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)

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

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

Survey

Bacteria

Phytoplankton

Benthic diatoms Cladocerans

Amphibians

Macrophytes

Macroinvertebrates

© D. Ercken

Survey

© D. Ercken

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

BETABETA

GAMMAGAMMA

A

B

C

ALPHAALPHA

D E

Structure of diversity in a pond complex

Bacteria

CU

MU

LAT

IVE

NU

MB

ER

OF

SP

EC

IES

NUMBER OF PONDS

10

20

30

40

50

60

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49

BACTERIA (total 55; average 11.2)

NUMBER OF PONDS

CU

MU

LAT

IVE

NU

MB

ER

OF

SP

EC

IES

/TA

XA

90%

18 poelen

110

Regional species/taxa richness (gamma)

Structure of diversity in a pond complex

Bacteria

CU

MU

LAT

IVE

NU

MB

ER

OF

SP

EC

IES

NUMBER OF PONDS

10

20

30

40

50

60

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49

NUMBER OF PONDS

CU

MU

LAT

IVE

NU

MB

ER

OF

SP

EC

IES

/TA

XA

Why is structure of diversity important?

HIGH BETA DIVERSITYHIGH BETA DIVERSITY

HIGH ALPHA DIVERSITYHIGH ALPHA DIVERSITY

SIMILAR GAMMA SIMILAR GAMMA DIVERSITYDIVERSITY

BUT: different effect on diversity if ponds disappear

PHYTOBENTHOSS

peci

es C

ount

(C

umul

ativ

e)

Samples

0

50

100

150

200

250

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

Phytoplankton

Spe

cies

Cou

nt (

Cum

ulat

ive)

Samples

20

40

60

80

100

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

Macroinvertebrates

Specie

s C

ount (C

um

ula

tive)

Samples

20

30

40

50

60

70

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

Zooplankton

Spe

cies

Cou

nt (

Cum

ulat

ive)

Samples

0

5

10

15

20

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49

Macrophytes watervegetatie

Spe

cies

Cou

nt (

Cum

ulat

ive)

Samples

0

5

10

15

20

25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

Amphibia

Spe

cies

Cou

nt (

Cum

ulat

ive)

Samples

3.0

3.5

4.0

4.5

5.0

5.5

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39

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

Organism group

Bacte

ria

Phytoben

thos

Phytopla

nkton

Zooplankt

on

Mac

roin

verte

brate

s

Mac

rophyt

es

Amphib

ians

Tur

nove

r ra

te p

er s

ampl

e

0,00

0,02

0,04

0,06

0,08

0,10

0,12

Based on Shannon diversity

0 = no turnover 1= each sample is completely different from every other sample

Turnover rate per sample (beta diversity)

Main drivers?

Hydrology (data 1994-1995 inbo)

Main drivers?

Strong zonation: phytobenthos, phytoplankton, bacteriaSpatially correlated eutrophication gradientImportant role of periodically filled ditch, polluted up to 1996

Community composition

Community composition

Diatoms

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

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