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Soil Biology & Biochemistry 41 (2009) 606–610

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Soil Biology & Biochemistry

journal homepage: www.elsevier .com/locate/soi lb io

Home-field advantage accelerates leaf litter decomposition in forests

Edward Ayres a,*, Heidi Steltzer a, Breana L. Simmons a, Rodney T. Simpson a, J. Megan Steinweg a,Matthew D. Wallenstein a, Nate Mellor a, William J. Parton a, John C. Moore a, Diana H. Wall a,b

a Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, CO 80523, USAb Department of Biology, Colorado State University, Fort Collins, CO 80523, USA

a r t i c l e i n f o

Article history:Received 12 August 2008Received in revised form11 December 2008Accepted 17 December 2008Available online 12 January 2009

Keywords:Carbon cyclingFunctional equivalenceLocal adaptationPlant–soil interactionsSoil biodiversity

* Corresponding author. Tel.: þ1 970 491 1984; faxE-mail address: edayres@nrel.colostate.edu (E. Ayr

0038-0717/$ – see front matter � 2009 Elsevier Ltd.doi:10.1016/j.soilbio.2008.12.022

a b s t r a c t

Several leaf litter decay studies have indicated that decomposition occurs more rapidly when litter isplaced beneath the plant species from which it had been derived than beneath a different plant species(i.e. home-field advantage, HFA), although support for this notion has not been universal. We provide thefirst quantification of HFA in relation to leaf litter decomposition using published litter mass loss datafrom forest ecosystems in North America, South America, and Europe. Our findings indicate that HFA iswidespread in forest ecosystems; on average litter mass loss was 8% faster at home than away. Wehypothesize that HFA results from specialization of the soil biotic community in decomposing litterderived from the plant above it. Climate and initial litter quality data can be used to explain about 70% ofthe variability in litter decomposition at a global scale, leaving about 30% unexplained. We suggest thatHFA be recognized as a factor that explains some of this remaining variability.

� 2009 Elsevier Ltd. All rights reserved.

1. Introduction

Biogeochemical models can explain w70% of the variation inlitter decomposition at continental scales based on a few climateand initial litter quality parameters, such as mean annual temper-ature and precipitation, C to N ratio, and lignin concentration(Gholz et al., 2000; Trofymow et al., 2002; Parton et al., 2007).Numerous factors that may explain the remaining w30% of varia-tion have been proposed, including interactions among litter types,UV light, soil biodiversity, and soil chemistry (Heneghan et al.,1999; Gonzalez and Seastedt, 2001; Gartner and Cardon, 2004;Bardgett, 2005; Austin and Vivanco, 2006). It has also been sug-gested that litter may decompose faster in an area dominated bythe plant species from which it derived (i.e. at home) than in anarea dominated by another plant species (i.e. away), which hasbeen called ‘home-field advantage’ (HFA, Gholz et al., 2000).However, the ubiquity and magnitude of home-field advantage inrelation to litter decomposition is currently unknown.

Studies of the effect of plant–soil feedbacks on the growth ofplant species when grown in ‘home’ versus ‘away’ soil havereported both positive and negative feedbacks at home (Van derPutten et al., 1993; Bever, 1994; Bever et al., 1997; De Deyn et al.,

: þ1 970 491 1965.es).

All rights reserved.

2003; Kardol et al., 2006). In contrast to plant growth, leaf litter–soil feedbacks might be expected to consistently result in positivefeedbacks at home, i.e. faster litter decay rates (HFA). This isbecause 1) leaf litter from different plant species often variesconsiderably in structure and chemical composition, e.g. leaf shape,specific leaf area, carbon to nitrogen ratio, and lignin concentration(McClaugherty et al., 1985; Aerts, 1997; Gholz et al., 2000; Santiago,2007); and 2) leaf litter inputs are a major source of nutrients andenergy for soil biota (Cebrian, 1999; Wardle, 2002), which theyaccess by decomposing the litter. As a result, there is likely to becompetition among soil biota for these nutrients, which may createa selective pressure for organisms that are particularly efficient atbreaking down litter derived from the plant species above them,resulting in HFA (i.e. faster decomposition of litter at home thanaway). Indeed, providing the soil biotic community and theirassociated plant species remain in contact with one another, thespecialization of the soil community in decomposing litterproduced by that plant species could be reinforced over timethrough physiological adaptation (short-term) and evolution (long-term) of the soil biota.

