| 1. |
- Bohlin, Jonas, et al.
(författare)
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Mapping forest attributes using data from stereophotogrammetry of aerial images and field data from the national forest inventory
- 2017
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Ingår i: Silva Fennica. - : Finnish Society of Forest Science. - 0037-5330 .- 2242-4075. ; 51
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Tidskriftsartikel (refereegranskat)abstract
- Exploring the possibility to produce nation-wide forest attribute maps using stereophotogrammetry of aerial images, the national terrain model and data from the National Forest Inventory (NFI). The study areas are four image acquisition blocks in mid-and south Sweden. Regression models were developed and applied to 12.5 m x 12.5 m raster cells for each block and validation was done with an independent dataset of forest stands. Model performance was compared for eight different forest types separately and the accuracies between forest types clearly differs for both image-and LiDAR methods, but between methods the difference in accuracy is small at plot level. At stand level, the root mean square error in percent of the mean (RMSE%) were ranging: from 7.7% to 10.5% for mean height; from 12.0% to 17.8% for mean diameter; from 21.8% to 22.8% for stem volume; and from 17.7% to 21.1% for basal area. This study clearly shows that aerial images from the national image program together with field sample plots from the NFI can be used for large area forest attribute mapping.
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| 2. |
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| 3. |
- Bensch, Staffan, et al.
(författare)
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Temporal dynamics and diversity of avian malaria parasites in a single host species
- 2007
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Ingår i: Journal of Animal Ecology. - : Wiley. - 1365-2656 .- 0021-8790. ; 76:1, s. 112-122
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Tidskriftsartikel (refereegranskat)abstract
- We have used molecular methods to unravel a remarkable diversity of parasite lineages in a long-term population study of great reed warblers Acrocephalus arundinaceus that was not foreseen from traditional microscopic examination of blood smears. This diversity includes eight Haemoproteus and 10 Plasmodium lineages of which most probably represent good biological species.Contrary to expectation, the relative frequency of parasite lineages seemed not to change over the 17-year study period and we found no effects of the parasites on a male secondary sexual ornament (song repertoire size) and two measures of fitness (adult survival and production of recruited offspring).We discuss whether the absence of fitness consequences of the parasites might relate to the fact that we have studied the host at the breeding sites in Europe, whereas the transmission seems to take place at the wintering sites in Africa, where the naive birds encounter the parasites for the first time and the resulting primary infections likely make them sicker than during the chronic phase of the infection.The prevalence of the three most common lineages appeared to fluctuate in parallel with a periodicity of approximately 3-4 years. Theoretical models based on intrinsic interactions between parasite antigen and host immune genes cannot explain such dynamics, suggesting that knowledge of extrinsic parameters such as vector distribution and alternative hosts are required to understand these patterns.
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| 4. |
- Jonzen, Jonas, et al.
(författare)
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Skogliga grunddata : digitala kartor för skogsbruket
- 2016
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Ingår i: Fakta. Skog. - 1400-7789.
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Annan publikation (populärvet., debatt m.m.)abstract
- Skogliga grunddata är digitala raster-kartor som beskriver tillståndet i skog och mark. De skogliga variablerna är i huvudsak framtagna genom en sambearbetning av laserdata från Lantmäteriets nationella laserskanning och provytor från Riksskogstaxeringen. De digitala kartorna som beskriver skogsmarken är till stor hjälp för privata skogsägare, skogstjänstemän, myndigheter, m fl. Data är dels tillgängligt för gratis nedladdning, men det finns även möjligheter att titta på kartorna med hjälp av interaktiva webverktyg. Lantmäteriets laserskanning påbörjades 2009 och fortgår än idag. Endast delar av fjällkedjan återstår. Grundtanken med laserskanningen var att få en bra höjdmodell över landet. En bra höjdmodell ger stor nytta vid all samhällsplanering, men är även till hjälp vid klimatanpassning. Riksskogstaxeringen samlar årligen in data om Sveriges skogstillstånd med permanenta och tillfälliga provytor. Dessa provytor är koordinatsatta och är väl spridda över hela landet. I detta projekt har provytor från Riksskogstaxeringen kombinerats med laserdata för att ta fram rasterkartor med uppgifter om virkesvolym, grundyta, medelhöjd, medeldiameter och trädbiomassa.
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| 5. |
- Jonzén, Niclas, et al.
(författare)
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Population dynamics of the Swedish Ornithological Society.
- 2003
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Ingår i: Ornis Svecica. - 1102-6812. ; 13:4, s. 107-114
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- It has recently been recognized that there is declining interest in ornithology among the younger generations. In this paper we analyse the short and long-term dynamics of the Swedish Ornithological Society (SOF) and the Swedish Society for Nature Conservation (SNF) by using analytical tools from population ecology. We first show that the increasing number of SOF and SNF members is not the result of a constant proportion of ornithologists or people interested in nature conservation among a growing Swedish population. Hence, the number of members most likely reflects the true interest in joining organizations such as SOF. We also demonstrate that the growth rate of SOF can be fairly well estimated, but the possible equilibrium size is uncertain. Removing the long-term trend reveals a cyclic pattern with a period of 23 years. This pattern was not found when analysing the SNF data and we discuss the observed patterns in relation to human and member generation time. Finally, we present an improved population model based on data up to 1998 and show how model predictions compare with the observed number of members in year 2002.
