| 1. |
- Asplund, Maria. E., 1970, et al.
(author)
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Dynamics and fate of blue carbon in a mangrove-seagrass seascape : influence of landscape configuration and land-use change
- 2021
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In: Landscape Ecology. - : Springer. - 0921-2973 .- 1572-9761. ; 36, s. 1489-1509
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Journal article (peer-reviewed)abstract
- Context Seagrass meadows act as efficient natural carbon sinks by sequestering atmospheric CO2 and through trapping of allochthonous organic material, thereby preserving organic carbon (C-org) in their sediments. Less understood is the influence of landscape configuration and transformation (land-use change) on carbon sequestration dynamics in coastal seascapes across the land-sea interface. Objectives We explored the influence of landscape configuration and degradation of adjacent mangroves on the dynamics and fate of C-org in seagrass habitats. Methods Through predictive modelling, we assessed sedimentary C-org content, stocks and source composition in multiple seascapes (km-wide buffer zones) dominated by different seagrass communities in northwest Madagascar. The study area encompassed seagrass meadows adjacent to intact and deforested mangroves. Results The sedimentary C-org content was influenced by a combination of landscape metrics and inherent habitat plant- and sediment-properties. We found a strong land-to-sea gradient, likely driven by hydrodynamic forces, generating distinct patterns in sedimentary C-org levels in seagrass seascapes. There was higher C-org content and a mangrove signal in seagrass surface sediments closer to the deforested mangrove area, possibly due to an escalated export of C-org from deforested mangrove soils. Seascapes comprising large continuous seagrass meadows had higher sedimentary C-org levels in comparison to more diverse and patchy seascapes. Conclusion Our results emphasize the benefit to consider the influence of seascape configuration and connectivity to accurately assess C-org content in coastal habitats. Understanding spatial patterns of variability and what is driving the observed patterns is useful for identifying carbon sink hotspots and develop management prioritizations.
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| 2. |
- Björklund, Jesper, 1979, et al.
(author)
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Advances towards improved low-frequency tree-ring reconstructions, using an updated Pinus sylvestris L. MXD network from the Scandinavian Mountains
- 2013
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In: Journal of Theoretical and Applied Climatology. - : Springer Science and Business Media LLC. - 0177-798X .- 1434-4483. ; 113:3-4, s. 697-710
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Journal article (peer-reviewed)abstract
- The dendrochronological use of the parameter maximum density (MXD) in Pinus Sylvestris L., at high latitudes, has provided valuable insights into past summer temperature variations. Few long MXD chronologies, from climatically coherent regions, exist today, with the exception being in northern Europe. Five, 500-year-long, Fennoscandian, MXD chronologies were compared with regard to their common variability and climate sensitivity. They were used to test Signal-free standardization techniques, to improve inferences of low-frequency temperature variations. Climate analysis showed that, in accordance with previous studies on MXD in Fennoscandia, the summer temperature signal is robust (R (2) > 50 %) and reliable over this climatically coherent region. A combination of Individual standardization and regional curve standardization is recommended to refine long-term variability from these MXD chronologies and relieve problems arising from low replication and standardization end-effects.
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| 3. |
- Gunnarson, Björn E., et al.
(author)
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Legacies of pre-industrial land use can bias modern tree-ring climate calibrations
- 2012
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In: Climate Research (CR). - : Inter-Research Science Center. - 0936-577X .- 1616-1572. ; 53:1, s. 63-76
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Journal article (peer-reviewed)abstract
- In Scandinavia, dendrochronological reconstructions of past climate have mostly been based on tree-ring data from forests in which there has been, supposedly, very little or no human impact. However, human land use in sub-alpine forests has a substantially longer history and more profound effects on the forest ecosystems than previously acknowledged. Therefore, to assess human influence on tree-ring patterns over the last 500 yr, we have analyzed tree-ring patterns using trees from 2 abandoned Sami settlements and a reference site with no human impact-all situated in the Tjeggelvas Nature Reserve in north-west Sweden. The hypothesis was that land use legacies have affected tree-ring patterns, and in turn, the resulting palaeoclimate inferences that have been made from these patterns. Our results show that climate signals are strongest at the reference site and weakest at one of the settlement sites. From the 1940s to the present, tree growth at this settlement site has been significantly lower than at the reference site. Lower tree growth at old settlements may have resulted from rapid changes in the traditional land use, or following the abrupt change when the settlements were abandoned. Without site-specific know ledge of past land use, there is a high risk of accidently sampling trees that have been affected by human-induced disturbances in the past. This may create bias in the climate signals inferred from such trees, and hence bias the outcome of climate reconstructions. We therefore recommend sampling several separate sites in study areas to improve the robustness of inferences.
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| 4. |
- Linderholm, Hans W., 1968, et al.
(author)
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Dendroclimatology in Fennoscandia – from past accomplishments to future potential
- 2010
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In: Climate of the Past. - : Copernicus GmbH. - 1814-9324 .- 1814-9332. ; 6, s. 93-114.
