| 1. |
- Myers-Smith, Isla H., et al.
(författare)
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Complexity revealed in the greening of the Arctic
- 2020
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Ingår i: Nature Climate Change. - : Springer Science and Business Media LLC. - 1758-678X .- 1758-6798. ; 10:2, s. 106-117
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Tidskriftsartikel (refereegranskat)abstract
- As the Arctic warms, vegetation is responding, and satellite measures indicate widespread greening at high latitudes. This ‘greening of the Arctic’ is among the world’s most important large-scale ecological responses to global climate change. However, a consensus is emerging that the underlying causes and future dynamics of so-called Arctic greening and browning trends are more complex, variable and inherently scale-dependent than previously thought. Here we summarize the complexities of observing and interpreting high-latitude greening to identify priorities for future research. Incorporating satellite and proximal remote sensing with in-situ data, while accounting for uncertainties and scale issues, will advance the study of past, present and future Arctic vegetation change.
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| 2. |
- Egelkraut, Dagmar D., 1989-
(författare)
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Long-lasting ecological legacies of reindeer on tundra vegetation
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Reindeer can have strong effects on the plant species composition and functioning of tundra ecosystems, and often promote a transition towards a graminoid-dominated vegetation type. As a result, they influence many ecological processes, such as nutrient dynamics, soil biotic composition and functioning, and carbon storage. Several studies suggest that the effect of reindeer on vegetation may follow predictable patterns and could induce an alternative stable vegetation state. However, little empirical data on the long-term stability of reindeer effects on vegetation exist, as it is inherently challenging to study these ecological processes experimentally on a sufficiently long timescale. The main objective of this thesis was therefore to gain a better understanding of the long-term ecological processes following reindeer-induced vegetation shifts.In order to gain a more mechanistic insight in what initially drives this transition, I used a field-based grazing simulation experiment in which I separated defoliation, trampling, moss removal and the addition of feces. This allowed me to test the relative contribution of reindeer-related activities to initiating the shift from moss and heath- dominated tundra towards a graminoid-dominated vegetation state. Additionally, I studied the long-term ecological stability following such a vegetation shift. I did this by addressing historical milking grounds (HMGs): sites where high reindeer concentrations associated with historical traditional reindeer herding practices induced a vegetation transition from shrubs towards graminoids several centuries earlier, but which were abandoned a century ago. Studying HMGs allowed me to address: 1. The potential stability of reindeer-induced vegetation shifts; 2. The ecological mechanisms contributing to the long-term stability of these vegetation shifts; and 3. How such long-lasting vegetation changes influence soil carbon- and nutrient cycling.I found that trampling by reindeer is an important mechanism by which reindeer cause vegetation change. Addressing HMGs further revealed that this vegetation change can be hightly persistent, as the studied HMGs showed only a low encroachment at the surrounding borders in the last 50 years. The vegetation in the core areas of all studied HMGs had remained strikingly stable, and were hardly invaded by surrounding shrubs. Interestingly, soil nutrient concentrations and microbial activities were still different from the surrounding area as well, and even comparable to actively grazed areas. Even after many centuries of changed vegetation composition and soil processes, there was no difference in total carbon sequestration. This suggests that the environmental conditions for microbial decomposition were more important than vegetation composition for the soil carbon stocks, in our study site.After studying the contemporary habitat use of HMGs by reindeer and other herbivores, investigating the potential plant-soil feedbacks mechanisms and detailed soil analyses, I concluded that several ecological mechanisms contribute to the long-term stability of HMGs: first, the altered soil biotic and abiotic conditions appear to have a stronger advantage for HMG vegetation than for the surrounding tundra vegetation. Furthermore, I found a clear browsing preference of small rodents on single shrubs proliferating in HMGs, causing a strong limitation on shrub expansion. Moreover, the dense established sward of graminoids likely poses a strong direct competition for space and nutrients, hindering seedling establishment. Finally, I conclude that HMGs are highly stable on relevant ecological timescales, and propose how the concepts of historical contingency and ASS can be applied to understand stability of these reindeer-induced vegetation transitions.
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| 3. |
- Horstkotte, Tim, 1981-, et al.
