1. Case study: Tommelen bomb craters (Hasselt) WWII - 1944 High density ponds (ca 110 ponds;12 ha), similar age, same soil (light sandy loam) (Part of WP1: Biodiversity at multiple spatial scales: patterns and driving variables)

2. 1) Investigate how diversity is structured in a pond complex (high density, small spatial scale) for a diverse set of organisms groups 2) What are the main drivers of communities inhabiting ponds 3) Recommendations concerning pond(complex) management and conservation (in combination with management-experiment). Aims

3. Survey of 49 ponds (spring & summer 2007): - physical & chemical variables (nutrients, turbidity, oxygen,…) - morphology (depth, surface,…) - fluctuations in groundwater Survey

4. Bacteria Phytoplankton Benthic diatoms Cladocerans Amphibians Macrophytes Macroinvertebrates © D. Ercken Survey © D. Ercken

5. Alpha diversity: Alpha diversity: diversity within a particular area or ecosystem (e.g. number of species in a pond) Beta diversity: Beta diversity: change in species diversity between two ecosystems Gamma diversity: Gamma diversity: overall diversity for different ecosystems within a region (e.g. Tommelen) D C BETA GAMMA A B C ALPHA D E Structure of diversity in a pond complex

6. BACTERIA (total 55; average 11.2) NUMBER OF PONDS CUMULATIVE NUMBER OF SPECIES/TAXA 90% 18 poelen 110 Regional species/taxa richness (gamma) Structure of diversity in a pond complex

7. NUMBER OF PONDS CUMULATIVE NUMBER OF SPECIES/TAXA Why is structure of diversity important? HIGH BETA DIVERSITY HIGH ALPHA DIVERSITY SIMILAR GAMMA DIVERSITY BUT: different effect on diversity if ponds disappear

8. Phytobenthos (221; 35.6) Amphibians (5*; 4) Macrophytes (21; 4 – 111; 17) Zooplankton (21; 5) Macroinvertebrates (65; 28.6) Phytoplankton (135; 23) 37 ponds 34 ponds 3 ponds11 ponds 33 ponds 29 ponds

9. Based on Shannon diversity 0 = no turnover 1= each sample is completely different from every other sample Turnover rate per sample (beta diversity)

10. Main drivers?

12. Hydrology (data 1994-1995 inbo) Main drivers?

13. Strong zonation: phytobenthos, phytoplankton, bacteria  Spatially correlated eutrophication gradient  Important role of periodically filled ditch, polluted up to 1996 Community composition

14. Diatoms

15. Most important structuring variables linked with eutrophication gradient & vegetation cover Bacteria: total nitrogen, % open water, surface, oxygen Phytoplankton: emerse vegetation, oxygen, SO4 Phytobenthos: total nitrogen, % open water, presence of fish, alcalinity Zooplankton: total phosphorus, maximum depth, density of Hydra, successional stage Macroinvertebrates: transparency, fish, oxygen, temperature Macrophytes: maximum depth, degree of sludge, pH Amphians: (only larvae): fish (remark, fish only in ponds connected to ditch) Community composition

16. Species poor ponds > subset of species rich ponds? (nestedness analysis) Relatively high beta diversity within most groups of organisms: loss of ponds can result in pronounced loss of diversity But strong variation in beta diversity between groups of organisms Zonal/spatial patterns (mainly linked with local pond characteristics) Strong effect of « ditch » on pond communities (introduction of fish, variable quality of incoming water,…) Prospectives & Management recommendation