Extinction debt and colonization credit in highly fragmented forest landscapes Nitra, Jens 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, Prignitz Data according to Hansen et al 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 Species richness 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? Colonizatio n credit Relaxation time Time Species richness Habitat creation New equilibrium [adapted from Kuussaari et al. 2009, TREE 24]

Landscape level scheme Richness in equilibrium habitat Colonization credit Time Species richness 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 Digitize and classify forests Prussian Gov. Map ca. 1880

1780 Large areas covered with deciduous forests Approx Patches 32% cover

% Loss 6000 Patches = Fragmentation 5% cover –36% ancient –64% 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 configuration Species richness Patch area Patch 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 = P < 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 Deciduous forest area Number of Patches

ED: Conclusions Rapid payment of extinction debt Habitat loss / fragmentation New equilibrium Extinction debt Relaxation time Time Species richness 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: Species richness 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 patches P = 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? Colonizatio n credit Time Species richness 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

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