Extinction debt and colonization credit in

highly fragmented forest landscapes

Nitra, 27.05.15Jens Kolk & Tobias Naaf

• Question: Do historical land cover changes influence present-day plant species richness of temperate deciduous forests?

• Dramatic changes:

• Extinction debt and colonization credit

Introduction

2000 – 2012 Brazil 1780 – 1880 Germany, PrignitzData according to Hansen et al. 2013 Kolk & Naaf 2015, Biol. Cons. 182

Extinction debt

• Time-delayed extinctions, debt to be paid in future

Habitat loss /fragmentation

New equilibrium

Extinction debt

Relaxation time

Time

Speci

es

rich

ness

Where are we right now?

ED not paid at all?

ED paid half?

ED paid completely?

[adapted from Kuussaari et al. 2009, TREE 24]

Colonization credit

• Time-delayed colonization, credit depleted in the future

Where are we right now?

CC still there?

CC depleted half?

CC depleted completely?

Colonization credit

Relaxation time

Time

Speci

es

rich

ness

Habitat creation

New equilibrium

[adapted from Kuussaari et al. 2009, TREE 24]

Landscape level scheme

Richness in equilibrium habitat

Colonization credit

Time

Speci

es

rich

ness Ancient forest

Post-agricultural forest

Habitat creation

Extinction debt

Habitat fragmentation

Raw difference

Ancient forest: Continuously forest since at least 1780

Post-agricultural forest: Recently established on agricultural land

Study area

• Flat terrain

• Intensive agriculture

• 5% deciduous forest cover

• Main deciduous tree species– Oak (Quercus robur)– Beech (Fagus

sylvatica)– Alder (Alnus

glutinosa)

©Neuenhausen-prics.de

©Groundhopping-Merseburg

Land use history

Georeferencing ~ 350 ticks

Rectification

Overlay with 2008 Aerials + TK25 map

Schmettau Map 1767-1787

Digitize and classify forests

Prussian Gov. Map ca. 1880

1780

• Large areas covered with deciduous forests

• Approx. 1000 Patches

• 32% cover¯0 5 10

Kilometers

2008

• 92% Loss• 6000 Patches =

Fragmentation

• 5% cover– 36% ancient– 64% post-

agricultural ¯0 5 10Kilometers

ancient

post-agricultural

Extinction debt of forest specialists in ancient forests

Extinction debt

• Land use history data• Specialists occurrence in 104 patches• Hypothesis:

Strong relationship with historical patch configurationSp

ecie

s ric

hnes

s

Patch areaPatch connectivity

Weak relationship with present-day patch configuration

[adapted from Kuussaari et al. 2009, TREE 24]

Convallaria majalis

Sanicula europaea

Paris quadrifolia

ED: Results

• Present day configuration always explains SR better

• However, historical connectivity significant

β = 0.12, P = 0.023

P < 0.001 n.s.

Forest specialists richness dependent on present-day area and connectivity

Kolk & Naaf 2015, Biol. Cons. 182 Method: Negative binomial GLM

ED: Discussion

• Extinction debt almost paid

• Historical connectivity last glimpse of ED

• Massive area loss in short time

• Fragmentation after 1880

1780 1880 2008

1780 1880 2008

Deciduous forest area

Number of Patches

ED: Conclusions

• Rapid payment of extinction debt

Habitat loss /fragmentation

New equilibrium

Extinction debt

Relaxation time

Time

Speci

es

rich

ness

Where are we right now?

ED not paid at all?

ED paid half?

ED paid completely?

[adapted from Kuussaari et al. 2009, TREE 24]

ED paid completely!(almost)

Colonization credit of forest specialists in post-agricultural forests

Colonization credit

• Specialists in 110 post-agricultural patches• We now know: Extinction debt largely

paid• Predict SR using the ancient patches• Hypothesis:

Speci

es

rich

ness

Time, Patch connectivity

Observed richness in post-agricultural forest patches

Predicted richness from ancient equilibrium patches

Colonization

credit

CC: Results

• Mean colonization credit 4.7 species• Up to 9 in highly isolated patches• Credit for specialists was not smaller in

older patchesP = 0.341

P < 0.001

CC: Conclusions

• Recovery may take several centuries (if ever)

Where are we right now?

CC still there?

CC depleted half?

CC depleted completely?

Colonization credit

Time

Speci

es

rich

ness

Habitat creation

New equilibrium

[adapted from Kuussaari et al. 2009, TREE 24]

CC still there!

CC remains

Summary

Question: Do historical land cover changes influence present-day plant species richness of temperate deciduous forests?

• Yes, mainly due to colonization credit

• Extinction debt may be paid rapidly

• Colonization may take a long time

• Land use history is important

Thank you for your attention!