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| 6. |
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| 7. |
- Jonzén, Niclas, et al.
(författare)
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Rapid advance of spring arrival dates in long-distance migratory birds
- 2006
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 312:5782, s. 1959-1961
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Tidskriftsartikel (refereegranskat)abstract
- Several bird species have advanced the timing of their spring migration in response to recent climate change. European short-distance migrants, wintering in temperate areas, have been assumed to be more affected by change in the European climate than long-distance migrants wintering in the tropics. However, we show that tong-distance migrants have advanced their spring arrival in Scandinavia more than short-distance migrants. By analyzing a long-term data set from southern Italy, we show that long-distance migrants also pass through the Mediterranean region earlier. We argue that this may reflect a climate-driven evolutionary change in the timing of spring migration.
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| 8. |
- Jonzén, Niclas, et al.
(författare)
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Response to comment on "Rapid advance of spring arrival dates in long-distance migratory birds"
- 2007
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 315:5812, s. 598-598
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Both's comment questions our suggestion that the advanced spring arrival time of long-distance migratory birds in Scandinavia and the Mediterranean may reflect a climate-driven evolutionary change. We present additional arguments to support our hypothesis but underscore the importance of additional studies involving direct tests of evolutionary change.
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| 9. |
- Jonzén, Niclas, et al.
(författare)
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Sharing the bounty-Adjusting harvest to predator return in the Scandinavian human-wolf-bear-moose system
- 2013
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Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 265, s. 140-148
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Tidskriftsartikel (refereegranskat)abstract
- The increase and range extension of wolves (Canis lupus L) and brown bears ( Ursus arctos L) in Scandinavia inevitably impacts moose (Alces alces L.) populations and, as a consequence, the size and composition of the hunter harvest must be adjusted. We used a sex- and age-structured moose population model to delineate optimal harvest strategies under predation and to compare the resulting harvest composition with the strategy commonly implemented in practice. We examined how much moose density or adult sex ratio needs to change to fully compensate for losses to predation. We found a harvest allocation pattern in commonly used practical management across calves, bulls and cows that indicated a trade-off strategy between maximising the number of shot moose, the yield biomass and the number of shot prime bulls. This strategy performed quite well with respect to all yield measures and yielded an age structure most similar to the strategies maximising harvest biomass and prime bulls. Unless predation pressure was very high, the harvest loss could be completely compensated for by allowing a higher moose density. In other situations the current hunting strategy was not possible to implement and the moose density needed to sustain predation even without hunting increases dramatically. An alternative option to balance the predation loss was to accept a more female-biased sex ratio in the winter population. Hence, it may be possible to keep 50% calves in the harvest and still obtain the same total harvest if the proportion of bulls in the harvest is increased to compensate for predation. The increase of large carnivores competing with moose hunting creates conflicts and will inevitably reduce harvest yield unless hunting strategies change. We show how increased moose density and redistribution of the harvest towards bulls can mitigate this conflict and we provide a web-based tool, where stakeholders can compare the long-term effects of alternative management decisions and eventually adjust their hunting strategy accordingly. (C) 2013 Elsevier B.V. All rights reserved.
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| 10. |
- Jonzen, Niclas, et al.
(författare)
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Stochastic demography and population dynamics in the red kangaroo Macropus rufus
- 2010
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Ingår i: Journal of Animal Ecology. - : Wiley. - 0021-8790 .- 1365-2656. ; 79:1, s. 109-116
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Tidskriftsartikel (refereegranskat)abstract
- 1. Many organisms inhabit strongly fluctuating environments but their demography and population dynamics are often analysed using deterministic models and elasticity analysis, where elasticity is defined as the proportional change in population growth rate caused by a proportional change in a vital rate. Deterministic analyses may not necessarily be informative because large variation in a vital rate with a small deterministic elasticity may affect the population growth rate more than a small change in a less variable vital rate having high deterministic elasticity. 2. We analyse a stochastic environment model of the red kangaroo (Macropus rufus), a species inhabiting an environment characterized by unpredictable and highly variable rainfall, and calculate the elasticity of the stochastic growth rate with respect to the mean and variability in vital rates. 3. Juvenile survival is the most variable vital rate but a proportional change in the mean adult survival rate has a much stronger effect on the stochastic growth rate. 4. Even if changes in average rainfall have a larger impact on population growth rate, increased variability in rainfall may still be important also in long-lived species. The elasticity with respect to the standard deviation of rainfall is comparable to the mean elasticities of all vital rates but the survival in age class 3 because increased variation in rainfall affects both the mean and variability of vital rates. 5. Red kangaroos are harvested and, under the current rainfall pattern, an annual harvest fraction of c. 20% would yield a stochastic growth rate about unity. However, if average rainfall drops by more than c. 10%, any level of harvesting may be unsustainable, emphasizing the need for integrating climate change predictions in population management and increase our understanding of how environmental stochasticity translates into population growth rate.
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