Recovery Of Native Plant Communities Research Articles

Forest topsoil salvage and placement depth affects oil sands reclamation in the boreal forest.

Reclamation of disturbances from oil sands mining requires effective soil management to ensure successful plant establishment and to promote recovery of native plant communities. In this study we investigated the effects of salvage depths (shallow vs. deep) and placement depths (shallow vs. deep) of forest topsoil on plant establishment, species richness, and soil properties in two substrate types (sand and peat-mineral). Shallow salvage led to greater tree stem densities and higher canopy cover for most plant groups, although there was no significant difference in species richness between shallow and deep salvages. Deep placement generally resulted in greater canopy cover, while its effect on plant density was very small for most plant groups. On peat-mineral substrate, fewer differences were detected between shallow and deep salvage, and multiple treatments resulted in greater cover. Findings suggest that a balance between maximizing the area over which propagules are redistributed and providing sufficient resources for successful plant establishment is necessary. Forest topsoil from shallow salvages and deep placements is recommended when targeting increased site productivity and species diversity. In contrast, deep salvage should be used when the primary objective is to obtain maximum reclamation material volume. Salvage depth effects may be influenced by substrate type, with peat-mineral substrate providing more favourable conditions for plant establishment. Further research is needed to assess the long-term impacts of different salvage and placement depths on plant community development and the potential effects of substrate properties on soil and plant response.

(Not) sweeping invasive alien plants under the carpet: results from the use of mulching sheets for the control of invasive Carpobrotus spp.

Biological invasions represent a global threat to biodiversity. Particular attention should be made to the management of alien plants. The species from the Carpobrotus genus are well-known invasive plants native to South Africa, whose detrimental effects on native communities are widely documented. These impacts have become particularly important in terms of their invasive potential on small Mediterranean islands, where they often threaten particular ecosystems and endemic species. We report the experience from the efforts to eradicate this species from the island of Giannutri (Tuscan Archipelago, Italy)—an action included within the EU LIFE project “RESTO CON LIFE”—where the species occurred on about 14,000 m2 of coastal vegetation. The eradication employed an integrated approach with two control methods (manual removal and covering with mulching sheets) and involved mosaic rocky cliff coastal vegetation and disturbed areas with loose soil close to the cliffs. We present here the results obtained from five years of monitoring using permanent plots. Carpobrotus spp. exerted strong impacts on the invaded plant communities, with significant depletion and replacement of native species. Both of the control methods proved effective in the suppression of the mat formed by the invasive species and led to a positive response of native vegetation. Nevertheless, the recovery of native plant communities differed depending on the type of substratum, taking longer on rocky cliffs due to the harsher conditions. Improvements were driven by nitrophilous species in the plots treated with mulching sheets.

Effects of Ailanthus altissima Invasion and Removal on High-Biodiversity Mediterranean Grasslands.

Ailanthus altissima is one of the worst invasive plants in Europe in several habitat types, including high-biodiversity grasslands. The aim of this work was to evaluate the impact of the invasive A. altissima on high-biodiversity grassland vegetation and the effects of its removal on the recovery of native plant communities. The study area was within the Alta Murgia National Park (SE Italy). Seventeen vegetation quadrats were sampled in invaded grasslands and nine quadrats were sampled in nearby uninvaded areas. A. altissima was removed from six quadrats, which were sampled for two years after plant removal. Cluster analysis and non-metric multidimensional scaling ordination were used to identify and visualize the general vegetation pattern. Generalised Linear Models with different error structures were used to analyse the effects of A. altissima on native grasslands and vegetation recovery after removal. Results showed that the invasion of A. altissima changed drastically the community composition, reduced plant richness and diversity. Invaded stands had a greater presence of ruderal and widely distributed taxa, as opposed to a lesser presence of endemic and Mediterranean ones. The differences in the community composition between invaded and uninvaded quadrats became clearly detectable when A. altissima plants exceeded a threshold of 1 m of height and 50% of coverage. After A. altissima removal, the recovery of the grassland community was not completely achieved after two years.

