Jacob Nabe-Nielsen

Diversity and distribution of lianas in a neotropical rain forest, Yasuní National Park, Ecuador

Lianas (woody vines) contribute substantially to the diversity of woody plants in YasuniNational Park, Eastern Ecuador. In total 606 individuals, belonging to 138 species, were found in two 20-m × 100-m plots. The liana diversity was higher than in any comparable study, but the density was relatively low. Sapin- daceae and Leguminosae were the most species-rich families, whereas Legumino- sae and Celastraceae were the most abundant families. The number of liana indi- viduals as well as the number of liana species was partially explained by forest structure, but 92% of the variation in number of liana species depended on the number of liana individuals. Areas with high density of small trees had high liana density, and areas with a high number of tree saplings had a relatively high divers- ity of climbing lianas. The probability of trees being colonized by lianas increased with tree diameter. The presence of one liana on a tree increased its risk of being colonized by additional lianas.

The Effects of Landscape Modifications on the Long-Term Persistence of Animal Populations

Background The effects of landscape modifications on the long-term persistence of wild animal populations is of crucial importance to wildlife managers and conservation biologists, but obtaining experimental evidence using real landscapes is usually impossible. To circumvent this problem we used individual-based models (IBMs) of interacting animals in experimental modifications of a real Danish landscape. The models incorporate as much as possible of the behaviour and ecology of four species with contrasting life-history characteristics: skylark (Alauda arvensis), vole (Microtus agrestis), a ground beetle (Bembidion lampros) and a linyphiid spider (Erigone atra). This allows us to quantify the population implications of experimental modifications of landscape configuration and composition. Methodology/Principal Findings Starting with a real agricultural landscape, we progressively reduced landscape complexity by (i) homogenizing habitat patch shapes, (ii) randomizing the locations of the patches, and (iii) randomizing the size of the patches. The first two steps increased landscape fragmentation. We assessed the effects of these manipulations on the long-term persistence of animal populations by measuring equilibrium population sizes and time to recovery after disturbance. Patch rearrangement and the presence of corridors had a large effect on the population dynamics of species whose local success depends on the surrounding terrain. Landscape modifications that reduced population sizes increased recovery times in the short-dispersing species, making small populations vulnerable to increasing disturbance. The species that were most strongly affected by large disturbances fluctuated little in population sizes in years when no perturbations took place. Significance Traditional approaches to the management and conservation of populations use either classical methods of population analysis, which fail to adequately account for the spatial configurations of landscapes, or landscape ecology, which accounts for landscape structure but has difficulty predicting the dynamics of populations living in them. Here we show how realistic and replicable individual-based models can bridge the gap between non-spatial population theory and non-dynamic landscape ecology. A major strength of the approach is its ability to identify population vulnerabilities not detected by standard population viability analyses.

Possible Causes of a Harbour Porpoise Mass Stranding in Danish Waters in 2005

An unprecedented 85 harbour porpoises stranded freshly dead along approximately 100 km of Danish coastline from 7–15 April, 2005. This total is considerably above the mean weekly stranding rate for the whole of Denmark, both for any time of year, 1.23 animals/week (ranging from 0 to 20 during 2003–2008, excluding April 2005), and specifically in April, 0.65 animals/week (0 to 4, same period). Bycatch was established as the cause of death for most of the individuals through typical indications of fisheries interactions, including net markings in the skin and around the flippers, and loss of tail flukes. Local fishermen confirmed unusually large porpoise bycatch in nets set for lumpfish (Cyclopterus lumpus) and the strandings were attributed to an early lumpfish season. However, lumpfish catches for 2005 were not unusual in terms of season onset, peak or total catch, when compared to 2003–2008. Consequently, human activity was combined with environmental factors and the variation in Danish fisheries landings (determined through a principal component analysis) in a two-part statistical model to assess the correlation of these factors with both the presence of fresh strandings and the numbers of strandings on the Danish west coast. The final statistical model (which was forward selected using Akaike information criterion; AIC) indicated that naval presence is correlated with higher rates of porpoise strandings, particularly in combination with certain fisheries, although it is not correlated with the actual presence of strandings. Military vessels from various countries were confirmed in the area from the 7th April, en route to the largest naval exercise in Danish waters to date (Loyal Mariner 2005, 11–28 April). Although sonar usage cannot be confirmed, it is likely that ships were testing various equipment prior to the main exercise. Thus naval activity cannot be ruled out as a possible contributing factor.

