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Scale-dependent effects of nitrogen deposition on plant diversity

24TH CCE workshop and 30th task force meeting in Rome 7 – 10 April 2014

Lukas Kohli, Tobias Roth, Beat Rihm and Beat Achermann

Hintermann & Weber AG | 3Scale dependent effets of N deposition | 8.4.2014|

Introduction

Do we overestimate N deposition effects onregional biodiversity when surveying at a local scale?

What size of N deposition model grid is suitable to detect effects on biodiversity?

biodiversity

grid size of N deposition

Hintermann & Weber AG |

Modelled nitrogen deposition 2007

Scale dependent effets of N deposition | 8.4.2014|

Hintermann & Weber AG | Scale dependent effets of N deposition | 8.4.2014| 5

Swiss Biodiversity monitoring

landscape scalelocal scale

→ national monitoring program for biodiversity since 2001 → see: www.biodiversitymonitoring.ch → two spatial scales


Source: Koordinationsstelle BDM 2011

Local scale: Species diversity in habitats Z9


Hintermann & Weber AG | Source: Koordinationsstelle BDM 2011

Species diversity in Landscapes Z7



Landscape scale: sampling grid unit / transect



Transects of about 2.5 km length

Survey of vascular plants along the transects (2.5 m to the right and to the left)

N deposition modelled at hectare grid; average of cells containing parts of the transect

Investigations at landscape level Z7

◦ ●

●

1 km



Analysis with general additive model GAM

• Elevation [m.a.s.l.]• Annual precipitation [mm yr-1]• Slope [degree]• Moisture value [mean F-values; Landolt et al. 2010]• Light value [mean L-values; Landolt et al. 2010]• Calcareous content [6 levels; Swiss Environmental domains] • Nitrogen deposition [kg N ha-1 yr-1]

Effects of N deposition were compared to the situationat background deposition (1kg N ha-1 yr-1)-> reduction of plant diversity in %

11Hintermann & Weber AG | Scale dependent effets of N deposition | 8.4.2014|

Local vs. landscape scale



Does plot size matter?Chalcraft et al., 2008. Ecology, 89, 2165-2171:…a focus on the effects of N enrichment on biodiversity at small spatial scales may often overestimate (and sometimes underestimate) declines in regional biodiversity by failing to recognize the effects of N on ß diversity.

• Do we overestimate N deposition effects onregional biodiversity when surveying at a local scale?

• Is the effect for different groups alike?



• Species richness

• Oligotrophic speciesadapted do nutrient poor conditionsLandolt et al. 2010

• Target species for the agricultural sectorFOEN & FOAG 2008

Arnica montana

Centaurea montana


Species richness

0 10 20 30 40

0

-20

-40

-60

N deposition kg ha-1 yr-1 N deposition kg ha-1 yr-1

Red

uctio

n of

pla

nt d

iver

sity

%

0 10 20 30 40



Oligotrophic species

0 10 20 30 40

0

-20

-40

-60


Red

uctio

n of

pla

nt d

iver

sity

%

0 10 20 30 40



Target species for the agricultural sector

0 10 20 30 40

0

-20

-40

-60


Red

uctio

n of

pla

nt d

iver

sity

%

0 10 20 30 40




The plot size matters

• We overestimated effects of N deposition onregional biodiversity when upscaling from small plots

• The effect varied for the different groups

• Species richness little difference

• Effects of N deposition on oligotrophic species and on target species for the agricultural sector are much stronger on a small scale

• Generalisations from experimental studies may be critical

18Hintermann & Weber AG | Scale dependent effets of N deposition | 8.4.2014|

Effect of grid size ofN deposition model


Grid size resolution

Dore et al., 2012. Biogeosciences, 9, 1597-1609:In areas with generally low exceedance and for montane vegetation types, the exceedance statistics were more sensitive to model data resolution.



Does grid size of deposition models matter?

• What is the biggest grid size of N deposition model to detect effects on biodiversity?

• Is size the same for different groups?


average of cells containing parts of the transect (average 25% of cells)

grid of 0.5 km side length➜

Mean N deposition of all cells of 1x1 km and

Grids with 5, 10, 25 and 50 km side length

with its origin at N 45° 35.143 E 5°

31.050


1 km

●




50x50 km

1x1 km


Species richness

0

-10

-20

-30

Side length (km) of grid cells in N deposition model

Red

uctio

n of

pla

nt d

iver

sity

%

0.5 1 5 25 5010


Oligotrophic species

0

-10

-20

-30


Red

uctio

n of

pla

nt d

iver

sity

%

0.5 1 5 25 5010


Target species for the agricultural sector

0

-10

-20

-30


Red

uctio

n of

pla

nt d

iver

sity

%

0.5 1 5 25 5010



Grid size matters• The smaller the grid, the stronger are the predicted effect

of N deposition

• No difference between 0.5 and 1 km side length

• Effects of N deposition on biodiversity were not detected with grids > 5 km side length


Acknowledgement

all the botanists Beat Rihm, Tobias Roth and Beat Achermannn Federal Office for the Environment you for the attention

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