Sue McIntyre

Plant functional classifications: from general groups to specific groups based on response to disturbance

Predicting the effects of anthropogenic changes in climate, atmospheric composition and land use on vegetation patterns has been a central concern of recent ecological research. This aim has revived the search for classification schemes that can be to group plant species according to their response to specified environmental factors. One way forward is to adopt a hierarchical classification, where different sets of traits are examined depending on growth form. Also, at the level of interpretation, the environmental context and purpose of functional classifications need to be specified explicitly, so that global generalizations can be made by comparing across environments functional classifications derived from similar methodologies.

Assisted Colonization and Rapid Climate Change

Moving species outside their historic ranges may mitigate loss of biodiversity in the face of global climate change.

Plant life-history attributes: their relationship to disturbance response in herbaceous vegetation.

I Species composition and disturbance state (level of soil disturbance, grazing and water addition) were recorded for 120 (30-m2) plots in temperate grassland of the New England Tablelands (Australia). Three different classificatory schemes were used, based on (a) life-form (sensu Raunkiaer); (b) dispersal unit morphology and (c) vegetative reproduction. We analysed the effects of the different disturbance types and intensities on number and proportion of species belonging to these groups. The results were used to describe the spectrum of life-histories likely to be present at sites in different states of exogenous disturbance. 2 Soil disturbed sites had proportionately more therophytes, versatile/flat rosettes and wind dispersed species. Two features are likely to lead to success in soil disturbed sites: ability to colonize open space (e.g. therophytes, wind dispersal) and capacity to capture resources effectively (e.g. flat architecture of rosettes). Non-disturbed sites had more geophytes, chamaephytes, phanerophytes, proto-hemicryptophytes and erect rosettes, with greater numbers of vegetatively reproducing species. 3 Heavily grazed sites had higher proportions of therophytes and versatile/flat rosettes and species with mobile seeds than sites with light grazing. Moderately grazed sites had increased proportions of versatile and erect rosettes and more species with adhesive seeds (mainly grasses). Lightly grazed sites had a greater diversity in terms of evenness of all life-forms, dispersal morphologies and reproductive modes. 4 Water enriched sites had fewer geophytes and phanerophytes and some chamaephytes, erect rosettes and proto-hemicryptophytes. This loss was only partially compensated by a gain in versatile and partial rosettes but richness decreased overall. Water enrichment was unrelated to dispersal unit morphology or the potential for vegetative reproduction. 5 Of the three attributes examined, life-form was most useful in characterizing community response to different disturbance types. Traits related to regeneration (seed morphology and capacity of vegetative reproduction) were relevant to soil disturbance only. Our results support the use of such classifications for monitoring the effects of disturbance.

Disturbance response in vegetation – towards a global perspective on functional traits

. Previous work on trait correlation patterns has contributed to the identification of broad patterns of plant distribution along environmental gradients in vegetation. However, these general trends may conceal subtle mechanisms of response that are specific to particular types of disturbance. To address this, we propose a generic methodology for the analysis of traits, using herb-dominated vegetation as a model. Hypothetical biological traits are identified for testing against disturbance gradients. The traits were selected for their perceived relevance to disturbance response generally, but also include a specific focus on domestic livestock grazing. The analysis is structured hierarchically to enable attributes to be analysed within major life forms. A different selection of traits is identified as being relevant to each major life form. Flexible adaptation in the use of the trait set is suggested as a way of comparing functional response to disturbance over a series of locations. For example, assemblages will vary in their representation of the major life forms, and it may be relevant to analyse traits within a subset of these life-form groups. Because individual studies encompass a limited range of environmental variation, and local floras may be constrained by their evolutionary context, similar approaches need to be tested over a range of vegetation types and geographic situations. A significant advance in functional trait analysis could be achieved if individual studies provide explicit descriptions of their evolutionary and ecological context from a global perspective.

Plant functional types: are we getting any closer to the Holy Grail?

