| 1. |
- Irminger Street, Therese, et al.
(författare)
-
Removal of woody vegetation from uncultivated field margins is insufficient to promote non-woody vascular plant diversity
- 2015
-
Ingår i: Agriculture, Ecosystems & Environment. - : Elsevier BV. - 1873-2305 .- 0167-8809. ; 201, s. 1-10
-
Tidskriftsartikel (refereegranskat)abstract
- Uncultivated field margins are one of the most frequent non-crop habitat types in contemporary, highintensity agricultural landscapes and may therefore be important for the persistence of many farmland species. Managing field margins in a way that preserves, and preferably enhances, their value for biodiversity is therefore important. In the present study, we evaluate how the flora of uncultivated field margins is affected by the removal of woody vegetation as prescribed by an agri-environment scheme (AES) under the Swedish Rural Development Program 2007–2013. We used generalized linear mixed models and detrended correspondence analysis to compare the flora of open (cleared) and more overgrown field margins, located within agricultural landscapes of different complexity, in Scania, S. Sweden. As expected, there was a negative effect of management on woody species. However, the local (1m2) and transect (100 m) level richness of non-woody species did not differ significantly between management categories, and there were no differences in the within-transect variability of non-woody species (local b diversity) or the species composition (0.25m2 plots) in managed and unmanaged field margins. Our results show that the removal of woody vegetation from uncultivated field margins, as prescribed by the evaluated AES, is unlikely to benefit non-woody plant species. The species composition of the sampled field margins suggests that inclusion of appropriate field layer management alone is unlikely to be sufficient to improve habitat conditions for grassland species unless measures are taken to counteract eutrophication. Landscape type, on the other hand, influenced both the total richness and the richness of each of the species groups that were considered to be of particular conservation value in the present study: field margins in the complex agricultural landscapes were significantly richer than those in the simple ones. Maintaining non-crop habitat at the landscape scale is likely to be a necessary first step in the prevention of a further decline of farmland plants.
|
|
| 2. |
|
|
| 3. |
- Dalmayne, Jonas, et al.
(författare)
-
Assessment of fine-scale plant species beta diversity using WorldView-2 satellite spectral dissimilarity
- 2013
-
Ingår i: Ecological Informatics. - : Elsevier BV. - 1574-9541. ; 18:november, s. 1-9
-
Tidskriftsartikel (refereegranskat)abstract
- Plant species beta diversity is influenced by spatial heterogeneity in the environment. This heterogeneity can potentially be characterised with the help of remote sensing. We used WorldView-2 satellite data acquired over semi-natural grasslands on The Baltic island of Öland (Sweden) to examine whether dissimilarities in remote sensing response were related to fine-scale, between-plot dissimilarity (beta diversity) in non-woody vascular plant species composition within the grasslands. Fieldwork, including the on-site description of a set of 30 2 m × 2 m plots and a set of 30 4 m × 4 m plots, was performed to record the species dissimilarity between pairs of same-sized plots. Spectral data were extracted by associating each plot with a suite of differently sized pixel windows, and spectral dissimilarity was calculated between pairs of same-sized pixel windows. Relationships between spectral dissimilarity and beta diversity were analysed using univariate regression and partial least squares regression. The study revealed significant positive relationships between spectral dissimilarity and fine-scale (2 m × 2 m and 4 m × 4 m) between-plot species dissimilarity. The correlation between the predicted and the observed species dissimilarity was stronger for the set of large plots (4 m × 4 m) than for the set of small plots (2 m × 2 m), and the association between spectral and species data at both plot scales decreased when pixel windows larger than 3 × 3 pixels were used. We suggest that the significant relationship between spectral dissimilarity and species dissimilarity is a reflection of between-plot environmental heterogeneity caused by differences in grazing intensity (which result in between-plot differences in field-layer height, and amounts of biomass and litter). This heterogeneity is reflected in dissimilarities in both the species composition and the spectral response of the grassland plots. Between-plot dissimilarities in both spectral response and species composition may also be caused by between-plot variations in edaphic conditions. Our results indicate that high spatial resolution satellite data may potentially be able to complement field-based recording in surveys of fine-scale species diversity in semi-natural grasslands.
|
|
| 4. |
|
|
| 5. |
- Eklundh, Lars, et al.
(författare)
-
Investigating the use of Landsat thematic mapper data for estimation of forest leaf area index in southern Sweden
- 2003
-
Ingår i: Canadian Journal of Remote Sensing. - 1712-7971. ; 29:3, s. 349-362
-
Tidskriftsartikel (refereegranskat)abstract
- The study aims at investigating the use of Landsat thematic mapper (TM) for mapping leaf area index (LAI) in coniferous and deciduous forests in southern Sweden. LAI has been estimated in the field with optical measurements, allometric equations, and litter-trap data, and empirical relationships between LAI estimates and satellite-measured reflectances have been analysed. Several common vegetation indices and multiple regressions where estimated LAI is predicted as a function of various spectral bands are tested. The results indicate significant relationships between Landsat TM reflectances and parameters related to LAI, and the relationships are improved when separating coniferous and deciduous stands. The best relationships occur between Landsat TM data and the product of effective LAI as estimated with the LAI-2000 instrument and a needle clumping factor (L-G), which explains about 80% of the variation in coniferous stands and about 50% of the variation in deciduous stands. The best single bands in coniferous stands are the middle-infrared bands (TM5 and TM7), and the best vegetation index is the moisture stress index (TM5/TM4). The best single band in deciduous stands is TM4, and the best vegetation index is the simple ratio (SR).
|
|
| 6. |
- Eriksson, Helena, et al.
