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- 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. |
- 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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| 3. |
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| 4. |
- Lämås, Tomas, et al.
(författare)
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Tree retention practices in boreal forests: what kind of future landscapes are we creating?
- 2015
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Ingår i: Scandinavian Journal of Forest Research. - : Informa UK Limited. - 0282-7581 .- 1651-1891. ; 30, s. 526-537
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Tidskriftsartikel (refereegranskat)abstract
- Tree retention practices promoting biodiversity may reshape future boreal forest production landscapes. Using the Heureka system, scenarios of 0%, 5%, and 20% retained patches at the stand level were projected over 200 years in a 533 ha boreal landscape. Visualizations of future forest states at a landscape scale and a more detailed scale were made based on the projections. The no retention results in no forest >120 years old, and no large trees (diameter at breast height >40 cm for conifers and >35 cm for broadleaved trees) 100 years from now. With retention levels of 5% and 20%, the area of old forest will comprise 7% and 19% of the total area, respectively. The average number of large trees per ha will be 4 and 13, respectively. Deadwood volumes will be 2.5 times higher at 5% retention and 4 times higher at 20% retention compared to no retention. Landscape visualizations indicate that retention patches covering 5% will marginally modify the visual impression, compared to clear-cuts, while 20% cover will create a much more varied landscape. We conclude that the retention approach is essential for restoring natural conditions. Landscape transformation will be slow and depend on starting conditions and retention levels.
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| 6. |
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| 7. |
- Nilsson, Mats, et al.
(författare)
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A nationwide forest attribute map of Sweden predicted using airborne laser scanning data and field data from the National Forest Inventory
- 2017
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Ingår i: Remote Sensing of Environment. - : Elsevier BV. - 0034-4257 .- 1879-0704. ; 194, s. 447-454
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Tidskriftsartikel (refereegranskat)abstract
- The National Mapping Agency in Sweden has conducted an airborne laser scanning (ALS) campaign covering almost the entire country for the purpose of creating a new national Digital Elevation Model (DEM). The ALS data were collected between 2009 and 2015 using Leica, Optech, Riegi, and Trimble scanners and have a point density of 0.5-1.0 pulses/m(2). A high resolution national raster database (12.5 m x 12.5 m cell size) with forest variables was produced by combining the ALS data with field data from the Swedish National Forest Inventory (NFI). Approximately 11500 NFI plots (10 meter radius) located on productive forest land, inventoried between 2009 and 2013, were used to create linear regression models relating selected forest variables, or transformations of the variables, to metrics derived from the ALS data. The resulting stand level relative RMSEs for predictions of stem volume, basal area, basal-area weighted mean tree height, and basal-area weighted mean stem diameter were in the ranges of 17.2-22.0%, 13.9-18.2%, 5.4-9.5%, and 8.7-13.1%, respectively. It was concluded that the predictions had an accuracy that were at least as good as data typically used in forest management planning. Above ground tree biomass was also included in the national raster database but not validated on a stand -level. An important part of the project was to make the raster database available to private forest owners, forest associations, forest companies, authorities, researchers, and the general public. Thus, all predicted forest variables can be viewed and downloaded free of charge at the Swedish Forest Agency's homepage (http://www. skogsstyrelsen.se/skogligagrunddata). (C) 2016 Elsevier Inc. All rights reserved.
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| 8. |
- Wikström, Anders, et al.
(författare)
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Fishing, reproductive volume and regulation: population dynamics and exploitation of the eastern Baltic cod
- 2016
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Ingår i: Population Ecology. - : Wiley. - 1438-390X .- 1438-3896. ; 58:1, s. 199-211
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Tidskriftsartikel (refereegranskat)abstract
- The relative importance of exploitation rate and environmental variability in generating fluctuations of harvested populations is a key issue in academic ecology as well as population management. We studied how the eastern Baltic cod (Gadus morhua) is affected by fishing and environmental variation by using a newly developed single species state-space model. Survey data and auxiliary environmental data were used to estimate the model parameters. The model was then used to predict future development of the eastern Baltic cod under different fishing mortalities and abiotic conditions. Abiotic condition was represented by an index: reproductive volume which is the volume of water suitable (in terms of salinity and oxygen content) for the successful development of the early life stages of Baltic cod. The model included direct density dependence, fishing, and a lagged effect of reproductive volume. Our analysis showed that fishing rate is approximately three times more important than reproductive volume in explaining the population dynamics. Furthermore, our model suggests either under- or over-compensatory dynamics depending on the reproductive volume and long term catch levels. It follows that fishing can either reduce or increase temporal oscillations of the cod stock depending on whether the dynamics is over- or undercompensatory, respectively. The sustainable level of fishing rate is however dependent on reproductive volume. Our model predicts a dual role of fishing rate, stabilizing when reproductive volume is high and destabilizing when it is low. Exploitation rate may therefore increase or decrease the risk of the population of cod dropping below a given biomass reference point depending on the environmental conditions, which has practical implications for fisheries management.
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