Elsevier

Forest Ecology and Management

Volume 270, 15 April 2012, Pages 153-162
Forest Ecology and Management

Do eucalypt plantations provide habitat for native forest biodiversity?

https://doi.org/10.1016/j.foreco.2012.01.019Get rights and content

Abstract

Plantation forestry contributes to the economic growth of many regions, but may also produce ecological impacts (e.g. on biodiversity) that can be reduced with proper management. We assessed the value of eucalypt plantations to favor habitat connectivity at the landscape scale by determining their ability to provide habitat for species associated with the natural vegetation. For this purpose, we compared diversity and composition of understory vegetation in low-management eucalypt plantations in young, intermediate (ready for harvest) and mature stages with pine plantations, native forests and shrublands. We estimated the true species richness with Chao2 estimators and compared among habitats the average species richness (at two different local scales: per plot and per site), Shannon indices and biovolume of herbs, shrubs and trees in the understory using ANOVAs or GLZs, depending on data distributions. Differences among habitats in understory species composition and functional types were compared with PERMANOVA, and were graphically represented using NMDS ordinations. At local scales, diversity tended to be higher in native communities (native forests and shrublands) and lower in plantations (lowest in intermediate eucalypt plantations). Diversity across all study sites was again lowest in eucalypt plantations in intermediate age, but was relatively high in other plantations, due to a high species turnover in young and mature eucalypt plantations. Eucalypt plantations were similar to shrublands in understory species composition and functional types when young, becoming more distant to them when older, and more similar to pine plantations and native forests. Native forests were the most distinctive community, with pine plantations being the most similar to them. Native forests harbored the rarest species and were also associated with seed dispersal by vertebrates (internally). Ant- and wind dispersal were the most common in shrublands and eucalypt plantations. Given the prevalence of eucalypt plantations in some regions, determining (and improving, if feasible) their ability to harbor biodiversity of native communities becomes a crucial goal, in order to increase landscape connectivity and favor species persistence at regional scales. In the study region, eucalypt plantations provide habitat for species typical of shrublands when young but do not contribute significantly to the maintenance of the understory biodiversity associated with native forests. Considering the distinctiveness of native forests, we favor protection and, where feasible, restoration of native forests over managing eucalypt plantations for biodiversity to best improve conservation outcomes.

Highlights

Understory diversity and composition in plantations and other communities was compared. ► Diversity was lower in plantations than in native communities at local scales. ► Species composition of eucalypt plantations was similar to shrublands when young. ► Native forests were the most distinctive community, and harboured the rarest species. ► Eucalypt plantations provide low habitat value to support native biodiversity.

Introduction

In many countries, plantation forestry depends on a few fast-growing tree species, often exotic. These species contribute significantly to the economic growth of many regions, but may also produce substantial changes in natural ecosystems, with impacts on biodiversity and ecosystem services, which can be nevertheless reduced with proper management, thus increasing the sustainability of this important economic sector (Richardson, 1998, Hartley, 2002).

Tree plantations are expanding worldwide, while natural forests are in decline and increasingly fragmented (FAO, 2010). Temperate forests have been highly influenced by human activities through history and their extension has been dramatically reduced throughout the world, mainly due to overexploitation and conversion to farmland and tree plantations (Hannah et al., 1995, Teixido et al., 2010). Among them, oak (e.g. Quercus robur) forests harbor a rich biodiversity, which is endangered as a consequence of their decline (Castro et al., 2001). In fragmented landscapes, species persistence depends on their ability to use different habitats, so that less suitable habitats may still favor the connectivity of the most suitable habitats in the landscape (Tischendorf and Fahrig, 2000, Lindenmayer, 2009). Remaining fragments of native habitats such as forests are often surrounded by a matrix of modified semi-natural habitats, such as tree plantations and crops, which can still provide habitat for species associated to natural forests (Lindenmayer and Hobbs, 2004, Brockerhoff et al., 2008). Given the relevance of tree plantations in many regions and the potential similarity between them and natural forests, at least in terms of abiotic conditions, it is important to determine their ability to harbor native biodiversity which would favor the connectivity of the landscape and, with it, the persistence of native populations at a regional scale (McIntyre and Hobbs, 1999, Bender and Fahrig, 2005).

The potential role of tree plantations for biodiversity conservation is controversial. Some point to lower biodiversity in plantations as compared to natural forests while others highlight their capacity to harbor native biodiversity (reviewed in Stephens and Wagner, 2007, Brockerhoff et al., 2008, Bremer and Farley, 2010). However, as pointed out by Stephens and Wagner (2007), many studies on the contribution of plantations to biodiversity are based on inappropriate comparisons. An appropriate comparison depends largely on the aims of the plantations, but, in a general sense, plantations should be at least compared with the land uses they usually replace. This should include comparisons to those replaced both directly and indirectly, i.e. considering also the potential vegetation in the replaced areas after natural succession. In addition, plantations are usually even-aged and subject to management. Management intensity and the age and structure of the stands determine the ability of plantations to harbor biodiversity (Lindenmayer and Hobbs, 2004). For example, plantations experience changes in environmental conditions related to age (e.g. canopy closure). These changes affect species differently, according to their habitat preferences, and may result in differences in diversity, structure and species composition between ages (Bunn et al., 2010). Management practices such as periodic clearing of understory vegetation might have more drastic effects than any competitive or allopathic effects of the planted trees (Atauri et al., 2004). For this reason, it is important to specify the management context of the study sites. Moreover, comparisons with other communities are often based on species diversity but do not consider differences/similarities in species composition, which is essential to assess the possible role of plantations in harboring native biodiversity.

