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Present-day vegetation helps quantifying past land cover in selected regions of the Czech Republic.

Abraham V, Oušková V, Kuneš P - PLoS ONE (2014)

Bottom Line: Decreasing the site radius has a similar effect as increasing the wind speed parameter.Increasing the background radius does not affect the estimates significantly.However, further adjustments to PPEs exceed the ranges of original values, so their relevance is uncertain.

View Article: PubMed Central - PubMed

Affiliation: Department of Botany, Faculty of Science, Charles University in Prague, Prague, Czech Republic; Department of Botany, Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic.

ABSTRACT
The REVEALS model is a tool for recalculating pollen data into vegetation abundances on a regional scale. We explored the general effect of selected parameters by performing simulations and ascertained the best model setting for the Czech Republic using the shallowest samples from 120 fossil sites and data on actual regional vegetation (60 km radius). Vegetation proportions of 17 taxa were obtained by combining the CORINE Land Cover map with forest inventories, agricultural statistics and habitat mapping data. Our simulation shows that changing the site radius for all taxa substantially affects REVEALS estimates of taxa with heavy or light pollen grains. Decreasing the site radius has a similar effect as increasing the wind speed parameter. However, adjusting the site radius to 1 m for local taxa only (even taxa with light pollen) yields lower, more correct estimates despite their high pollen signal. Increasing the background radius does not affect the estimates significantly. Our comparison of estimates with actual vegetation in seven regions shows that the most accurate relative pollen productivity estimates (PPEs) come from Central Europe and Southern Sweden. The initial simulation and pollen data yielded unrealistic estimates for Abies under the default setting of the wind speed parameter (3 m/s). We therefore propose the setting of 4 m/s, which corresponds to the spring average in most regions of the Czech Republic studied. Ad hoc adjustment of PPEs with this setting improves the match 3-4-fold. We consider these values (apart from four exceptions) to be appropriate, because they are within the ranges of standard errors, so they are related to original PPEs. Setting a 1 m radius for local taxa (Alnus, Salix, Poaceae) significantly improves the match between estimates and actual vegetation. However, further adjustments to PPEs exceed the ranges of original values, so their relevance is uncertain.

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Simulation of REVEALS estimates (proportion in log scale).Alnus-Capinus, Picea-Cerealia and Abies delimit three groups of terminal velocities of pollen: slow, medium and fast, which also represent the pattern of the rest of taxa not plotted here. Arrows show the change of estimates from control (full line) to scenario (dashed line); for details, see Table 2. (A) Simulation A: Increasing radius of the sedimentation basin under two wind speed velocities (B) Simulation B: Increasing radius of the area of the background pollen under two wind speed velocities. (C) Simulation C: Fixed versus increasing radius of the sedimentation basin of the second site. (D) Simulation D: Increasing pollen counts of Alnus and Picea under two radii of the sedimentation basin. The reference setting common to all control simulations is marked on the secondary horizontal axis by “REF”.
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pone-0100117-g004: Simulation of REVEALS estimates (proportion in log scale).Alnus-Capinus, Picea-Cerealia and Abies delimit three groups of terminal velocities of pollen: slow, medium and fast, which also represent the pattern of the rest of taxa not plotted here. Arrows show the change of estimates from control (full line) to scenario (dashed line); for details, see Table 2. (A) Simulation A: Increasing radius of the sedimentation basin under two wind speed velocities (B) Simulation B: Increasing radius of the area of the background pollen under two wind speed velocities. (C) Simulation C: Fixed versus increasing radius of the sedimentation basin of the second site. (D) Simulation D: Increasing pollen counts of Alnus and Picea under two radii of the sedimentation basin. The reference setting common to all control simulations is marked on the secondary horizontal axis by “REF”.

Mentions: (Figure 4) Pollen productivity and the dispersal term are inversely proportional to REVEALS estimates. Hence, the highest REVEALS estimates are those for Cerealia, which have the lowest PPE. However, Abies, the taxon with the highest PPE, does not have the lowest REVEALS estimates because it has a low dispersal term. The first two simulations (Figure 4A, 4B) show how parameters of the dispersal term – wind speed (u), fall speed (vg), radius of the sedimentation basin (R) and maximum range of the regional vegetation (Zmax) – influence REVELS vegetation estimates. Taxa within each simulation show a similar pattern to taxa with similar fall speed of pollen. Alnus-Capinus, Picea-Cerealia and Abies delimit three groups of taxa corresponding to three ranges of terminal velocities of pollen: slow (0.021–0.042 m/s), medium (0.056–0.06 m/s) and fast (0.12 m/s). All remaining taxa fall within one of these ranges (Table 1).