Asexual Regeneration Response of Ilex canariensis Poir. to Management of the Canopy of Pinus radiata D.Don

Exotic afforestation can provide suitable conditions for native shade-tolerant species restoration without threatening native forests. This study analyzes the impact of different thinning intensities of the canopy of an exotic Pinus radiata stand on the asexual regeneration response of Ilex canariensis, a native laurel forest species in the Canary Islands, Spain. The results provide useful indications for how to manage P. radiata stands to promote recovery of native plant communities. For different stand treatments were selected: stand clear cut, low intensity thinning (10–15%), high intensity thinning (25%), and a control. The stand clear cut management revealed Ilex canariensis individuals with a higher number of sprouts and more leaf cover; however, the height of these sprouts two years after the cut did not reach the values of individuals prior to this management. Consequently, the vitality index following clear cut management is significantly lower with respect to the other treatments. Thinning management is shown not to be so useful to promote the growth and vitality of Ilex canariensis individuals. The results suggest that thinning over 50% could be more appropriate in the case of Pinus radiata, allowing resprouting of Ilex canariensis in the understory and improvement in the vitality index.

Native plant community recovery after Carpobrotus (ice plant) removal on an island — results of a 10‐year project

AbstractQuestionSpecies of the genus Carpobrotus, or ice plant, are succulent mat‐forming perennial herbs often introduced for soil stabilization. They are common in coastal environments and may thus threaten island biodiversity. While their effects are well known on soils, plant communities and associated fauna, the effects of Carpobrotus control on vegetation recovery are poorly documented. The aim of the paper is to describe plant community trajectories after Carpobrotus removal.LocationBagaud: a 58‐ha Mediterranean island, southern France.MethodsCarpobrotus and its litter were removed in 2011–2012. Follow‐up controls of germinations and resprouts were carried out from then on. Plant communities were surveyed every year two years before and seven years after Carpobrotus removal: on two ca. 0.5‐ha sites (one coastal and one inland) and in three native plant communities used as potential references. Differences in resprouts, vegetation parameters, and Bray–Curtis similarity indices between years were tested. Plant community dynamics was studied through a non‐metric multidimensional scaling and two recovery indices.ResultsThe removal of Carpobrotus and its litter led to the recovery of diverse native plant communities. To prevent Carpobrotus return and ensure success, follow‐up controls were necessary for a period of at least seven years, but the amount of work decreased with time. The plant community recovering on the coastal site quickly reached a composition and structure similar to that of non‐invaded coastal vegetation, although some slow‐growing native species remain underrepresented (e.g., Crithmum maritimum and Limonium pseudominutum). The plant community recovering on the inland site was still very different from the surrounding matorral vegetation because of its slow colonization dynamics, particularly in the presence of competitive herbaceous species.ConclusionBoth sites now provide diverse native plant communities with a more diversified composition and structure (plant heights, litter, bare ground patches) than the plant communities which used to be associated with Carpobrotus mats.

Species composition and structure of an exotic Quercus suber stand on the island of Gran Canaria (Canary Islands)

Aim of the study: Although introduced tree species have been recognized as adversely affecting native ecosystems, conversely, some studies suggest they can facilitate recovery and promote the establishment of native plant communities. This study tests whether a native plant community is established under the closed canopies of an exotic species by analyzing regeneration and plant species composition.Area of study: Finca de Osorio, a public property of the Cabildo de Gran Canaria included in the Doramas Rural Park (Canary Islands, Spain).Main results: The results reveal that sapling regeneration is dominated by the exotic species, though some native ones are also present. The sapling regeneration community did not differ from the tree canopy composition, so, a native plant community recovery cannot be expected to occur. In addition, other introduced species were also present in the sapling composition community.Research highlights: The laurel forest of the Canary Islands is the most emblematic plant community of the Canary Island archipelago. The studied area dominated by Q. suber does not favor the regeneration of the native plant community. Thus, restoration programs will be required to enhance the native plant community and the area covered by this highly disturbed plant ecosystem on the island of Gran Canaria.Keywords: catalytic effect; invasion; laurel forest; plant community.

Short-Term Vegetation Responses to Invasive Shrub Control Techniques for Amur Honeysuckle (Lonicera maackii [Rupr.] Herder)

Invasive shrubs in forest understories threaten biodiversity and forest regeneration in the eastern United States. Controlling these extensive monotypic shrub thickets is a protracted process that slows the restoration of degraded forest land. Invasive shrub removal can be accelerated by using forestry mulching heads, but evidence from the western United States indicates that mulching heads can promote exotic species establishment and mulch deposition can reduce native plant species abundance. We compared the effectiveness of the mulching head and the “cut-stump” method for controlling the invasive shrub Amur honeysuckle (Lonicera maackii), as well as their impacts on native plant community recovery, in mixed-hardwood forests of Indiana. After two growing seasons, mulching head treatment resulted in greater L. maackii regrowth and regeneration. The recovery of native plant abundance and diversity following shrub removal did not differ between the two methods. However, mulch deposition was associated with increased abundance of garlic mustard (Alliaria petiolata), an invasive forb. Increasing mulching head treatment depth reduced L. maackii regrowth, but additional study is needed to determine how it affects plant community responses. The mulching head is a promising technique for invasive shrub control and investigating tradeoffs between reducing landscape-scale propagule pressure and increased local establishment will further inform its utility.

