1,721,020 research outputs found
Vertebrate predator-prey interactions in a seasonal environment
No full textThe High Arctic, with its low number of species, is characterised by a relatively simple ecosystem, and the vertebrate predator-prey interactions in the valley Zackenbergdalen in Northeast Greenland are centred around the collared lemming Dicrostonyx groenlandicus and its multiple predators. In this chapter, we examine these interactions in a climatic context through the predator-lemming model developed for the more southerly Greenlandic site, Traill empty set (Gilg et al., 2003, Science 302, 866-868), parameterised by means of data from the BioBasis monitoring programme to reflect the situation in Zackenbergdalen. Despite large differences in relative predator densities between these two locations, the two lemming populations exhibit remarkably similar and synchronous population fluctuations. Also, in both lemming populations the annual fluctuations seem primarily driven by a 1-year delay in stoat Mustela erminea predation and stabilising predation from the generalist predators, in Zackenbergdalen mainly the arctic fox Alopex lagopus. In Zackenbergdalen, however, the coupling between the specialist stoat and the lemming population is relatively weak. During summer, the predation pressure is high, and in most years so high that the lemming population declines during summer. This heavy predation pressure is also reflected in the summer behaviour of the lemmings, and lemmings spend most of their time under ground, and when above, they devote equal amounts of time to being vigilant and foraging. In most winters, predation by the only remaining predator, the stoat, is insufficient to regulate the lemming population. In the predator-lemming model, seasonality plays an important role in determining the. growth rate of the lemming population as well as the density of the various lemming predators. We therefore examined how variation in the relative length of seasons affected the pattern of fluctuation in the lemming population by gradually advancing or delaying the time of onset of winter. In contrast to advanced winter onset, delayed winter onset led to increased periodicity. The climatic conditions, hence, affect not only the seasonal but also the inter-annual dynamics of the collared lemming population in Zackenbergdale
Population dynamical responses to climate change
No full textit is well established that climatic as well as biological factors, in concert, form the mechanistic basis for our understanding of how populations develop over time and across space. Although this seemingly suggests simplicity, the climate-biology dichotomy of population dynamics embraces a bewildering number of interactions. For example, individuals within a population may compete for space and other resources and, being embedded in an ecosystem, individuals in any population may also interact with individuals of competing species as well as those from adjacent trophic levels. In principal, the effects of climate change may potentially extend through any of these interactions. In this chapter, we focus on the extent to which evolutionarily distinct species at different trophic levels respond to similar changes in climate. By using a broad spectrum of statistically and ecologically founded approaches, we analyse concurrently the influence of climatic variability and trophic interactions on the temporal population dynamics of species in the terrestrial vertebrate community at Zackenberg. We describe and contrast the population dynamics of three predator species (arctic fox Alopex lagopus, stoat Mustela erminea and long-tailed skua Stercorarius longicaudus), two herbivore species (collared lemming Dicrostonyx groenlandicus and musk ox Ovibos moschatus) and five wader species (common ringed plover Charadrius hiaticula, red knot Calidris canutus, sanderling Calidris alba, dunlin, Calidris alpina and ruddy turnstone Arenaria interpres) with respect to intra-specific density dependence, consumer-resource interactions and direct as well as indirect inter-trophic level mediated effects of varying snow-cover. We found that the temporal population dynamics of all three predators, both herbivores and three out of five wader species, displayed significant direct density dependence. Only two species (sanderling and long-tailed skua) displayed dynamics characterised by delayed density dependence. The direct effects of previous winter's snow were related to over-wintering strategies of resident and migrating species, respectively. The dynamics of all four resident species were significantly affected by variations in snow-cover and explained up to 65% of their inter-annual dynamics. The three predators differed in their numerical response to changes in prey densities. Whereas the population dynamics of arctic fox were not significantly related to changes in lemming abundance, both the stoat and the breeding of long-tailed skua were mainly related to lemming dynamics. The predator-prey system at Zackenberg differentiates from previously described systems in high-arctic Greenland, which, we suggest, is related to differences in the compositions of predator and prey species. The significant inter-trophic interactions are centred on the collared lemming as a result of which there is a significant potential for indirect climate effects mediated across the established consumer-resource interaction
Zackenberg in a circumpolar context
No full textThroughout 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
Soil and Plant Community Characteristics and Dynamics at Zackenberg