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Journal article (peer-reviewed)abstract
- Fennoscandia has a strong tradition in dendrochronology, and its large tracts of boreal forest make the region well suited for the development of tree-ring chronologies that extend back several thousands of years. Two of the world’s longest continuous (most tree-ring chronologies are annually resolved) tree-ring width chronologies are found in northern Fennoscandia, with records from Tornetr¨ask and Finnish Lapland covering the last ca. 7500 yr. In addition, several chronologies between coastal Norway and the interior of Finland extend back several centuries. Tree-ring data from Fennoscandia have provided important information on regional climate variability during the mid to late Holocene and have played major roles in the reconstruction of hemispheric and global temperatures. Tree-ring data from the region have also been used to reconstruct large-scale atmospheric circulation patterns, regional precipitation and drought. Such information is imperative when trying to reach better understanding of natural climate change and variability and its forcing mechanisms, and placing recent climate change within a long-term context.
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| 5. |
- Gunnarson, Björn, et al.
(author)
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Improving a tree-ring reconstruction from west-central Scandinavia : 900 years of warm-season temperatures
- 2011
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In: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 36:1-2, s. 97-108:36, s. 97-108
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Journal article (peer-reviewed)abstract
- Dendroclimatological sampling of Scots pine (Pinus sylvestris L.) has been made in the province of Jamtland, in the west-central Scandinavian mountains, since the 1970s. The tree-ring width (TRW) chronology spans several thousand years and has been used to reconstruct June August temperatures back to 1632 BC. A maximum latewood density (MXD) dataset, covering the period AD 1107-1827 (with gap 1292-1315) was presented in the 1980s by Fritz Schweingruber. Here we combine these historical MXD data with recently collected MXD data covering AD 1292-2006 into a single reconstruction of April September temperatures for the period AD 1107 2006. Regional curve standardization (RCS) provides more low-frequency variability than non-RCS and stronger correlation with local seasonal temperatures (51% variance explained). The MXD chronology shows a stronger relationship with temperatures than the TRW data, but the two chronologies show similar multi-decadal variations back to AD 1500. According to the MXD chronology, the period since AD 1930 and around AD 1150-1200 were the warmest during the last 900 years. Due to large uncertainties in the early part of the combined MXD chronology, it is not possible to conclude which period was the warmest. More sampling of trees growing near the tree-line is needed to further improve the MXD chronology.
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| 6. |
- Cunningham, LK, et al.
(author)
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Reconstructions of surface ocean conditions from the North East Atlantic and Nordic Seas during the last Millennium
- 2013
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In: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 23:7, s. 921-935
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Journal article (peer-reviewed)abstract
- We undertake the first comprehensive effort to integrate North Atlantic marine climate records for the last millennium, highlighting some key components common within this system at a range of temporal and spatial scales. In such an approach, careful consideration needs to be given to the complexities inherent to the marine system. Composites therefore need to be hydrographically constrained and sensitive to both surface water mass variability and three-dimensional ocean dynamics. This study focuses on the northeast (NE) North Atlantic Ocean, particularly sites influenced by the North Atlantic Current. A composite plus regression approach is used to create an inter-regional NE North Atlantic reconstruction of sea surface temperature (SST) for the last 1000 years. We highlight the loss of spatial information associated with large-scale composite reconstructions of the marine environment. Regional reconstructions of SSTs off the Norwegian and Icelandic margins are presented, along with a larger-scale reconstruction spanning the NE North Atlantic. The latter indicates that the ‘Medieval Climate Anomaly’ warming was most pronounced before ad 1200, with a long-term cooling trend apparent after ad 1250. This trend persisted until the early 20th century, while in recent decades temperatures have been similar to those inferred for the ‘Medieval Climate Anomaly’. The reconstructions are consistent with other independent records of sea-surface and surface air temperatures from the region, indicating that they are adequately capturing the climate dynamics of the last millennium. Consequently, this method could potentially be used to develop large-scale reconstructions of SSTs for other hydrographically constrained regions.
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| 7. |
- Perry, Diana, et al.
(author)
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Spatial risk assessment of global change impacts on Swedish seagrass ecosystems
- 2020
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In: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 15:1
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Journal article (peer-reviewed)abstract
- Improved knowledge on the risk in ecologically important habitats on a regional scale from multiple stressors is critical for managing functioning and resilient ecosystems. This risk assessment aimed to identify seagrass ecosystems in southern Sweden that will be exposed to a high degree of change from multiple global change stressors in mid- and endof- century climate change conditions. Risk scores were calculated from the expected overlap of three stressors: sea surface temperature increases, ocean acidification and wind driven turbid conditions. Three high-risk regions were identified as areas likely to be exposed to a particularly high level of pressure from the global stressors by the end of the century. In these areas it can be expected that there will be a large degree of stressor change from the current conditions. Given the ecological importance of seagrass meadows for maintaining high biodiversity and a range of other ecosystem services, these risk zones should be given high priority for incorporation into management strategies, which can attempt to reduce controllable stressors in order to mitigate the consequences of some of the impending pressures and manage for maintained ecosystem resilience.
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| 8. |
- Drobyshev, Igor, et al.