Impact of the arundo wasp, Tetramesa romana (Hymenoptera: Eurytomidae), on biomass of the invasive weed, Arundo donax (Poaceae: Arundinoideae), and on revegetation of riparian habitat along the Rio Grande in Texas

ABSTRACTAn invasive grass, Arundo donax, occupies thousands of hectares of arid riparian habitat along the Rio Grande in Texas and Mexico, and has negative impacts on national security, water resources, and riparian ecosystems. The shoot-tip-galling wasp Tetramesa romana was released in 2009 between Brownsville and Del Rio, Texas, and has dispersed over 800 km along the river channel. Plots along the river were surveyed for shoot counts of arundo and all other plant species in 2016 at seven sites in regions in which prior studies had documented a 22% decline in arundo biomass (estimated from live shoot length) from 2007 to 2014. Estimated live biomass declined a further 32% between 2014 and 2016. Native plants accounted for 86% of the 44 species encountered in plots. Individual plots averaged five plant species, and arundo was most abundant in only 9 of 21 plots. Arundo live biomass and shoot density were negatively associated with plant diversity, indicating that live arundo interferes with germination and/or survival of other plant species. The proportion of dead shoots in plots, proportion of wasp-galled shoots, and density of exit holes made by emerging adult wasps per metre live main shoot length were positively associated with plant diversity in a combined model. Regressions indicated that the effects of wasp damage measures on diversity were mediated through their effects on main shoot mortality. By reducing live arundo biomass, the arundo wasp is fostering recovery of native plant communities at riparian sites along the Rio Grande.

Recovery of native plant communities in southwest Ohio afterLonicera maackiiremoval1

Abstract Lonicera maackii (Rupr.) Herder (Amur honeysuckle) is one of the most important invasive plants in the Ohio Valley. Because of its phenology and dense canopy, L. maackii can exclude native herbs and interfere with regeneration of woody plants. In 2005, in a county park in southwest Ohio, I established modified Whittaker plots in four stands with a gradient of L. maackii cover ranging from 24 yr old to 40 yr old. The L. maackii canopies were removed by herbicides in fall 2005. Plant cover was monitored from 2005 to 2013. After 8 yr, there was an increase in species richness and herbaceous cover at all sites. Herbaceous species turnover was generally greater at sites with greater initial L. maackii cover. All of the most-common herbaceous species increased or maintained their coverage; most of the species that increased were those that bloom in late spring or summer. The abundances of other invasive species also increased, including Alliaria petiolata (M. Bieb.) Cavara & Grande (garlic mustard). Ho...

A new model of landscape-scale fire connectivity applied to resource and fire management in the Sonoran Desert, USA.

Understanding where and when on the landscape fire is likely to burn (fire likelihood) and the predicted responses of valued resources (fire effects) will lead to more effective management of wildfire risk in multiple ecosystem types. Fire is a contagious and highly unpredictable process, and an analysis of fire connectivity that incorporates stochasticity may help predict fire likelihood across large extents. We developed a model of fire connectivity based on electrical circuit theory, which is a probabilistic approach to modeling ecological flows. We first parameterized our model to reflect the synergistic influences of fuels, landscape properties, and winds on fire spread in the lower Sonoran Desert of southwestern Arizona, and then defined this landscape as an interconnected network through which to model flow (i.e., fire spread). We interpreted the mapped outputs as fire likelihood and used historical burned area data to evaluate our results. Expected fire effects were characterized based on the degree to which future fire exposure might negatively impact native plant community recovery, taking into account the impact of repeated fire and major vegetation associations. We explored fire effects within habitat for the endangered Sonoran pronghorn antelope and designated wilderness. Model results indicated that fire likelihood was higher in lower elevations, and in areas with lower slopes and topographic roughness. Fire likelihood and effects were predicted to be high in 21% of the currently occupied range of the Sonoran pronghorn and 15% of the additional habitat considered suitable. Across 16 designated wilderness areas, highest predicted fire likelihood and effects fell within low elevation wilderness areas that overlapped large fire perimeters that occurred in 2005. As ongoing changes in climate and land cover are poised to alter the fire regime across extensive and ecologically important areas in the lower Sonoran Desert, an analysis of fire likelihood and effects can contribute new and important information to fire and fuels management. Our novel approach to modeling fire connectivity addresses challenges in quantifying and communicating wildfire risk and is applicable to other ecosystems and management issues globally.

