Melissa McCormickKatalin SzlaveczBrenda NietoLijun XiaDennis WhighamEffects of non-native earthworms on mycorrhizal fungi and tree seedling growth

"On a global basis...the two great destroyers of biodiversity are, first habitat destruction and, second, invasion by exotic species - E.O. WilsonImage from The Nature Conservancys Wildland Invasive Species Task Forceethanzuckerman.comappomattoxnews.com

Invasive SpeciesAn invasive species is an alien species whose introduction does, or is likely to cause, economic or environmental harm or harm human health

In the U.S. there are nearly 6,600 non-native speciesInvasive species have influenced all U.S. ecosystemsThe current annual environmental, economic, and health-related costs of invasive species exceed those of all other natural disasters combined (estimated at $122 Billion in 2000).Ehrenfeld 1997, Cox 1999, Rossman 2001, USGS 2010, Pimentel et al. 2000.

Below-ground biological invasions have gone largely unnoticed until recently:

Apart from a few familiar cases of Argentine fire ants (Solenopsis invicta) in Oceania and North America,the Formosan termite (Coptotermes formosanus) in South Africa and the southeastern United States,and the New Zealand flatworm (Arthurdendyus triangulatus) in the British Isles.Invaders under our feetPhotos courtesy Chi-han Chang

Hendrix et al. 2008. Pandoras box contained baitExotic earthworms around the world

Exotic Earthworms in North AmericaAfter last Ice Age many unutilized opportunitiesJames, 1995Reynolds,1995NativeIntroduced

Introduced earthworms now occur in every biogeographic region in all but the driest or coldest habitat types on Earth.Earthworm invadersHendrix et al. 2008

Earthworms

BAD?GOOD?

Earthworm species differBouche 1977Eisenoides loennbergi - NativeLumbricus friendi - EuropeanLumbricus rubellus - EuropeanOctolasion lacteum - EuropeanAmynthas hilgendorfi- Asian

MycorrhizasINTRODUCTIONSource: Smith & Read 1997

http://www.paintthelight.net/BotanyProject/Activities/adaption_plants.htmMycorrhizae have been identified in fossils of plants as early as 400mya and are considered crucial to plants adapting to life on land (Taylor et al. 1995, Taylor & Krings 2005, Krings et al. 2007).

Nearly all forest plants are mycorrhizal...except for some invasive species.ECMAMConifers,Oaks, Hickories,Beeches,Birches,ChestnutTulip poplar,Sweetgum, Maples,Ashes,Elms,Sycamore

How do we look at fungi in the soil?Extract DNA from soilThere are LOTS of fungi in the soil!Up to 150 species in 0.5g of soil.2 samples 15cm apart may share only 25% of their species.We use specific PCR primers to look only at the DNA from the fungi we are interested in.Fungal DNASoil core

Quantifying fungi in the soil:

A field experiment48 plots (1mx1m) were trenched to 50 cm depth, lined with mesh screen and backfilled. Smithsonian Environmental Research Center (SERC), Edgewater, MD

Earthworms were removed from half of the plots by repeated electroshocking. Manipulating earthworms

Leaf litter was added (beech on one side and tulip poplar on the other) and seedlings planted in the plots. Tree seedlings and leaf litter

Soil Processes:Decomposition Respiration Abundance of microbial taxa (qPCR):Mycorrhizal fungiECM (Tomentella, Russula) AM Tree seedling performanceGrowth (biomass) ? Plant mycorrhizal colonization Measured variables / expectations

**Decomposition:

Decomposition was greater in forests with earthworms if mesh size allowed earthworms to access leaf litter.Szlavecz et al. In press

Respiration was higher in plots with earthworms, especially on the side with tulip poplar leaf litter.Mature ForestSuccessional ForestRespiration:

Proportional Abundance (ng DNA/g dry soil/total quantified DNA)0.000.020.040.060.080.100.120.14SiteTomentellaAM fungiRussulaNo EarthwormsEarthwormsSite p

Oak Beech Log above-ground biomass (mean g + se)Forest Ageno EW EW P=0.07P=0.09Oaks and beeches grew less in plots with earthworms. Maples grew more.Tree seedling growthFew Tulip poplar seedlings survived in old forests and none in old forest plots without earthworms.Alex Binck-3.5-3.0-2.5-2.0-1.5Tulip 0

Key ConclusionsEarthworm activities affected mycorrhizal fungi and tree seedlings:Mycorrhizal fungi were less abundant in plots with earthworms.Earthworms affected growth of red oak and beech but not maple or tulip poplar.Earthworm effects on tree seedlings differed with species:Changes to nutrients affected early successional trees (+).Changes to mycorrhizal fungi affected late successional trees (-).

What does this mean forour forests?Forest composition may change:Early successional trees may be better able to use nutrients made available by earthworms and may dominate longer.Invasive plants may increase.Forest floor habitat for ground-nesting birds may decrease.Keep non-native earthworms out of forests where they havent already invaded:Increase awareness of bait release, moving plants, compost (especially vermicomposting), and mulch.

AcknowledgementsUSDA-CSREES 2007-35320-18375NSF (EAR-0748442)Smithsonian Womens CommitteeFunding:Field Help:Jay ONeillAlex BinckMatt SieversScott PitzHelen HuangNatalie BrayChi-Han ChangMike Bernard

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