(författare)
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Pastures under pressure : Effects of other land users and the environment
- 2022
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Ingår i: Reindeer Husbandry and Global Environmental Change. - London : Routledge. - 9781000593402 - 9780367632670 ; , s. 76-98
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Bokkapitel (refereegranskat)abstract
- Reindeer husbandry has a long history of sharing landscapes with a multitude of other forms of land use. By competing for space, industrial resource developments from the early 20th century onwards have affected where, when and how the landscape can be used for reindeer grazing. Extending from the local to the landscape level, these impacts can reduce pastures either directly or indirectly as a result of increasing landscape fragmentation or changing reindeer behaviour. Furthermore, environmental drivers influence the dynamics of forage availability or accessibility for reindeer. The observed trend of shrinking pastures in the three countries is caused by these cumulative impacts. As a consequence, grazing pressure on the remaining pastures increases, and it curtails reindeer herders’ options to respond to the challenges of climate change. Reversing the continuing decrease in pastures requires the restoration of grazing resources and increasing landscape connectivity to facilitate movement and grazing rotation. However, socio-political incentives are also required to sustain reindeer pastures in the future. This includes an increase in the influence of reindeer herders on land use decisions and the inclusion of their traditional ecological knowledge of pasture management to identify alternative approaches to natural resource management.
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| 4. |
- Karlsson, Per Erik, et al.
(författare)
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The vulnerability of northern European vegetation to ozone damage in a changing climate An assessment based on current knowledge
- 2021
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The potential vulnerability of vegetation at northern latitudes to ozone damage was assessed based on current knowledge with regard to air ozone concentrations and leaf ozone uptake as well as to plant traits affecting ozone tolerance. The focus was on the northern European arctic, alpine and northern boreal vegetation zones, with a special focus on high-altitude vegetation. In particular, we analysed if there are increasing risks for ozone impacts on northern vegetation due to high spring ozone concentrations in relation to climate change induced shifts such as e.g. an earlier start of the growing season. The ozone concentrations in these regions are characterized by the influence of a combination of conditions caused by high latitudes and high altitudes. Ozone concentrations increase with altitude and the difference in ozone concentrations between day and night are smaller at high-altitude and high-latitude sites. Summer periods with long daylight conditions potentially promote the leaf ozone uptake through the open stomata. The aims of this report were: • To assess the current state of knowledge regarding the potential vulnerability of far northern vegetation to ozone damage, today and in the future • To provide advice for policy implications regarding necessary ozone precursor emission abatement • To provide advice for future research and monitoring of ozone impacts on the vegetation at northern latitudes Ongoing environmental changes affecting far northern latitude ecosystems were reviewed. Current and novel methods were described for how to estimate the time of year during which the ozone exposure for vegetation should be accumulated. Time trends for ozone concentrations at northern latitudes were analysed. Ozone episodes with high concentrations at far northern latitudes were described. Source attributions of northern ozone concentrations were analysed. Environmental conditions at far northern latitudes that might be important for ozone damage were evaluated. Plant traits that can influence the ozone vulnerability were discussed. Current experimental results for ozone injury on northern plant species were evaluated. Future scenarios for ozone impact on northern vegetation were discussed. Some important results from the analyses are described below. At high altitudes and high latitudes, the ozone concentrations are relatively similar during day- and night-time. Furthermore, at high latitudes, the long daylight duration during the summer has the potential to increase the duration of the daily period with plant gas exchange and leaf ozone uptake. Therefore, the absorption of ozone through the stomata may potentially be higher at northern latitudes. However, measurements of light intensity and quality at northern sites in combination with a simple calculation example illustrated that this probably was not the case, since the potential added ozone uptake in the early morning and late evening at northern sites may be cancelled out by a lower ozone uptake in the middle of the day, as compared to southern sites. Both data on budburst and data on ecosystem CO2 exchange as well as meteorological observations show that there has been a development towards an earlier start of the growing season during the year, with approximately 0.5 – 1 day per year. Thus, there is clear evidence for an earlier start of the growing season, which is likely to continue. However, the timing of the spring ozone maximum