Recovery of Native Plant Communities following Control of Terracina Spurge (Euphorbia terracina): Three Case Studies from South-west Western Australia

Terracina spurge or Geraldton carnation weed ( Euphorbia terracina ) is an invasive weed that impacts native plant communities across southern mainland Australia and in the United States (USA), including southern California and Pennsylvania. There are, however, few published accounts of appropriate control techniques or recovery of native vegetation following removal of this species. We report here on the results of three adaptive management projects investigating effective control of Terracina Spurge and subsequent recovery of Banksia woodlands, coastal shrublands, and sedgeland communities in the Swan Coastal Plain bioregion, south-west Western Australia. In Banksia woodlands the herbicide metsulfuron-methyl (600g/kg) (Brush-Off® ) in combination with hand removal of adult plants was effective at controlling Terracina spurge. Although there was some initial off target damage to native flora, after five years of repeated application the Banksia woodland within the treated area is regenerating. In sedgelands of the Holocene dune swales and in coastal shrublands 750g/kg triasulfuron (Logran® ) was very effective, reducing Terracina spurge populations significantly in the first two years. The treatment resulted in little damage to native flora. At both sites a significant difference in species abundance between years was attributed mostly to a decrease in the cover of Terracina spurge but also an increase in cover of several species of native flora. The results indicate triasulfuron is an effective tool for the management of Terracina spurge in coastal plant communities potentially leading to the protection and restoration of significant areas of the conservation estate within the Swan Coastal Plain bioregion and beyond.

Vegetation Recovery 16 Years after Feral Pig Removal from a Wet Hawaiian Forest

AbstractNonnative ungulates can alter the structure and function of forest ecosystems. Feral pigs in particular pose a substantial threat to native plant communities throughout their global range. Hawaiian forests are exceptionally vulnerable to feral pig activity because native vegetation evolved in the absence of large mammalian herbivores. A common approach for conserving and restoring forests in Hawaii is fencing and removal of feral pigs. The extent of native plant community recovery and nonnative plant invasion following pig removal, however, is largely unknown. Our objective was to quantify changes in native and nonnative understory vegetation over a 16 yr period in adjacent fenced (pig‐free) vs. unfenced (pig‐present) Hawaiian montane wet forest. Native and nonnative understory vegetation responded strongly to feral pig removal. Density of native woody plants rooted in mineral soil increased sixfold in pig‐free sites over 16 yr, whereas establishment was almost exclusively restricted to epiphytes in pig‐present sites. Stem density of young tree ferns increased significantly (51.2%) in pig‐free, but not pig‐present sites. Herbaceous cover decreased over time in pig‐present sites (67.9%). In both treatments, number of species remained constant and native woody plant establishment was limited to commonly occurring species. The nonnative invasive shrub, Psidium cattleianum, responded positively to release from pig disturbance with a fivefold increase in density in pig‐free sites. These results suggest that while common native understory plants recover within 16 yr of pig removal, control of nonnative plants and outplanting of rarer native species are necessary components of sustainable conservation and restoration efforts in these forests.

Eradication of invasive herbivores: usefulness and limits for biological conservation in a changing world

