BIOLIEF 2011: Linking invasive species and ecosystems
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Foreword BIOLIEF 2011: Linking invasive species and ecosystems Invasive species impacts on ecosystem functioning (i.e., the stocks and fluxes of energy and materials and their stability over time; sensu Pacala and Kinzig, 2002) have traditionally been much less investigated than their impacts on particular species or communities (Parker et al., 1999; Sousa et al., 2011). General hy- potheses, frameworks, and theories about the ecosystem-level im- pacts of invaders are noticeably lacking and a number of fundamental questions in the field e such as how species affect ecosystem functioning, how frequently they do so, which invasions will change ecosystem functioning, and which ecosystem functions are affected more often or more severely by invaders e remain open or were just partially answered by ecologists (Strayer, 2012). To achieve reliable general answers to these questions it becomes necessary the study of a highly diverse and unbiased array of spe- cies and ecosystems, followed by conceptual integration and syn- thesis across taxonomic groups and geographical regions (Py sek et al., 2008; Jeschke et al., 2012). The BIOLIEF meeting series (Launched with BIOLIEF e World Conference on Biological Invasions and Ecosystem Functioning, Porto, Portugal; October 27 to 30, 2009) was conceived as an oppor- tunity to present and revisit knowledge on the impacts of invasive species on the functioning of distinct ecosystems across the globe, meanwhile exploring possible avenues for progress and conceptual integration in the field (see Sousa et al., 2011). BIOLIEF 2011 e 2nd World Conference on Biological Invasion and Ecosystem Func- tioning (Mar del Plata, Argentina; November 21 to 24, 2011) continued the effort and success of its predecessor, congregating ca. 250 participants from 31 countries across the five continents. This Special Issue gathers together research presented or discussed at this second meeting, which in one way or another is functional to the BIOLIEF foundational goals. Both review papers and empirical case studies are included in this volume. They jointly cover a variety of invasive organisms (algae, trees, grasses, shrubs, bamboos, insects, mollusks, verte- brates) and ecosystem types (e.g., tropical and subtropical forest, Andean and subantarctic forest, temperate montane woodland, temperate and riparian grasslands, coastal dunes, streams, lakes, freshwater wetlands). This volume is also particularly rich in field studies from South America e i.e., a world region that has tradi- tionally made a minor proportional contribution to invasive spe- cies research e and places a major focus on understudied invasive species (i.e., species that were not listed amongst the fifty most intensively studied; see Py sek et al., 2008). The term “inva- sive” is used here and throughout this volume to denote species that spread from a point of introduction or origin, either colonizing new habitats or becoming overly abundant in its original range (i.e., stages III to V in the framework suggested by Colautti and Mac Isaac, 2004). This definition encompasses both native and non-native species as causative of invasion processes (see Válery et al., 2008, 2013; Carey et al., 2012; Simberloff et al., 2012) and irrespective of whether their impacts could be deemed as large or small, desirable or not. The contents of this Special Issue are organized into the following three main sections based on the kinds of impacts they emphasize: (A) Invasive Species Impacts on a Particular Ecosystem Function: Invasive species impacts on the stocks and transformations of particular materials are the most frequent focus of studies in this Special Issue. Seven out of the 16 papers in this volume can be grouped under this category. Four of them evaluate different aspects of the effect of invasive plants on litter decomposition rates. Spirito et al. compared litter decomposition and soil respira- tion between grassland assemblages dominated by native (Paspa- lum quadrifarium) and non-native (Festuca arundinacea) species in the Eastern Inland Flooding Pampas, Argentina. Furey et al. compared leaf attributes and decomposability in litter of native and invasive woody species (Ligustrum lucidum, Gleditsia triacan- thos and Pinus elliotti) from the Chaco Montane woodlands, Argentina. Aragón et al. compared leaf attributes and decomposi- tion rates of litter from exotic (L. lucidum and Morus sp.) and native tree species (Cinnamomun porphyria and Cupania vernalis) in invaded (Ligustrum-dominated) and native secondary forests of Northwestern Argentina. Mincheva et al. compared litter decom- position rates and fungal communities between a native grassland and an adjacent area invaded by Japanese knotweed (Fallopia japonica) both