Environmentally induced clonal reproduction and life history traits of the liana Machaerium cuspidatum in an Amazonian rain forest, Ecuador

The population structure of the canopy liana Machaerium cuspidatum Kuhlm. & Hoehne (Fabaceae) was studied in ten transects covering a total of 2.5 ha of tropical rain forest in Yasuní National Park, eastern Ecuador. The aim was to investigate how trellis availability, topographic position and light availability affected the population density and structure of the most abundant liana species in the area. The environmental variation affected plants in different size classes differently. Large plants (diameter ≥ 1 cm) were almost exclusively found in areas with low canopy and dense undergrowth. These areas had the highest density of suitable host plants. Seedling-sized plants (height < 30 cm) and saplings (height ≥ 30 cm but diameter < 1 cm) occurred more frequently and withhigher density in steep upland areas than in the floodplains, presumably due to elevated seedling mortality in the periodically flooded areas. Seedling-sized plants and saplings did not grow in areas with elevated light levels, and although plants of all sizes were highly clumped, this clumping rarely coincided with patches with abundant canopy gaps. Machaerium cuspidatum reproduces clonally when branches re-root and break off from the parentplant. The density of clonally produced plants was high in areas where the density of sexually produced plants was low, whereas the total density varied little among habitat types. A higher proportion of the seedling-sized plants were of sexual origin in the upland areas. An environmentally induced increase in the production of independent ramets enables M. cuspidatum to persist in the floodplains. This shows that plants may expand theirrealised niches to habitats with a low potential for seedling survival if high seedling mortality can be compensated for by increased clonal reproduction.

Timber tree regeneration along abandoned logging roads in a tropical Bolivian forest

Sustainable management of selectively logged tropical forests requires that felled trees are replaced through increased recruitment and growth. This study compares road track and roadside regeneration with regeneration in unlogged and selectively logged humid tropical forest in north-eastern Bolivia. Some species benefited from increased light intensities on abandoned logging roads. Others benefited from low densities of competing vegetation on roads with compacted soils. This was the case for the small-seeded species Ficus boliviana C.C. Berg and Terminalia oblonga (Ruiz & Pav.) Steud. Some species, e.g. Hura crepitans L., displayed patchy regeneration coinciding with the presence of adult trees. Our results suggest that current management practices could be improved by intensifying logging in some areas to improve regeneration of light demanding species. Sufficient seed input in logged areas should be ensured by interspersing large patches of unlogged forest with logged areas. This may also assist regeneration of species that perform poorly in disturbed areas.

Demography of Machaerium cuspidatum, a shade-tolerant neotropical liana

The population dynamics of the liana Machaerium cuspidatum (Fabaceae) were studied in an Amazonian forest in Ecuador using a stage-classified matrix model. Growth, mortality and number of new seedlings were recorded over two 1.5-y periods in eight 20 × 250-m transects. The population growth rate (λ) was 1.032, which was significantly higher than 1. The dynamics of the species were most influenced by survival of large plants, which is typical for slow-growing woody species. λ varied little among years or transects in spite of the high seedling production in one period. The importance of canopy openness and crown height for population growth was studied using bootstraps on λ for different subsets of the whole population. The results suggest that the population growth rate was lower in tall forest (height > 10 m) than in the population in general. The population growth rates in areas with shaded understorey and in low forest (≤ 20 m) were the same as for the whole population. A life table response experiment (LTRE) revealed that the lower λ in tall forest resulted from lower growth and survival of large plants in tall forest. These results indicate that the species is shade-tolerant but that it is sensitive to variations in forest dynamics. The dominance of the species and the increasing population size suggest that the forest has had a low disturbance rate for a long time.