1 Laboratoire d’Ecologie Alpine, CNRS UMR 5553, Université Joseph Fourier, BP 53X, 38041 Grenoble Cedex 9, France. sandra.lavorel@ujf-grenoble.fr 2 Instituto Multidisciplinario de Biología Vegetal (CONICET – UNC) and FCECFyN, Universidad Nacional de Córdoba, Argentina 3 Department of System Ecology, Institute of Ecological Science, Vrije Universiteit, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands 4 Centre d’Ecologie Fonctionnelle et Evolutive, CNRS UMR 5175, 1919 route de Mende, 34293 Montpellier Cedex 5, France 5 School of Geographical Sciences, University of Bristol, University Road, Bristol BS8 1SS, UK 6 CSIRO Sustainable Ecosystems, GPO Box 284, Canberra ACT 2601, Australia 7 Centro de Estudios Ambientales del Mediterraneo (CEAM), C/ Charles R. Darwin 14, Parc Tecnologic, 46980 Paterna, Valencia, Spain

Plant response to disturbance in a Mediterranean grassland: How many functional groups?

. Data referring to changes in vegetation composition resulting from cattle exclosure and ploughing in a Portuguese pasture dominated by annuals were used to test hypotheses regarding the biology of species favoured or eliminated by disturbance in semi-natural herbaceous communities. These hypotheses were tested in two ways. First we compared the distribution of six a priori groups – grasses, small rosettes, large rosettes, small species with leafy stems, large species with leafy stems, legumes – across grazed, ploughed and undisturbed plots. In a second set of analyses we examined changes in the frequencies of individual biological attributes in response to grazing and ploughing. These analyses were carried out separately for grasses and dicot forbs. Overall, the species composition showed little response to either grazing or ploughing, though species dominance changed. This lack of responsiveness of species composition was attributed to the long history of intensive land use which has resulted in the loss of disturbance-intolerant species over entire landscapes. When considering a priori groups, small rosettes were indifferent to disturbance. grazing and ploughing showed that dominated. Large rosettes, large species with leafy stems and legumes were generally intolerant to both grazing and ploughing, though individual species may increase in response to disturbance. Small species with leafy stems were the only group favoured by grazing whereas ploughing favoured grasses. As to individual traits, grazing excluded large grass species with heavy seeds and promoted a flat rosette canopy structure and a small size, along with a moderate dormancy and protected inflorescences. In forbs, grazing favoured small species, as expected, while it excluded tall species, and, in contrast to earlier results, a rosette canopy. These attributes were consistent with responses of the a priori groups, though it would not have been possible to reconstruct groups directly from the attribute list. Ploughing had no effect on any of the forb traits. As to grass traits, flat- and short-statured species increased and heavy-seeded species decreased. Our analysis revealed two advantages of establishing plant functional classifications within life forms. Subgroups within forbs had contrasting types of behaviour. For the same trait patterns could differ within the grass group from within the forb group. Finally, this analysis emphasizes the need for plant functional classifications aiming at the identification of syndromes of co-occurring attributes rather than of lists of isolated traits of which actual combinations are not specified.

How environmental and disturbance factors influence species composition in temperate Australian grasslands

. A distinctive feature of Australian vegetational history is the abruptness of change since European settlement, involving the influx of exotic species and the imposition of exogenous disturbances which are novel in both intensity and character. This can produce two sources of habitat variability: the natural patterns arising from environmental variation, as well as an overlying effect of disturbance. The relative importance of these two types of variables were compared in temperate herbaceous vegetation. Canonical Correspondence Analysis showed that environment and disturbance had similar contributions to floristic variability. Individually, lithology, altitude and soil disturbance were the strongest variables while slope position, grazing and water enrichment were slightly less important. Despite generally low levels of site specificity, groups of species associated with lithology, slope position, altitude and different disturbance regimes were identified. Exotic species were associated with higher levels of disturbance, but showed levels of environmental specialization similar to the native component. Through combination of this analysis with a previous analysis of species richness for the same data set, it became evident that environmental variation mostly resulted in species substitutions while disturbances led to losses of species, with partial replacement by exotics. Synthesizing these results, we identified three broad groups in relation to tolerance of levels of exogenous disturbance: (1) intolerant species - native taxa intolerant of severe disturbances and constituting the species - rich component of the vegetation; (2) tolerant species - exotic and native taxa occurring at both disturbed and undisturbed habitats and (3) disturbance specialists - predominantly exotic species, correlated with high levels of disturbance.