Over the past 25 years, the international scientific community has recognized that biotic invasion is a major anthropogenic threat to ecosystems worldwide (Mack et al., 2000). More recently, it has been shown that in addition to major ecological impacts on many Earth biotas (Walther et al., 2002), climate change is expected to benefit invaders (Frenot et al., 2005; Walther et al., 2009). Facing such probable synergistic threats, we need a strong scientific background both to better understand these processes and to advise conservation managers and the public (Towns, 2011). The longterm monitoring of ecosystems undergoing restoration programmes, following eradication of one or several invasive species, is not only a major way to assess the impact of invaders but it can also reveal some of the unpredicted negative effects associated with management actions (Zavaleta, Hobbs & Mooney, 2001; Courchamp, Chapuis & Pascal, 2003; Bergstrom et al., 2009). When eradication projects take place in archipelagoes, the variety of islands often offer contrasting situations in terms of the presence/ absence of introduced species, and monitoring provides invaluable information, including comparisons with control sites (Chapuis, Frenot & Lebouvier, 2002; Croll et al., 2005; Fukami et al., 2006; Towns et al., 2009). The Iles Kerguelen, where our study was carried out (Brodier et al., 2011), offered such a situation. When restoration programmes were initiated on the Iles Kerguelen in 1991 (Chapuis et al., 1995), the expected trajectory of vegetation cover after the rabbit eradication was the recovery of native plant communities. Specifically, we predicted the re-establishment of the keystone native species, the Kerguelen cabbage, Pringlea antiscorbutica, extirpated by rabbits (Chapuis, Barnaud & Bousses, 1994). Then, following the re-colonization event, we predicted that the most favourable habitats would be rehabilitated with a subsequent improvement in both native vertebrate (burrowing seabirds) and macroinvertebrate communities. Twenty years later, our initial predictions are neither fully supported nor rejected. The removal of rabbits from Ile Verte was beneficial to blue petrels, Halobaena caerulea, as expected, and to its native predator, the brown skua, Catharacta skua (Brodier et al., 2011). However, converse to expectations, the increase in blue petrels did not result directly from the restoration of the plant cover but through an apparently more complex mechanism involving interspecific competition with rabbits. Suppressing rabbits’ interference in burrow occupancy by breeding blue petrels highlighted an unreported competition process with a closely related sympatric petrel species, the Antarctic prion, Pachyptila desolata (Bonnaud & Courchamp, 2011). Therefore, the rabbit eradication restored competitive processes between native species, a result inaccessible without longterm monitoring of the ecosystem as a whole. Concerning changes in the vegetation cover, our monitoring programme demonstrated that our initial assumption was partly wrong, mainly in relation to the unexpected consequences of climate change: after rabbit eradication on three islands (Chapuis et al., 2001), native communities did not restore. In fact, native monospecific Acaena magellanica communities started to regress, allowing an important increase of invasive plant species (Chapuis, Frenot & Lebouvier 2004). Invasion has been facilitated by the regression of A. magellanica due to the increased frequency of summer droughts, a trend observed over the last 15 years in Iles Kerguelen (Lebouvier et al., 2011). As a consequence, an increase in soil erosion has also been detected, particularly on the main island where rabbits affect plant cover (Robin, Chapuis & Lebouvier, 2011). Unexpected cascade effects that could only be detected, thanks to the long-term monitoring in the context of climate change, raise new issues with regard to the biological conservation in the context of restoration. In our view, environmental managers are now facing three options on Kerguelen: (1) ‘Laissez faire’, to investigate the consequences of climate change on the dynamics of communities (including biotic and abiotic interactions); (2) pursue the rabbit removal to improve plant cover in areas threatened by erosion processes, even if promoting the development of invasive plant species (at least in the medium term); and (3) limit the development of invasive plants while maintaining enough cover to fix soils and prevent erosion, using rabbit as an auxiliary species (see Walther et al., 2009). This latter option has gained some indirect support, as documented by one of us (JLC) in February 2011. On Ile du Cimetiere, rabbits have been maintained at low density over recent Animal Conservation. Print ISSN 1367-9430

Recovery of soil and vegetation in semi-arid Australian old fields

Due to the harsh environmental conditions of arid and semi-arid regions, recovery of native plant communities after abandonment from cultivation is hypothesised to be slow and unlikely to return to pre-disturbance condition. We examined vegetation and soil parameters along a ∼100 year chronosequence of agricultural field abandonment in semi-arid grasslands in south-eastern Australia to quantify resilience. Native species richness, abundance and composition converged towards those of uncultivated grasslands, and there was a replacement of initial exotic dominance by native perennial grasses. Thus, the vegetation did not enter an alternative stable state and the community variables studied showed some resilience. However, many native species failed to recolonise, and native species richness, composition and abundance remained significantly different from uncultivated grasslands over the span of the study. Soils demonstrated post-abandonment recovery, with differences to uncultivated grassland in most nutrients becoming non-significant by ∼50 years, and soils did not appear to be the main driver of vegetation patterns with time-since-abandonment. The basic patterns of community reassembly did not appear to be fundamentally different from temperate northern hemisphere old field succession and suggest that secondary succession in Australian semi-arid grasslands may be constrained by seed availability rather than environmental conditions.