(författare)
-
Estimating LAI in deciduous forest stands
- 2005
-
Ingår i: Agricultural and Forest Meteorology. - : Elsevier BV. - 1873-2240 .- 0168-1923. ; 129:1-2, s. 27-37
-
Tidskriftsartikel (refereegranskat)abstract
- The leaf area index (LAI), was estimated in deciduous forests of southern Sweden using different estimation techniques. The effective LAI (L-e) was estimated optically by measurements with the gap fraction instrument LAI-2000 and corrections for the aggregation of leaves were achieved by using the TRAC (Tracing Radiation and Architecture of Canopies) instrument. Two methods for correcting the contribution of the woody material were tested. The aim was to find the most reliable estimation technique, and therefore the measurements were compared with LAI estimated from litter fall collection. Optically estimated L-e was correlated with litter trap LAI, indicating that L-e can be used as an estimate of LAI in deciduous forests of the same characteristics as tested here. The litter fall collection technique involves knowledge about the specific leaf area (SLA). Since, we found that SLA varied between leaves picked from top positioned branches and leaves picked from low positioned branches as well as between different species, we suggest some caution when interpreting the values.
|
|
| 7. |
- Hall, Karin
(författare)
-
Crop Monitoring in Sweden
- 1989
-
Ingår i: International Journal of Remote Sensing. - 1366-5901. ; , s. 461-484
-
Tidskriftsartikel (refereegranskat)
|
|
| 8. |
- Hall, Karin, et al.
(författare)
-
Inventorying management status and plant species richness in semi-natural grasslands using high spatial resolution imagery
- 2010
-
Ingår i: Applied Vegetation Science. - 1402-2001. ; 13:2, s. 221-233
-
Tidskriftsartikel (refereegranskat)abstract
- Question Can we reliably estimate grazing intensity, indicators of grazing intensity (i.e. field-layer height and shrub-cover), and vascular plant species richness in semi-natural grasslands from high spatial resolution satellite data? Location The Baltic Island of Oland (Sweden). Methods Fieldwork included the on-site description of grazed and ungrazed areas and shrub-cover within 107 semi-natural grassland sites. Field-layer height and vascular plant species richness (total within-site and mean small-scale species richness) were recorded within the sites. Digital classification of QuickBird data was performed to identify grazed and ungrazed areas and shrub-cover. Vegetation indices were generated to analyze the performance of satellite data for estimating field-layer height, and the spectral heterogeneity was used to characterize the within-site environmental heterogeneity. Results The proportion of digitally classified grazed area explained 45% of the variation in field-layer height and 43% of the variation in shrub-cover. Field-layer height was significantly related to vegetation indices. A linear model with three explanatory variables (spectral richness(red), spectral richness(NIR), and shrub-cover) explained 47% of the variation in total within-site species richness. Conclusions High spatial resolution imagery may assist in the monitoring of the processes that follow the cessation of grazing, on the scale of individual grassland sites. Measures of spectral heterogeneity acquired by high spatial resolution imagery can be used in the assessment of total within-site vascular plant species richness in semi-natural grassland vegetation.
|
|
| 9. |
- Hall, Karin, et al.
(författare)
-
Spectral heterogeneity of QuickBird satellite data is related to fine-scale plant species spatial turnover in semi-natural grasslands
- 2012
-
Ingår i: Applied Vegetation Science. - 1402-2001. ; 15:1, s. 145-157
-
Tidskriftsartikel (refereegranskat)abstract
- Abstract Question: Can satellite data be related to fine-scale species diversity and does the integrated use of field and satellite data provide information that can be used in the estimation of fine-scale species diversity in semi-natural grassland sites? Location: The Baltic Island of Oland (Sweden). Methods: Field work including the on-site description of 62 semi-natural grassland sites (represented by three 0.5m0.5m plots per site) was performed to record response variables (total species richness, mean species richness and species spatial turnover) and field-measured explanatory variables (field-layer height and distance between plots). Within each site, QuickBird satellite data were extracted from a standardized sample area by associating each field plot with a 33 pixel window (1 pixel = 2.4m2.4 m). Explanatory variables (the normalized difference vegetation index and spectral heterogeneity) were generated from the satellite data. Correlation tests, univariate regressions, variance partitioning and multivariate linear regressions were used to analyse the associations between response and explanatory variables. Results: There was a significant association between the spectral heterogeneity of the near-infrared band and the field-measured spatial turnover of species. The most parsimonious explanatory model for each response variable included both field-measured and satellite-generated explanatory variables. The models explained 30–35% of the variation in species diversity (total richness 36%, mean richness 31%, species turnover 33%). Conclusions: High spatial resolution satellite data are capable of supplying fine-scale habitat information that is relevant for the monitoring and conservation management of fine-scale plant diversity in semi-natural grasslands.
|
|
| 10. |
|
|