No full textArctic soils hold large amounts of nutrients in the weatherable minerals and the soil organic matter, which slowly decompose. The decomposition processes release nutrients to the plant-available nutrient pool as well as greenhouse gases to the atmosphere. Changes in climatic conditions, for example, changes in the distribution of snow, water balance and the length of the growing season, are likely to affect the complex interactions between plants, abiotic and biotic soil processes as well as the composition of soil micro- and macro-fauna and thereby the overall decomposition rates. These interactions, in turn, will influence soil-plant functioning and vegetation composition in the short as well as in the long term. In this chapter, we report on soils and. plant communities and their distribution patterns in the valley Zackenbergdalen and focus on the detailed investigations within five dominating plant communities. These five communities are located along an ecological gradient in the landscape and are closely related to differences in water availability. They are therefore indirectly formed as a result of the distribution of landforms, redistribution of snow and drainage conditions. Each of the plant communities is closely related to specific nutrient levels and degree of soil development including soil element accumulation and translocation, for example, organic carbon. Results presented here show that different parts of the landscape have responded quite differently to the same overall climate changes the last 10 years and thus, most likely in the future too. Fens represent the wettest sites holding large reactive buried carbon stocks. A warmer climate will cause a permafrost degradation, which most likely will result in anoxic decomposition and increasing methane emissions. However, the net gas emissions at fen sites are sensitive to long-term changes in the water table level. Indeed, increasing maximum active layer depth at fen sites has been recorded together with a decreasing water level at Zackenberg. This is in line with the first signs of increasing extension of grasslands at the expense of fens. In contrast, the most exposed and dry areas have less soil carbon, and decomposition processes are periodically water limited. Here, an increase in air temperatures may increase active layer depth more than at fen sites, but water availability will be critical in determining nutrient cycling and plant production. Field manipulation experiments of increasing temperature, water supply and nutrient addition show that soil-plant interactions are sensitive to these variables. However, additional plant-specific investigations are needed before net effects of climate changes on different landscape and plant communities can be integrated in a landscape context and used to assess the net ecosystem effect of future climate scenarios
Introduction
No full textOur continuously changing global environment requires continuous and detailed monitoring for us to understand how ecosystems are structured and function in response to climatic changes. Understanding the arctic ecosystems is of particular importance (Oechel et al., 1997). Indeed, rather than in boreal and temperate regions, the forecasted climatic changes will be first and most pronounced in the Arctic. Hence, performing long-term monitoring of an arctic ecosystem provides us with the unique ability to not only give "early warnings" of climate change impacts but also, and perhaps even more important, predict how and where in the ecosystem these will be most pronounced and with what consequences for stability, structure and function. Since 1995, Zackenberg Ecological Research Operations (ZERO) has monitored annually over 1500 variables concurrently across the physical and biological compartments of a single high-arctic terrestrial ecosystem in central Northeast Greenland. This makes ZERO the most integrated and comprehensive long-term monitoring and research programme presently operating in the Arctic. This book explores the complex physical and ecological long-term dynamics of a high-arctic terrestrial ecosystem. Since the book is based on data from ZERO, this introductory chapter presents the structural and organisational foundation for ZERO. Following our introduction are four chapters providing the climatic and ecological background together with a presentation of the study area. The rest of the book is devoted entirely to the physical, ecological and ecosystem processes
Thermoregulatory behavior in a warming Arctic : bed site selection by Svalbard reindeer (Rangifer tarandus platyrhynchus) in summer
Full text linkClimate change leads to rapidly increasing mean temperatures, and the climate warming is particularly pronounced in the Arctic. In Arctic mammals with long generation times, evolution of physiological and morphological traits may not be fast enough to keep up with the rapid climate warming. However, thermoregulatory behavior can possibly serve as an important buffer for negative effects from climate change, but this is poorly understood. In this study, I investigated if the Arctic, cold adapted, free-ranging Svalbard reindeer (Rangifer tarandus platyrhynchus) used cool bed sites as a part of their thermoregulation in summer. I predicted that Svalbard reindeer select cooling substrates, as snow and mire, as bed sites, and increasingly so at high ambient temperatures. I also predicted that they select cool ground as bed sites when cooling substrates are absent, and that the preference increases with ambient temperatures. In addition, I investigated if the bed site selection differed between age and sex of the individuals, as larger individuals are expected to have a higher need to select cooler bed sites compared to smaller individuals during warm ambient temperatures. I visually detected resting reindeer in field and recorded habitat variables and ground temperature both at 371 bed sites and random control sites 10 and 100 meters distant. Bed site selection was analyzed using resource selection functions. I found that the Svalbard reindeer preferred bed sites on cool substrates (snow and mire) as well as cool ground on days with warm ambient temperature. The preference for both cooling substrates and cool ground did not depend on age or sex. This study hence demonstrated that all age and sex categories of Svalbard reindeer used bed sites for thermoregulation, indicating heat stress during warm periods in summer. The study was conducted in an environment where neither predatory threat or insect harassment (monitored, but found insignificant) influenced the bed site selection. As such, this study is among the first to provide conclusive evidence of the use of bed sites as thermal refugee, without confounding factors. It is also the first study to find a selection for ground temperature by a cold adapted ungulate in a habitat where cold and wet cooling substrates and shade from canopy are not involved. The study contributes to the understanding of how a highly cold adapted Arctic ungulate adapt to increasing temperatures, which are expected to continue in the future.M-N
Late Quaternary environmental and cultural changes in the Wollaston Forland Region, Northeast Greenland
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