is also shifted towards earlier in the year. There is presently no evidence for an increasing overlap between the growing season and the ozone peak. Despite this, there is a potential for increased ozone uptake to vegetation in spring due to the earlier growing start of vegetation and increased uptake of ozone to vegetation in May. The impact of this on the accumulated phytotoxic ozone dose for northern vegetation needs to be investigated further. The overall conclusions about the present and near future ozone vulnerability of northern vegetation were: • There remain uncertainties regarding to what extent northern vegetation is affected by ozone exposure. • According to current knowledge, we could not find evidence that expected changes in ozone concentrations and climate would make the northern arctic, alpine and subalpine vegetation substantially more vulnerable to ozone than other types of European vegetation. • The risk of significant and lasting negative impact of the current exposure to ozone on northern boreal forests is most likely not greater than for boreonemoral and nemoral forests in southern Fennoscandia. • However, peak ozone concentrations occurring in spring and early summer may affect vegetation at northern latitudes in Fennoscandia since the start of the growing season in the future may occur earlier during the year. The policy implications that can be derived from these conclusions were: • The current state of knowledge implies that ecosystems in the far north are not more susceptible to ozone than vegetation in other parts of Europe. Hence, we cannot advocate for a stronger reduction of ozone precursors emissions based exclusively on the ozone sensitivity of vegetation in the far north. • Policies designed to reduce emissions of ozone precursors to protect vegetation in other parts of Europe as well as in the entire northern hemisphere are likely to suffice to protect vegetation in northern Fennoscandia. There are important remaining knowledge gaps. Our conclusions are based on important, but limited observations. Experimental evidence from investigations specifically designed to study ozone sensitivity of high-altitude vegetation in northern Europe are to a large extent lacking. It is recommended that further experimental research is undertaken to directly compare the ozone sensitivity of plants of high-latitude/high-altitude origin with that of plants (species, genotypes) representative of regions of the southern part of the Nordic region. This research should include the characteristics of the high-latitude climate and other conditions. A specific research question is if the new ozone critical levels for European vegetation based on PODYSPEC (Mapping Manual, 2017) are correct, both regarding calculation methodology as well as impact assessments? In particular, there is a lack of information about the degree of stomata closure during nights in high-latitude area plants. This is important for the modelling of ozone uptake (dry deposition) in these areas and requires coordinated measurement campaigns in close cooperation with modelers. Further research questions may be related to the future development of the northern regions – e.g. oil and gas extraction including flaring, shipping, more tourism and climate change – how will that affect the ozone exposure of in the northern vegetation? Do future ozone precursor emission scenarios describe this correctly? Will warm and dry summers like 2018 become more frequent in connection with climate change, and how will this affect ozone impacts on vegetation? There are currently very few, long term ozone monitoring stations in the arctic and alpine vegetation zones, in particular at high altitudes. Given the expected increase in anthropogenic activities in these areas in combination with climate change, it is strongly recommended to increase the number of high-altitude ozone monitoring sites in these regions.
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| 5. |
- Laptander, Roza, et al.
(författare)
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Critical seasonal conditions in the reindeer-herding year : A synopsis of factors and events in Fennoscandia and northwestern Russia
- 2024
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Ingår i: Polar Science. - : Elsevier. - 1873-9652 .- 1876-4428. ; 39
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Forskningsöversikt (refereegranskat)abstract
- In this article, we identify what herders in Fennoscandia and northwestern Russia see as critical conditions and events in the annual reindeer herding cycle. Indigenous Sámi and Yamal reindeer herders identify eight seasons, each of which has crucial importance in its own way. Differences in perception between Fennoscandian and northwestern Russian reindeer herders about good and bad seasonal conditions are based on the degree of climatic and geographic variation, herd control and the variety of simultaneous pressures on pastures. The scope and speed of ongoing climate change in the Arctic will profoundly modify these conditions, and consequently shape critical events and outcomes in reindeer herding. The resulting challenges need to be assessed in the context of social and economic dynamics. Reindeer herders throughout Fennoscandia and Russia are concerned about future prospects of their livelihood. To adapt to climate change and develop new strategies, reindeer herders must have access to pastures; they must retain their mobility and flexibility; and their participation in land-use decisions must be endorsed.
