Pond managementPond management

Pond management Pond management

Data Natuurpunt Data Natuurpunt (last 15 years)(last 15 years)::

Management of > 200 ponds in Flanders Management of > 200 ponds in Flanders (preliminary results)(preliminary results)

33%

21%

34%

9%

1%2%

Pond management Pond management Data Natuurpunt Data Natuurpunt (last 15 years)(last 15 years)::

Creation of 1049 new ponds in Flanders Creation of 1049 new ponds in Flanders Regionaal LandschapRegionaal Landschap

Provinciale domeinenProvinciale domeinen

NatuurpuntNatuurpunt

Agentschap Natuur & BosAgentschap Natuur & Bos

Provinces & MunicipalitiesProvinces & Municipalities

Private personsPrivate persons

… …

Pond management Pond management

Dredging (sludge removal): often used management techniqueDredging (sludge removal): often used management technique

Dredging needed Dredging needed silting up silting up

What is the effect of dredging?What is the effect of dredging?

Tommelen pond complex: Case studyTommelen pond complex: Case study

Management - dredging Management - dredging

Ponds in Tommelen dredged in October 2008

MOVIE(see website Pondscape: www.pondscape.be)

Case study: managementCase study: management

Case study: managementCase study: management

Physical & chemical variablesPhysical & chemical variables (nutrients, turbidity, oxygen, ...) (nutrients, turbidity, oxygen, ...)

MorphologyMorphology (depth, surface area, …) (depth, surface area, …)

Different organism groupsDifferent organism groups* Bacteria* Bacteria * Macroinvertebrates * Macroinvertebrates * Diatomea * Diatomea * Amphibians* Amphibians * Phytoplankton* Phytoplankton * Vegetation* Vegetation* Zooplankton* Zooplankton

Sampling:Sampling:- Spring & summer 2007 & 2008 - Spring & summer 2007 & 2008 pre-dredgingpre-dredging

- Spring & summer- Spring & summer 2009 2009 post-dredgingpost-dredging

Dredging in 2008 Dredging in 2008 effect in 2009? effect in 2009?

Management - dredging Management - dredging

Effect dredging on environmental factors?Effect dredging on environmental factors?

After dredging:After dredging: Higher suspended matterHigher suspended matter Higher chlorophyll concentrationsHigher chlorophyll concentrations

More open waterMore open water (also independent of ditch)(also independent of ditch)

Could affect communities Could affect communities

Effect of ditch on environmental factors?Effect of ditch on environmental factors?

Before dredging: Before dredging: Less vegetation and higher Less vegetation and higher conductivityconductivity

After dredging:After dredging: No effect of ditchNo effect of ditch

So effect of ditch is partly ‘filtered’ out due to dredgingSo effect of ditch is partly ‘filtered’ out due to dredging

Management - dredging Management - dredging

Effect dredging on macroinvertebrates?Effect dredging on macroinvertebrates?

Number of taxaNumber of taxa Total diversityTotal diversity

Spring 2007 Spring 2007 (pre-dredging)(pre-dredging) 21.5 +- 6.821.5 +- 6.8 5454

Spring 2008 Spring 2008 (pre-dredging)(pre-dredging) 20.1 +- 4.420.1 +- 4.4 5454

Spring 2009 Spring 2009 (post-dredging)(post-dredging) 9.4 +-9.4 +- 3.33.3 3434

Less taxa after managementLess taxa after management (also independent of ditch)(also independent of ditch)

Mostly rare taxa disappear after managementMostly rare taxa disappear after management

Ditch no effect on taxon richnessDitch no effect on taxon richness

Management - dredging Management - dredging

Effect dredging on macroinvertebrates?Effect dredging on macroinvertebrates? DREDGING

2007 2008 2009C C C

D = dredgingD D

Taxon Richness

20

10

C = control

CC D

Management - dredging Management - dredging

Ponds dredged in the mid-90’s: difference with other ponds?Ponds dredged in the mid-90’s: difference with other ponds?

Current macroinvertebrate communities: no significant effectCurrent macroinvertebrate communities: no significant effect

Current environmental features: no significant effectCurrent environmental features: no significant effect

No proof for longterm negative No proof for longterm negative effect on macroinvertebrate effect on macroinvertebrate communitiescommunities

Reduction of macroinvertebrate richness right after dredging Reduction of macroinvertebrate richness right after dredging

Reduction of richness probably recovers after a few yearsReduction of richness probably recovers after a few years

Before managementBefore management Year after management Year after management

Management - macroinvertebratesManagement - macroinvertebrates

High beta diversity in Tommelen:High beta diversity in Tommelen:

Conserving only a few ponds is not sufficient Conserving only a few ponds is not sufficient

Rare species seem mostly affected immediatly after dredging:Rare species seem mostly affected immediatly after dredging:

Do not dredge all ponds in an area at the same timeDo not dredge all ponds in an area at the same time

Spread management over several yearsSpread management over several years

Management - macroinvertebratesManagement - macroinvertebrates

Other sampling campaigns

- Multiscale survey

- Age experiment

Multiscale survey

125 ponds in Belgium & Luxembourg125 ponds in Belgium & Luxembourg

Hierarchical designHierarchical design

Reveal spatial scales Reveal spatial scales of of pond biodiversitypond biodiversity

Samples taken & being analysedSamples taken & being analysed

- Physical & chemical variables - Physical & chemical variables

- Morphology- Morphology

- Different organism groups- Different organism groups

Age effect

Effect age on communities Effect age on communities Important information for creation of new pondsImportant information for creation of new ponds

Age classes: Age classes: 0-5 years0-5 years

5-10 years5-10 years

10-25 years10-25 years

> 25 years> 25 years

Samples taken (83 ponds)Samples taken (83 ponds)

- Physical & chemical variables- Physical & chemical variables

- Morphology- Morphology

- Different organism groups- Different organism groups