(author)
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Multi-century reconstruction of fire activity in Northern European boreal forest suggests differences in regional fire regimes and their sensitivity to climate
- 2014
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In: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 102:3, s. 738-748
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Journal article (peer-reviewed)abstract
- Forest fires are one of the main disturbance agents in boreal and temperate ecosystems. To decipher large-scale temporal and spatial patterns of past fire activity in Scandinavia, we analysed the synchronicity of dendrochoronologically reconstructed fire events in a large network of sites (n=62; 3296 samples, 392 individual fire years) covering a wide geographical gradient (56.5-67.0 degrees N and 9.3-20.5 degrees E) over AD 1400-1900. We identified large fire years (LFY) as years with regionally increased forest fire activity and located the geographical centres of climatic anomalies associated with synchronous LFY occurrence across the region, termed LFY centroids. The spatial pattern of LFY centroids indicated the presence of two regions with climatically mediated synchronicity of fire occurrence, located south and north from 60 degrees N. The return intervals of LFYs in Scandinavia followed a Weibull distribution in both regions. Intervals, however, differed: a period of 40years would carry a 0.93 probability of LFY occurrence in the southern region, but only a 0.48 probability of LFY occurrence in the northern region. Over 1420-1759, the northern region was characterized by significantly higher temporal variability in LFY occurrence than the southern region. Temporal correlation of LFYs with reconstructed average summer temperature and total precipitation was evident mainly for the northern region. LFYs in this region were associated with positive temperature and negative precipitation anomalies over Scandinavia and with colder and wetter conditions in more southern parts of the European subcontinent. Synthesis. Historical patterns of the occurrence of large fire years (LFY) in Scandinavia point towards the presence of two well-defined zones with characteristic fire activity, with the geographical division at approximately 60 degrees N. The northern and mid-boreal forests, although exhibiting lower LFY frequencies, appeared to be more sensitive to past summer climate, as compared to the southern boreal forests. This would imply that fire regimes across Scandinavia may show an asynchronous response to future climate changes.
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| 9. |
- Seftigen, Kristina, 1985, et al.
(author)
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Reconstructed drought variability in southeastern Sweden since the 1650s
- 2013
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In: International Journal of Climatology. - : Wiley. - 0899-8418 .- 1097-0088. ; 33:11, s. 2449-2458
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Journal article (peer-reviewed)abstract
- In this study, we present the first regional reconstruction of summer drought for southeastern Sweden. The June–July standardized precipitation index (SPI) was reconstructed over the period 1650–2002 based on Pinus sylvestris L. tree-ring width data, where the reconstruction could account for 41.6% of the total variance in the instrumental record over 1901–2002. Our reconstruction suggests an overall wet 18th century and a dry 19th century. The most outstanding pluvial phase in the pre-instrumental period took place in the mid-1720s and lasted over 50 years, while multi-decadal periods of below average moisture conditions were reconstructed in the 1660s–1720s, 1800s-early 30s, and in the 1840s–50s. Several of these dry spells have previously been found in reconstructions from Sweden and Finland, indicating that our reconstruction reflects large-scale moisture anomalies across eastern Fennoscandia. Comparison of the SPI estimates with mid-tropospheric pressure patterns suggests that summertime drought is associated with positive pressure anomalies over British Isles and the North Sea, while an eastward movement of the Icelandic low-pressure systems over the western part of central Fennoscandia results in wetter than normal June–July conditions over the region of interest. Copyright 2012 Royal Meteorological Society
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| 10. |
- Bartolino, Valerio, et al.
(author)
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Forecasting fish stock dynamics under climate change: Baltic herring (Clupea harengus) as a case study
- 2014
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In: Fisheries Oceanography. - : Wiley. - 1054-6006 .- 1365-2419. ; 23:3, s. 258-269
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Journal article (peer-reviewed)abstract
- Climate change and anthropogenic disturbances may affect marine populations and ecosystems through multiple pathways. In this study we present a framework in which we integrate existing models and knowledge on basic regulatory processes to investigate the potential impact of future scenarios of fisheries exploitation and climate change on the temporal dynamics of the central Baltic herring stock. Alternative scenarios of increasing sea surface temperature and decreasing salinity of the Baltic Sea from a global climate model were combined with two alternative fishing scenarios, and their direct and ecosystem-mediated effects (i.e., through predation by cod and competition with sprat) on the herring population were evaluated for the period 2010-2050. Gradual increase in temperature has a positive impact on the long-term productivity of the herring stock, but it has the potential to enhance the recovery of the herring stock only in combination with sustainable fisheries management (i.e., F-msy). Conversely, projections of herring spawning stock biomass (SSB) were generally low under elevated fishing mortality levels (F-high), comparable with those experienced by the stock during the 1990s. Under the combined effects of long-term warming and high fishing mortality uncertainty in herring SSB projections was higher and increasing for the duration of the forecasts, suggesting a synergistic effect of fishery exploitation and climate forcing on fish populations dynamics. Our study shows that simulations of long-term fish dynamics can be an informative tool to derive expectations of the potential long-term impact of alternative future scenarios of exploitation and climate change.
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