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| 6. |
- Parmentier, Frans Jan W., et al.
(författare)
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A distributed time-lapse camera network to track vegetation phenology with high temporal detail and at varying scales
- 2021
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Ingår i: Earth System Science Data. - : Copernicus GmbH. - 1866-3508 .- 1866-3516. ; 13:7, s. 3593-3606
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Tidskriftsartikel (refereegranskat)abstract
- Near-surface remote sensing techniques are essential monitoring tools to provide spatial and temporal resolutions beyond the capabilities of orbital methods. This high level of detail is especially helpful to monitor specific plant communities and to accurately time the phenological stages of vegetation - which satellites can miss by days or weeks in frequently clouded areas such as the Arctic. In this paper, we describe a measurement network that is distributed across varying plant communities in the high Arctic valley of Adventdalen on the Svalbard archipelago with the aim of monitoring vegetation phenology. The network consists of 10 racks equipped with sensors that measure NDVI (normalized difference vegetation index), soil temperature, and moisture as well as time-lapse RGB cameras (i.e. phenocams). Three additional time-lapse cameras are placed on nearby mountains to provide an overview of the valley. We derived the vegetation index GCC (green chromatic channel) from these RGB photos, which has similar applications as NDVI but at a fraction of the cost of NDVI imaging sensors. To create a robust time series for GCC, each set of photos was adjusted for unwanted movement of the camera with a stabilizing algorithm that enhances the spatial precision of these measurements. This code is available at 10.5281/zenodo.4554937 (Parmentier, 2021) and can be applied to time series obtained with other time-lapse cameras. This paper presents an overview of the data collection and processing and an overview of the dataset that is available at 10.21343/kbpq-xb91 (Nilsen et al., 2021). In addition, we provide some examples of how these data can be used to monitor different vegetation communities in the landscape.
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| 7. |
- Parmentier, Frans Jan W., et al.
(författare)
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Vulnerability and resilience of the carbon exchange of a subarctic peatland to an extreme winter event
- 2018
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 13:6
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Tidskriftsartikel (refereegranskat)abstract
- Extreme winter events that damage vegetation are considered an important climatic cause of arctic browning - a reversal of the greening trend of the region - and possibly reduce the carbon uptake of northern ecosystems. Confirmation of a reduction in CO2 uptake due to winter damage, however, remains elusive due to a lack of flux measurements from affected ecosystems. In this study, we report eddy covariance fluxes of CO2 from a peatland in northern Norway and show that vegetation CO2 uptake was delayed and reduced in the summer of 2014 following an extreme winter event earlier that year. Strong frost in the absence of a protective snow cover - its combined intensity unprecedented in the local climate record - caused severe dieback of the dwarf shrub species Calluna vulgaris and Empetrum nigrum. Similar vegetation damage was reported at the time along ∼1000 km of coastal Norway, showing the widespread impact of this event. Our results indicate that gross primary production (GPP) exhibited a delayed response to temperature following snowmelt. From snowmelt up to the peak of summer, this reduced carbon uptake by 14 (0-24) g C m-2 (∼12% of GPP in that period) - similar to the effect of interannual variations in summer weather. Concurrently, remotely-sensed NDVI dropped to the lowest level in more than a decade. However, bulk photosynthesis was eventually stimulated by the warm and sunny summer, raising total GPP. Species other than the vulnerable shrubs were probably resilient to the extreme winter event. The warm summer also increased ecosystem respiration, which limited net carbon uptake. This study shows that damage from a single extreme winter event can have an ecosystem-wide impact on CO2 uptake, and highlights the importance of including winter-induced shrub damage in terrestrial ecosystem models to accurately predict trends in vegetation productivity and carbon sequestration in the Arctic and sub-Arctic.
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| 8. |
- Rasmus, Sirpa, et al.