located at a plain in the Piedmont Region, Northern Italy. All four studies indicate changes in the overall rates of litter decomposition due to plant invasions, including both increases and decreases. On another note, Montti et al. illustrates that invasive bamboos (Chusquea ramosissima and C. tenella) have higher photosynthetic capacity per unit of dry mass than trees in the semideciduous Atlantic Forest of Argentina. Higher photosynthetic capacity in bamboos contributes to their superior colonization ability in forest gaps relative to co-occurring tree saplings and may lead to altered carbon cycling and storage in the ecosystem under a scenario of increasing forest disturbance. Two other studies evaluate the effects of animals on particular ecosystem functions. Relva et al. tested the effects of a 7-year, non-native deer (Cervus elaphus and Dama dama) exclusion on litter and soil properties in an Andean-Patagonian forest, Argentina. Their results show that nutrient content in litter and soil was not affected by deer exclusion despite deer effects on the structure, composition, and abundance of understory vegetation (see Relva Contents lists available at ScienceDirect Acta Oecologica journal homepage: www.elsevier.com/locate/actoec Acta Oecologica 54 (2014) 1e3 1146-609X/$ e see front matter Ó 2013 Elsevier Masson SAS. All rights reserved. http://dx.doi.org/10.1016/j.actao.2013.09.009
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Foreword
BIOLIEF 2011: Linking invasive species and ecosystems
Invasive species impacts on ecosystem functioning (i.e., thestocks and fluxes of energy and materials and their stability overtime; sensu Pacala and Kinzig, 2002) have traditionally beenmuch less investigated than their impacts on particular species orcommunities (Parker et al., 1999; Sousa et al., 2011). General hy-potheses, frameworks, and theories about the ecosystem-level im-pacts of invaders are noticeably lacking and a number offundamental questions in the field e such as how species affectecosystem functioning, how frequently they do so, which invasionswill change ecosystem functioning, and which ecosystem functionsare affected more often or more severely by invaders e remainopen or were just partially answered by ecologists (Strayer, 2012).To achieve reliable general answers to these questions it becomesnecessary the study of a highly diverse and unbiased array of spe-cies and ecosystems, followed by conceptual integration and syn-thesis across taxonomic groups and geographical regions (Py�seket al., 2008; Jeschke et al., 2012).
The BIOLIEF meeting series (Launched with BIOLIEF e WorldConference on Biological Invasions and Ecosystem Functioning,Porto, Portugal; October 27 to 30, 2009) was conceived as an oppor-tunity to present and revisit knowledge on the impacts of invasivespecies on the functioning of distinct ecosystems across the globe,meanwhile exploring possible avenues for progress and conceptualintegration in the field (see Sousa et al., 2011). BIOLIEF 2011 e 2ndWorld Conference on Biological Invasion and Ecosystem Func-tioning (Mar del Plata, Argentina; November 21 to 24, 2011)continued the effort and success of its predecessor, congregatingca. 250 participants from 31 countries across the five continents.This Special Issue gathers together research presented or discussedat this secondmeeting, which in oneway or another is functional tothe BIOLIEF foundational goals.
Both review papers and empirical case studies are included inthis volume. They jointly cover a variety of invasive organisms(algae, trees, grasses, shrubs, bamboos, insects, mollusks, verte-brates) and ecosystem types (e.g., tropical and subtropical forest,Andean and subantarctic forest, temperate montane woodland,temperate and riparian grasslands, coastal dunes, streams, lakes,freshwater wetlands). This volume is also particularly rich in fieldstudies from South America e i.e., a world region that has tradi-tionally made a minor proportional contribution to invasive spe-cies research e and places a major focus on understudiedinvasive species (i.e., species that were not listed amongst the fiftymost intensively studied; see Py�sek et al., 2008). The term “inva-sive” is used here and throughout this volume to denote speciesthat spread from a point of introduction or origin, either colonizingnew habitats or becoming overly abundant in its original range(i.e., stages III to V in the framework suggested by Colautti and
1146-609X/$ e see front matter � 2013 Elsevier Masson SAS. All rights reserved.http://dx.doi.org/10.1016/j.actao.2013.09.009
Mac Isaac, 2004). This definition encompasses both native andnon-native species as causative of invasion processes (see Váleryet al., 2008, 2013; Carey et al., 2012; Simberloff et al., 2012) andirrespective of whether their impacts could be deemed as largeor small, desirable or not.
