling Language (UML) in this process. An analysis of group interaction reveals several tensions in the process of knowledge integration, which can be grouped into three overarching dualities: ‘simplicity versus complexity’, ‘constraining versus containing’ and ‘defining versus refining’. As group members take different positions with regard to these dualities, these represent sources of tension and potential ‘stuckness’ of the GMB. Hence the question arises how the group can manage duality in ways that take the GMB beyond its opposing forces. We suggest that knowledge integration processes may benefit from early recognition of the dualities at hand and strategies aimed at creating ‘thirdness’, including some suggestions on the concrete forms such ‘thirdness’ may take.     

Seasonal modulation of flight speed among nocturnal passerine migrants: differences between short- and long-distance migrants

Migrating birds are expected to fly at higher airspeeds when minimizing time rather than energy costs of their migratory journeys. Spring migration has often been suggested to be more time selected than autumn migration, because of the advantage of early arrival at breeding sites. We have earlier demonstrated that nocturnal passerine migrants fly at higher airspeeds during spring compared to autumn, supporting time-selected spring migration. In this study, we test the hypothesis that seasonal airspeeds are modulated differently between short- and long-distance migrants, because of a stronger element of time selection for autumn migration over long distances. In support of this hypothesis, we demonstrate that the seasonal difference in airspeed is significantly larger (spring airspeed exceeding autumn airspeed by a factor of 1.16 after correcting for the influence of altitude, wind and climb/descent on airspeed) among short-distance compared to long-distance (factor 1.12) migrants. This result is based on a large sample of tracking radar data from 3 years at Falsterbo, South Sweden. Short-distance migrants also tend to fly with more favourable winds during autumn, indicating relaxed time constraints (being able to afford to wait for favourable winds) compared to long-distance migrants. These results indicate surprisingly fine-tuned seasonal modulation of airspeed and responses to wind, associated with behavioural strategies adapted to different levels of time selection pressures during spring and autumn migration.     

Exaggerated orientation scatter of nocturnal passerine migrants close to breeding grounds: comparisons between seasons and latitudes

Using tracking radars, we investigated the variability of flight directions of long-distance nocturnal passerine migrants across seasons (spring versus autumn migration) and sites at the southern (56° N) and northern (68° N) ends of the Scandinavian Peninsula (Lund versus Abisko). Whilst most migrants at Lund are on passage to and from breeding sites in Fennoscandia, the majority of the migrants at Abisko are close to their breeding sites, and migration at Abisko thus to a large degree reflects initial departure from breeding sites (autumn) or final approach to breeding destinations (spring). The radar data were used to test predictions about differences in orientation and wind drift effects between adult and juvenile birds (a large proportion of autumn migrants consists of juvenile birds on their first journey), between situations far away from or near the goals and between different phases of migration (initial departure, en route passage, final approach to goal). The concentrations (both total and within-night concentrations) of flight directions differed significantly between seasons as well as sites, with the highest concentration at Lund in spring (mean vector length of track directions, r = 0.79) and lowest at Abisko during spring (r = 0.35). Partial wind drift and partial compensation were recorded at Lund, with a similar effect size in spring and autumn, whilst possible wind drift effects at Abisko were obscured by the large directional scatter at this site. The results from Lund support the prediction that the high proportion of juveniles in autumn contributes to increase the directional scatter during this season, whilst there was no support for predictions of differential wind drift effects between seasons and situations with different goal distances. The most striking and surprising result was the exceedingly large scatter of flight directions at Abisko, particularly in spring. We suggest that such an exaggerated scatter may be associated with final approach orientation, where migrants reach their specific goals from all various directions by final navigation within a more wide-ranging goal region. The larger scatter of autumn flight directions at Abisko compared to Lund may be due to exploratory flights in variable directions being more common at initial departure from breeding sites than later during migratory passage. These surprising results highlight the importance of studying and analysing orientation during final approach to (and initial departure from) migratory goals for understanding the orientation systems of migratory birds.     

Is habitat amount important for biodiversity in rocky shore systems? A study of South African mussel assemblages

Habitat-forming species on rocky shores are often subject to high levels of exploitation, but the effects of subsequent habitat loss and fragmentation on associated species and the ecosystem as a whole are poorly understood. In this study, the effects of habitat amount on the fauna associated with mussel beds were investigated, testing for the existence of threshold effects at small landscape scales. Specifically, the relationships between mussel or algal habitat amount and: associated biodiversity, associated macrofaunal abundance and density of mussel recruits were studied at three sites (Kidd’s Beach, Kayser’s Beach and Kini Bay) on the southern and south-eastern coasts of South Africa. Samples, including mussel-associated macrofauna, of 10 × 10 cm were taken from areas with 100 % mussel cover (Perna perna or a combination of P. perna and Mytilus galloprovincialis) at each site. The amount of habitat provided by mussels and algae surrounding the sampled areas was thereafter determined at the 4.0 m² scale. A number of significant positive relationships were found between the amount of surrounding mussel habitat and the abundances of several taxa (Anthozoa, Malacostraca and Nemertea). Likewise, there were positive relationships between the amount of surrounding algal habitat and total animal abundance as well as abundance of mussel recruits at one site, Kini Bay. In contrast, abundance of mussel recruits showed a significant negative relationship with the amount of mussel habitat at Kayser’s Beach. Significant negative relationships were also detected between the amount of mussel habitat and species richness and total abundance at Kidd’s Beach, and between amount of mussel habitat and the abundance of many taxa (Bivalvia, Gastropoda, Maxillopoda, Ophiuroidea, Polychaeta and Pycnogonida) at all three sites. No threshold effects were found, nor were significant relationships consistent across the investigated sites. The results indicate that the surrounding landscape is important in shaping the structure of communities associated with these mussel beds, with significant effects of the amount of surrounding habitat per se. The strength and the direction of habitat effects vary, however, between shores and probably with the scale of observation as well as with the studied dependent variables (e.g. diversity, abundance, mussel recruitment, species identity), indicating the complexity of the processes structuring macrofaunal communities on these shores.