(författare)
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Policy documents considering biodiversity, land use, and climate in the European Arctic reveal visible, hidden, and imagined nexus approaches
- 2024
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Ingår i: One Earth. - : Cell Press. - 2590-3330 .- 2590-3322. ; 7:2, s. 265-279
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Tidskriftsartikel (refereegranskat)abstract
- The Arctic is experiencing rapid and interlinked socio-environmental changes. Therefore, governance approaches that take the complex interactions between climate change, biodiversity loss, increasing land use pressures, and local livelihoods into account are needed: nexus approaches. However, an overview of whether and to what extent Arctic policies address these nexus elements in concert has been missing. Here we analyzed a large sample of publicly available assessment reports and policy documents from the terrestrial European Arctic. Our results show that, although nexus approaches are widely adopted in Arctic policy reporting, the emphasis varies among the governance levels, and documents underestimate certain interactions: local communities and traditional livelihoods are seldom seen as actors with agency and impact. Practical implementations were identified as potential advancements in Arctic governance: ecosystem-specific, technological, and authoritative solutions; co-production of knowledge; and adaptive co-management. Implementation of nexus approaches can promote more holistic environmental governance and guide cross-sectoral policies.
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| 9. |
- Riseth, Jan Åge, et al.
(författare)
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Sámi traditional ecological knowledge as a guide to science : snow, ice and reindeer pasture facing climate change
- 2011
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Ingår i: Polar Record. - : Cambridge University Press. - 0032-2474 .- 1475-3057. ; 47:3, s. 202-217
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Tidskriftsartikel (refereegranskat)abstract
- Scientific studies of challenges of climate change could be improved by including other sources of knowledge, such as traditional ecological knowledge (TEK), in this case relating to the Sámi. This study focuses on local variations in snow and ice conditions, effects of the first durable snow, and long term changes in snow and ice conditions as pre-requisites for understanding potential future changes. Firstly, we characterised snow types and profiles based on Sámi categories and measured their density and hardness. Regression analysis showed that density can explain much of the variation in hardness, while snow depth was not significantly correlated with hardness. Secondly, we found that whether it is dry/cold or warm/wet around the fall of the first durable snow is, according to Sámi reindeer herders, crucial information for forecasting winter grazing conditions, but this has had limited focus within science. Thirdly, elderly herders’ observations of changes in snow and ice conditions by ‘reading nature’ can aid reinterpretation of meteorological data by introducing researchers to alternative perspectives. In conclusion we found remarkable agreement between scientific measurements and Sámi terminology.We also learnt that TEK/science cooperation has much potential for climate change studies, though time and resources are needed to bridge the gap between knowledge systems. In particular, TEK attention to shifts in nature can be a useful guide for science.
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| 10. |
- Stark, Sari, et al.
(författare)
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The ecosystem effects of reindeer (Rangifer tarandus) in northern Fennoscandia : past, present and future
- 2023
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Ingår i: Perspectives in plant ecology, evolution and systematics. - : Elsevier. - 1433-8319 .- 1618-0437. ; 58
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Forskningsöversikt (refereegranskat)abstract
- The semi-domesticated nature of the reindeer (Rangifer tarandus L.) makes it a distinct case among the world's herbivores. Here, we review the literature on how reindeer shape vegetation and soil carbon and nitrogen cycles in northernmost Fennoscandia. We first describe main historical events that shaped the present-day grazing patterns in the different countries, then discuss the methodological considerations needed for interpreting evidence from grazer exclosures in ecological and environmental contexts. We argue that it is critical to be aware that these experiments do not measure the effect of grazing per se, but rather, they measure the responses of existing ecosystem structure and function to the sudden cessation of grazing in an environment, which was to a large degree shaped by it. Studies show that the direction and the magnitude of the effects of reindeer on vegetation and soil processes vary across habitats and depend on both the current land-uses and the historically formed grazing regimes; knowledge of the history is thus a key prerequisite for understanding the role of reindeer in ecosystems. As a general trend, reindeer affect soil nutrient cycles to a stronger extent in subarctic than in boreal ecosystems. In sites where reindeer have changed soil nutrient availability, they indirectly modify vegetation and productivity even after the cessation of grazing. We reason that the concepts of cultural and natural landscapes are not mutually exclusive in the case of reindeer ranges. Understanding how the intensity and seasonal timing of both past and present grazing direct ecosystem changes under climate warming is crucial for predicting future ecosystem structures and functioning in northern Fennoscandia as well as ecosystems in general.
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