The contents of this Special Issue are organized into thefollowing three main sections based on the kinds of impacts theyemphasize:
(A) Invasive Species Impacts on a Particular Ecosystem Function:Invasive species impacts on the stocks and transformations ofparticular materials are the most frequent focus of studies inthis Special Issue. Seven out of the 16 papers in this volume canbe grouped under this category. Four of them evaluate differentaspects of the effect of invasive plants on litter decompositionrates. Spirito et al. compared litter decomposition and soil respira-tion between grassland assemblages dominated by native (Paspa-lum quadrifarium) and non-native (Festuca arundinacea) species inthe Eastern Inland Flooding Pampas, Argentina. Furey et al.compared leaf attributes and decomposability in litter of nativeand invasive woody species (Ligustrum lucidum, Gleditsia triacan-thos and Pinus elliotti) from the Chaco Montane woodlands,Argentina. Aragón et al. compared leaf attributes and decomposi-tion rates of litter from exotic (L. lucidum andMorus sp.) and nativetree species (Cinnamomun porphyria and Cupania vernalis) ininvaded (Ligustrum-dominated) and native secondary forests ofNorthwestern Argentina. Mincheva et al. compared litter decom-position rates and fungal communities between a native grasslandand an adjacent area invaded by Japanese knotweed (Fallopiajaponica) both located at a plain in the Piedmont Region, NorthernItaly. All four studies indicate changes in the overall rates of litterdecomposition due to plant invasions, including both increasesand decreases.
On another note, Montti et al. illustrates that invasive bamboos(Chusquea ramosissima and C. tenella) have higher photosyntheticcapacity per unit of dry mass than trees in the semideciduousAtlantic Forest of Argentina. Higher photosynthetic capacity inbamboos contributes to their superior colonization ability in forestgaps relative to co-occurring tree saplings and may lead to alteredcarbon cycling and storage in the ecosystem under a scenario ofincreasing forest disturbance.
Two other studies evaluate the effects of animals on particularecosystem functions. Relva et al. tested the effects of a 7-year,non-native deer (Cervus elaphus and Dama dama) exclusion onlitter and soil properties in an Andean-Patagonian forest, Argentina.Their results show that nutrient content in litter and soil was notaffected by deer exclusion despite deer effects on the structure,composition, and abundance of understory vegetation (see Relva
Foreword / Acta Oecologica 54 (2014) 1e32
et al., 2010). Cooper et al. estimated changes in the amount of waterhold by epiphytic tank bromeliads (Tillandsia utriculata) after inva-sion of the bromeliad-eating weevil (Metamasius callizona) in theEnchanted Forest Sanctuary, Florida, USA. Their calculations indi-cate that water hold in T. utriculata phytotelmata decreased to 3%of its baseline amount (i.e., from 17,000 to 400 L across ca.200 ha) after just 27 months from weevil arrival.
(B) Invasive Species Impacts on Other Organisms with PutativeConsequences for Ecosystem Functioning: Organisms drive ormodulate a variety of processes that affect the transport and trans-formation of material and energy in ecosystems (see Jones andLawton, 1995; Chapin et al., 1996). Therefore, changes in the rela-tive abundance of species and organismal functional traits due tobiological invasions are expected to have reverberating impacts onecosystem functioning (see Simberloff, 2011). Three studies in thisSpecial Issue illustrate significant impacts of invasive species onother organisms that may affect distinct aspects of ecosystemfunctioning. Abreu et al. compared seedling communities underinvasive (Schizolobium parahyba) and native trees at the SeasonalSemideciduous Forest, Southeastern Brazil. Decreased seedlingdensity, basal area, and richness under invasive trees suggestimportant consequences for forest regeneration and productivityas long as this invasion continues. Alberio and Comparatorecompared plant communities and environmental variables inareas of coastal dune grassland invaded by trees (Populus albaand Acacia longifolia) and adjacent uninvaded areas. Decreasedplant cover and richness, together with larger soil particle sizein invaded areas indicate that invasive trees would be profoundlyaltering grassland functioning. Ayup et al. compared understoryvegetation structure and avian communities between forestpatches dominated by invasive trees (Ligustrum lucidum) andnative secondary forest patches in the Northwestern ArgentineanYungas. Decreased understory cover, together with lower birdabundance and richness in Ligustrum-invaded patches suggestchanges in understory production, forest regeneration, trophictransfer to birds, and seed dispersal by frugivores that might allinteract with each other leading to complex dynamics ofecosystem transformation.