Is it worthwhile scaring geese to alleviate damage to crops? – An experimental study

Summary 1. Increasing population sizes of geese are the cause of numerous agricultural conflicts in many regions of the Northern Hemisphere. Scaring is often used as a tool to chase geese away from fields, either as a means to protect vulnerable crops or as part of goose management schemes to drive geese to accommodation areas. Geese are quick to habituate to stationary scaring devices; hence, active scaring by humans is often employed. However, it remains undocumented how much effort is required for active scaring to be effective. 2. We explored the relationship between intensity of active human scaring on field use and behaviour by geese. Using an experimental framework, we applied four different scaring doses per day (geese were scared either 2, 5, 7 or 10 times per day), to random pastures in a pinkfooted goose spring staging area in mid-Norway, and recorded goose flock sizes, fleeing response distances, and average weekly goose densities assessed by dropping densities. In addition, we counted droppings in fields without scaring. We used mixed models to test for changes in the effects of different scaring doses over time and compared observed with predicted dropping levels. 3. Cumulative dropping densities increased at different rates depending on the scaring dose. Scaring dosage did not affect flock size and fleeing response distance during the study period, but both flock sizes and fleeing response distances changed with time. 4. Scaring dose 2 did not show any decrease in relative goose use compared to the fields without scaring, whereas doses 5, 7 and 10 all showed 74–78% fewer droppings by the end of the spring staging period, indicating a possible threshold between dose 2 and 5. The largest effect of scaring appeared during the first week of scaring. 5. Synthesis and applications. This study is the first to show a dose–response relationship between active scaring and field use of flocking geese. For individual farmers, the study provides guidance on the level of scaring effort needed to be cost-effective. If implemented as part of a management scheme with subsidy/accommodation areas in combination with systematic and persistent scaring, it can be used as a tool to keep geese away from areas where they are not wanted, thereby assisting in the alleviation of goose–agriculture conflicts. The approach in this study can be adapted and used in a wider range of wildlife interactions with human economic interests.

Characteristics and propagation of airgun pulses in shallow water with implications for effects on small marine mammals

Airguns used in seismic surveys are among the most prevalent and powerful anthropogenic noise sources in marine habitats. They are designed to produce most energy below 100 Hz, but the pulses have also been reported to contain medium-to-high frequency components with the potential to affect small marine mammals, which have their best hearing sensitivity at higher frequencies. In shallow water environments, inhabited by many of such species, the impact of airgun noise may be particularly challenging to assess due to complex propagation conditions. To alleviate the current lack of knowledge on the characteristics and propagation of airgun pulses in shallow water with implications for effects on small marine mammals, we recorded pulses from a single airgun with three operating volumes (10 in3, 25 in3 and 40 in3) at six ranges (6, 120, 200, 400, 800 and 1300 m) in a uniform shallow water habitat using two calibrated Reson 4014 hydrophones and four DSG-Ocean acoustic data recorders. We show that airgun pulses in this shallow habitat propagated out to 1300 meters in a way that can be approximated by a 18log(r) geometric transmission loss model, but with a high pass filter effect from the shallow water depth. Source levels were back-calculated to 192 dB re µPa2s (sound exposure level) and 200 dB re 1 µPa dB Leq-fast (rms over 125 ms duration), and the pulses contained substantial energy up to 10 kHz, even at the furthest recording station at 1300 meters. We conclude that the risk of causing hearing damage when using single airguns in shallow waters is small for both pinnipeds and porpoises. However, there is substantial potential for significant behavioral responses out to several km from the airgun, well beyond the commonly used shut-down zone of 500 meters.