Tarping as an Alternative for Perennial Pepperweed (Lepidium latifolium) Control

AbstractPerennial pepperweed (Lepidium latifolium) is a potential threat to biodiversity and ecosystem function in the communities that it invades. The mechanism for its successful invasion of riparian and wetland environments includes reproduction via seed and root propagules and its ability to withstand long duration flooding and saline conditions once established. Controlling this species presents a number of challenges for land managers, including difficult property access, limited herbicide choice, and the varied success of weed control measures. In this study, we tested the efficacy of a nonchemical-modified tarp treatment, and compared posttreatment stem counts to herbicide treatments with Mow–glyphosate and chlorsulfuron in a wildland setting. We found that tarping applied in combination with a mow and till treatment was effective at controlling perennial pepperweed at levels similar to herbicide treatments with Mow–glyphosate and with Mow–chlorsulfuron. However, Mow–Till–Tarp treatment is extremely time consuming and has the potential to limit native plant community recovery.

Does invasive plant management aid the restoration of natural ecosystems?

Invasive alien plants of natural ecosystems, commonly referred to as weeds, can reduce the abundance and diversity of native flora and fauna, and alter ecosystem processes. Using Australia’s 20 ‘Weeds of National Significance’ (WoNS), we investigated how natural ecosystems responded following their management. We reviewed the literature and surveyed land managers involved in WoNS management programs by distributing a questionnaire through various e-mail networks. While most of the 95 papers reviewed measured the effect of management on the target WoNS, only 18 assessed the response of other plant species. In these studies, native plant species did not necessarily recover following management and in many instances the managed WoNS was replaced by other weed species. Three other studies investigated the response of invertebrate communities and an ecosystem process following WoNS management but none examined the response of vertebrates or microbial communities. A total of 168 replies were received to the land manager survey. Of the 142 land managers who evaluated their WoNS management program, 86 monitored the response of native plant species and/or other weeds, mostly using qualitative assessments. These managers reported no vegetation response after management of the WoNS (7%) or re-colonisation by a combination of native and weed species (52%) or only by native plants (33%) or the targeted WoNS (2%). Our results emphasise the need to select sites for weed management that are less degraded and thus have a higher likelihood of natural recovery and/or to incorporate activities that facilitate recovery of native plant communities in conjunction with weed removal.

Recovery of native plant communities after the control of a dominant invasive plant species, Foeniculum vulgare: Implications for management

The control and/or removal of a dominant invasive species is expected to lead to increases in native species richness and diversity. Small pilot studies were performed on Santa Cruz Island (SCI), California, in the early 1990s to test the efficacy of different methods on the control of Foeniculum vulgare (fennel) and management’s effects on native species recovery. We chose a treatment that showed significant native species recovery, applied it at the landscape scale, and followed its effects on fennel infested plant communities. We tested the hypothesis that results from small-scale studies translate to the landscape level. We found that although the control of fennel translated from the small to landscape scale, decreasing from an average of 60% to less than 3% cover, native species recovery did not occur in the landscape study as it did in the pilot studies. Invasive fennel cover was replaced by non-native grass cover over time. Unexpectedly, fennel cover in untreated fennel plots decreased significantly (though not as drastically) from over 60% cover to just under 40% cover while native species richness in untreated areas increased significantly. The correlation between precipitation and changes in native and non-native species richness and abundance in this study imply that changes in species abundances were highly correlated with environmental fluctuations. The lack of a native seedbank and the accumulation of non-native grass litter likely prevented the recovery of native species in treated areas. Greater vertical complexity found in fennel communities, which increased visitation by frugivorous birds and likely increased native seed dispersal, may have been responsible for the increase in native species richness in the untreated areas. These results suggest that successful invasive species control and native species recovery experiments conducted at small scales may not translate to the landscape level, and active restoration should be an organic component of such large-scale projects.

Recovery of native plant communities after eradication of rabbits from the subantarctic Kerguelen Islands, and influence of climate change

The introduction of rabbits in 1874 into the Kerguelen archipelago had a significant impact on plant communities: the most sensitive species Pringlea antiscorbutica and Azorella selago disappeared and Acaena magellanica became dominant in most of the coastal areas. To study the recovery of native plant communities, rabbits were eradicated by poisoning on two islands. This produced a significant increase in species richness on both islands with a decline in the cover of some native species (primarily A. magellanica) and an increase in the abundance of alien species (especially Taraxacum officinale). Other native species showed signs of increased abundance but overall responses were slow. These trends are obviously due to the removal of grazing, but recent changes in climatic conditions (warming and drought) may also be responsible for the decline or slow recovery of native species, and for the success of introduced species. Owing to the effects of present climate changes on plant communities, eradication of alien herbivores may not be always appropriate for the conservation of native biota in the subantarctic islands, and regulation of populations should be explored.