Transplant studies where leaf litter from different plant specieswere swapped among areas dominated by different plant speciesindicate that litter may decompose faster in its home environment(Bocock et al., 1960; Hunt et al., 1988; Gholz et al., 2000; Negrete-Yankelevich et al., 2008; Vivanco and Austin, 2008), although thisdoes not always occur (Prescott et al., 2000; Chapman and Koch,

E. Ayres et al. / Soil Biology & Biochemistry 41 (2009) 606–610 607

2007). However, the magnitude of the decomposition-related HFAhas not been quantified, in part due to the lack of a suitable method,and its prevalence remains unknown. We calculated HFA using datafrom field-based reciprocal litter transplant experiments conductedin forests in temperate and tropical regions in North America, SouthAmerica, and Europe and show that decomposition-related HFA iscommon in forests.

2. Materials and methods

Reciprocal litter transplant experiments, where leaf litter fromspecies A and B were decomposed at sites a (dominated by speciesA) and b (dominated by species B), have been used to separate site-specific effects from litter quality effects on decomposition.However, these experiments can also be used to test for HFA,although this has rarely been done. We calculated HFA using pub-lished litter mass loss data from field-based experiments thatreciprocally transplanted tree litter and monitored its decomposi-tion using litter bags (Table 1). Since some sites have inherentlyfaster rates of decomposition than other sites due to, for example,differences in temperature or the availability of nutrients, littermass loss by each species was expressed as relative mass loss (i.e. asa percentage of total mass loss at that site by both species).

Table 1Studies used to calculate home-field advantages. Tree–tree litter transplants were usedcalculate HFAs shown in Fig. 1b.

Species Location Duration

Tree–tree litter transplantsAbies albaa–Acer pseudoplatanusb Poland 2Acer platanoides–Acer pseudoplatanus Poland 2Bellucia sp.–Bertholettia excelsa North-east Brazil 1Betula pendula–Acer pseudoplatanus Poland 2Calophyllum brasiliense–Copaifera langsdorffii South-east Brazil 0.7Calophyllum brasiliense–Esenbeckia leiocarpa South-east Brazil 0.7Calophyllum brasiliense–Guapira opposita South-east Brazil 0.7Carpinus betulus–Acer pseudoplatanus Poland 2Copaifera langsdorffii–Esenbeckia leiocarpa South-east Brazil 0.7Eucalyptus urophylla–Bellucia sp. North-east Brazil 1Eucalyptus urophylla–Bertholettia excelsa North-east Brazil 1Eucalyptus urophylla–Vismia sp. North-east Brazil 1Fagus sylvatica–Acer pseudoplatanus Poland 2Fraxinus uhdei–Metrosideros polymorpha Hawaii, USA 1G. opposita–Copaifera langsdorffii South-east Brazil 0.7G. opposita–Esenbeckia leiocarpa South-east Brazil 0.7Larix deciduas–Acer pseudoplatanus Poland 2Northofagus dombeyi–Northofagus nervosa Western Argentina 1N. dombeyi–Northofagus obliqua Western Argentina 1N. nervosa–N. obliqua Western Argentina 1Picea abies–Acer pseudoplatanus Poland 2Picea glauca–Populus tremuloides Western Canada 5Pinus contorta–Populus tremuloides Colorado, USA 2Pinus nigra–Acer pseudoplatanus Poland 2Pinus strobus–Acer saccharum Wisconsin, USA 2Pinus sylvestris–Acer pseudoplatanus Poland 2Populus grandidentata–Acer saccharum Wisconsin, USA 2Pseudotsuga menziesii–Acer pseudoplatanus Poland 2Quercus alba–Acer saccharum Wisconsin, USA 2Quercus robur–Acer pseudoplatanus Poland 2Quercus rubra–Acer pseudoplatanus Poland 2Quercus petraea–Fraxinus excelsior UK 1.2Tilia cordata–Acer pseudoplatanus Poland 2Tsuga canadensis–Acer saccharum Wisconsin, USA 2Vismia sp.–Bertholettia excelsa North-east Brazil 1