Eucalypts (chiefly E. globulus, E. grandis, E. nitens and E. camaldulensis) have become the most widely planted hardwood species in the world, mostly for paper production. The success of eucalypts can be attributed to their fast growth, coppicing ability, wide adaptability to soils and climate, and the unpalatability of its leaves (Turnbull, 1999). However, the expansion of eucalypt plantations has raised concerns regarding ecosystem degradation (e.g. loss of biodiversity) and eucalypts have become a major source of conflicts between foresters and conservationists in many countries. Studies on the effects of eucalypt plantations on biodiversity are surprisingly scarce considering the spread of these plantations around the world, but some point to lower biodiversity in eucalypt plantations as compared to other communities (e.g. Bará-Temes et al., 1985, Pina, 1989, Basanta et al., 1989, Proença et al., 2010a). In contrast, other studies show their positive effect in regeneration of native understory plants (e.g. in Ethiopia, Michelsen et al., 1996, Yirdaw and Luukkanen, 2003).

In this study, we analyzed the diversity and composition of understory plants in the most common plant communities in the natural and semi-natural landscape in the study region (NW Spain): low-management eucalypt plantations of three different age-stages (young, intermediate and mature) as compared to natural forests, shrublands and pine plantations, which are the communities most commonly replaced by eucalypt plantations, directly or indirectly, and thus are the most appropriate for comparison (Stephens and Wagner, 2007). Understory plants are used here as appropriate biodiversity indicators as their diversity is often correlated with that of other taxonomic groups (Kati et al., 2004, Rodrigues and Brooks, 2007). In addition, understory plants are especially significant in temperate forests in terms of total diversity, and favor the development and diversity of other groups (Gilliam, 2007). They are also important ecosystem service providers (Quijas et al., 2010). Our aim in this study is to assess the value of eucalypt plantations to favor habitat connectivity at a landscape scale by determining their ability to provide habitat for species associated with the natural vegetation.

Section snippets

Study area context

The NW of Spain (Galicia) is the most important forestry region in the country (Manuel and Gil, 2002). E. globulus has been intensively cultivated in this region, mostly for the paper industry (Riesco, 2004), and has multiplied its cover by 6 over the last 25 years, both by intentional planting and natural spread (Manuel and Gil, 2002). Most plantations are privately owned in small, scattered holdings (83% of the area covered by eucalypts in pure stands) which leads to excessive land

Biovolume

Plant biovolume in the understory (of herbs, shrubs, trees, and total) differed among habitats (χ25df > 6.6, P < 0.001, Fig. 1). Shrub biovolume clearly determined the trend in total biovolume, which decreased from shrublands to native forests, with intermediate values in eucalypt and pine plantations (Fig. 1). Native forests had the highest tree species biovolume in the understory (seedlings, small saplings), followed by mature eucalypt and pine plantations (Fig. 1). Herbaceous biovolume was

Diversity patterns

At local scales (plot and site), diversity was generally higher in native communities (native forests and shrublands) and lower in plantations. Total diversity, i.e. accumulated across all study sites, was lowest in eucalypt plantations in intermediate age, but was relatively high in other plantations, and similar to that in native forests. This was mainly due to a higher dissimilarity among sites (species turnover) in young and mature eucalypt plantations. In the case of young plantations,

Conclusions

Low-management plantations can harbor high amounts of plant biovolume in the understory although with relatively low local diversity. Although successional changes were found within the understory of eucalypt plantations with increasing age, key components of native forests were not found in mature eucalypt forests. Pine plantations supported an understory that was more similar to that in native forests, but failed also to provide a suitable habitat for the most characteristic species of native

Role of the funding source

The sponsors had no role on the collection, analysis and interpretation of data; in the writing of the manuscripts; nor in the decision to submit the article for publication.

Acknowledgements

We thank Cristina E. Ramalho for helpful discussions on the study, Cristina Vences and Paola Acuña for assistance in the field, and Adolfo Cordero for comments on the manuscript. This research was funded by Project 08MRU024371PR (Consellería de Innovación e Industria, Plan INCITE, Xunta de Galicia) to MCC. MCC was supported by an Isidro Parga Pondal Contract (Xunta de Galicia). Comments of two anonymous referees and the editor contributed to increase the quality of the manuscript.

References (89)

  • D. MacDonald et al.