(C) Invasive Species Effects on Multiple Ecosystem Functions. As in-formation about the ecosystem impacts of a particular species accu-mulates, it becomes evident that a single species can affect multiplefunctions, and often in a simultaneous way (see, for example,Eviner and Chapin, 2003; Gutiérrez and Jones, 2006). Five papershere compile information about the distinct ecosystem impacts ofparticular invasive species. Muñoz-Vallés et al. summarize theknown and potential impacts of the invasive leguminous shrubRetama monosperma on the biotic composition and functioning ofcoastal dune ecosystems in Southwestern Spain. Horgan et al. re-view the impacts of invasive apple snails (Ampullaridae) on thefunctioning and services of tropical and subtropical wetlandsaround the globe. Reid and Torres combine field surveys and liter-ature review to explore the known and possible ecosystem-levelimpacts of the invasive, mat-forming diatom Didymosphenia gemi-nata in Patagonian rivers. Valenzuela et al. review the impacts ofnon-native vertebrates in the Tierra del Fuego archipelago, charac-terize their underlyingmechanisms, and suggest priorities forman-agement. McLaughlan et al. revisit the 10 species listed as the“worst” invaders in Europe (see Vilá et al.. 2010) and check for ev-idence regarding their positive and negative impacts on distinctecosystem services.
In sum, the papers in this volume illustrate the variety of issuesand approaches that are currently of interest for scientists studyingthe ecosystem impacts of invasive species and add research frommany understudied systems to our knowledge of the field. Theresearch presented here can certainly aid in resolving open general
questions on the topic when combined with study cases from thegeneral literature. As an example of the latter and an epilogue tothis volume, Gutiérrez et al. approach the general question ofhow invasive species affect ecosystem functioning by depictinggeneral mechanistic linkages between invasive species and thedistinct biotic and abiotic components of ecosystems. Understand-ing how invasive species interact with other drivers of ecosystemfunctioning is particularly important for ecosystem managementin a context where the ecological impacts of human developmentare multiple and diverse in nature (Crowl et al., 2008; Strayer,2010, 2012). This final paper aims at providing conceptual toolsto link invasive species impact and spread with the dynamics ofother ecosystem process drivers and ultimately, to better integratethe study of invasive species impacts into an ecosystemperspective.
There is still much work to be done in responding open generalquestions on the impacts of invasive species on ecosystem func-tioning. Clearly, the field is ripe for moving from the study of im-pacts on particular ecosystem functions to the analysis of impactson multiple interacting processes and drivers of ecosystem change.Such a change of research focus from the invasion to the ecosystem(see Strayer, 2012) certainly holds promise for progress in thedevelopment of general hypotheses, frameworks, and theory. Wevery much hope that this Special Issue can serve to propel thatprogress and that ecosystem-focused research on biological inva-sions become more represented in the literature as well as futureBIOLIEF meetings.
Acknowledgments
We thank the authors and reviewers for their insightful contri-butions and their efforts in meeting with the volume preparationschedule. Support and guidance from Drs. Carlos Bernstein (SpecialIssueManaging Editor) and Roger Arditi (Acta Oecologica Editor-in-Chief) were essential for the development of this Special Issue. BIO-LIEF 2011 received financial support from CONICET, Argentina(RD0173-11, Meeting Organization Grant to J. Gutiérrez). We arealso indebted to Keynote Speakers, Scientific Committee members,volunteers, and registered participants at BIOLIEF 2011, who havemade the meeting a huge success.
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Jorge L. Gutiérrez*
Facultad de Ciencias Exactas y Naturales & CONICET, UniversidadNacional de Mar del Plata, Mar del Plata, Argentina
Visiting Scientist, Cary Institute of Ecosystem Studies, Millbrook,NY 12545, USA
M. Gabriela PalomoGrupo de Investigación y Educación en Temas Ambientales (GrIETA),
Mar del Plata, Argentina
Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”(MACN-CONICET), Buenos Aires, Argentina
Pablo D. RibeiroGrupo de Investigación y Educación en Temas Ambientales (GrIETA),
Mar del Plata, Argentina
Instituto de Investigaciones Marinas y Costeras (IIMyC-CONICET),Universidad Nacional de Mar del Plata, Mar del Plata, Argentina
*Corresponding author. Cervantes Saavedra 1875, Mar del Plata(B7603CNI), Argentina. Tel.: +54 2234842886.
E-mail address: [email protected] (J.L. Gutiérrez).
Available online 8 November 2013