Grass–tree litter transplantsAgropyron smithii–Pinus contorta Wyoming/Colorado, USA 1Bouteloua gracilis–Pinus contorta Wyoming/Colorado, USA 1Andropogon gerardii–Juniperus virginiana Kansas, USA 2

a First species corresponds to first mass loss value.b Second species corresponds to second mass loss value.c Mean mass loss across both mesh sizes was used to calculate HFA.

ARMLa ¼Aa � 100

Aa þ Ba

where, ARMLa represents the relative mass loss of litter from speciesA at site a, and Aa and Ba represent the percent mass loss of leaflitter from two plant species decomposing at site a, respectively.The measures of relative mass loss were used to calculate HFA.

HFAI ¼�

ARMLa þ BRMLb

2

�ARMLb þ BRMLa

2

�� 100� 100

where, HFAI (HFA index) represents the percent faster mass loss oflitter when it decomposes at home versus away and is a net valuefor both species (A and B) involved in the reciprocal transplant.There is a more sophisticated method to determine HFA that wasdeveloped for the study of sports teams (Clarke and Norman, 1995)and which could be used to determine the magnitude of HFA foreach individual species. However, this method requires three ormore reciprocally transplanted litters, whereas most decomposi-tion studies have only involved two-way reciprocal transplants.

The advantage of calculating the HFA index is that it quantifiesthe extent to which litter decomposes faster (or slower) at home(i.e. areas dominated by that plant species). If litter mass lossis simply analyzed using an ANOVA a significant ‘litter� site’

to calculate HFAs shown in Fig. 1a and grass–tree litter transplants were used to

(yrs) Total mass loss (%) Litter bag meshsize (mm)

Reference

29a–46b 0.3 Hobbie et al. (2006)48–44 0.3 Hobbie et al. (2006)67–92 1 Barlow et al. (2007)33–48 0.3 Hobbie et al. (2006)35–60 2 Castanho and de Oliveira (2008)38–81 2 Castanho and de Oliveira (2008)43–73 2 Castanho and de Oliveira (2008)45–43 0.3 Hobbie et al. (2006)52–69 2 Castanho and de Oliveira (2008)92–57 1 Barlow et al. (2007)92–87 1 Barlow et al. (2007)92–79 1 Barlow et al. (2007)29–47 0.3 Hobbie et al. (2006)88–50 1.5 Rothstein et al. (2004)55–69 2 Castanho and de Oliveira (2008)60–90 2 Castanho and de Oliveira (2008)33–48 0.3 Hobbie et al. (2006)24–17 2 Vivanco and Austin (2008)25–25 2 Vivanco and Austin (2008)17–26 2 Vivanco and Austin (2008)31–44 0.3 Hobbie et al. (2006)78–76 1.5 Prescott et al. (2000)31–49 1.6� 1.8 & 3� 4c Gonzalez et al. (2003)33–45 0.3 Hobbie et al. (2006)60–75 0.1 McClaugherty et al. (1985)44–46 0.3 Hobbie et al. (2006)59–71 0.1 McClaugherty et al. (1985)34–42 0.3 Hobbie et al. (2006)69–73 0.1 McClaugherty et al. (1985)36–48 0.3 Hobbie et al. (2006)42–46 0.3 Hobbie et al. (2006)63–88 10 Bocock et al. (1960)37–48 0.3 Hobbie et al. (2006)49–71 0.1 McClaugherty et al. (1985)83–92 1 Barlow et al. (2007)