Zackenberg in a circumpolar context

Throughout the Northern Hemisphere, changes in local and regional climate conditions are coupled to the recurring and persistent large-scale patterns of pressure and circulation anomalies spanning vast geographical areas, the so-called teleconnection patterns. Indeed, the atmospheric fluctuations described by the North Atlantic Oscillation (NAO) are closely associated with the last four decades of inter-annual variability in local snow and ice conditions observed in the Arctic. Since the NAO has also been connected with changes in the global climate, the behaviour of species, communities and other ecosystem elements at Zackenberg in relation to the NAO enables us to view these in circumpolar and global contexts. Large-scale systems like the NAO constitute the link between the global change and local climate variability to which ecosystem components respond. Here, we place selected ecosystem elements from the monitoring programme Zackenberg Basic presented in previous chapters in a circumpolar context related to NAO-mediated climatic changes. We begin by linking the local variability in winter weather conditions at Zackenberg to fluctuations in the NAO. We then proceed by linking the observed intra- and inter-annual behaviour of selected ecosystem elements to changes in the NAO. The functional ecosystem characteristics in focus are landscape gas exchange dynamics phenological patterns at different trophic levels, consumer-resource dynamics and community stability. The influence of the NAO is presented and discussed in a broader perspective based on information obtained from other arctic localities. The relation between the NAO and the Zackenberg winter weather, is nonlinear, reflecting differential effects of the NAO as the index moves between high and low phases. The inverse hyperbolic relationship found between the NAO and the amount of winter snow was also evident as non-linear response in organisms and systems to inter-annual changes in the NAO. Responses investigated included growth and reproduction in plants and animals, population dynamics and synchrony, inter-trophic interactions and community stability together with system feedback dynamics. (Less)

Diurnal variation in the behaviour of the Pink-footed Goose (Anser brachyrhynchus) during the spring stopover in Trøndelag, Norway

AbstractDuring the spring migration, the Pink-footed Goose Anser brachyrhynchus stops in mid-Norway to refuel before continuing its flight to the Svalbard breeding grounds. While in mid-Norway the geese feed on pasture, stubble and newly sown grain fields. Here, we describe the diurnal variation in goose behaviour at a staging site and assess the extent to which behavioural patterns are attributable to physiological factors (digestibility of the food) and environmental conditions (flock size, type and frequency of disturbance and distance to roost). We found that feeding activity peaked at mid-day, whereas the birds were most alert in the morning and afternoon. The behaviour of Pink-footed Goose also varied with habitat type, disturbance level and distance to roost. The diurnal variation in feeding activity differed from behaviour reported for geese on the wintering grounds, indicating that the birds have different energetic and nutrient demands when at spring staging sites. Seasonal changes in habitat availability as well as density dependence may also affect the birds’ behavioural patterns. A sporadic, unpredictable disturbance reduced the proportion of geese feeding to a greater extent than a predictable, recurrent disturbance, but feeding activity was highest under undisturbed conditions.ZusammenfassungVeränderungen im Verhalten von Kurzschnabelgänsen (Anser brachyrhynchus) im Tagesverlauf während ihrer Frühlingsrast in Trøndelag, Norwegen Während des Frühjahrszuges rasten Kurzschnabelgänse in Mittelnorwegen, um vor ihrem Weiterflug in die Brutgebiete in Spitzbergen nochmals Nahrung aufzunehmen. In Mittelnorwegen fressen diese Gänse auf Weideland, Stoppelfeldern und frischer Getreidesaat. Diese Untersuchung beschreibt die tageszeitlichen Veränderungen im Verhalten der Gänse an einem Rastplatz und beurteilt, inwieweit Verhaltensmuster mit physiologischen Faktoren (Verdaubarkeit des Futters) und Umweltbedingungen (Gruppengröße, Art und Häufigkeit von Störungen und Entfernung vom Schlafplatz) in Verbindung gebracht werden können. Die Futteraufnahme hatte ihren Höhepunkt um Mittag, während die Vögel am Morgen und Nachmittag am wachsamsten waren. Das Verhalten der Kurzschnabelgänse unterschied sich auch in Abhängigkeit von Habitat, Ausmaß von Störungen und der Entfernung vom Schlafplatz. Die tageszeitlichen Veränderungen in der Nahrungsaufnahme unterschieden sich von denen, die über Gänse im Winterquartier berichtet wurden, was darauf hindeutet, dass die Vögel während ihrer Frühjahrsrast unterschiedliche energetische und Nährstoff-Anforderungen haben. Auch saisonale Veränderungen in der Habitatverfügbarkeit und Dichteabhängigkeit könnten die Verhaltensmuster der Vögel beeinflussen. Sporadische, unvorhersehbare Störungen verringerten den Anteil an fressenden Gänsen in stärkerem Maße als vorhersagbare, wiederkehrende Störungen, aber die Fraßaktivität war am höchsten unter ungestörten Bedingungen.