Birds in eucalypt and pine forests: landscape alteration and its implications for research models of faunal habitat use

Abstract Most studies of faunal habitat fragmentation are based on a human perspective of the landscape in which landscape elements are classified as habitat and non-habitat. Moreover, many landscape models that define “habitat patches” assume that the same set of patches will be suitable for all taxa or a broad range of taxa. McIntyre and Hobbs [Conservation Biology 13 (1999) 1282] recently proposed a model in which landscapes can be classified according to the amount of habitat remaining and in which the remaining habitat can correspond to a continuum or gradient of modification. The perception of a landscape as being intact, variegated, fragmented or relictual [sensu Conservation Biology 13 (1999)] will depend on the capacity of individual species to utilise modified habitat. We suggest that although the continuum concept of habitat use is reasonably well established for plants, faunal studies have often ignored the notion of a gradient of habitat use and have classified landscape areas simplistically and inappropriately as either habitat or non-habitat. Data on birds in southeastern Australia are used to illustrate how the binary view of habitat can be incorrect. Birds were sampled in landscapes that ranged from intact to relictual as defined from an anthropocentric perspective. Our data: (1) illustrated a wide range of bird responses to habitat modification including many that might have been overlooked using a simple binomial approach to habitat classification, and (2) highlighted the fact that the way in which humans perceive landscapes may not correspond to how some elements of the biota perceive the same landscape. Viewing landscapes as a species-specific gradient of states of remaining habitat and condition has important implications for undertaking studies of human impacts on biodiversity and also integrating conservation considerations in production environments. It also challenges the effectiveness of “quick fixes” such as species-based biodiversity surrogates schemes and the uncritical use of generic landscape indices to save “habitat” because the assumption that all species will conform to the same landscape pattern will not hold.

Natural Grassy Vegetation and Native Forbs in Temperate Australia: Structure, Dynamics and Life-Histories

This paper describes aspects of the structure, floristics and dynamics of natural grassy vegetation in temperate Australia. The community structure of this vegetation type can be conceptualised using a matrix-interstitium model which may be useful in studies of the dynamics of forb populations and the role of disturbances in grassland management. Disturbance alters the balance between the matrix and interstitial components and is important for herbaceous communities as an agent in changes to, and losses of, native species. Life history characteristics conferring tolerance of disturbance upon native forbs are discussed, and the ruderal nature of the exotic component is suggested as a characteristic leading to the replacement of native forbs by exotic species, where substantial exogenous disturbance occurs. Despite the demonstrated importance of exogenous disturbances in influencing native species diversity and exotic invasions, there is still a poor understanding of the specific and interactive effects of various disturbances and the roles of particular plant traits in determining forb survival. Further research, utilising comparative or functional group approaches, is required to explain responses of natural grassy communities and native forbs. Such studies would provide opportunities for developing ecological theory and improving the management of natural grassy communities and their native forbs.

Plant traits predict impact of invading species: an analysis of herbaceous vegetation in the subtropics

The need to predict potential invasion impact of plant species is important for setting weed-management priorities and determining quarantine restrictions for newly imported plant material. We analysed the naturalised plant component of a herbaceous plant community in sub-tropical eucalypt woodlands subjected to various disturbances associated with agricultural activities. The native and naturalised plant species did not differ in the proportions of different life forms, although life-history differed, with the naturalised group having more annual and biennial, and relatively fewer perennial species. We classified the naturalised assemblage into high-and low-impact species and compared the plant-trait and habitat characteristics of the two groups. Low-impact species covered a range of levels of habitat specialisation whereas high-impact species tended to have moderate to low levels of specialisation and to be less tolerant of grazing. Seven traits were found to be significantly associated with impact. Stepwise regression indicated a high level of redundancy in the data, owing to attributes being correlated. For all species, four attributes were significant in determining impact: very wide lateral spread, C4 photosynthesis, tall height and large leaves. For forbs, only two attributes (large seeds, adhesion/ingestion mode of seed dispersal) were significant in the overall model. We identified the following eight functional types amongst the naturalised species: (i) high-impact C4 lawn grasses, (ii) high-impact C4 bulky tussock grasses, (iii) moderate-impact annual grasses, (iv) moderate-impact tall annual forbs, (v) moderate-impact spreading forbs, (vi) moderate-impact woody forbs, (vii) low-impact legumes and (viii) low-impact small ruderals. In the subtropical woodland environment perennial C4 grasses appear to present the greatest invasive threat to herbaceous native communities, whereas forbs of wide lateral spread, with large animal-dispersed seeds are also problematic. The results support a case for limiting further importation of horticultural and forage material into Australia.