11–7 1 Hunt et al. (1988)16–8 1 Hunt et al. (1988)51–47 0.2� 0.6 Norris et al. (2001)

E. Ayres et al. / Soil Biology & Biochemistry 41 (2009) 606–610608

interaction could indicate that HFA occurred, but it would not bepossible to determine the magnitude of the HFA. None of the papersincluded in our analysis attempted to quantify the magnitude ofHFA in their study.

Here we use mass loss data to calculate the decomposition-related HFA since mass loss was the most widely reported decom-position measure; however, other variables, such as nutrient lossfrom litter, could also be used. Criteria for including studies in theanalysis were: 1) they involved field-based reciprocal litter trans-plants among at least two plant species; 2) they employed litterbags; and 3) they reported litter mass loss data (or decompositionrate constants) for each litter species in stands of each species. Theprimary focus of most of the studies from which we calculated theHFA index was to investigate the relative importance of litter qualityand site on decomposition, not HFA (which is an interaction betweenlitter and site). Indeed, some of the studies do not even mention thepotential for HFA; therefore, it is unlikely that there is a bias in thepublication of papers that either do or do not exhibit HFA.

Mean litter mass loss values were estimated from graphs whendata were not presented in the text or tables. Where litter mass lossdata was reported at several time points, the HFA index wascalculated using mass loss data averaged across all time points. Inthe case of Hobbie et al. (2006), only litter decomposition rateconstants (k) were reported, rather than litter mass; therefore, weused the reported values of k to calculate mass loss after 1 year (thestudy by Hobbie et al., lasted 2 years). It was not possible to performa meta-analysis without the raw litter mass loss data, becausewithout this information the variation associated with the HFAvalue cannot be determined.

3. Results

We demonstrate that HFA typically accelerates leaf litterdecomposition in forests (Fig. 1a). Of 35 reciprocal leaf littertransplants among a variety of tree species, 77% exhibited a netstimulation of decomposition at home and the mean HFA

-20 0 20 40

a

Home-field advantage

(% faster decomposition at home)

Fig. 1. Tree litter in forests typically decomposed faster at home than away (a), indicating thand grass litters were reciprocally transplanted. Each bar represents a reciprocal transplan

(8.0�1.8%; �SE) was significantly greater than zero (P< 0.01; t-test). Indeed, decomposition was at least 10% faster at home in 34%of the reciprocal transplants, whereas there were no cases thatexhibited a reduction of decomposition of over 10% at home.

In addition, in two out of three cases where grass and tree litterwere reciprocally transplanted, HFA was substantially greater thanreciprocal litter transplants between trees (Fig. 1b). However, thelimited number of grass–tree reciprocal transplants precludesstatistical analysis of this data.

4. Discussion

We hypothesize that the decomposition-related HFA that weidentified is due to specialization of soil biota in the decompositionof litter produced by the plant above them. As noted above, plantlitter varies considerably in physical structure and chemicalcomposition, which influences its decomposition (McClaughertyet al., 1985; Aerts, 1997; Gholz et al., 2000; Santiago, 2007), andthese differences, as well as other plant traits (e.g. quality ofbelowground inputs, growth form, and influence on soil structure),often result in different soil communities associated with differentplant species (Griffiths et al., 1992; Grayston et al., 1998; Priha et al.,1999; Porazinska et al., 2003; Bardgett and Walker, 2004). Soilorganisms, including microbes, protozoa, nematodes, micro-arthropods, and macro-fauna, mediate the decomposition ofdetritus from which they derive energy and nutrients, which likelyresults in competition among soil biota. Therefore, there may beselection for soil biota that specialize in decomposing the litter ofthe plant species above them, hence HFA.