    Agricultural abandonment in mountain areas of Europe: environmental consequences and policy response

    J. Environ. Manage.

    (2000)
  • V.M. Proença et al.

    Plant and bird diversity in natural forests and in native and exotic plantations in NW Portugal

    Acta Oecol.

    (2010)
  • V. Proença et al.

    Resistance to wildfire and early regeneration in natural broadleaved forest and pine plantation

    Acta Oecol.

    (2010)
  • S. Quijas et al.

    Plant diversity enhances provision of ecosystem services: a new synthesis

    Basic Appl. Ecol.

    (2010)
  • A.L. Teixido et al.

    Impacts of changes in land use and fragmentation patterns on Atlantic coastal forests in northern Spain

    J. Environ. Manag.

    (2010)
  • E. Yirdaw et al.

    Photosynthetically active radiation transmittance of forest plantation canopies in the Ethiopian highlands

    For. Ecol. Manage.

    (2004)
  • C. Zhang et al.

    Allelopathic effects of eucalyptus and the establishment of mixed stands of Eucalyptus and native species

    For. Ecol. Manage.

    (2009)
  • M.J. Anderson et al.

    PERMANOVA + for PRIMER: Guide to Software and Statistical Methods

    (2008)
  • M.J. Anderson et al.

    Navigating the multiple meanings of β diversity: a roadmap for the practicing ecologist

    Ecol. Lett.

    (2011)
  • J.A. Atauri et al.

    Effects of management on understory diversity in the forest ecosystems of Northern Spain

    Environ. Manage.

    (2004)
  • L. Augusto et al.

    High rates of nitrogen fixation of Ulex species in the understory of maritime pine stands and the potential effect of phosphorus fertilization

    Can. J. For. Res.

    (2005)
  • S. Bará-Temes et al.

    Efectos ecológicos del Eucalyptus globulus en Galicia

    (1985)
  • S.S. Bargali et al.

    Changes in soil characteristics in eucalypt plantations replacing natural broad-leaved forests

    J. Veg. Sci.

    (1993)
  • M. Basanta et al.

    Diversity measurements in shrubland communities of Galicia (NW Spain)

    Vegetatio

    (1989)
  • F. Bellot

    La vegetación de Galicia

    (1966)
  • D.J. Bender et al.

    Matrix structure obscures the relationship between interpatch movement and patch size and isolation

    Ecology

    (2005)
  • S.F. Bongiorno

    Land-use and summer bird populations in Northwestern Galicia, Spain

    Ibis

    (1982)
  • L.L. Bremer et al.

    Does plantation forestry restore biodiversity or create green deserts? A synthesis of the effects of land-use transitions on plant species richness

    Biodiv. Conserv.

    (2010)
  • E.G. Brockerhoff et al.

    Plantation forests and biodiversity: oxymoron or opportunity?

    Biodiv. Conserv.

    (2008)
  • W.A. Bunn et al.

    Change within and among forest communities: the influence of historic disturbance, environmental gradients, and community attributes

    Ecography

    (2010)
  • A.N. Caiafa et al.

    Forms of rarity of tree species in the southern Brazilian Atlantic rainforest

    Biodiv. Conserv.

    (2010)
  • R.M. Callaway

    Effect of shrubs on recruitment of Quercus Douglasii and Quercus Lobata in California

    Ecology

    (1992)
  • M. Calvino-Cancela

    Gulls (Laridae) as frugivores and seed dispersers

    Plant Ecol.

    (2011)
  • E.B. Castro et al.

    Los Bosques Ibéricos: Una interpretación geobotánica

    (2001)
  • Castroviejo, S. (Coord.), 2008. Flora Ibérica. Plantas Vasculares de la Península Ibérica e Islas Baleares. Real Jardín...
  • K.R. Clarke et al.

    PRIMER v6: User Manual/Tutorial

    (2006)
  • R.K. Colwell et al.

    Interpolating, extrapolating, and comparing incidence-based species accumulation curves

    Ecology

    (2004)
  • Colwell, R.K., 2005. EstimateS: Statistical Estimation of Species Richness and Shared Species from Samples. Ver. 7.5....
  • R.K. Colwell et al.

    Estimating terrestrial biodiversity through extrapolation

    Philos. Trans. R. Soc.

    (1994)
  • A. Cordero

    Cuando los árboles no dejan ver el bosque: Efectos de los monocultivos forestales en la conservación de la biodiversidad

    Acta Biol. Colomb.

    (2011)
  • V.A. Cramer et al.

    Old Fields: Dynamics and Restoration of Abandoned Farmland

    (2007)
  • W. Duan et al.

    Community comparison and determinant analysis of understory vegetation in six plantations in South China

    Restor. Ecol.

    (2010)
  • A.E. Eycott et al.

    Ecological patterns of plant diversity in a plantation forest managed by clearfelling

    J. Appl. Ecol.

    (2006)
  • FAO, 2010. Global Forest Resources Assessment. FAO,...
  • Cited by (113)

    View all citing articles on Scopus
    View full text