Present-day vegetation helps quantifying past land cover in selected regions of the Czech Republic.

Abraham V, Oušková V, Kuneš P - PLoS ONE (2014)

Simulation of REVEALS estimates (proportion in log scale).Alnus-Capinus, Picea-Cerealia and Abies delimit three groups of terminal velocities of pollen: slow, medium and fast, which also represent the pattern of the rest of taxa not plotted here. Arrows show the change of estimates from control (full line) to scenario (dashed line); for details, see Table 2. (A) Simulation A: Increasing radius of the sedimentation basin under two wind speed velocities (B) Simulation B: Increasing radius of the area of the background pollen under two wind speed velocities. (C) Simulation C: Fixed versus increasing radius of the sedimentation basin of the second site. (D) Simulation D: Increasing pollen counts of Alnus and Picea under two radii of the sedimentation basin. The reference setting common to all control simulations is marked on the secondary horizontal axis by “REF”.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4061133&req=5

pone-0100117-g004: Simulation of REVEALS estimates (proportion in log scale).Alnus-Capinus, Picea-Cerealia and Abies delimit three groups of terminal velocities of pollen: slow, medium and fast, which also represent the pattern of the rest of taxa not plotted here. Arrows show the change of estimates from control (full line) to scenario (dashed line); for details, see Table 2. (A) Simulation A: Increasing radius of the sedimentation basin under two wind speed velocities (B) Simulation B: Increasing radius of the area of the background pollen under two wind speed velocities. (C) Simulation C: Fixed versus increasing radius of the sedimentation basin of the second site. (D) Simulation D: Increasing pollen counts of Alnus and Picea under two radii of the sedimentation basin. The reference setting common to all control simulations is marked on the secondary horizontal axis by “REF”.
Mentions: (Figure 4) Pollen productivity and the dispersal term are inversely proportional to REVEALS estimates. Hence, the highest REVEALS estimates are those for Cerealia, which have the lowest PPE. However, Abies, the taxon with the highest PPE, does not have the lowest REVEALS estimates because it has a low dispersal term. The first two simulations (Figure 4A, 4B) show how parameters of the dispersal term – wind speed (u), fall speed (vg), radius of the sedimentation basin (R) and maximum range of the regional vegetation (Zmax) – influence REVELS vegetation estimates. Taxa within each simulation show a similar pattern to taxa with similar fall speed of pollen. Alnus-Capinus, Picea-Cerealia and Abies delimit three groups of taxa corresponding to three ranges of terminal velocities of pollen: slow (0.021–0.042 m/s), medium (0.056–0.06 m/s) and fast (0.12 m/s). All remaining taxa fall within one of these ranges (Table 1).

Bottom Line: Decreasing the site radius has a similar effect as increasing the wind speed parameter.Increasing the background radius does not affect the estimates significantly.However, further adjustments to PPEs exceed the ranges of original values, so their relevance is uncertain.

View Article: PubMed Central - PubMed

Affiliation: Department of Botany, Faculty of Science, Charles University in Prague, Prague, Czech Republic; Department of Botany, Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic.

ABSTRACT
The REVEALS model is a tool for recalculating pollen data into vegetation abundances on a regional scale. We explored the general effect of selected parameters by performing simulations and ascertained the best model setting for the Czech Republic using the shallowest samples from 120 fossil sites and data on actual regional vegetation (60 km radius). Vegetation proportions of 17 taxa were obtained by combining the CORINE Land Cover map with forest inventories, agricultural statistics and habitat mapping data. Our simulation shows that changing the site radius for all taxa substantially affects REVEALS estimates of taxa with heavy or light pollen grains. Decreasing the site radius has a similar effect as increasing the wind speed parameter. However, adjusting the site radius to 1 m for local taxa only (even taxa with light pollen) yields lower, more correct estimates despite their high pollen signal. Increasing the background radius does not affect the estimates significantly. Our comparison of estimates with actual vegetation in seven regions shows that the most accurate relative pollen productivity estimates (PPEs) come from Central Europe and Southern Sweden. The initial simulation and pollen data yielded unrealistic estimates for Abies under the default setting of the wind speed parameter (3 m/s). We therefore propose the setting of 4 m/s, which corresponds to the spring average in most regions of the Czech Republic studied. Ad hoc adjustment of PPEs with this setting improves the match 3-4-fold. We consider these values (apart from four exceptions) to be appropriate, because they are within the ranges of standard errors, so they are related to original PPEs. Setting a 1 m radius for local taxa (Alnus, Salix, Poaceae) significantly improves the match between estimates and actual vegetation. However, further adjustments to PPEs exceed the ranges of original values, so their relevance is uncertain.

Show MeSH
Related in: MedlinePlus