There is some support for the notion that soil biota areresponsible for decomposition-related HFA. For example, Hansen(1999) added birch, maple, and oak litter individually to a mixed-hardwood forest floor and monitored colonization by micro-arthropods and litter decomposition. Oak litter supported greaterpopulations of oribatid mites that burrow into leaves, possibly asa result of the thick structure of oak leaves. This corresponded to

0 10 100 150 200 250

b

Home-field advantage

(% faster decomposition at home)

at HFA is common. HFA was even more pronounced between biomes (b), i.e. when treet between two species.

E. Ayres et al. / Soil Biology & Biochemistry 41 (2009) 606–610 609

faster decomposition of oak leaves, suggesting that oak litterpromotes soil biota that stimulate its decomposition (Hansen,1999). However, contrary to this hypothesis, an experiment thatincubated leaf litter from three tree species with soil biota frombeneath each tree species did not observe faster decompositionwhen litter was in the presence of its home or ‘indigenous’ soilcommunity (Ayres et al., 2006). Although, as noted by the authors,the short duration of this experiment, the artificial environmentalconditions, and the exclusion of meso- and macro-fauna may havelimited the ability to detect HFA (Ayres et al., 2006).

Specialization of soil biota in decomposing certain types of leaflitter could be manifested in many different ways. Soil organismsproduce specific enzymes to break down different litter substrates,but individual species or taxa often cannot produce enzymes forsome substrates. For example, lignolytic fungi are one of the feworganisms that can break down lignin efficiently (Paul, 2007);therefore, it is not surprising that fungi are often more abundantbeneath plants that produce litter with greater lignin concentra-tions (e.g. Ingham et al., 1989; Coleman et al., 1990). A similar effectmay occur with differences in the natural history of soil animalsand their ability to decompose litter of different shapes or thick-nesses, as indicated above in the study by Hansen (1999). Finally,soil animals may have behavioral traits that could create HFA. Forexample, animals adapted to certain litter types may selectivelybury that litter as a food store or to line nests or tunnels. If so, wemay have underestimated the magnitude of HFA on litter mass loss(from the soil surface) since it would not have been possible for soilanimals to remove litter from litter bags.

Based on the rationale that differences in the soil bioticcommunity beneath different plant species create the decomposi-tion-related HFA, we predict that HFA will increase with greaterdifferences in litter quality between two litter types. This predictionis consistent with the particularly large HFA in two out of threeinstances where tree and grass litter, which have very pronounceddifferences in litter quality and structure, were transplanted andallowed to decompose (Fig. 1b).

Biogeochemical models can explain w70% of the variation inlitter decomposition at continental scales based on a fewclimate andinitial litter quality parameters, such as mean annual temperatureand precipitation, C to N ratio, and lignin concentration (Gholz et al.,2000; Trofymow et al., 2002; Parton et al., 2007). Numerous factorsthat may explain the remaining w30% of variation have beenproposed, including interactions among litter types, UV light, soilbiodiversity, and soil chemistry (Heneghan et al.,1999; Gonzalez andSeastedt, 2001; Gartner and Cardon, 2004; Bardgett, 2005; Austinand Vivanco, 2006). Based on our findings, and the studies we usedto calculate HFA, we feel that HFA should be added to this list.

In conclusion, it is apparent that HFA is common in forestecosystems, where it accelerates litter mass loss by 8% on average. Inaddition, HFA may have implications for other aspects of decompo-sition, such as nutrient release, and potentially could be disrupted bythe migration of plant and soil species in response to climate change.

Acknowledgements

This work was in supported, in part, by a British EcologicalSociety Early Career Project Grant awarded to EA and HS and a USNational Science Foundation grant awarded to EA, HS, and MDW.This work is a product of the Soil Ecology Think Tank at the NaturalResource Ecology Laboratory, Colorado State University.

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